Spent Fuel Storage and Transportation Sub-Arena

Objective

Utilize risk information on a case-by-case basis to prioritize and address regulatory initiatives in spent fuel storage and radioactive materials transportation.

Basis

SECY-99-100 and SECY-04-0182, as well as the related staff requirements memorandum (SRM), provide the conceptual framework for risk-informing the NRC's waste activities. Guidance on how to apply this framework is provided in "Risk-Informed Decision-Making for Material and Waste Applications". In particular, individual risk-informed applications must meet the established screening criteria.

In this subarena, the NRC staff is limited in its ability to risk-inform the agency's regulatory activities because it is not cost-beneficial to perform risk-assessment of each of the numerous storage or transport designs. As a result, the agency has conducted (or sponsored) risk assessments for a few selected designs. In addition, the staff may apply risk assessments to specific activities on a case-by-case basis, provided that the screening criteria are met. For example, the staff has completed and documented a pilot study PRA of a dry cask storage facility, and determined that the risk from that facility was negligibly small.

The goal described below meets the screening criterion for cost/benefit by assessing risk impacts by judgment.

Goals

The staff has established the following goal for risk-informed and performance-based activities in this subarena:

• Produce updated versions of NUREG-1536, "Standard Review Plan for Dry Cask Storage Systems," and NUREG-1567, "Standard Review Plan for Spent Fuel Dry Storage Facilities."

Summary Description

Holders of, and applicants for, certificates of compliance for spent fuel dry storage systems must provide the specifications of the spent fuel to be stored in their storage systems’ designs per 10 CFR 72.236(a). Those specifications that are significant are included in the contents specifications in the conditions and technical specifications (TS) of the designs’ certificates of compliance (CoC). For the systems’ shielding and radiation protection design, these specifications include the maximum burnup, minimum enrichment, and minimum cooling time, among others. The shielding and radiation protection analyses use demonstrate that the systems’ shielding design is sufficient to meet the requirements in 10 CFR 72.104 and 10 CFR 72.106 per 10 CFR 72.236(d). With the increasing complexities of the contents specifications proposed as authorized system contents, the CoC’s TS describing the authorized contents have become voluminous, with many pages dedicated to defining the authorized combinations of maximum burnup, minimum cooling time, and minimum enrichment. Review of applications with such numerous contents specifications has also become burdensome.

Thus, the goal of this activity is to provide a means for defining authorized storage system contents by a method of evaluation (MOE) for identifying spent fuel contents as authorized for storage in the storage system. A storage system CoC that uses an appropriately defined MOE for determining authorized contents and which general licensees using the system must follow, could then meet 10 CFR 72.236(a) through incorporation of the MOE in lieu of providing detailed and numerous values for the contents specifications in the CoC and TS. The shielding and radiation protection analyses for the storage system, in its safety analysis report, could then use a radiation source term(s) that is representative of the authorized contents that the MOE would define, to show compliance with 10 CFR 72.236(d).

Previous Fiscal Years

FY 2020

The staff explored an MOE approach for spent fuel dry storage system shielding design certification applications under 10 CFR Part 72. This approach was a new concept in FY 2020 to enhance risk-informed review approaches using an MOE to define authorized contents, for shielding purposes, for spent fuel dry storage systems. During FY 2020, the staff conducted public meetings with NEI where this new approach was discussed. The MOE approach seeks to meet the spent fuel specification requirements in 10 CFR 72.236(a) and the shielding performance goals as specified in 10 CFR 72.236(d) using an approved methodology rather than an explicit definition of the contents of the storage system.

FY 2021

In public interactions in late FY 2020, a storage system CoC holder was identified to prepare and submit a topical report to pilot development and review of an MOE for defining authorized spent fuel contents. An initial topical report was submitted in early FY 2021. Based on staff review of the initial report and interactions between the staff and the CoC holder, the CoC holder revised the topical report and submitted it for review in mid FY 2021. The staff is in process of review, having accepted the topical for review after an acceptance review. The staff plans to complete its review in FY 2022, issuing any needed requests for additional information and engaging in any needed public interactions with the CoC holder. The staff will issue a safety evaluation report upon conclusion of the review.

Summary Description

As shown in existing probabilistic risk assessment studies, the risk associated with dry cask storage under 10 CFR Part 72 is very low. The NRC is engaged in multiple activities with the goal being to enhance the framework for spent fuel storage.  The results would be to enable the staff to perform more risk-informed regulatory reviews, improve guidance, streamline casework activities, help assess 10 CFR 72.48 changes, and evaluate requests for exemptions to the regulation while maintaining appropriate margins of safety and security.  One of these activities is the development of what is called the graded approach for determining the content and format of certificates of compliance (including their appendices).

The graded approach takes into consideration quantitative and qualitative risk insights, as well as key regulatory requirements to ensure dry storage system certificates of compliance contain the necessary storage system design information and requirements for maintaining safety and security and ensuring that the associated regulatory requirements are met.

