Attachment 10 Los Alamos Report on dosimetry of Kiwi air crews "Gamma and Neutron Dose Measurements of [] Aircrews during Kiwi-A Three Operation," by E. R. Ballinger, in Biological and Medical Research Group (H-4) of the Health Group -- Semiannual Report, July through December 1960, Los Alamos, pp. 335-338. LOS ALAMOS SCIENTIFIC LABORATORY OF THE UNIVERSITY OF CALIFORNIA - LOS ALAMOS NEW MEXICO S-4 REPORT SECTION REPRODUCTION COPY BIOLOGICAL AND MEDICAL RESEARCH GROUP (H-4) OF THE HEALTH DIVISION - SEMIANNUAL REPORT JULY THROUGH DECEMBER 1960 Gamma and Neutron Dose Measurements of Aircrews during Kiwi-A Three Operation (E. R. Ballinger) INTRODUCTION Since the latter part of 1950, it has been common practice to sample the fission products of nuclear detonations and field reactor effluent by means of aircraft. Crew members have routinely worn gamma film dosimetry. Due to the fact that at the time of nuclear detonations the air-craft were considerably beyond the mean free path of neutrons and that the neutron hazard post detonation was inconsequential, no serious attempts were made to monitor aircrews for neutron dose. The sampling of the effluent of Kiwi-A and Kiwi-A Prime during full power runs was similarly monitored primarily for gamma dose. Certain film badge discrepancies resultant of these runs suggested the possibility that thermal neutrons might be contributing in some cases to the gamma film badge reading. If, in fact, such a condition existing, then the probability that fast neutrons might be contributing a significant portion of the body does could not be neglected. Consequently, all aircraft and crew members on Kiwi-A Three operation were equipped with gamma and neutron dosimetry. 335 METHODS AND MATERIALS All aircrew members of the aircraft wore gamma-neutron film packets from LASL and REECO plus gamma packets from Wright- Patterson Air Force Base, Ohio. All aircrew members were special lithium-shielded gamma film badges and swallowed gamma film capsules ~ 3 hours prior to the sampling mission. of crew member had base line Human counter measurements ~ 1 week prior to the mission. All aircraft were equipped with 20-kilo polyethylene jugs containing 10 times normal physiological saline solution (15 g Na/kilo H2O). All aircraft were equipped with a gamma film packet hung in air in the after-compartment, a lithium-shielded gamma film packet at a similar position, as well as a neutron film packet. Following the mission, all films were returned to their original sources for reading. The crew members who received Human Counter base line studies were returned to LASL and counted ~ 20 hours post mission. RESULTS AND DISCUSSION Highest gamma readings in all cases were found on the unshielded gamma film packet hung in air in the after-compartment of the aircraft. Lowest gamma readings in all cases were on the lithium-shielded gamma film packet similarly placed and on the unshielded gamma packet on the copilot. The lithium-shielded 336 crew member badges were damaged to the preclusion of reading by packing procedures. Thus, for the particular configuration of the sampling passes and distance from the reactor, it would appear that the thermal neutron effect amounted to a 20 to 30 per cent exaggeration on an unshielded gamma film packet and that the shielding built in around the copilot reduced his gamma exposure over that of the pilot by ~ 10 per cent and over that of the in- air dose in the after-compartment by ~ 20 to 30 per cent. Neutron dosimetry from film packets in the after-compartment of the aircraft, when uncorrected for RBE, was in reasonable agreement with Human Counter measurements, when corrected for incident neutron energy. Neutron badges worn by crew members gave unreliably low numbers. The neutron exposure, as measured in the after-compartment, amounted to ~ 1/3 to 1/4 of the gamma dose uncorrected for RBE. Actual dose and distance and velocity values are omitted for classification purposes. DISCUSSION Thermal neutron effect on gamma film badges cannot be disregarded on aircraft sampling missions when sampling activities are being carried out before reactor shutdown. 337 A pair of lithium-shielded and unshielded film badges in the after-compartment of the aircraft probably gives the most reproducible gamma value, is the simplest way to determine the presence of thermal neutrons using only gamma film, and probably represents the maximum possible exposure to a crew member. A neutron film packet in the after-compartment of the aircraft similarly gives the most reproducible and reliable value and again probably represents the maximum possible exposure to a crew member. Of the film capsules swallowed ~ 3 hours prior to the mission, were recovered and undamaged by gastric contents. Reading were roughly 2/3 of the externally worn film badge. The polyethylene jugs filled with 10 times normal physiological saline were installed in the aircraft in anticipation of the possibility that the neutron dose to crew member would be below the measurable limits of the LASL Human Counter. This, however, was not the case, and the actual body counts of the crew members themselves were used to indicate their thermal neutron dose. 338 The Use of Graphite-CO2 Ionization Chambers for the Determination of Gamma Flux and the Effective Transmission of the Front Penthouse Face of Test Cell "C" during Kiwi-A Prime and Kiwi-A Three (F. C. V. Worman) INTRODUCTION During the planning of Project Rover, a request was made for the fabrication of a high intensity gamma rate meter to be used for the measurement of gamma flux from the Kiwi reactors. The graphite-CO2 ionization chamber instrument with a 6-decade range was built and is described in Los Alamos Scientific Laboratory Report LA-2361(1). This instrumentation was used on Kiwi-A Prime and Kiwi-A Three for the purpose of measuring gamma flux in the presence of neutrons and to determine the transmission of the front test cell wall for gamma radiation. METHODS Two instruments were used during the high power runs of the Kiwi series. One chamber was placed in the penthouse of Test Cell "C" at a distance of ~ 20 ft from the center of the reactor. This chamber had the same location for Plans 116B of Kiwi-A Prime and 216B of Kiwi-A Three. Readings at this station expressed a dose rate with 4.75 ft of concrete intervened between the station and reactor. 339