WT-1320(EX) EXTRACTED VERSION OPERATION REDWING - PROJECT 2.66a Early Cloud Penetrations Human Experiment #133 Ernest A. Pinson, Col, USAF Kermit C. Kaericher, Capt, USAF James E. Banks, 1st LT, USAF John d'H. Hord, Maj, USAF Air Force Special Weapons Center Kirtland Air Force Base, NM 24 February 1960 NOTICE: This is an extracted version of WT-1320, OPERATION REDWING. Approved for public release; distribution is limited. Extracted version prepared for Director DEFENSE NUCLEAR AGENCY Washington, DC 20305-1000 20 March 1987 FOR REFERENCE SEE (3PM01.gif) FOREWORD Classified material has been removed in order to make the information available on an unclassified, open publication basis, to any interested parties. The effort to declassify this report has been accomplished specifically to support the Department of Defense Nuclear Test Personnel review (NTPR) Program. The objective is to facilitate studies of the low levels of radiation received by some individuals during the atmospheric nuclear test program by making as much information as possible available to all interested parties. The material which has been deleted is either currently classified as Restricted Data or Formerly Restricted Data under the provisions of the Atomic Energy Act of 1954 (as amended), or is National Security Information, or has been determined to be critical military information which could reveal system or equipment vulnerabilities and is, therefore, not appropriate for open publication. The Defense Nuclear Agency (DNA) believes that though all classified material has been deleted, the report accurately portrays the contents of the original. DNA also believes that the deleted material is of little or no significance to studies into the amounts, or types, of radiation received by any individuals during the atmospheric nuclear test program. 2 WT-1320 OPERATION REDWING - PROJECT 2.66a EARLY CLOUD PENETRATIONS (U) Ernest A.Pinson, Col, USAF Kermit C. Kaericher, Capt, USAF James E. Banks, 1st Lt, USAF John d'H. Hord, Maj, USAF Air Force Special Weapons Center Kirtland Air Force Base, New Mexico 3 DEDICATION This report is dedicated to Paul Marcus Crumley, Captain, United States Air Force, who gave his life on the 18th day of May, 1956 in prosecution of this work. He did much of the work of assembling the material and planning all the details necessary to the proper conduct of the project. May this report and the value of this work stand as a small evidence that he did not die in vain. Note: Paul Crumley was killed in a takeoff crash. 4 ABSTRACT Twenty-seven penetrations of six radiation clouds from multimegaton-range detonations were made at times ranging from 20 to 78 minutes after detonation and at altitudes ranging from 20,000 to 50,000 feet. Sixteen of these penetrations were earlier than 45 minutes and seven were earlier than 30 minutes. Maximum radiation dose rates as high as 800 r/hr were encountered, and several flights yielded total radiation doses to the crew of 25 r. It was found that the average radiation dose rate in the mushroom of the cloud from a 100-percent-fission-yield detonation would be: D = 1.0 x 105t-1.7 Where: D = average dose rate, r/hr t = time after detonation, minutes This relationship holds for times from 3 to 80 minutes after detonation. The average dose rate in the stern of the cloud from water-surface bursts was found to be less than the dose rate in the mushroom by a factor of from five to ten. The radiation dose rate in the cloud is independent of yield, but is proportional to the ratio of fission yield to total yield. In a high tropopause area, a flight through a cloud from a 100-percent-fission-yield multimegaton-range weapon in a high-performance aircraft may be made at 45,000 feet at a time of 20 minutes after detonation. The average mission dose of this flight would be 25 r. At 30,000 feet, a penetration of the stem of the cloud may be made as early as 10 minutes after detonation with a radiation dose of the same magnitude. The dosage received on the return to base flight because of contamination on the aircraft (B-57B) was found to be about 25 percent of the total mission dose for flights lasting about 50 minutes after the cloud penetration. An investigation of the internal radiation hazard encountered by the flight crews was conducted. The results are given in Appendix C. The internal hazard was found to be insignificant compared to the external hazard. 5 FOREWORD This report presents the final results of one of the projects participating in the military-effect programs of Operation Redwing. Overall information about this and the other military-effect projects can be obtained from WT-1344, the "Summary Report of the Commander, Task Unit 3." This technical summary includes: (1) tables listing each detonation with its yield, type, environment, meteorological conditions, etc.; (2) maps showing shot locations; (3) discussion of results by programs; (4) summaries of objectives, procedures, results, etc., for all projects; and (5) a listing of project reports for the military-effect programs. 6 PREFACE The authors wish to acknowledge the assistance of a large number of persons who contributed to the success of Project 2.66. Doctors W.H. Langham, E.C. Anderson, P.S. Harris, and others in the Health Division of the Los Alamos Scientific Laboratory rendered an invaluable contribution to the project in their assessment of the negligible significance of the internal radiation hazard. This was done by means of measurements in the human counter and urinalyses as reported in Appendix C. The following members of the Air Force Special Weapons Center, Kirtland Air Force Base, New Mexico, contributed materially to the execution of general or specific parts of the project: Major J.L. Dick and MSgt J.M. Pulliam who assisted in the film measurements of total dose and of contamination on the aircraft, and Capt R.F. Merian, 1st Lt. M.V. Harlow, Jr., 1st Lt. D.L. Endsley, 2d Lt. R.L. Capener, and MSgt W.P. Schaus, Sr., who contributed to the development, maintenance, and repeated calibration of the electronic instruments. The same individuals installed these instruments in the aircraft prior to each shot and read out the data after each shot. Lt Col L.A. Kiley and 1st Lt W.C. Jones rendered excellent rear-echelon logistic support to the project. G.E. Koch aided the project materially by providing technical advice on the electronic instrumentation at the test site. The project is indebted to the Tactical Air Command for the assignment of the aircraft and the selection of exceptionally fine officers and maintenance personnel to support the flight requirements of the project. The officers and men of the flight element, under command of Lt Col W.B. Furman, performed an outstanding job of maintaining and flying these aircraft. The project officers are grateful to these officers and men for their contributions to the success of the flights and, hence, the success attained by the project. 7-8 CONTENTS DEDICATION---------------------------------------------------- 4 ABSTRACT------------------------------------------------------ 5 FOREWORD------------------------------------------------------ 6 PREFACE------------------------------------------------------- 7 CHAPTER 1 INTRODUCTION--------------------------------------- 13 1.1 Objective------------------------------------------- 13 1.2 Background and Theory------------------------------- 13 CHAPTER 2 PROCEDURE------------------------------------------ 15 2.1 Operation------------------------------------------- 15 2.2 Instrumentation------------------------------------- 15 2.2.1 KAEC Model M1432 Automatic-Recording Radiation Ratemeter (P Meter)---------------- 16 2.2.2 Bioscel Radiation Ratemeter------------------ 17 2.2.3 Sigmatron Radiation Integrating Dosimeter---- 18 2.2.4 Other Dosimeters----------------------------- 18 2.2.5 Intervalometer------------------------------- 19 2.2.6 Photopanel----------------------------------- 20 2.3 Description of Required Data------------------------ 20 2.3.1 Total Radiation Dose------------------------- 21 2.3.2 Length of Time in Cloud---------------------- 21 2.3.3 Radiation Dose in Cloud---------------------- 21 2.3.4 Dose on Return Flight------------------------ 21 2.3.5 Maximum Dose Rate in Cloud------------------- 21 2.3.6 Average Dose Rate in Cloud------------------- 21 2.3.7 Dose Rate at Cloud Exit---------------------- 22 2.3.8 Decay Rate on Return Flight------------------ 22 2.3.9 Contamination Factor------------------------- 22 2.4 Master Data