Taking credit for the reduced reactivity of spent nuclear fuel in criticality analyses is referred to
as burnup credit. Criticality safety evaluations employing burnup credit require validation of the
depletion and criticality calculation methods and computer codes with available measurement
data. To address the issues of burnup credit criticality validation, the U.S. Nuclear Regulatory
Commission initiated a project with Oak Ridge National Laboratory to (1) develop and establish

This paper provides insights into the neutronic similarities between a representative high-capacity rail-transport cask containing typical pressurized water reactor (PWR) spent nuclear fuel assemblies and critical reactor state-points, referred to as commercial reactor critical (CRC) state-points. Forty CRC state-points from five PWRs were analyzed, and the characteristics of CRC state-points that may be applicable for validation of burnup-credit criticality safety calculations for spent fuel transport/storage/disposal systems were identified.

The purpose of this study is to provide insights into the neutronic similarities that may exist between a
generic cask containing typical spent nuclear fuel assemblies and commercial reactor critical (CRC) state-
points. Forty CRC state-points from five pressurized-water reactors were selected for the study and the
type of CRC state-points that may be applicable for validation of burnup credit criticality safety
calculations for spent fuel transport/storage/disposal systems are identified. The study employed cross-

Spent fuel transportation and storage cask designs based on a burnup credit approach must
consider issues that are not relevant in casks designed under a fresh-fuel loading assumption. For
example, the spent fuel composition must be adequately characterized and the criticality analysis
model can be complicated by the need to consider axial burnup variations. Parametric analyses are
needed to characterize the importance of fuel assembly and fuel cycle parameters on spent fuel

Taking credit for the reduced reactivity of spent nuclear fuel (SNF) in criticality analyses is referred to as burnup credit (BUC). Criticality safety evaluations require validation of the computational methods with critical experiments that are as similar as possible to the safety analysis models, and for which the keff values are known. This poses a challenge for validation of BUC criticality analyses, as critical experiments with actinide and fission product (FP)

The American Nuclear Society (ANS) appreciates the opportunity to comment on the draft Nuclear Waste Administration Act (NWAA). The ANS is a not-for-profit, international, scientific, and educational organization with nearly 12,000 members worldwide. The core purpose of ANS is to promote awareness and understanding of the application of nuclear science and technology. As an organization, it has published a number of position statements regarding the issue of spent fuel and radioactive waste.

The American Nuclear Society (ANS) supports the safe, controlled, licensed, and regulated interim
storage of used nuclear fuel (UNF) (irradiated, spent fuel from a nuclear power reactor) until disposition
can be determined and completed. ANS supports the U.S. Nuclear Regulatory Commission’s (NRC’s)
determination that “spent fuel generated in any reactor can be stored safely and without significant
environmental impacts for at least 30 years beyond the licensed life for operation.

It is increasingly apparent that the United States will require a large expansion of nuclear power
generation capacity to meet its future baseload electricity needs while reducing greenhouse gas
emissions. As a result, Congress and the Administration must act to update U.S. nuclear fuel
cycle policy to address these realities. This will likely require a multifaceted approach involving
some combination of on-site/centralized dry cask interim storage, nuclear fuel recycling, and
emplacement of high-level wastes in long-term geological storage.

More than 45 million shipments of radioactive materials have taken place in the United States
over the last three decades, with a current rate of about three million per year. The majority of
these radioactive shipments consist of radiopharmaceuticals, luminous dials and indicators,
smoke detectors, contaminated clothing and equipment, and research and industrial sources.
Fewer than 3,500, or 0.01%, have been involved in any sort of accident, incident, or anything

The American Nuclear Society (ANS) supports (1) the development and use of geological
repositories for disposal of high-level radioactive wastes and (2) expeditious processing of the
Yucca Mountain license application in an open, technically sound manner. Geological disposal
means placing the wastes hundreds of feet underground and far from the biosphere. The U.S.
Nuclear Regulatory Commission (NRC) is following a legislatively well-defined regulatory
process to evaluate the safety of the proposed Yucca Mountain Site to meet both the scientific