AN EXPERIMENTAL STUDY OF THE INTEGRAL PROPERTIES OF $sup 235$U AND $sup 239$Pu IN AN INTERMEDIATE ENERGY SPECTRUM, AND COMPARISON WITH THEORETICAL PREDICTION.
Present-day methods of calculation for thermal and fast reactors involve the use of multigroup cross-section sets derived from basic nuclear data files. Since the accuracy of the calculations depends ultimately on the accuracy of these data, it is important to test them against results of 'integral experiments' in critical or sub-critical assemblies. The present report describes integral experiments designed to provide a sensitive test of the U235 and Pu239 cross-sections spectrum-averaged over the 'intermediate' energy range from about 10 eV to 10 keV. This is an area where the fissile nuclide cross-section data, particularly that for radiative capture, are still inadequately defined, as evidenced by the considerable discrepancies between various determinations. The difficulties stem from the problems of resolving and analysing the properties of closely spaced resonances and particularly in separating the fission and capture contributions. From the parameters of the resolved resonances, the distributions of the partial widths must be derived in order to provide a sound basis for the calculation of the averaged properties in the unresolved region, which constitute a significant part of the region of interest. The correct assignment of the fission and capture widths and their distributions is also necessary for the calculation of the spectrum-average capture to fission ratio (a), which has an important bearing on conversion and breeding ratios. Unlike the situation for the thermal and fast neutron regions (i.e. those below and above that considered here), where many critical and sub-critical assemblies have been made, very few integral experiments suitable for adequately testing the U235 and Pu239 data in the intermediate energy range have been reported. Hence the decision, in 1965, to undertake the work described here.
- Research Organization:
- Atomic Energy Establishment, Winfrith, England (United Kingdom)
- NSA Number:
- NSA-23-052478
- OSTI ID:
- 4736761
- Report Number(s):
- AEEW-R-586
- Country of Publication:
- United Kingdom
- Language:
- English
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Related Subjects
CROSS SECTIONS
ENERGY
ERRORS
KEV RANGE
NEUTRONS
PLUTONIUM 239
SPECTRA
URANIUM 235
PLUTONIUM ISOTOPES Pu-239/neutron cross sections spectrum-averaged from 0.001 to 10 keV
(E/T)
URANIUM ISOTOPES U-235/neutron cross sections spectrum-averaged from 0.001 to 10 keV
(E/T)