Sheet----------------------------------- 22 CHAPTER 3 RESULTS AND DISCUSSION----------------------------- 23 3.1 Time and Altitude of Penetration-------------------- 23 3.2 Length of Time in the Radioactive Cloud------------- 23 3.3 Radiation Dose Rates in the Cloud------------------- 26 3.3.1 Radiation Dose Rates in the Cloud versus Nature of the Yield------------------- 26 3.3.2 Radiation Dose Rate versus Altitude of Penetration------------------------------- 26 3.3.3 Radiation Dose Rate versus Time After Detonation----------------------------------- 27 3.4 Radiation Doses------------------------------------- 30 3.5 Cloud Dimensions and Transit Doses at Various Altitudes------------------------------------------- 30 3.6 Contamination Factor-------------------------------- 31 9 3.7 Decay of Contamination on the Aircraft-------------- 31 3.8 Conditions of Flight Within the Radioactive Cloud--- 32 3.9 Effectiveness of Instrumentation-------------------- 33 CHAPTER 4 CONCLUSIONS AND RECOMMENDATIONS-------------------- 36 4.1 Conclusions----------------------------------------- 36 4.2 Recommendations------------------------------------- 37 APPENDIX A TYPICAL MASTER DATA SHEET------------------------- 38 APPENDIX B TYPICAL PLOT OF P METER AND BIOSCEL DATA---------- 40 APPENDIX C EVALUATION OF INTERNAL RADIATION HAZARD----------- 41 C.1 Objective------------------------------------------- 41 C.2 Background and Theory------------------------------- 41 C.3 Procedure------------------------------------------- 41 C.4 Results and Discussion------------------------------ 42 C.4.1 Human Counter-------------------------------- 42 C.4.2 Activity in Urine---------------------------- 44 C.5 Conclusions----------------------------------------- 46 C.6 Recommendations------------------------------------- 51 REFERENCES---------------------------------------------------- 52 TABLES 2.1 Summary of Sources of Required Data----------------- 20 3.1 Summary of Cloud Penetration Data------------------- 24 3.2 Comparison of Average Dose Rates in Apache and Navajo Clouds at Equivalent Times and Altitudes----- 28 3.3 Average Radiation Dose Rate in Diameter of, and Radiation Dosage in Transit of, Radioactive Clouds from Megaton-Yield Weapons at Various Altitudes at 20 Minutes After Detonation------------ 31 3.4 The Relative Sensitivities of Radiation Measuring Instruments as a Function of X- and Gamma Ray Energy------------------------------------ 34 C.1 Results of Measurements in Human Counter------------ 42 C.2 Gamma Activity in Urine as Measured in Human Counter (K40 Channel)------------------------------- 44 C.3 Beta Activity in Urine Samples---------------------- 45 C.4 Analysis of Urine for Plutonium--------------------- 50 FIGURES 2.1 Block diagram of automatic recording radiation ratemeter (P meter)--------------------------------- 16 2.2 Block diagram of Bioscel radiation ratemeter-------- 17 2.3 Block diagram of Sigmatron radiation-integrating dosimeter------------------------------------------- 19 3.1 Dose rate versus altitude for three shots corrected to 100-percent fission yield-------------- 27 10 3.2 Average gamma radiation dose rate in an atomic cloud as a function of time after detonation-------- 29 3.3 Approximate diameters (in miles) of radioactive clouds from 500-kt and 5-Mt weapons at various altitudes (in thousands of feet)-------------------- 32 C.1 Increase in whole-body gamma activity as a function of external gamma dose--------------------- 43 C.2 Total beta activity in urine as a function of external gamma dose--------------------------------- 47 C.3 Specific beta activity in urine as a function of external gamma dose--------------------------------- 48 C.4 Specific beta activity in urine as a function of increased gamma activity as measured in human counter--------------------------------------------- 49 11-12 Chapter 1 INTRODUCTION 1.1 OBJECTIVE The objective of this project was to measure the radiation dose and dose rate one would experience in flying through the cloud resulting from a megaton-range weapon and some factors affecting personnel safety in the event of an operational situation requiring flights through such clouds. Specific information was sought on the radiation dose rates inside the cloud, the total dose received in flying through such a cloud, the total dose received on the return flight after flying through the cloud, the internal radiation dose due to inhalation of fission products during such flights, and the conditions of flight inside the cloud. This information was needed by the operational commands of the Air Force in their planning to insure the most-effective utilization, consistent with crew safety, of aircraft in cloud areas. 1.2 BACKGROUND AND THEORY During Operation Greenhouse the first significant data on gamma dose rates within atomic clouds were collected. These are reported in Reference 1. The data were collected by drone aircraft flown through the clouds from devices ranging in yield from _____ and at times of from 3 to 25 minutes after detonation. Reference 1 shows average gamma dose rates within the cloud to be of the orders of 104 r/hr _____ after _____ detonation. Further measurements of gamma dose rates within atomic clouds were made during Operation Upshot-Knothole and reported in Reference 2. Dose-rate-measuring instruments were mounted in parachute-borne canisters, and the dose-rate instruments previously used by the Naval Radiological Defense Laboratory (NRDL) during Operation Greenhouse (Reference 1) were mounted in QF-80 drone aircraft. Both the canisters and the QF-80's passed through only the head, or mushroom, of the clouds resulting from devices ranging in size from ______. Dose rates of the order of 104 r/hr were measured from _____ after detonation. A compilation of the Greenhouse and Upshot-Knothole average dose rates as a function of time after detonation is presented graphically in Reference 2. These points are also included in Figure 3.2 of this report. The time after detonation for each point is the approximate time after detonation at which the airplane or canister entered the cloud. A least-squares analysis of the data showed that the best-fit line had the equation: D = 1.31 x 10 5t-2.06 Where D = average dose rate, r/hr 13 t = time after detonation, minutes Consideration of Reference 2 led to the following generalizations which were used as guides in the initial planning of this project: (1) The dose rate in the cloud is relatively independent of yield. (2) Within a factor of two, the average dose rate in a cloud is given by Equation 1.1. The first manned penetrations at early times after detonation (17 to 41 minutes) were made during Operation Teapot. These penetrations were made through clouds from devices ranging in yield from 8 to 30 kt. The average dose rate in the cloud as measured during these penetrations is shown graphically in Figure 3.2. The gamma radiation dose rate within the atomic cloud resulting from kiloton-range weapons has received theoretical consideration in References 3, 4, 5, 6, and 7. The outstanding features of many of these calculations were the very-high gamma dose rates predicted for very early times because of small cloud size and high fission-product concentration. 14 Chapter 2 PROCEDURE 2.1 OPERATION Five B-57B aircraft which were instrumented to measure gamma radiation dose rate, integrated dose, and conditions of flight were through the clouds resulting from the detonation _____ in yield _____. On the day prior to a shot, all the instrumentation was checked for proper operation, installed in the aircraft, and readied for use. The flight crews were briefed on the desired flight pattern, altitudes and times of penetration, and forecast development characteristics of the cloud. These characteristics included size, stabilization levels, and drift. All aircraft took off at predetermined times in order to permit proper positioning at shot time. After the shot was fired, the cloud was surveyed visually by the director in the lead aircraft. Positions and times of penetration were then established. Penetrations were made at intervals of from 4 to 10 minutes and at varying altitudes. This time spacing permitted some of the results of the first penetrations to be used in planning the succeeding penetrations. Two types of maneuver were utilized in the penetration phase. In both cases the cloud was approached in straight and level flight. After entering the visible cloud, the pilot either executed a standard 180-degree turn and made his exit or continued on a straight course through the cloud. The type of maneuver to be employed was decided prior to the penetration run. However, the aircrews were briefed on emergency procedures which permitting changing from the straight-through to the 180-degree-turn maneuver at their discretion if excessively high dose rates were encountered. A dose rate two times greater than the predicted dose rate was considered excessive. Upon exist from the cloud, the aircraft returned to base and the records were removed immediately for analysis. 