The central void reactivity in the Oak Ridge enriched uranium (93.2) metal sphere
Description
The central reactivity void worth was measured in the Oak Ridge unmoderated and unreflected uranium (93.20 wt% 235U) metal sphere by replacement measurements in a small (0.460-cm-diam) central spherical region in an 8.7427-cm-radius sphere. The central void worth was 9.165 ± 0.023 cents using the delayed neutron relative abundances and decay constants of Keepin, Wimett, and Zeigler to obtain the reactivity in cents from the stable reactor period measurements using the Inhour equation. This value is slightly larger than measurements with GODIVA 1 with larger cylindrical samples of uranium (93.70 wt% 235U) in the center: 135.50 ± 0.12 cents/mole for GODIVA 1 and 138.05 ± 0.34 cents/mole for the Oak Ridge sphere measurements, and the difference could be due to sample size effect. The central worth in Δk units was calculated by neutron transport theory methods to be 6.02 ± 0.01 x 10-4 Δk. The measured and calculated values are related by the effective delayed neutron fraction. The value of the effective delayed neutron fraction obtained in this way from the Oak Ridge sphere is 0.00657 ± 0.00002, which is in excellent agreement with that obtained from GODIVA 1 measurements, where the effective delayed neutron fraction was determined as the increment between delayed and prompt criticality and was 0.0066. From these Oak Ridge measurements, using the delayed neutron parameters of ENDF-B/VI to obtain the reactivity from the stable reactor period measurements, the central void worth is 7.984 ± 0.021 cents, and the inferred effective delayed neutron fraction is 0.00754. This central void worth and effective delayed neutron fractions are 14.2% higher than those obtained from use of the Keepin et al. delayed neutron data and produce a value of delayed neutron fraction in disagreement with GODIVA 1 measurements, thus questioning the usefulness of the relative abundances and decay constants of the six-group delayed neutron parameters of ENDF-B/VI for uranium for obtaining the reactivity from the measured reactor period using the Inhour equation
Availability note (English)
Available from INIS in electronic form; ALSO AVAILABLE FROM OSTI AS DE98003639; NTIS; US GOVT. PRINTING OFFICE DEP.
Files
Restricted
The record is publicly accessible, but files are restricted to users with access.
Additional details
Publishing Information
- Imprint Pagination
- 33 p.
- Report number
- ORNL-TM--13349
INIS
- Country of Publication
- United States
- Country of Input or Organization
- United States
- INIS RN
- 30009435
- Subject category
- S22: GENERAL STUDIES OF NUCLEAR REACTORS; S21: SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS;
- Descriptors DEI
- COMPARATIVE EVALUATIONS; DELAYED NEUTRON FRACTION; DOLLARS; GODIVA REACTOR; NUCLEAR DATA COLLECTIONS; REACTIVITY WORTHS; REACTOR KINETICS; REACTOR PERIOD; URANIUM 235; VOID COEFFICIENT; ZERO POWER REACTORS
- Descriptors DEC
- ACTINIDE NUCLEI; ALPHA DECAY RADIOISOTOPES; EVALUATION; EVEN-ODD NUCLEI; EXPERIMENTAL REACTORS; HEAVY NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; KINETICS; MINUTES LIVING RADIOISOTOPES; NUCLEI; RADIOISOTOPES; REACTIVITY COEFFICIENTS; REACTIVITY UNITS; REACTORS; RESEARCH AND TEST REACTORS; SPONTANEOUS FISSION RADIOISOTOPES; URANIUM ISOTOPES; YEARS LIVING RADIOISOTOPES; ZERO POWER REACTORS
Optional Information
- Contract/Grant/Project number
- Contract AC05-96OR22464
- Funding organization
- USDOE Office of Energy Research, Washington, DC (United States)