DISCLAIMER The following is a staff memorandum or other working document prepared for the members of the Advisory Committee on Human Radiation Experiments. It should not be construed as representing the final conclusions of fact or interpretation of the issues. All staff memoranda are subject to revision based on further information and analysis. For conclusions and recommendations of the Advisory Committee, readers are advised to consult the Final Report to be published in 1995. TAB F - PART III þþþDRAFTþ FOR DISCUSSION PURPOSES ONLYþþþ MEMORANDUM TO: Members of the Advisory Committee on Human Radiation Experiments FROM: Advisory Committee Staff DATE: September 7, 1994 RE: Historical Background on U.S. Nuclear Testing U.S. nuclear weapons testing began on July 16, 1945, with the explosion of the "Trinity" device near Alamogordo, New Mexico. Recognizing that future nuclear tests would have to be conducted further from populated areas, the military carried out the next two series of tests--Operation "Crossroads" in 1946, and Operation "Sandstone" in 1948--at the Pacific Proving Grounds. Concern with the difficult logistics of conducting tests in mid- ocean, as well as worry about the physical security of a proving ground located outside the continental United States, prompted establishment of the Nevada Test Site [NTS] on December 18, 1950, by order of President Truman. Between November 1958 and mid- September 1961, U.S. nuclear testing was suspended under the terms of an informal test moratorium arranged with the Soviet Union. Subsequent to the signing of the Partial Test-ban Treaty in 1963, all U.S. nuclear tests would be conducted underground. Between July 1945 and the voluntary suspension of testing in September 1992, the United States carried out a total of 1,051 nuclear tests worldwide; 925 of these have been at the Nevada Test Site. (This total includes 204 previously-unannounced tests, disclosed by Department of Energy Secretary O'Leary at her December 7, 1993 press conference.) U.S. nuclear tests are described in DOE documents as being for four distinct, if related, purposes: "weapons effect," "weapons related," "safety experiment," and "Plowshare," the last being the AEC's program to develop so-called peaceful nuclear explosives in the late 1950s and early 1960s. In addition to the Nevada Test Site and the Pacific Proving Grounds, several nuclear tests for specialized purposes were also carried out over the South Atlantic in 1958, and underground in Colorado, New Mexico, Mississippi, and Alaska during the 1960s and 1970s. A majority of U.S. nuclear tests appear to have been so- called proof tests to determine whether and how well a prototype weapon would work. Second most numerous were tests meant to determine the effect of a bomb on military equipment or personnel; such tests included biomedical experiments on animals, tests of the psychological impact on troops nearby the explosion, and possibly other human subject experiments. Starting in the late 1950s, a large number of tests were safety related, reflecting an increased concern with the accidental detonation of a stockpiled nuclear weapon, and the enhanced prospect of a ban on nuclear testing. 1 By its very nature, nuclear weapons testing is an inexact science. Especially in the early days of the nuclear arms competition with the Soviet Union, when entirely new types of experimental weapons were being rapidly developed and tested, it was not uncommon for a particular yield to exceed estimates by 50% or more. Such was the case in the November 1952 "Mike" proof-of-concept test of the first U.S. hydrogen bomb, and in the March 1954 "Bravo" test of a prototype U.S ICBM warhead. Even as late as the 1970s, the unpredictability of yields led to the unintentional "venting" of radiation from underground nuclear weapons tests. Recognizing from the outset that continental testing might be more risky to nearby populations than tests carried out in the Pacific, the AEC determined that only relatively low-yield weapons would be exploded at the Nevada Test Site. Accordingly, an AEC study of potential test sites in the United States concluded, on December 13, 1950, that "[s]hots up to 25,000 tons TNT equivalent can certainly, and shots up to 50,000 tons equivalent can probably, be detonated within acceptable safety limits in the continental U.S." [Attached as Document 1.] As a general rule, therefore, only so-called tactical nuclear weapons and the atomic triggers, or "primaries," of multistage strategic thermonuclear weapons were tested in Nevada. The Pacific Proving Grounds remained the site for megaton and multimegaton hydrogen bomb tests. Because of greater-than-expected yields, however, the "50- kiloton rule" was not always followed