2.2 INSTRUMENTATION The last two were not radiac devices, but were included in this section for convenience of presentation. A description of each device is given below. All radiation-measuring devices were calibrated at NBS prior to the operation. They were recalibrated intermittently at the test site using a Co__ source. 15 Pages 16 through 19 were deleted 2.3 DESCRIPTION OF REQUIRED DATA In order to satisfy the purposes of this project, accurate information was required on the following parameters: (1) time of penetration of the radioactive cloud; (2) total radiation dose on the flight; (3) radiation dose accumulated in transit of the radioactive cloud; (4) length of time required to fly through the cloud; (5) radiation dose accumulated on the flight back to base due to contamination on the aircraft; (6) maximum dose rate in the radioactive cloud; (7) dose rate in the crew compartment immediately after exit from the cloud due to contamination on the aircraft; (8) the rate of decay of this contamination; and (9) conditions of flight inside the radioactive cloud, i.e., turbulence and icing. All of these data, except the last, were recorded automatically with the instrumentation described in Section 2.2. The items of information desired from each flight and the instruments which were used to provide them are summarized in Table 2.1. Most of the information was available directly from the installed instrumentation, while some additional information was obtained by indirect methods as indicated in Sections 2.3.1 through 2.3.9. It should be noted that these indirect methods constituted, in every case, a duplicate method for obtaining a check on the same data obtained by one or more direct measurements. In addition, the pilot (and observer when present) made observations during the flight on the following parameters: (1) dimensions of the cloud at various altitudes prior to penetration; (2) time and altitude of penetration; (3) type of penetration; (4) 20 length of time in the radioactive cloud; (5) maximum dose rate in the cloud; (6) dose rate in the cockpit on exit from the cloud due to contamination on the aircraft; (7) accumulated dose in the cockpit at time of exit from the cloud; and (8) degree of turbulence and icing noted during passage through the radioactive cloud. These observations were reported to the flight director in the air and were transcribed from the pilot's and director's notes during the postflight debriefing. These observations by the pilot duplicated information recorded automatically by the instrumentation in the aircraft in all cases except icing conditions in the cloud. 2.3.1 Total Radiation Dose. The total radiation dose was measured directly by the Sigmatrons, quartz-fiber dosimeters, NBS film packs, and Rad-Safe film badges. It was also obtained by integrating the area under the dose-rate-versus-time curves yielded by the P meter and the Bioscel mounted in the photopanel. 2.3.2 Length of Time in Cloud. The pilot flashed the marker light on the photopanel at the times which he considered to be his entry and exit from the cloud. Time in the visible cloud was then computed by observation of the clock in the photopanel pictures. Time in the radiation cloud was obtained from the P meter and Bioscel data. These two instruments provided curves of dose rate as a function of time. For purposes of this calculation, the entry and exit were considered to be those times at which the dose rate was 5 percent of the maximum rate observed. 2.3.3 Radiation Dose in Cloud. The radiation dose received in the cloud was measured by integration of the area under the P meter and Bioscel curves between cloud entry and cloud exit. The Sigmatron in the photopanel also gave a direct indication of dose in the cloud. It required only that the meter be observed in the film frames where the market light occurred. The NBS film packs gave an indirect measure of the dose in the cloud. This was computed by subtracting the return flight dose which was calculated from the T1B decay-rate measurements from the total dose indicated by the film packs. 2.3.4 Dose on Return Flight. The radiation dose on the return flight was measured directly by the P meter, Bioscel, and Sigmatron. In each instance all that was necessary was to subtract the dose in the cloud from the total dose. The difference was the dose received on the return flight. An indirect method of obtaining that portion of the radiation dose received after exit from the cloud and during the return flight was by extrapolation of the decay-rate curve measured by the T1B after the aircraft was on the ground back to cloud-exit time and integration of the area under the curve from cloud-exit time to time of landing. 2.3.5 Maximum Dose Rate in Cloud. The maximum dose rate in the cloud was taken directly from the P meter and Bioscel curves. The pilot also observed the maximum dose rate indicated by the Bioscel meter in the cockpit. 2.3.6 Average Dose Rate in Cloud. The average dose rate in the cloud was calculated by dividing the dose received in the cloud by the time in the cloud. Both of these were provided directly by the P meter, Bioscel, and Sigmatron. Since the dose in the cloud was obtained indirectly from the NBS film packs, these were also an indirect source for the average dose rate in the cloud. 21 2.3.7 Dose Rate at Cloud Exit. The dose rate at cloud exit due to contamination on the aircraft was taken directly from the P meter and Bioscel curves. It was also derived by extrapolation of the decay-rate curve from the T1B decay measurements. 2.3.8 Decay Rate on Return Flight. The decay rate of the contamination during the return flight was obtained directly from the P meter curves. It was also obtained by extrapolation of the decay rate curve from the T1B decay measurements made during the first few hours after the aircraft landed. 2.3.9 Contamination Factor. The contamination factor is expressed in percent per minute in the cloud and is defined as: Dose rate in cockpit at cloud exit (Average dose rate in cloud)(Minutes in cloud) x 100 (2.1) It is a measure of the degree to which this type of aircraft (B-57B) becomes contaminated by flight through the cloud as reflected by the radiation dose in the crew compartment after exit from the cloud. It is significant in predicting that portion of the total dose which is derived from contamination on the aircraft during the flight back to base. It is calculated directly from data recorded by the P meter. The contamination factor was computed also using the dose rate at cloud exit as derived from T1B measurements and the average dose rate in the cloud indicated by the NBS film packs. 2.4 MASTER DATA SHEET The large mass of data was summarized on a master data sheet. One of these sheets was filled out for each penetration flight. A typical sheet is shown in Appendix A. Some additional data on radiation dose rates in the cloud at times later than 1 hour after detonation were obtained through the courtesy of the Test Aircraft Unit. These data were collected during the cloud-sampling operations of this unit. 22 Chapter 3 RESULTS and DISCUSSION These penetrations were made at times of from 20 to 78 minutes after detonation. The indicated altitudes of penetration varied generally from 30,000 feet to 50,000 feet, with one penetration being made at 20,000 feet. Penetrations were made through clouds from land-surface, water-surface, and air detonations. Maximum dose rates as high as 800 r/hr were encountered in some of the early penetrations, and several flights yielded total radiation doses to the crew of 15 r. On other flights, the whole-body radiation dose as measured by Rad-Safe film badges was as low as 100 mr. The dosage authorized by the Surgeon General of the Air Force and the Commanded of Joint Task Force Seven for the aircrews on this project was 50 r, with a limiting planning dosage of 25 r for any single penetration. No penetrations were made in which the maximum dose to be expected, as measured by Rad-Safe film badges, would exceed 25 r. The experimental plan provided to be satisfactory, and data to satisfy the objectives of this project were obtained. The data are presented in Table 3.1. The sections which follow discuss the results as they appear in the table. 