Previous Fiscal Years

FY 2020

In FY 2020, the staff continued work on the graded approach for spent fuel certificates of compliance. The goal of this approach is to streamline the certification and oversight of spent fuel dry storage designs following the principles of risk-informed regulations. The graded approach provides the framework and criteria for establishing an appropriate level of information in spent fuel storage systems’ certificates of compliance and their appendices as well as a uniform format for the certificates and their appendices. The graded approach provides criteria to determine the information and requirements that are of sufficient safety or risk significance that they should be included in the certificate of compliance and its appendices and that information and those requirements which may remain in the other licensing basis documents for a dry storage system design (e.g., final safety analysis reports) to which regulatory processes such as 10 CFR 72.48 may be applied. In a January 8, 2020, letter to the Nuclear Energy Institute, the NRC endorsed the use of the graded approach program (ADAMS Accession No. ML19353D373). In FY 2021, the staff plans to explore additional activities that will incentivize the use of the graded approach.

FY 2021

In FY 2021, the staff began exploring the potential need for guidance to facilitate implementation of the graded approach and review of applications using it. The staff plans to continue that exploration in FY 2022, considering the lessons learned and experience gained from review of applications with the graded approach, including the pilot amendment and recent applications seeking to use the graded approach.

Summary Description

Capitalizing on the Division of Fuel Management's efforts to enhance the spent fuel storage licensing process over the last several years, on November 8, 2019, NEI submitted a white paper containing sixteen recommendations to explore further enhancements related to dry storage performance safety margin.  The goal of the white paper is to leverage industry experience with loading and maintenance of dry cask spent nuclear fuel storage systems to identify improvements to the regulatory framework for licensing these systems.  The staff has held eight workshops during this fiscal year to align on the recommendations, develop implementations plans, and status implementation efforts.  In general, the white paper, and more importantly, the staff's leadership on this initiative align well with the agency's direction to become a modern risk-informed regulator, especially as the staff develops plans to further risk-inform its approach to spent fuel storage licensing.  The staff has made great progress in implementing changes that address several of the of the sixteen recommendations in the white paper.

In addition to the method of evaluation (MOE) topical report, other initiatives related to the overall effort identified in this website include:  Regulatory Framework for Spent Fuel Storage and Transportation and the Risk Tool for Spent Fuel Dry Cask Storage.

Previous Fiscal Years

FY 2020

In FY 2020, the staff has been reviewing the Holtec Thermal Evaluation Topical Report (TR). This review implements an approach that reduces numerous reviews of analysis calculations by the staff during licensing actions and, instead includes a generic approval (topical report, Quality Model) for the bulk of the steps required to complete numerical modeling calculations. The process of implementing the TR in our reviews will incorporate all regulatory tools at our disposal and will achieve efficiencies in licensing reviews that have incorporated risk insights.

FY 2021

On September 14, 2021, staff issued a final safety evaluation report for the first topical report related to Holtec's spent fuel storage systems. The topical report involves a generic and risk-informed approach on heat load zone configurations. This approach, when adopted for a given Holtec design, will reduce the number of future license amendments. (ADAMS Accession No. ML21125A186).

Summary Description

The NRC staff is developing a guidance document to include risk information in the review of dry cask license applications and license amendments. The tool is based on risk studies, past safety evaluation reports, and staff expert knowledge. This dry cask Risk Tool would be used to rate specific licensing actions in four different color coordinated results which correspond to high (red), medium (yellow), or low (green) risk, and outside the scope of the tool (blue). This preliminary risk rating can then be used alongside other information and staff experience to determine the level of review required for a specific requested licensing action.

Previous Fiscal Years

FY 2020

The development of the dry cask Risk Tool began in September 2019.  Major activities have included the construction of the draft tool by Idaho National Laboratory followed by review and contributions from a working group of senior NRC technical reviewers.  Work on this project is now transitioning from development of the Risk Tool to creating a guidance document for implementation and developing training materials for educating staff in its application.  A public meeting to communicate the tool to industry stakeholders took place on September 9th (ADAMS Accession No. ML20248H381).

The level of effort required for evaluating a requested licensing action will also depend on the quality of the application, uniqueness of the design, and the methodology used for demonstrating compliance.  The inclusion of the dry cask Risk Tool in the planning of reviews will support allocating more time to difficult/high risk items to further ensure adequate safety, while making lower risk reviews more efficient.

FY 2021

NRC staff developed materials to improve training and use of the Risk Tool to aid in its introduction as a part of technical safety reviews. These materials include internal documents and sites that allow staff to obtain training and supporting documents whenever they are needed. Additionally, staff completed the Risk Tool Job Aid (ML20318A270), a document that walks Risk Tool users through the process and points out important factors to be considered in a risk informed review.

In the spring of 2021, the Risk Tool was used on two dry storage cask license amendments in order to evaluate its impact on the review process and develop a lessons learned report. The first cases involving the Risk Tool showed its capability of grading design changes by risk level, which can then be used for planning and implementation of a technical review. The findings of the pilot will be finalized and shared with management and stakeholders. These lessons learned will also be used to target research funding to improve the Risk Tool and its supporting documents.