New Reactors Under Test At Harwell

Press, Volume XCIII, Issue 27912, 8 March 1956, Page 16

New Reactors Under Test At Harwell

LONDON, January 26.

The United Kingdom Atomic Energy Authority announced last night that two new research reactors, or atomic piles, are operating at Harwell—Zeus (zero enery uranium system) and Zetr (zero energy thermal reactor). They are part of Britain’s programme for investigating different types of- reactors. and the announcement of Zetr is, by implication, an encouraging reassurance that the Atomic Energy Authority is taking a long view on a line of development which should eventually be extremely promising. Zetr is a new type of research renuclear calculations on which the design of the fast reactor being built ar Dounreay in the north the Scotland depends, and in many essentials it is a full-scale model of the Dounreay reactor. Continuous Processing Zetr is a new type of research reactor. the inclusion of which in the British experimental programme had not before been made known. Its purpose is to obtain information of value in the design of “homogeneous” reactors, in which the nuclear fuel is circulated in solution and in which chemical processing would probably in the long run be made continuous. Experimental reactors of this type have been operated in the United States, and their absence from the British programme hitherto has led to some criticism. However, the official view, lately confirmed by Sir John 1 Cockroft, Director of the Atomic Enery Research Establishment, is that as a contribution to an expanding power programme they belong to rather a late stage of development. The only previous indication that work on them was in progress in Britain was a statement by Sir John Cockcroft that, on account of having built-in facilities for chemical processing, a reactor of this type would be a highly specialised chemical plant, and that it was being studied with the help of the chemical industry—presumably in its chemical aspects. The new reactor will make it possible to study the operation of homo-

geneous reactors under simplified conditions. In the final reactor there would be present not only fissile material (plutonium, uranium 235, or unranium 233), as mentioned in the Atomic Energy Authority’s announcement. and ordinary heavy water, but also further material (uranium 238 or thorium) from which new fissile material would be formed continuously and also fisison products, such as are formed necessarily in the working of any nuclear reactor. Attractive Possibilities The announcement indicates that the experimental reactor is being operated in the first instance with only the fissile material and the water in which it is dissolved. In this way information which will later be of use in design can *be obtained, and the effects of fission products studied at different levels of concentration. This would tie in with the study of arrangements for continuous processing which, judging from Sir John Cockcroft’s statement, would appear to be already under review. Homogeneous reactors offer attractive possibilities, especially when working on the uranium-233/thorium cycle. In this cycle thorium is the raw material and the uranium-233. which is the fissile material, is made from it in the reactor. Such a reactor should be able to produce as much, or more, fissile material as it consumed.

The starting up of a homogeneous reactor involves a large initial investment of fissile material. At the United Nations conference on the Peaceful Uses of Atomic Energy, held at Geneva last August, it was pointed out by Dr. J. V. Dunworth, head of the reactor physics division at Harwell, that for this reason homogeneous reactors would for some time be unable to contribute usefully to an expanding power programme. He pointed out also that reactors of the Calder Hall type could, in principle, be converted to work wholly or in part on the thorium cycle, and that it would be of advantage to proceed first to this type of working, and only later to embark on the building of homogeneous reactors for other than experimental purposes.