3.1 TIME AND ALTITUDE OF PENETRATION The times of penetration varied as indicated above. _____ Succeeding penetrations were at higher altitudes through the intermediate zone between the stem and mushroom or through the mushroom. All penetrations below 40,000 feet were considered to be penetrations of the stem. Penetrations between 40,000 and 45,000 feet were intermediary between the stem and mushroom. Penetrations above 45,000 feet were in general through the mushroom of the cloud. During Shot Cherokee, a 5,000-foot air detonation, the top of the stem was above 43,000 feet. 3.2 LENGTH OF TIME IN THE RADIOACTIVE CLOUD The length of time in the cloud recorded in Table 3.1 represents the period of time from the moment the radiation intensity reached a value of 5 percent of the maximum intensity noted in the cloud until the intensity subsequently diminished to this 5 percent value. In penetrations of the stem or mushroom, this time corresponded closely to the time in the visible cloud reported by the pilot. However, in penetrations just below the altitude of the mushroom, the length of time in the radiation field was usually longer than that in the visible cloud by a factor comparable to the time the plane was beneath the overhanging mushroom but was not in the visible cloud. The length of time in the radiation field is used in Table 3.1, since the dimensions of the radiation field are of greater interest in this report than the dimensions of the visible cloud. The time required to pass through the radiation cloud varied from 1 minute for stem penetrations to about 5 minutes for the mushroom penetrations of the clouds from the higher-yield 23 FOR REFERENCE SEE (3pm02.gif) 24 FOR REFERENCE SEE (3pm03.gif) 25 detonations. More-detailed information on cloud size as a function of time after detonation, yield of detonation, and altitude are presented in a later section of this report. 3.3 RADIATION DOSE RATES IN THE CLOUD The maximum and average radiation dose rates recorded for each penetration by the various instruments previously described are given in Table 3.1. The maximum dose rate recorded on each flight through the cloud was about twice the average dose rate recorded for the total period in the cloud by the same instrument. The average dose rates in the cloud recorded by the P meter and Bioscel were generally 100 percent and 15 percent, respectively, higher than that determined by film dosimetry. Since film dosimetry is more widely accepted as an indicator of whole-body radiation dosage, the film data were used to give dose rates or dosages in all figures and tables presented in this report, unless otherwise specified. Appendix B shows a typical plot of the dose rates in the cloud recorded by the P meter and Bioscel, together with data which were extracted therefrom for presentation in Table 3.1. The radiation dose rates observed in the cloud were a function of three primary factors: (1) the nature of the yield of the detonation, i.e., the ratio of the fission yield to the total yield; (2) the altitude at which the penetration was made with respect to the position or height of the mushroom; and (3) the length of time after detonation at which the penetration was made. 3.3.1 Radiation Dose Rates in the Cloud versus Nature of the Yield. Since fission yield is the primary contributor to radioactivity prevailing in the cloud, it is to be expected that the dose rates noted in the cloud would be proportional to the ratio of the fission yield to the total yield. Thus, if two separate detonations of essentially the same total yield took place in a similar situation, one in which the fission yield constituted 50 percent of the total yield and one in which the fission yield constituted 5 percent of the total yield, then one would expect that the dose rate in the cloud of the former at any specified altitude and time after detonation would be ten times that in the cloud from the latter. This proved essentially to be the case when one compares the dose rates after detonation (Table 3.2). Therefore, when presenting the dose rate and dosage data from Table 3.1 in other figures and tables in this report, an adjustment is made to a 100-percent-fission-yield detonation in accordance with the ratio of the fission yield to the total yield of the detonation concerned. 3.3.2 Radiation Dose Rate versus Altitude of Penetration. It was observed in these penetrations that the dose rates at the lower altitudes (30,000 to 40,000 feet) were considerably lower than at higher altitudes in or near the mushroom. Evidently, the radioactive fission-product particles are much more concentrated per unit volume in the mushroom than in the stem. Data on average dose rates versus altitudes from three shots in which penetrations were made at widely differing altitudes between 30,000 and 50,000 feet are shown in Figure 3.1. In this figure all the dose rates are adjusted to 100-percent-fission yield and to a common time of 20 minutes after detonation. It is concluded from these data that the dose rate in the stem of clouds from the water-surface or air detonations of megaton-yield devices at an altitude below 40,000 feet is a factor of one-fifth to one-tenth that in the mushroom. Since the stem is also much smaller in diameter than the mushroom, one can fly through the stem as early as 10 minutes after 26 FOR REFERENCE SEE (3pm04.gif) 27 FOR REFERENCE SEE (3pm05.gif) 28 FOR REFERENCE SEE (3pm06.gif) 29 3.4 RADIATION DOSES The total gamma-radiation dose received on a penetration flight can be broken down into two parts: the dose received in the cloud and the dose received on the return flight. The return flight dose for the B-57B was found to be approximately 15 percent of the total dose when the return flight was of about 50 minutes duration. Section 2.3 of this report explains the various direct and indirect methods used to measure the dosage received by the crew, both in the cloud and on the return flight. Data collected by these various methods is presented in Table 3.1. The maximum total dose received by any crew during a penetration flight associated with this project was approximately 16 r, as measured by film dosimetry. It is significant to note that the highest radiation doses received did not correspond to the earliest penetrations. The dose received in the cloud was a function of the average dose rate in the cloud and the time spent in the cloud. For each shot the first penetration usually was made at the lowest altitude, and succeeding penetrations were made at higher altitudes. This plan was followed so that in the event turbulence was encountered, it could be tolerated better at the lower altitude. Thus the earliest penetrations were made through the stem of the cloud. Since the dose rate in the stem was lower than the dose rate in the mushroom at the same time after detonation and since the diameter of the stem was a third to a half of that of the mushroom, lower dosages were received by the crews who made the earlier penetrations of the stem of the cloud than by those crews who made later penetrations of the mushroom. This was true for all shots. 