Volume #23 - 134.|
DEFENCE AND SECURITY ISSUES
U.S. THERMONUCLEAR TESTS
Memorandum from Deputy Under-Secretary of State for External
to Secretary of State for External Affairs
August 9th, 1956|
U.S. THERMO NUCLEAR TESTS|
I believe you will be interested in the attached report which has been prepared by Mr. Barton who attended the recent U.S. thermo nuclear tests with General McNaughton.93
NUCLEAR WEAPONS TESTS AT U.S. PACIFIC PROVING GROUNDS - REPORT
For the first time since 1946, the United States Government this year invited a group of foreign nationals to witness nuclear tests at its Pacific Proving Ground. The ten Canadians and five British officials who attended the tests thus became the first persons, other than Americans or Russians, to see a thermo nuclear explosion.
2. The observer group totalled twenty, - five Canadian and five United States representatives of the Permanent Joint Board on Defence, five officers representing the Canadian armed forces, and five officers representing the United Kingdom services (including one from the Civil Defence branch of the Home Office). We travelled by air to Eniwetok, arriving on July 14 and departing for home on July 21.
3. The Pacific Proving Ground is an ocean area of approximately 400 miles by 300 miles, embracing Eniwetok and Bikini atolls. These atolls are situated at about 11º North Latitude, about 2800 miles west and slightly south of Hawaii, Eniwetok being about 200 miles west of Bikini. The physiography and climate of these atolls have an important influence on the conduct of nuclear tests and merit a few words of comment. Each consists of a coral reef surrounding a lagoon of roughly circular shape about twenty miles in diameter. At frequent intervals the reef rises above water-level, forming a chain of small islets surrounding the lagoon. Even the largest of these islets is no more than two miles long and less than a mile wide, and some are little more than sand bars. All but the smallest have a heavy tropic vegetation, except where it has been cleared off by the Task Force conducting the tests.
4. The climate is warm and very humid but is made quite pleasant by the trade winds, which blow almost continuously. It is the presence of these trade winds, blowing from East to West, coupled with the absence of the movement of air masses or fronts which are characteristic in more temperate latitudes, which makes this area so suitable for nuclear tests.
Organization and Conduct of the Tests
5. All nuclear weapons tests are conducted by a permanent organization, Joint Task Force 7, with its headquarters in Washington. At present the Commander of the Task Force is a rear admiral, with officers of the same rank from the army, navy and air force as his deputies. In addition, there is a scientific deputy representing the AEC. All of these officers were at the Pacific Proving Ground during the four months (April-July) of the test series just concluded.
6. The task force is divided into five task groups - army, navy, air force, scientific, and construction (a civilian contractor). The total number of personnel fluctuates, but at the time of recent tests totalled more than 13,000, with all the logistic support, including aircraft, ships, and vehicles that one would expect the Americans to provide for an operation of this kind. The cost of the 1956 series, excluding the cost of the weapons, was estimated to be $150 million.
7. The test series just completed consisted of a total of 17 shots, of which 5 or 6 were in the megaton range. The shots were fired in a variety of ways; by air drop, from towers, on the ground, and from barges anchored in shallow water on the reef of the atoll. Megaton bombs were fired at Bikini and kiloton weapons at Eniwetok in order to limit the danger to the extensive base facilities at the latter atoll.
8. The primary factor in determining whether or not a shot can be fired is the direction of the wind at various altitudes. The difficulties experienced at the time of the Fortunate Dragon incident clearly taught the experts a lesson, and as a consequence the weather prediction facilities established for the tests are very elaborate and the criteria which must be met before a shot can be fired have been set within very narrow limits. Weather stations have been established on all the islands within a distance of 500 miles from Eniwetok, destroyers proceed several hundred miles on set courses and take wind measurements by means of rockets which discharge chaff which in turn is tracked by radar, and a squadron of 12 B50 weather aircraft take regular observations. I am inclined to think that it is these precautionary measures rather than the development of a weapon with limited fall-out, to which Admiral Strauss referred when he said recently that the tests indicated that the fall-out problem could be localized.
9. The measurement of the effects of the shots is carried out mainly by aircraft, although extensive use is also made of instruments set up on islands in the test atoll and on ships. A typical test might involve the deployment of a dozen operational aircraft stationed at pre-determined positions and altitudes in the vicinity of the explosion. Some aircraft will be taking pictures, others will be designated as penetration aircraft to fly through the cloud taking samples, and still others will be assigned an effects role and situated so as to take advantage of the blast, thermal, or radioactive effect, as the case may be. In the case of surface-fired weapons, an operational aircraft, e.g. the B-52, is always flown on a course so that it will be in the same position relative to the explosion as it would if it had dropped the bomb. We were given a very complete briefing on this phase of the operation and the RAF and RCAF took copious notes. The U.K. representatives will no doubt have a tale to tell the planners of their 1957 Christmas Island operation.
Test Shots Witnessed by Canadian Observers
10. Our group was fortunate in being able to see two shots, the final ones of the series. The shots were planned for Wednesday and Thursday, July 18 and 19, but because the winds were not quite satisfactory at all altitudes they were postponed day by day until the following Saturday and Sunday. Both shots were fired just before dawn, so we saw the fireballs in darkness but were able to follow the clouds in daylight.
