A Critical Comparison of Measured and Calculated Fission Ratios for ZPR-III Assemblies

Technical Report · Sat Sep 01 04:00:00 EDT 1962

DOI:https://doi.org/10.2172/4777176· OSTI ID:4777176

Davey, W. G. ^[1]

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1. Argonne National Lab., Idaho Falls, ID (United States); UK Atomic Energy Authority (UKAEA) (United Kingdom)

A critical comparison of measured and calculated central fission ratios for 18 ZPR-III fast reactor assemblies was made with the object of examining the accuracy of computation of spectra and of the fission cross sections used. This comparison uses fission ratios measured with Kirn absolute fission chambers and computed with ANL cross section Set 635. The Kirn chambers and experimental technique are described. It is shown that ratios measured with threshold detectors must be corrected for the effects of inelastic scattering in the chamber walls. Possible sources of error in the experimental technique are discussed, and experimental evidence for the validity of the method is presented. The derivation of ANL Set 635 is described. It is shown that Set 635 is a modification of the Yiftah, Okrent, and Moldauer ANL Set 135 and that the central spectra and fission ratios calculated with the two sets are generally similar. The U²³⁴and U²³⁶ fission cross sections are not given in Sets 135 and 835; these were taken from ANL Set 179. The measured and calculated fission ratios obtained with U²³³, U²³⁴, U²³⁵, U²³⁶, Pu²³⁹, and Pu²⁴⁰ were compared, both to search for trends which might occur with progressive changes in spectra, and also to determine the accuracy of prediction of ratios. It was found that the calculated relative fission rates of Pu²³⁹ and U²³³ are within about ± 1$$\frac{1}{2}$$% of the measured values, and the calculated rates for Pu²⁴⁰, U²³⁶, and U²³⁸ relative to either Pu²³⁹ or U²³³ are within ± 3$$\frac{1}{2}$$% to ± 5%of the measured values. However, calculated fission rates for U²³⁵ and U²³⁴ are about 6% low and 8% high, respectively, relative to those of the other five isotopes.

• Research Organization: Argonne National Laboratory, Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Atomic Energy Commission (AEC)
• DOE Contract Number: W-31109-ENG-38
• NSA Number: NSA-17-000702
• OSTI ID: 4777176
• Report Number(s): ANL-6617
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CRITICAL ASSEMBLIES
CRITICALITY
CROSS SECTIONS
Cross Sections
ERRORS
FAST NEUTRONS
FISSION
FISSION CHAMBERS
FISSION RATIO
Fission Chamber
INELASTIC SCATTERING
Kirn
MATHEMATICS
MEASURED VALUES
NEUTRON DETECTION
Nuclear Criticality Safety Program (NCSP)
PLUTONIUM 239
PLUTONIUM 240
RADIATION DETECTORS
REACTORS
RESONANCE NEUTRONS
SCATTERING
SPECTRA
Spectra
THERMAL NEUTRONS
THRESHOLD DETECTORS
URANIUM 233
URANIUM 234
URANIUM 235
URANIUM 236
URANIUM 238
ZPR-3