in Nevada. Moreover, the exigencies of the Cold War sometimes led to the yield being deliberately exceeded. In June 1953, for example, "Climax," a last-minute addition to Operation "Upshot-Knothole," resulted in the air-dropping of a 61-kiloton bomb at the Nevada Test Site.1 {1 According to the former technical director of the Armed Forces Special Weapons Project, "Climax" was predicted to have a yield of 70 kilotons, and was air-dropped rather than being exploded on a tower to reduce the danger of fallout. The weather forecast on the day of the shot "indicated the remote possibility of radioactive fission debris rain-out on Salt Lake City, but the decision was made to go ahead." Frank H. Shelton, Reflections of a Nuclear Weaponeer [Colorado Springs, 1988], p. 6-15. Minutes of an AEC meeting two weeks before the test indicate that AEC Chairman Gordon Dean raised the question of whether a public announcement should be made "concerning the unusually high yield of the device to be tested." The test director at Nevada counseled that such an announcement was unnecessary, since "the greater power of this device would probably not be noticed by persons in nearby communities." [Attached as Document 2.]} The largest atmospheric shot at Nevada, codenamed "Hood," was exploded from a balloon and yielded 74 kilotons in July 1957. Concern with the possible health effects upon nearby populations of radiation from continental testing evidently prompted a debate behind closed doors within the U.S. government.2 {2 According to Stewart Udall's recent book, Division of Biology and Medicine director Dr. Shields Warren "was deliberately excluded" from the August 1, 1950 AEC conference that considered safety hazards from the proposed continental test site. Instead, General James Cooney, head of the Radiological branch of the AEC's Division of Military Application, and a forceful advocate of continental testing, told those present "he felt that Shields Warren and others in the radiobiology field would accept" the figure of 25 roentgens whole-body radiation as "an emergency acceptable dose." Stewart L. Udall, The Myths of August: A Personal Exploration of Our Tragic Cold War Affair with the Atom [Pantheon, 1994], p. 221; Frederick Reines, "Discussion of Radiological Hazards Associated with a Continental Test Site for Atomic Bombs," LAMS-1173, September 1, 1950.} A similar debate, involving several of the same participants, later revolved around the question of deploying troops near atomic explosions at NTS. 2 For example, in planning Operation "Tumbler-Snapper," a series of low-yield atmospheric tests to be held in Nevada during spring 1952, the AEC's Division of Military Applications endorsed a Defense Department recommendation that troop observers be positioned as close as 7000 yards from ground zero [attached as Document 3]; DBM's Shields Warren dissented [attached as Document 4]. This dispute was evidently settled by an April 2, 1952 letter from AEC Chairman Dean [attached as Document 5], which advised that "the Commission would enter no objection to stationing troops at not less than 7000 yards from ground zero," provided that proper precautions were taken. Opinion within the AEC itself continued to be split on the issue of the hazards from continental testing. In spring 1953, the DMA's General Cooney expressed concern "that the precautions taken by AEC were extreme and caused undue public concern." Two months later, however, AEC Chairman Lewis Strauss passed along Shields Warren's "concern that the Commission might have underestimated the seriousness of the fall-out problem." In February 1955, Strauss himself revealed at a closed AEC meeting that he, too, had begun having reservations about use of the Nevada site, starting "in the spring of 1953," but had not previously shared these doubts with other members of the Commission or Congress. Despite this on-going dispute within the AEC, nuclear testing, and troop participation in nuclear tests, continued at Nevada. In March 1955, for example, some 533 soldiers observed shot "Turk," a 43-kiloton explosion, from a trench located 5000 yards from ground zero as part of a military exercise, Desert Rock VI, during Operation "Teapot." Ultimately, it appears that the pressures of the Cold War determined that continental testing would continue. In a March 1954 comment on the report of an AEC commission studying the problems at NTS, the then-chair of the Commission's Advisory Committee on Biology and Medicine, E.O. Stakman, concluded that it was "essential to continue the Nevada Proving Grounds in order to achieve maximum speed in the development of weapons. Speed is essential to national survival." [Attached as Document 6.] 3 c:\wpwin60\wpdocs\6briefin\nts (tcs)