Reactivity impact of delayed neutron spectra on MCNP calculations

Journal Article · Sat Jul 01 04:00:00 EDT 2000 · Transactions of the American Nuclear Society

OSTI ID:20104497

Mosteller, R D; Werner, C J

The new features in MCNP4C, the latest version of the MCNP Monte Carlo code, include the capability to sample from delayed as well as prompt fission emission spectra. Previous versions of MCNP all have sampled exclusively from prompt spectra. Delayed neutrons typically account for <1% of all neutrons emitted from fission, but the emission spectra for delayed neutrons are somewhat softer than those for prompt neutrons. Because of the softer spectrum, delayed neutrons are less likely to leak from the system, and they also are less likely to cause fission in isotopes that have an effective threshold for fission (e.g., {sup 238}U and {sup 240}Pu). Consequently, the inclusion of delayed neutron spectra can have a small but significant effect on reactivity calculations. This study performs MCNP4C calculations for a series of established benchmarks and quantifies the reactivity impact of the delayed neutron spectra.

• Research Organization: Los Alamos National Lab., NM (US)
• OSTI ID: 20104497
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 82; ISSN 0003-018X; ISSN TANSAO
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
BENCHMARKS
DELAYED NEUTRONS
FISSION SPECTRA
M CODES
PROMPT NEUTRONS
REACTIVITY
REACTOR KINETICS