3.5 CLOUD DIMENSIONS AND TRANSIT DOSES AT VARIOUS ALTITUDES The total dose received in transit of a radioactive cloud is dependent on two factors: the average dose rate and the length of time required to pass through the cloud. The latter is a function of cloud diameter and the speed of the airplane. All penetrations on this project were made with B-57B aircraft having a speed of about 7 mpm. Table 3.3 shows representative cloud diameters at various altitudes for detonations of multimegaton yields. The values given in this table are not those measured on any particular shot but are average values for the six shots in which this project participated. The average dose rates, shown in r per minute in the table, are likewise based on the results of the twenty-six penetrations made at altitudes of from 30,000 to 50,000 feet on the six shots. These average radiation dose rates have been adjusted to 100-percent-fission yield. The transit dose, expressed in r, is based on the average cloud diameter shown in the table, the average dose rate shown in the table, and an aircraft speed of 7 mpm. It should be noted that all the shots during this operation were under a high tropopause (about 50,000 to 55,000 feet). No scientific information was available to this project on cloud size and height for multimegaton-yield devices in an area where the tropopause occurs at a lower altitude. It is the feeling of the authors that the clouds resulting from devices of 0.5 Mt or larger yields would spread out little beneath the tropopause and that a large portion of the cloud would push on through the tropopause. The information shown in Table 3.3 is based on a time of 20 minutes after a water-surface detonation. Assuming a decay rate in the cloud of t-1.7, the average dose rate at 10 minutes after detonation would be about a third of the value shown. Figure 3.3 shows the comparative size, at various altitudes, of the radioactive clouds at 20 minutes 30 after detonation for 500-kt and 5-Mt devices. Considering Table 3.3 and Figure 3.3, it may be concluded that one may fly through the cloud from any yield 100-percent-fission weapon in a high-performance aircraft at an altitude of 45,000 feet at 20 minutes after detonation for an expected radiation dose of 25 r. Under the same conditions, one may fly through the cloud (stem) at 30,000 to 40,000 feet as early as 10 minutes after detonation for a radiation dose of 15 r or less. TABLE 3.3 AVERAGE RADIATION DOSE RATE IN DIAMETER OF, AND RADIATION DOSAGE IN TRANSIT OF, RADIOACTIVE CLOUDS FROM MEGATON-YIELD WEAPONS AT VARIOUS ALTITUDES AT 20 MINUTES AFTER DETONATION Assumptions: (1) 100-percent-fission-yield detonation; (2) aircraft speed of 420 knots; (3) tropopause at 55,000 feet; and (4) water-surface or air burst. Altitude Cloud Radiation Transit Cloud Radiation Transit Diameter Dose Rate Dose Diameter Dose Rate Dose ft x 103 miles r/min r miles r/min r 30 5 0.5 0.4 7 0.5 0.5 35 7 0.8 0.8 10 0.8 1.2 40 10 2.5 4 15 2.5 5 45 15 12 25 20 8 25 50 20 10 30 35 15 75 55 0 -- -- 40 -- -- 3.6 CONTAMINATION FACTOR The contamination factor was defined and discussed in Section 2.3.9. Values given in Table 3.1 are from computations made using each of the methods of calculation which were described. The average contamination factor for B-57B aircraft is 0.6 + 0.2 percent per minute. Both methods of calculation gave about the same value. With a contamination factor of this magnitude, a return to base flight of several hours duration after an early penetration of a radioactive cloud would result in a radiation dose to the crew, during the return flight, of about 25 percent of the total dose. One extremely high contamination factor computed for a penetration of the Shot Apache cloud at 20,000 feet is discussed in Section 3.8. The contamination factor for any particular type of aircraft is a function of the distance between the crew compartment and the residual contamination on the aircraft. In general, the engines are the most highly contaminated portion of the aircraft after flight through a radioactive cloud. Project 2.3 of Operation Teapot measured contamination factors on several different types of aircraft and concluded the contamination factor to be higher for those aircraft where the crew compartment was close to the engine or engines (see Reference 8). 3.7 DECAY OF CONTAMINATION ON THE AIRCRAFT The two methods used to measure the rate of decay of gamma radiation in the cockpit because of contamination on the aircraft gave essentially similar results, as shown in 31 FOR REFERENCE SEE (3pm07.gif) 32 However, no turbulence was experienced just outside the radioactive cloud during the penetration flights. Icing was encountered in several of the penetrations of clouds from water-surface detonations. Evidently the radioactive cloud was warmer than the surrounding air and was saturated with moisture carried up from the surface. This was also suggested by the moisture clouds which formed around the radioactive cloud after these detonations. When the relatively cold aircraft flies into the warmer saturated radioactive cloud, moisture condenses and freezes on the aircraft. From 30,000 to 45,000 feet, this icing caused no problem with these aircraft. However, at 50,000 feet, near the maximum altitude capability of these aircraft, this icing was sufficient to result in overheating of the jet engines and made it necessary to reduce power and descend after only a couple of minutes in the cloud. It is not known whether this icing condition would exist in the cloud from a land surface or air detonation. A penetration of the stem of the cloud from the Shot Apache (water surface) detonation was made at 20,000 feet, 53 minutes after detonation. The maximum dose rate in the cloud, as measured by the P meter, was 0.4 r per minute; the time in the cloud was 20 seconds. There was a large amount of moisture and mud present in the stem of the cloud at this altitude. The leading edges of the aircraft became covered with a visible muddy contamination, which was sufficiently dense on the forward part of the windshield and canopy to obstruct good vision for the pilot. At cloud-exit time the dose rate in the cockpit, because of contamination adhering to the aircraft, was equal to the maximum dose rate experienced inside the cloud. The contamination factor on the aircraft for this penetration was calculated to be 300 percent per minute. This was possible, since so much contamination stuck to the aircraft during the brief time it was in the cloud. The aircraft as flows through a rain shower about 20 minutes after exit from the radioactive cloud, and the contamination on the aircraft was reduced by a factor of three. Visibility through the windshield returned to normal. The dosage received on the return flight was 99 percent of the total mission dose for this penetration. The results of this penetration point out the inadvisability of flying through the stem of the cloud from a water-surface detonation. A penetration made at an early time, where the dose rate in the cockpit after exit from the cloud might be quite high, could result in a large mission dose, even through the aircraft was in the cloud for a very short time. It can also be noted that flying through a rain shower as soon as possible after cloud exit is an effective means of reducing the dosage received on the total mission. 3.9 EFFECTIVENESS OF INSTRUMENTATION Not all of the instrumentation installed in the aircraft operated satisfactorily on every flight. However, in no case did an aircraft penetrate the cloud without sufficient instrumentation functioning properly to provide the necessary data to satisfy the objectives of this project. Film methods were 100 percent successful in measuring the total dose received by the aircrew on the mission. The photopanel functioned on every penetration, with good pictures resulting from each instrument. On one penetration the pilot set the camera speed on the "slow" position, resulting in one picture every 20 seconds while in the cloud, instead of the desired rate of three pictures per second. The automatic recording instruments were designed to measure radiation rates up to 2,000 r/hr. On penetrations where the dose rates were quite low, continuous data were not obtained on the return flight. In these cases the total mission dose was always less than 2 r. The P meter failed to function on only two of the flights. Thus, satisfactory operation of this instrument was obtained in more than 90 percent of the flights. On 33 the two occasions where the P meter failed to function, the fault was in the method of installation and not in the instrument itself. Some trouble was experienced with the Bioscel and Sigmatron. Both these instruments were battery powered. Even with frequent checks of the battery voltages, satisfactory performance was obtained only about 75 percent of the time. Zero drift was especially troublesome in the Bioscel, leading to poor results at low dose rates. The Sigmatron was designed to measure up to 25 r on the low range. Total dosages smaller than 1 r were not reliably indicated by this instrument. Film measurements were considered to be accurate to + 20 percent. Measurements made with the T1B were considered accurate to + 15 percent. The P meter, Bioscel, and Sigmatron were accurate to + 20 percent when exposed to Co__. As pointed out in Section 3.3, the P meter gave readings which were about a factor of two higher than film badges. Greater sensitivity and response of this instrument to low energy gamma radiation were thought to be the reasons for this discrepancy. How- TABLE 3.4 THE RELATIVE SENSITIVITIES OF RADIATION MEASURING INSTRUMENTS AS A FUNCTION OF X- AND GAMMA RAY ENERGY Values given are normalized to the