Preliminary experiments using acetylacetone in the presence of ethylenediaminetetraacetic acid to separate major quantities of beryllium from fission products are reported. Using 2M beryllium solutions, decontamination factors of the order of 10/sup 3/ were obtained with trace quantities of the more important fission products. This is sufficiently encouraging for the work to be repeated at higher activity levels.

A programme is given to calculate the critical sized and the two-group flux distributions in a cylindrical reactor with identical top and bottom reflectors. The core is not reflected on the sides. In addition to the size and the flux distributions the programme outputs the initial fuel investment together with parameters which will enable evaluation of the fission heat release distribution. The output of a parameter to enable the manual calculation of coolant outlet temperature from a gas cooled reactor is also available. The programme may be used for reflector salvage studies, for heat distribution calculations, or as a check programme for a more ambitious calculations.

An analysis of the behavior of the asymptotic flux on either side of a strongly absorbing grey slab in an otherwise uniform medium, with an arbitrary distribution of sources, leads to a method of accounting for the effect of the slab within the framework of the diffusion approximation. It is necessary to introduce a new parameter, the linear extrapolation distance at the surface of the slab in an anti-symmetrical neutron distribution.

A comparison of methods of capital cost estimation used for nuclear fuel reprocessing plants shows that, because of the special nature and complexity of such plants, cost estimation methods for conventional chemical plants involving the use of cost factors are not applicable and will give low estimates. Cost factors which are available from other countries where reprocessing plants are installed should be used with caution since those factors apply only for the particular design philosophy used and pertain to industrial conditions which are different in this county. Capital cost estimation methods involving direct take-offs from detailed design drawings are necessary to obtain reliable estimates. The methods of estimating operating costs for nuclear reprocessing and conventional chemical plants are similar.

A method is given for constructing the complete neutron spectrum for a well-moderated thermal reactor such a HIFAR, from the total effective flux, the temperature of the Maxwellian, the epithermal spectral index and the total integrated fission flux. A sample calculation is also included.

The major long lived activity induced in irradiated Pechiney and Brush BeO specimens is due to Se-46 arising from scandium present to the extent of about 1 p.p.m. The Brush specimens showed additional activities due to Fe-59 and Co-60 and to Cr-51. The levels of Cr-51 found are considerably higher than would be expected on the basis of stated chromium impurity levels suggesting that the chromium is introduced during handling of the samples on site. Approximate values of the dose rate are included.

A description is given of a method suitable for the automatic solution of certain optimum design problems on a digital computer for cases where the number of constraints imposed on the design is not greater than the number of design variables. The problem is transformed to one requiring the minimization or maximization of an unconstrained function, for which a gradient method is used.

Specimens of beryllium oxide based dispersion fuels containing between three and twenty-six volume per cent, of U02— Th02 solid solution were irradiated to fission densities of 2 to 14 x 1019 fissions/cm3 of total specimen (equivalent burn—ups of 80 to 230 per cent.) at temperatures of 600 - 850ºC. The experiment was primarily designed to investigate fission product damage although some fast neutron damage did occur in the matrix, the specimens showed excellent resistance to fission product damage; dimensional changes were small, fission product escape was generally only that expected by recoil and there was no sign of cracking due to thermal stresses although these reached estimated values of about 30,000 p.s.i. in some specimens, Metallographic examination showed that some weakening of the matrix grain boundaries had occurred and some preliminary x-ray results suggested that the matrix was in a state of strain. It is suggested that these effects could be due either to fast neutron damage in the matrix or swelling of the fuel particles. The experiment did not provide any conclusive evidence for the superiority of coarse fuel particles (100 - 180μ.) over fine fuel particles (< 10μ) although the dimensional changes and the degree of matrix strain …

Inhomogeneities in Brush UOX beryllium oxide observed in the powder and in cold pressed and sintered specimens have been removed by grinding the powder prior to fabrication, all grinding procedures reduced the densities obtained under standard sintering conditions, but some grain refinement was noted on sintering after short grinding periods. These effects are related to the introduction of alumina and silica impurities during ball milling. There is some indication that short grinding periods improve the strength of sintered specimens.

A self—abradory process is described for the small-scale preparation of 150 - 200 micron spheroidal particles of various UO2- ThO2 compositions. The particles can be sintered to high densities before or after dispersion in beryllium oxide. Because of the high compaction pressure used in making particles, they are strong enough to resist abrasion and crushing during mixing with beryllium oxide powder, after sintering, the particles consist of a (U, Th)02 solid solution with a small range of composition, but the overall composition does not vary from one particle to another. The types of porosity observed after sintering are consistent with the occurrence of two competitive mechanisms during spheroidisation, namely particle abrasion and particle build-up.