11. Saturday's shot was the largest in the 1956 series. Officially we were told it was in the 5-10 megaton range. We were given to understand privately that it was about 7-8 megatons - apparently the exact size of these experimental weapons cannot be predicted in advance and can only be determined on the basis of measurements made at the time of firing. It was fired from a barge anchored on the northern side of Bikini reef and we observed it from an aircraft flying at 17,000 feet sixty miles west of ground zero. Generally speaking, the spectacle conformed to the descriptions everyone has read, but we were particularly impressed by the intensity of the initial flash, which lit up the whole sky just as though the sun were out and which lasted for a surprisingly long time - perhaps 30 seconds, and by the brilliant lavender luminescence of the cloud, which lasted two or three minutes after the initial flash had disappeared and which was caused by ionizing radiation. The rapid formation of the cloud was dramatic - the stem shot up into the air like the Geneva fountain, developed the typical mushroom head, and then seemed to penetrate it and keep on going. Knowing our distance and altitude we were able to estimate, probably with fair accuracy, the size of the cloud. The stem seemed to be about 2 miles in diameter, and the base of the mushroom about 30,000 feet high (two minutes after the explosion). The mushroom head spread out and gained altitude at tremendous speed. After three or four minutes the stem had widened to perhaps 3 miles and the diameter of the cloud to 30 miles. Once the initial luminescence faded it took on a sinister slate gray colour which contrasted sharply with the other clouds in the sky. An hour later the cloud was still very sharply defined although by this time we were looking at it from Eniwetok, nearly 200 miles from ground zero. Our experts guessed that at this time the top of the cloud was at least 100,000 feet high and the diameter in the neighbourhood of 80-100 miles.
12. Because of other cloud formations it became increasingly difficult to see the man-made one, but we thought we could detect it as late as three hours after the time of firing.
13. We felt and heard nothing in the aircraft, but the fireball was clearly visible to personnel on the ground at Eniwetok (190 miles from the scene of the explosion) and the flash was seen at Kwajalein (about 400 miles from Bikini). A series of 12-14 shocks were felt at Eniwetok and a loud rumbling thunder was heard.
14. Sunday morning's test took place at Eniwetok atoll. The shot was fired from a barge anchored in the famous crater where the islet named Elugelab used to be until it was vaporized in the first thermo nuclear explosion three years ago. We saw the explosion from the island of Eniwetok, about 16 miles across the lagoon from ground zero. Officially we were informed that it was in the 100-500 kiloton range, and privately about 200 kilotons. Generally speaking, the sequence of events and effects was the same as for the previous day's test, except that the fireball was obviously smaller and of shorter duration, and the cloud was much more modest in size. However, since we were in the open, we were able to observe some effects which had not been possible the previous day. The most interesting was the blast of radiant heat which we felt on our faces for the few seconds of the duration of the fireball. It was just as though one had come in from out-of-doors and put his face within a foot or two of a Quebec heater with a hot fire. The stem of the cloud on this occasion was somewhat irregular and after perhaps three or four minutes seemed to be about 10,000 feet high and one-half mile in diameter. The mushroom was about 8 miles in diameter. It was obscured from our view shortly thereafter by intervening clouds. We felt the shock wave and heard a rumble of sound, but since there was a good breeze blowing in the direction of the explosion neither the shock wave nor the sound was very impressive. After the previous day's experience one might be inclined to deprecate this shot, but recollection of the fact that it was ten times as large as the Hiroshima explosion served as a useful antidote to any such ideas.
Incidental Impressions and Conclusions
15. It will be recalled that prior to the acceptance of the United States invitation to the test, there were some doubts about the usefulness of the attendance of members of the Canadian Section of the PJBD but that it was finally decided that they should go for the sake of good relations with their American colleagues. We learned in the course of the journey that the United Kingdom Government had had similar doubts and had come to the same conclusion.
16. In the light of our experience, it was the opinion of both the Canadian and U.K. observers that both Governments made the correct decision in sending senior representatives and that if this had not been done it would have been interpreted by the United States authorities as indicative of a lack of desire on our part for closer relations in this field. The U.S. officials at the Proving Ground repeatedly expressed the view that the limitation on cooperation imposed by their Atomic Energy Act had been undesirable; that our presence at the tests marked the first step in implementing the Canadian and British bilateral military atomic agreements; and that in future there should be a much more fruitful exchange of information within the terms of the bilateral agreements. Nevertheless, security remains very much of a preoccupation with U.S. atomic energy officials. We all had to read a lengthy security document and sign an undertaking not to discuss what we had seen except with persons properly cleared and with a need-to-know. The need-to-know criterion is applied very strictly, even to senior U.S. officers on the test force, and the information at their disposal is very narrowly compartmentalized. It is because of the undertaking we gave that this report has been so highly classified.
17. In concluding this report a comment on the question of
future United States thermo nuclear tests may be of interest to
the Department of External Affairs. There is every evidence, both
from the nature of the programme and the effort being made to
build up semi-permanent facilities, that so far as the AEC and
the Defence Department are concerned, testing will continue
throughout the foreseeable future. This was born out by a
conversation we had with the chief scientist of the project. He
said, however, that in his opinion the current test series would
bring to an end the period during which genuinely new scientific
data have been obtained. The consequence of this would be an
increasing difficulty in recruiting competent scientists for
future tests. He added that unfortunately the only true scientist
on the Commission, Dr. von Neumann, was dying of cancer, and the
significance of this development would be lost on his colleagues.