response of the P meter at 1,250 kev. Energy P meter Bioscel Sigmatron Dupont 502 Film kev 38 0.2 0.9 None <0.1 69 0.7 1.4 1.0 0.4 118 0.9 1.3 1.2 0.8 169 0.8 1.1 1.2 0.9 215 0.8 1.2 1.3 1.0 660 0.8 1.2 1.0 1.0 1,250 1.0 1.1 1.0 1.0 ever, a series of tests carried out at the National Bureau of Standards subsequent to the operation have shown that this was not the case. The P meter and Bioscel were exposed to X- and gamma rays of effective energies from 38 kev to 1,250 keve. Table 3.4 is a compilation of the results of these exposures. The data were normalized to the response of the P meter to gamma rays of 1,250 kev energy (Co__). The values for Dupont 502 photographic film were taken from Reference 9. This emulsion was the component of the NBS film badge which was used in this project. From Table 3.4 it can be seen that the sensitivities of the P meter and the film were nearly the same. Differences in sensitivity, then, could not account for the discrepancy between the measurements taken by the two devices. A temperature test revealed that the scintillation probe on the P meter was improperly compensated for temperature changes. Decreasing temperature caused an increase in probe current output, i.e., a higher reading. This increase in output varied from probe to probe but was found to amount to a factor of 1.5 to 2.0 at -50C. 34 An actual flight with the instrument produced a curve which gradually drifted upward. This flight was made at Kirtland Air Force Base. It simulated an actual cloud penetration, insofar as rate of climb and altitude were concerned. At maximum altitude the outside air temperature was between -45 and -50C. A 10 mc Co__ radiation source was affixed to the front of the probe and a continuous record was made of the dose rate from engine start to landing. The record showed an increase of 1.8 times the initial reading. This temperature dependence was undoubtedly the cause of the discrepancy between the P meter and NBS film dosimeters. During the Operation the Bioscel and Sigmatron read 15 percent and 25 percent higher, respectively, than did the film dosimeters. Reference to Table 3.4 indicates that the enhanced response of these two devices to lower energy radiation likely accounted for the differences. The flight instruments installed in the photopanel functioned properly on each flight. Indicated altitudes were considered to be correct to + 500 feet. Times of penetration were accurate to the nearest minute. The accelerometer installed in the photopanel was not considered to be reliable in giving indications of turbulence in flight. The maximum and minimum needles vibrated to the limit of their movement on takeoff. Photographic records were available of the meter fluctuations within the cloud but could not be correlated with the verbal reports of the pilots concerning conditions of flight within the cloud. 35 Chapter 4 CONCLUSIONS and RECOMMENDATIONS 4.1 CONCLUSIONS Twenty-seven penetrations of six radioactive clouds from multimegaton-yield detonations were made at times ranging from 20 to 78 minutes after detonation and at altitudes ranging from 20,000 to 50,000 feet. Sixteen of these penetrations were earlier than 45 minutes after detonation, and seven were earlier than 30 minutes. All penetrations made earlier than 45 minutes were bore-throughs in which the aircraft completely traversed the cloud from one side to the other at the penetrating altitude. Penetrations were made through clouds from air, land-surface, and water-surface detonations. Maximum dose rates as high as 800 r/hr were encountered in some of the early penetrations, and several flights yielded total radiation doses to the crew of approximately 15 r. Data collected on these flights and in conjunction with past studies of conditions prevailing within clouds from nuclear detonations warrant a number of conclusions regarding the feasibility of flying through such clouds at relatively early times after detonation. The average and maximum external gamma-radiation dose rates in the mushroom of the cloud from nuclear detonations are dependent on the penetration time and the fission-to-total-yield ratio of the detonation and are independent of the yield of the detonation. The average radiation dose rate in the mushroom of the cloud from a 100-percent-fission-yield detonation as a function of time from 3 to 80 minutes after detonation is given by the equation: D = 1.0 x 105t-1.7 (4.1) Where D = average dose rate, r/hr t = time after detonation, minutes This average dose rate, D, may vary by as much as a factor of two for any given penetration. Beyond 1 hour after detonation, when the mushroom begins to be dispersed by the winds, a more-rapid decay of the radiation dose rate in the cloud is noted in which the slope may be as great as -3 or -4. The radiation dose rate in the stem beneath the mushroom of clouds from water-surface or air detonations is less by a factor of five to ten than in the mushroom itself. In clouds from detonations in which the fission yield is less than 100 percent of the total yield, the radiation dose rate is reduced by a factor proportional to the ratio of the fission yield to the total yield. The accumulated radiation dose that one receives in transit through the cloud is a function of two primary factors: (1) the radiation dose rate in the cloud (related to time after detonation, to the ratio of the fission yield to the total yield, and to the portion of the cloud through which transit is made, i.e., stem or mushroom); and (2) the length of time spent within the cloud as determined by the speed of the aircraft and the horizontal 36 dimension of the cloud at the altitude of penetration. The diameters of the stem and mushroom increase somewhat with greater yields. Considering all these factors, two generalizations, substantiated by the penetrations actually flown, may be made: (1) with the tropopause at 55,000 feet, one may fly through the cloud from any yield for a 100-percent-fission weapon in a high-performance aircraft at an altitude of 45,000 feet at 20 minutes after detonation for an expected radiation dose of 25 r, (2) with the same height tropopause, one may fly through the cloud (stem) from any 100-percent-fission weapon at 30,000 feet as early as 10 minutes after detonation for a radiation dose of the same magnitude. Moderate to severe bumpy turbulence was encountered in one of the clouds penetrated at times of 22 to 40 minutes after detonation. Slight to no turbulence was encountered in the other clouds penetrated during a similar time range. Turbulence was not a problem in any of these penetrations, and it was considered not likely to be a serious problem in a penetration as early as 10 minutes after detonation. Icing was encountered in some of the penetrations but caused no difficulty, except in the case of two aircraft penetrating a cloud from a water-surface detonation at the maximum altitude of 50,000 feet. This icing forced the pilots of these aircraft to reduce power on the jet engines in order to avoid overheating. The contamination factor on the B-57B aircraft, as defined herein, averaged 0.6 + 0.2 percent per minute in penetrations of clouds from air, land-surface, and water-surface detonations. This factor enables one to estimate that portion of the total dose received which is accrued during the flight back to base after exit from the radioactive cloud. In the penetrations made for this project, the return flight took about 50 minutes, and the come-home dose averaged about 15 percent of the total. On return flights of 2- to 3 hours duration in this aircraft the come-home dose would be no more than 25 percent of the total dose for early penetrations of the cloud. In summary, the radiation hazard in clouds from nuclear weapons denies to aircraft in wartime only a small volume of sky for a short period of time after detonation. 4.2 RECOMMENDATIONS The information presented above should be used by flying operational commands in planning their defensive and offensive wartime missions. No consideration should be given to the use of filters in aircraft air intake systems for purposes of restricting entrance of fission-product cloud particles into the crew compartment inasmuch as the hazard to flight personnel from this source has been proved to be insignificant. 