This report investigates various calculational modeling issues associated with boilingwater-
reactor (BWR) fuel depletion relevant to burnup credit. To date, most of the efforts in
burnup-credit studies in the United States have focused on issues related to pressurized-waterreactor
(PWR) fuel. However, requirements for the permanent disposal of BWR fuel have
necessitated the development of methods for predicting the spent fuel contents for such fuels.
Concomitant with such analyses, validation is also necessary. This report provides a summary of

The Interim Staff Guidance on burnup credit for pressurized water reactor (PWR) spent nuclear fuel (SNF), issued by the United States Nuclear Regulatory Commission's (U.S. NRC) Spent Fuel Project Office, recommends the use of analyses that provide an "adequate representation of the physics" and notes particular concern with the "need to consider the more reactive actinide compositions of fuels burned with fixed absorbers or with control rods fully or partly inserted." In the absence of readily available information on the extent of control rod (CR) usage in U.S.

This report presents studies performed to support the development of a technically justifiable approach for
addressing the axial-burnup distribution in pressurized-water reactor (PWR) burnup-credit criticality
safety analyses. The effect of the axial-burnup distribution on reactivity and proposed approaches for
addressing the axial-burnup distribution are briefly reviewed. A publicly available database of profiles is
examined in detail to identify profiles that maximize the neutron multiplication factor, keff, assess its

Target accuracy on LWR neutronics parameters is 2 to 5 times lower than the a priori uncertainty (1σ)
due to nuclear data. This paper summarizes the experimental facilities and the integral measurements that are required
for code qualification. The rigorous use of integral information through trend analysis method is described. Trends
on JEF2 data from Keff measurements and P.I.Es are presented. These trends were accounted for in the new JEFF3
evaluations. The role of fundamental experiments, such as worth measurement of separated isotopes, is emphasized.

Subcritical source-driven noise measurements are simultaneous Rossi-a and randomly
pulsed neutron measurements that provide measured quantities that can be related to the
subcritical neutron multiplication factor. In fact, subcritical source-driven noise
measurements should be performed iii lieu of Rossi-a rneasurements because of the
additional information that is obtained from noise measurements such as the spectral ratio
and the coherencc functions. The basic understanding of source-driven noisc analysis

The Interim Staff Guidance on burnup credit (ISG-8, revision 2) for pressurized-water-reactor spent
nuclear fuel in storage and transport casks, issued in 2002 by the U.S. Nuclear Regulatory Commission’s
Spent Fuel Project Office, recommends an out-of-core burnup measurement to confirm the reactor record
and compliance with the assembly burnup value used for cask loading acceptance. This recommendation
is intended to prevent unauthorized loading (i.e., misloading) of assemblies due to inaccuracies in reactor

The purpose of this scientific analysis report, CSNF Loading Curve Sensitivity Analysis, is to establish the required minimum burnup as a function of initial enrichment for both pressurized water reactor (PWR) and boiling water reactor (BWR) commercial spent nuclear fuel (CSNF) that would allow permanent disposal of these waste forms in the geologic repository at Yucca Mountain. The relationship between the required minimum burnup and fuel assembly initial enrichment forms a loading curve.

The objective of this calculation is to evaluate commercial spent nuclear fuel (CSNF) bumup uncertainty based on pressurized water reactor (PWR) and boiling water reactor (BWR) records kept by each utility. The bumup uncertainties will be used to adjust either the waste package loading curves or the bumup values of assemblies shipped to the repository.
This engineering calculation supports the burnup credit methodology in Reference 1 and is performed in accordance with the AREVAIFANP procedures in References 2 and 3.

The validity of the computation of pressurized-water-reactor (PWR) spent fuel isotopic
composition by the SCALE system depletion analysis was assessed using data presented in the report.
Radiochemical measurements and SCALE/SAS2H computations of depleted fuel isotopics were
compared with 19 benchmark-problem samples from Calvert Cliffs Unit 1, H. B. Robinson Unit 2,
and Obrigheim PWRs. Even though not exhaustive in scope, the validation included comparison of
predicted and measured concentrations for 14 actinides and 37 fission and activation products.

Technical development on burn-up credit for spent LWR fuels had been performed at JAERI since
1990 under the contract with Science and Technology Agency of Japan entitled ‘Technical Development on
Criticality Safety Management for Spent LWR Fuels.’ Main purposes of this work are to obtain the
experimental data on criticality properties and isotopic compositions of spent LWR fuels and to verify burnup
and criticality calculation codes. In this work three major experiments of exponential experiments for