ML20050P103
| ML20050P103 | |
| Person / Time | |
|---|---|
| Issue date: | 02/25/2020 |
| From: | NRC/OCM |
| To: | |
| Shared Package | |
| ML20002B811 | List: |
| References | |
| M200225 | |
| Download: ML20050P103 (10) | |
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UCS Perspectives on Accident Tolerant Fuel Technologies and Licensing Process February 25, 2020 Dr. Edwin Lyman Director of Nuclear Power Safety Climate and Energy Program Union of Concerned Scientists
Is the purpose of accident-tolerant fuel development
- to make nuclear reactors safer?
- 2012 Consolidated Appropriations Act conference report: funding provided to develop and qualify meltdown-resistant, accident-tolerant nuclear fuels that would enhance the safety of light water reactors.
or
- to provide economic benefits to licensees?
- Ben Holtzman, NEI: There is no safety imperative for why we are going to be implementing ATF it is for determination of the benefits in economic space. (ACRS subcommittee meeting, 9/17/19)
- The Nuclear Energy Innovation and Modernization Act (NEIMA) implies both; but can both be realized?
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UCS position
- UCS believes that the primary purpose of ATF fuel development is to increase reactor safety margins
- But the NRC could undermine this goal
- If it continues to weaken its licensing standards to enable the ATF program to go forward
- If it approves ATF batch loading before obtaining and reviewing sufficient safety data for representative fuel under normal and accident conditions
- If it allows licensees to take credit for ATF to reduce safety margins in other areas for economic benefit 3
ATF safety benefits to date are modest at best
- It now appears that no currently identified ATF concept, either near- or longer-term, will be the safety silver bullet that Congress was hoping for:
- Marginal impact on anticipated operational occurrences and design basis accidents
- Modest increase in coping time during certain severe accidents (1-3 hours)
- Minimal impact on core damage frequency (CDF)
- Potential for additional uncertainties and even worse behavior than current fuels under some conditions
- Delamination of clad coatings and introduction of other new degradation mechanisms
- Breakaway oxidation of silicides and nitrides 4
Economic benefits to industry are unclear
- ATF licensing not likely to be a decisive factor in subsequent license renewal decisions
- Increased fuel cost but how much actual benefit from increased cycle length and burnup?
- Safety criteria may have to be changed to credit ATF
- Cladding strength criterion instead of minimum departure from nucleate boiling ratio
- Minimal impact on probabilistic risk assessment (PRA) suggests that ATF will not have a significant benefit for risk-informed applications 5
So whats the rush?
- The industry timetable for batch ATF loading by 2023 is unrealistic and may compromise safety
- Absence of specific and standardized testing requirements raises questions
- Lead test assemblies should be irradiated under representative conditions to the planned peak batch burnup and should undergo thorough post-irradiation examination (~ 8 years)
- Al Csontos, EPRI: Its between the vendors and NRC in terms of the negotiated maximum range for the highest burnup for the available possible data sets - ACRS subcommittee meeting, September 17, 2019
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Ensuring defense-in-depth
- In comments on the Interim Staff Guidance for chromium-coated fuel, NEI requested that
- the NRC weaken deterministic standards for ensuring fuel and cladding integrity
- The NRC state that fuel manufacturing process parameters will be off-limits for ATF reviews, even though some ATF properties will be very sensitive to manufacturing processes
- UCS is encouraged that the staff rejected these requests, which would reduce defense-in-depth 7
- The most apparent safety benefit of ATF is the potential for improved cladding and fuel behavior during loss-of-coolant accidents
- This could be addressed most efficiently through Commission approval of the stalled 50.46(c) rulemaking (in addition to ensuring reasonable assurance of adequate protection for current high-burnup fuels) 8
Licensing standards
- UCS was disappointed that the NRC decided not to require license amendments and exemptions for ATF LTA loading despite the reasoned objections of several staff members
- NRC still has an opportunity to change this policy before the more exotic ATF concepts (materials, enrichment >
5.0% U-235) are ready for LTA irradiation
- The NRC should not take safety shortcuts in reviewing applications for batch and full-core ATF loading
- NRC should favor licensing approaches that maximize opportunities for public input (rulemaking, license amendment requests, topical report reviews) 9
- CDF: Core damage frequency
- LTA: Lead test assembly
- UCS: Union of Concerned Scientists 10