37 Appendix A TYPICAL MASTER DATA SHEET Pilot's name, ran, and AFSN: Heath, Robert C., Capt, 25813A A/C Number: 527 Home station: Blytheville AFB, Arkansas Technical observer: None Shot: Dakota Time and date of shot: 0606, 25 Jun 56 Time of penetration: H-42 minutes Type of penetration: Bore-through Indicated altitude of penetration: 49,500 feet Pilot's observations: a. Estimated time in cloud: 180 seconds b. Highest dose rate in cloud: 350 r/hr c. Dose rate at could exit: 2 r/hr d. Integrated dose at cloud exit: 11 r e. Degree of turbulence in cloud: None Time of exit of crew from aircraft after landing: 0734 (H + 88 minutes) Instrument data: 1. Dose rate in cockpit at time of crew exit as indicated by: a. Bioscel meter in cockpit: 1 r/hr (+ 88 minutes) b. TLB in pilot's seat: 400 mr/hr (+ 90 minutes) c. TLB in observer's seat: 622 mr/hr (+ 90 minutes) 2. Total integrated radiation dose received on mission as indicated by: a. P meter: 11.5 r b. Bioscel in photopanel: 8.8 r c. Sigmatron in photopanel: 9.5 r d. Sigmatron in cockpit: 10 r e. Quartz-fiber dosimeters: 8 r f. NBS film packs (1) Nose compartment: 8.25 r (2) Pilot's compartment: 6.87 r (3) Observer's compartment: 7.38 r g. Rad-Safe film badge: 7.59 r 3. Time-in cloud as indicated by: a. P meter: 185 seconds b. Bioscel in photopanel: 135 seconds c. Marker light in photopanel: 153 seconds d. Pilot's estimate: 130 seconds 4. Integrated dose received in cloud as indicated by: a. P meter: 10 r b. Bioscel in photopanel: 7.5 r c. Sigmatron in photopanel: 7.5 r d. Sigmatron in cockpit: 8 r 5. Integrated dose on return flight as indicated by: a. P meter: 1.4 r b. Bioscel in photopanel: 1.3 r c. Sigmatron in photopanel: 2.0 r d. TLB readings in cockpit extrapolated to cloud-exit time and then integrated: 0.76 r 6. Maximum dose rate in cloud as indicated by: a. P meter: 400 r/hr b. Bioscel in photopanel: 300 r/hr c. Bioscel in cockpit (reported verbally to director): 350 r/hr 7. Average dose rate in cloud as indicated by: 38 a. P meter: 200 r/hr b. Bioscel in photopanel: 146 r/hr c. Sigmatron in photopanel: 146 r/hr d. Sigmatron in cockpit: 200 r/hr e. NBS film packs: 114 r/hr 8. Dose rate at cloud exit as indicated by: a. P meter: 2.9 r/hr b. Bioscel in photopanel: Too low to indicate accurately c. Bioscel in cockpit (reported verbally to director): 2 r/hr d. TLB readings extrapolated to cloud-exit time: 1.3 r/hr 9. Decay rate of contamination on aircraft as indicated by: a. P meter: -1.8 b. TLB readings: -1.5 10. Contamination factor computed from: a. P meter data: 0.5 pct per minute b. NBS film pack data and TLB data: 0.5 pct per minute 39 FOR REFERENCE SEE (3pm08.gif) 40 Appendix C EVALUATION of INTERNAL RADIATION HAZARD This appendix contains the results of an investigation of the internal radiation hazard to which the personnel of Project 2.66 were subjected during the course of Operation Redwing. It is felt that these results are of sufficient importance to be published as a part of the final report for the project. Since this investigation was not a part of Project 2.66 as it was proposed, and since it cannot easily be fitted into the Project 2.66 report, it is reported separately in this appendix. C.1 OBJECTIVE Whenever human beings are exposed to fission-product contamination the question arises as to the relative hazards of external radiation exposure and internal radiation exposure from inhaled and ingested material. An evaluation of these two hazards is of great significance and importance to the U.S. Air Force inasmuch as it will affect the design of aircraft pressurization systems and aircrew protective equipment. Although a considerable amount of experimentation had been done with small animals which were flown through nuclear clouds, the early cloud-penetration project of Operation Redwing was the first instance in which humans were studied in a similar situation. C.2 BACKGROUND AND THEORY Several theoretical studies have given some attention to the possible hazard resulting from the inhalation of fission products during flight through nuclear clouds. Two of these (References 5 and 6) have concluded that the hazard is negligible. The first experimental data on this point were gathered during Operation Greenhouse. These data are reported in Reference 10. In these experiments mice were flown through the stems of atomic clouds in well-ventilated cages on drone aircraft. The mice received external radiation doses ranging from a negligible quantity up to 200 r, as measured by film-pack and thymic-weight-loss methods. The evaluation of the results was complicated by a large amount of ingested activity as a result of the mice licking their contaminated fur. In spite of the uncertainty in the magnitude of this uptake by ingestion, the total amount of fission products found inside the mice was so small as to indicate that the hazard from internal exposure was negligible with respect to the external gamma radiation dose. In view of the uncertainties introduced by the indeterminate amount of ingested activity in the above experiment as well as the difficulty in the extrapolation of results from mouse to man, studies were made during Operation Upshot-Knothole using mice and monkeys. The results of these studies are given in Reference 2. The animals were placed in drone aircraft and flown through the mushroom of the clouds from two detonations. The internal radiation hazard resulting from the inhalation of fission products and unfissioned Pu239 and U235 during cloud passage appeared to be entirely insignificant compared to the external gamma dose. The ratio of the internal to external radiation hazard was about one to one hundred and was predicted to be independent of weapon yield. The development of the whole-body radiation counter at Los Alamos Scientific Laboratory (LASL) (Reference 11) provided a powerful new tool for the evaluation of the radiation emanating from human beings. It was therefore decided to make extensive investigation of the contamination encountered by the flight crews of the early cloud- penetration project in Operation Redwing. These crews would be the first human beings exposed to the cloud from megaton detonations at early times after detonation. The operational details of these cloud penetrations can be found in Chapter 2 of the main body of this report. C.3 PROCEDURE The technique used for the evaluation of the internal and external contamination of human beings included both counting in the whole-body counter and the analysis of 24-hour urine samples. Before his departure for the Eniwetok Proving Ground (EPG), each man was sent to Los Alamos for counting in the human counter. These counts established a baseline to which the later post-penetration counts could be compared. A 24-hour urine sample was also collected at this time. These pilots and observers participated in twenty-seven penetrations of the clouds from five nuclear detonations in the megaton range. These penetrations were made at times from 20 to 73 minutes after detonation and at altitudes of from 20,000 to 49,000 feet. The aircraft were B-57B's. No special filters were installed in the cockpit pressurization system. The pilots and technical observers were given free choice of the setting of their oxygen controls. A second urine sample was collected from each man during the 24-hour period immediately following his 41 penetration flight. These samples were flown to Los Alamos for evaluation on the first available sample return flight. Upon his return to the United States each man again went to Los Alamos for a second counting in the whole-body counter. This second trip to Los Alamos occurred about 5 to 10 days after the penetration flight. C.4 RESULTS AND DISCUSSION C.4.1 Human Counter. The whole-body counter is a scintillation counter which is capable of detecting the gamma radiation emitted by the human body. These radiations are separated into two energy groups. The lower energy group is nominally attributed to C_137, while the higher energy group is attributed to K40. The results of these counts are given in Table C.1. Since all the medium-lived fission products which might pose an internal hazard emit a gamma ray of sufficient energy to be recorded on the K40 channel, the C_137 channel may be ignored in an assessment of the internal hazard. The mean value for the K40 channel before departure for the EPG was 490 = 50 dis/sec. The mean value after return from the EPG was 600 = 100 dis/sec. Thus, it can be seen that the increase in hard gamma emanation from the entire group averaged 100 dis/sec. A value of 200 dis/sec amounts to only 0.006 uc of radioactive material. As will be seen later, this is a wholly insignificant amount. Of perhaps more interest and significance was the comparison of individual values before and after penetration