The purpose of this meeting was to give members of the two Committees and officers of the P.M.'s and External Affairs Departments the opportunity of hearing Professor Sir Leslie Martin, the Defence Scientific Adviser, speak on certain aspects of development of nuclear weapons, with particular reference to the nuclear control provisions of current disarmament proposals put forward in the United Nations Disarmament Sub-Committee.
Sir Leslie Martin gave an introductory comment on the effects of radiation and radioactive fall-out from test explosions of nuclear weapons and then commented on the five questions on which the Department of External Affairs sought information from the Defence Department.
Questions Asked by Department of External Affairs
Sir Leslie then commented on the five questions put to the Defence Department by this Department. For convenient reference the text of the questions is repeated here:
- 'The problem of establishing an effective system to police the control of nuclear tests, including the difficulty of detecting tests of small-scale tactical nuclear weapons'.
Sir Leslie said that tests of megaton bombs could not possibly go undetected. He thought also that there was little chance of tests of fission weapons of any significance to development going undetected. He did not think that there was great need in any event for further tests of small weapons. There was constant observation by stations on all the frontiers of the Communist world. Messrs. Lawrey3 and Rogers4 pointed out that this question had been asked because of the need for technical advice on proposals currently under consideration in the Disarmament Sub-Committee (e.g. the Soviet suggestion for a system of ground control posts and the U.S. suggestion of a cessation for three months.) They mentioned that J. Moch,5 the French representative in the Disarmament Sub-Committee, and also the Prime Minister of the United Kingdom6 in his Defence statement on 1 April had said that we could no longer be sure of detecting all tests that took place. Sir Leslie was asked to comment on Mr. Macmillan's further statement that the proposal put forward by Sir Anthony Eden7 in July 1956 (to get agreement on limitation of tests outside the framework of a general disarmament agreement) had been withdrawn because scientific experts had 'shot holes in it'. He said he could make no comment from a scientific angle and thought that perhaps political considerations were paramount in the Prime Minister's statement. Sir Leslie was inclined to discount the idea that a test might be prepared secretly even by the U.S.S.R. under cover of an international agreement. He pointed out that there were few sites where tests could be held.
- 'The problem of an inspection system over the production of fissionable material to ensure that it is used exclusively for peaceful purposes'. Sir Leslie commented briefly on this point, saying that the question of working out and installing an inspection system in atomic plants presented no serious difficulties. The plants themselves had to be large and could not be concealed. Trained personnel could fairly easily ensure that all fissionable materials produced in them were accounted for. However there was no known method of determining how much material had been produced in a reactor before the inspection system was installed nor of detecting stocks of material which had been assembled in bomb casings and stored away.
- 'The likelihood of the emergence of a “fourth country” possessing an effective nuclear or thermo-nuclear weapon, including among other things the extent to which nuclear capacity for peaceful purposes can be turned to warlike purposes'.
Sir Leslie said that France should be capable of manufacturing nuclear weapons in about twelve months. Japan was at present out of the field; she had good theoretical physicists but lacked the materials and equipment with which to produce fissionable material for bombs. China had excellent physicists, some of the best in the world. There was no prospect at the moment of China producing nuclear weapons, but if she were to obtain from another country an atomic plant similar to Calder Hall,8 she could manufacture enough plutonium for some weapons in about twelve months. The difficulty of finding suitable testing sites was a limiting factor. Potential 'fourth countries' usually did not have access to such sites.
- 'The problem of transferring fissionable materials from military stockpiles to peaceful uses'. Sir Leslie said that this proposal presented no serious difficulties. There was no problem in the measurement of the amount of fissionable material in a nuclear weapon and ensuring that all this material was accounted for in the transfer to peaceful uses. Moreover it was easier to reduce weapon-grade material to [a] state in which it was useful for peaceful but not warlike purpose than to reverse this process.
- 'The likely effect on the United Kingdom nuclear programme of the various proposals currently before the Disarmament Sub-Committee, such as a moratorium on or cessation of tests, the cessation of production for nuclear weapons purposes, or the transfer of fissionable materials from existing weapons purposes to peaceful uses'.
Messrs. Lawrey and Rogers explained that this question was prompted by our concern at the likely effect on the U.K.'s nuclear weapons programme of the suggestion made by Mr. Stassen in the Sub-Committee on 12 April (proposing the installation of a control system on the production of fissionable materials in March 1958, and the cessation of production for military purposes one month after the installation had been completed) and also the nuclear control provisions in the outline disarmament plan which Mr. Stassen had given Mr. Zorin on 31 May.9 Sir Leslie said he could not give an opinion on this question. He did say that U.K. was not yet able to produce megaton bombs though it should be in a position to do so soon. He also said that the U.K. for the present was intending to rely on missiles obtained from the United States.
The External Affairs representatives gained the impression that Sir Leslie Martin either was not closely informed about U.K. plans for ballistic missile development or did not want to be drawn into detailed discussion of it. He did remark that the problem of developing the inter-continental missile itself was greater than the problem of devising a suitable warhead. The missile's inherent inaccuracy had to be balanced by its destructive power and this meant a requirement for large quantities of fissionable materials, the United Kingdom's supply of which was limited. The United Kingdom's need for power was very great but not so desperate as to justify in itself the present rate of reactor development in the U.K., one objective of which was probably to produce more weapon-grade material.
[NAA: A1209, 1957/5688 part 1]