Monte Carlo criticality calculations use the power iteration method to determine the eigenvalue (keff) and eigenfunction (fission source distribution) of the fundamental mode. A recently proposed method for accelerating convergence of the Monte Carlo power iteration using Wielandt’s method has been implemented in a test version of MCNP5. The method is shown to provide dramatic improvements in c...

Rutherford backscattering and particle induced x-ray emission have been utilized to precisely characterize targets used in nuclear fission experiments. The method allows for a fast and non destructive determination of target thickness, homogeneity and element composition.

Uranium contains only one naturally occurring isotope, 235U, which will sustain a nuclear chain reaction using normal water to moderate and reflect neutrons. At present, this isotope is present in low abundance (0.72%), requiring enrichment to 3% or greater for effective use in commercial nuclear reactors. Two billion years ago, however, the natural abundance of 235U was approximately 3%. Evide...

3. System 14. Document Identifier DOE Spent Nuclear Fuel CAL-DSD-NU-000007 Rev OOA 5. Title Intact and Degraded Mode Criticality Calculations for the Codisposal of ATR Spent Nuclear Fuel in a Waste Package 6. Group Criticality 7. Document Status Designation I8J Preliminary 0 Final 0 Cancelled 8. NotesJComments This document does not impact any other organization outside Criticality, therefore a...

Fission fragments play a pivotal role in understanding the entire nuclear fission process, and their effects are widespread to all applications involving nuclear fission: reactor design and maintenance, waste removal, active and passive integration of nuclear materials, simulations, and the fundamental theories of fission. Currently, experimental data on the characteristic properties of fission...

A criticality accident occurred on September 30, 1999, in a conversion test facility at the JCO Tokai site. The accident was triggered by pouring an 18.8% enriched uranyl nitrate solution into a precipitation vessel beyond the critical mass. The accident continued for about 19 hours before the criticality could be stopped. during which time neutrons and gamma-rays were emitted continuously due ...

The NJOY Nuclear Data Processing System is widely used to convert evaluations in the Evaluated Nuclear Data Files (ENDF) format into forms useful for practical applications such as fission and fusion reactor analysis, stockpile stewardship calculations, criticality safety, radiation shielding, nuclear waste management, nuclear medicine procedures, and more. This paper provides a description of ...

Determining convergence of Monte Carlo criticality problems is complicated by the statistical noise inherent in the random walks of the neutrons in each generation. The latest version of MCNP5 incorporates an important new tool for assessing convergence: the Shannon entropy of the fission source distribution, Hsrc. Shannon entropy is a well-known concept from information theory and provides a s...