flights. Reference to Column 4 of Table C.1 shows that the K40 excess was near the total group mean for all men except those who penetrated the Shot TABLE C.1 RESULTS OF MEASUREMENTS IN HUMAN COUNTER This table records the data obtained on the high energy (K40) channel. Column 1 Column 2 Column 3 Column 4 Name Before After Difference dis/sec dis/sec dis/sec 480 505 25 465 455 -10 475 440 -35 665 775 110 545 585 40 640 590 -50 490 600 110 495 595 100 480 1,050 570 490 890 400 550 3,050 2,500 490 640 150 435 830 395 450 1,450 1,000 430 2,530 2,100 510 1,710 1,200 470 555 85 430 590 160 420 474 55 375 690 315 490 + 50 600 + 100 42 FOR REFERENCE SEE (3pm09.gif) 43 maximum amount observed was less than 0.07 uc. None of the gamma-emitting fission products except I131 have maximum permissible body burdens of less than 5 uc, while most are 100 uc or more. The maximum permissible body burden for I131 is 0.3 uc. The greatest observed activity was less than one fourth of this. All the counts were made within the period of one half life for I131. Thus, if all the activity were due to I131, the body burden could not possibly be more than one half the maximum permissible amount. The possibility of internal hazard from gamma emitting fission products is therefore conclusively eliminated in the case of flights through clouds from nuclear detonation. C.4.2 Activity in Urine. Gamma Activity. The 24-hour urine samples which were collected at the time of the visit to the human counter and after cloud penetration were also counted in the human counter. The results of these are shown in Table C.2. In no case was there any significant amount of activity. Therefore, the degree of internal contamination will be judged from the beta activity. Beta Activity. The 24-hour urine samples which were collected immediately after the penetration flights were measured for gross beta activity. In order to establish some sort of a baseline for normal individuals not exposed to radiation and for individuals at the EPG who did not participate in cloud penetration flights, samples were also collected from persons in these categories. Allquots of these urine samples were subjected to gross beta analysis. The data collected are given in Table C.3. TABLE C.2 GAMMA ACTIVITY IN URINE AS MEASURED IN HUMAN COUNTER (K48 CHANNEL) Column 1 Column 2 Column 3 Column 4 Name Before After Difference (dis/sec)/sample* (dis/sec)/sample*(dis/sec)/sample* 8 4 -4 0 0 0 3 4 1 0 12 12 0 3 3 0 3 3 0 0 0 0 0 0 7 3 -4 2 6 4 8 28 20 7 0 -7 0 12 12 0 4 4 -- 33 -- 00 0 -- 3 0 -3 0 0 0 -- 0 -- 0 3 3 * Samples collected for 24-hour period. 44 FOR REFERENCE SEE (3PM10.gif) 45 Column 1 of Table C.3 gives the name of each individual, his participation, and accumulated external gamma dose. Columns 2, 3, 4, and 5 are self-explanatory and give the data associated with the counting procedure. Almost all beta activity in normal urine is from the excretion of K46. The authors of Reference 12 have determined the daily urine excretion of potassium to be about 3 grams. This is equivalent to 5,400 beta dis/min. This compares favorably with the experimental values for the Los Alamos employees who were not exposed to radiation (6,000 + 1,300). Column 6 of Table C.3 shows the total number of dis/min observed for all urine samples. It will be noted that of the eight points which lie above the normal range, six were from Shot Apache, one was a non-penetrating EPG control, and one was an unexposed Los Alamos employee. The seventh Shot Apache participant was well below the normal range. Nearly all of the other individuals were also well below this normal range. Since so many of the values for total beta activity lie below the normal range, it was thought that perhaps loss of potassium through perspiration might account for these low values. Reference 13 gives the chemical composition of sweat to be 21 to 126 mg of potassium per 100 ml of sweat (cf. 29 to 294 mg of sodium per 100 ml). The maximum rate of sweat production is given as 17.7 to 38.2 ml/min. Assuming a potassium concentration of 50 mg/100 ml and a sweat production of 10 ml/min (not unreasonable at the EPG), a man could excrete as much as 1 gram of potassium in about 3 1/2 hours. No data are available on the actual amount of perspiration produced by the individuals under consideration. However, it seems reasonable to expect an inverse relationship to exist between urine volume and sweat production. Therefore, the total beta activity of the urine (Column 6) was divided by the total urine volume (Column 2). This quotient is shown in Column 7. The mean value for the unexposed Los Alamos employees was 5.2 + 0.8 (dis/min)/ml. Examination of the data revealed that five of the seven individuals who were above this normal range were Shot Apache participants, one was a Shot Zuni participant, and one was an unexposed Los Alamos control. All others, including two Shot Apache participants were within or below the normal range. There is no correlation between urine activity and external gamma dose when either method of expressing urine activity is used. The two plots of urine activity as a function of external gamma dose are given in Figures C.2 and C.3. Total urine beta activity is expressed as a function of hard gamma excess counts from the human counter in Figure C.4. There is a suggestion of a correlation between the two, but it certainly is not a good one. The radioactive decay of several of the urine samples was followed. The apparent radiological half times of the activity in these urine samples were about 4.5 days and 60 days. Fission products having half lives near 4.5 days are ____, Zr36, and Y__. Two having half lives of about 60 days are Te132 and Mo__. It is emphasized that these isotopes were not specifically identified. All the urine residues were sent to the Lamont Geophysical Laboratory of Columbia University to be analyzed for Sr__. In no case was any significant amount found. The samples were analyzed for plutonium at LASL. The results are shown in Table C.4. According to Reference 14 the maximum permissible concentration of plutonium in urine is 3 x 10-_ uc/ml or 7 (dis/min)/liter. The highest value observed here was 0.37 (dis/min)/liter, while most were much lower. In fact, these levels are such as are frequently characteristic of people who have had no exposure to plutonium. The significance of beta activity in urine can be summarized as follows: Beta activity in urine indicates activity within the body and is probably a true measure of the amount of internal fission-product contamination provided that the sample is not contaminated from an outside source during its collection. This contamination is a real possibility when the individual or his environment has been subject to fallout. Except for those individuals who participated in Shot Apache, all the beta activity was attributable to the excretion of natural K__. All others showed no internal contamination down to the limit of detection. This limit was about 1 x 10-3 uc or 2,250 dis/min. The normal daily K__ excretion was about 2 x 10-3uc or 4,450 dis/min. It is possible that the urine samples from the Shot Apache participants owed their activity to external contamination, inasmuch as two of the men (Kaericher and Pinson) were known to have had considerable surface contamination on their bodies. In any event, the levels observed were too low to constitute an internal radiation hazard. C.5 CONCLUSIONS A number of conclusions can be drawn from the data which are presented here. 1. No internal radiation hazard arises from flights through thermonuclear clouds, regardless of the oxygen control setting. Urine samples showed no significant amounts of gamma-emitting fission products, beta-emitting fission products, or unfissioned plutonium. 2. Flight through thermonuclear clouds may lead to some external fission-product contamination, but the amount is not significant from the standpoint of radiation hazard. 3. Individuals who participate in nuclear test operations, but who do not fly through thermonuclear clouds, 46 FOR REFERENCE SEE (3pm11.gif) 47 FOR REFERENCE SEE (3pm12.gif) 48 FOR REFERENCE SEE (3pm13.gif) 49 FOR REFERENCE SEE (3pm14.gif) 50 do not exhibit internal activity which is significantly different from the ordinary population. C.6 RECOMMENDATIONS It is recommended that no action be taken to develop filters for aircraft pressurization systems nor to develop devices to protect flight crews from the inhalation of fission products. 51 Pages 52 through 56 were deleted Pages 52 through 56 were deleted