BOOK REVIEWS

Cross Sections Important to Reactor Design (Peaceful Uses of Atomic Energy-Vol. 4). United Nations Publication, New York, 1956 vii + 357 pp. 54s.

This volume of the Proceedings of the 1955 Geneva Conference contains papers and discussions relevant to the nuclear properties important in the design of reactors, and to the techniques by which these properties have been measured.

The papers of sessions 15A and 16A dealing with techniques for neutron cross-section measure- ment are concerned mostly with the application of time-of-flight methods in conjunction with reactors or accelerators. The increasing resolution of choppers and pulsed accelerators enables the parameters of many resonances in a single nuclide to be determined; such data have practical importance for the calculation of resonance integrals and effective cross-sections in reactor spectra, while the statistical distribution of the neutron and fission widths of the resonances is proving of considerable theoretical interest. The measurement of average cross-sections in broad neutron spectra by means of the pile oscillator and mass spectrometer is also described. An outstanding paper reports a measurement of the total cross-section of Xels5, the important radioactive fission product, as a function of neutron energy.

Session 17A includes a number of papers describing results on total and fission cross-sections of uranium and plutonium isotopes. The data obtained in the various countries show in general an encouraging state of agreement, though a few rather serious discrepancies are revealed, for instance in the determination of absolute fission cross-sections for thermal neutrons. Session 18A deals with other parameters of fissile nuclei, such as the neutron yield per fission; a paper on the analysis of cross-section data from velocity selectors is also included.

In addition to containing a large amount of data of great importance to those engaged in reactor calculations (much of it only released at the Geneva Conference), this volume provides an excellent account of modern techniques for the determination of neutron cross-sections.

.I. E. S.

Production Tecbnolo~ of the Materials used for Nuclear Energy (Peaceful Uses of Atomic Energy- Vol. 8). pp. 627 + ix. United Nations (available from H.M.S.O.). Price in U.K. 70/-

THIS volume of the proceedings of the international conference at Geneva in August 1955 contains the papers and records of the sessions dealing with the extraction of uranium and thorium from their ores (27), the production of uranium and thorium metal (7), the analytical problems associated with these raw materials (31), and the technology of heavy water (lo), graphite (6), zirconium (6), and beryllium (8). There are in all 95 papers from 23 different countries, and it is obviously impossible in a short review to do more than indicate the general field and to draw attention to the highlights.

There are few uranium deposits to which the classical methods of physical ore grading can be applied economically, and even then higher recoveries are usually qbtained by leaching with either acid or alkali, depending on the type of the ore. Howeve? in some cases it is economic to remove nonuranium minerals by physical means, e.g. the removal of pyrite for sulphuric-acid manufacture. The aim of the leaching process is to produce as high a uranium recovery as possible with the minimum usage of leaching agent; inevitably the leach liquor contains many impurities and must be specially treated to recover a high grade of uranium concentrate. The discovery of the anion-exchange process

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