ML21019A019
| ML21019A019 | |
| Person / Time | |
|---|---|
| Issue date: | 01/21/2021 |
| From: | Hector Rodriguez-Luccioni NRC/NRR/DNRL/NLRP |
| To: | |
| Rodriguez-Luccioni H | |
| References | |
| Download: ML21019A019 (10) | |
Text
Extending Reactor Licenses to an Extreme TOPIC #2 Technical lssues for Mechanical Components JANUARY 21, 2021 PAUL GUNTER REACTOR OVERSIGHT PROJECT BEYOND NUCLEAR
Federal Register, June 21, 1996, pp. 31964-31966 Yankee Atomic Electric Co., Sacramento Municipal Utility District, Portland General Electric Co., and Southern California Edison,: Receipt of Petition and Issuance of NRC Directors Decision under 10 CFR 2.206 April 1, 1996, Nuclear Information Resource Service, Citizens Awareness Network and nine other public organizations requested the NRC to modify the possession only licenses for the Yankee Rowe, Rancho Seco, Trojan and San Onofre Unit 1 nuclear power stations to require a collaborative effort to document and research radiation embrittlement of their respective reactor pressure vessels (RPV) by suspending plans to bury the components until substantial metal and weld samples from the RPVs be harvested for analysis and materially archive the radiation embrittlement phenomenon.
Federal Register, June 21, 1996 (cont.)
Notice is also hereby given that by a Directors Decision (DD 96-07) dated June 14, 1996, the Director, Office of Nuclear Reactor Regulation, has denied the petition.
The NRC staff has concluded that sufficient information is already and will be available to the staff to satisfactorily and timely address such radiation embrittlement phenomenon in a manner which protects public health and safety
San Onofre Unit 1 reactor pressure vessel (770 tons) was the last of the previously referenced decommissioned reactors to arrive at its permanent burial site in Clive, Utah, July 2020, without being autopsied for archival samples.
Nevada Department of Transportation
Section 3.4. 2 Cast Austenitic Stainless Steel (CASS)
PNNL-27120 references many knowledge gaps identified in the literature including Expanded Materials Degradation Assessments(EMDA),
NUREG/CR-7153 to include reactor internals.
- 4. Knowledge gaps: There is data in the literature that suggests significant loss of fracture toughness for neutron exposures between 0.5 and 5 dpa due to the interaction of neutron and thermal embrittlement effects (Chopra 2015). This interaction needs to be understood for life extension.
- 5. Harvested materials can be used to address critical knowledge gaps in two areas: (1) calibration and validation of current accelerated testing procedures; and (2) assessment of the combined effects of thermal aging, coolant effects, and neutron irradiation. Degradation initiation and growth studies can be conducted with harvested materials.
New/improved ISI procedures may be developed to detect degradation.
The two references to knowledge gaps in Subsequent License Renewal Reviews were among numerous other references removed by the NRC revision of the federal laboratory report [PNNL 27120 Rev. 1].
Other revisions from the December 2017 published version that was pulled by NRC from three government websites further toned down findings that would require strategic harvesting of real world aged materials for analysis.
Other findings such as benchmarking of laboratory tests will require harvesting materials from reactors were toned down to harvesting would allow calibration of accelerated aging in the laboratory against long-term service in a reactor environment in PNNL-2712 Rev.1.
Expanded Materials Degradation Assessments(EMDA), NUREG/CR-7153, Volume 2, Aging of Core Internals and Piping Systems, Oct. 2012 The term knowledge gaps is used 40 times in EMDA just in Volume 2.
For example, The extent of knowledge gaps is impacted by the unknowns associated with synergisms between different degradation modes; for instance, the effort on SCC (stress corrosion cracking) of irradiation damage and thermal embrittlement, which are very time dependent. [p. 305]
Obviously, concern over how many times the term knowledge gap appears in technical documents used to qualify for license extension, of any duration, does not constitute adequate reason to scrub those determinations without also providing if and how those findings were addressed. Yet, messaging appears to have played a significant role in the NRC revision of the federal laboratorys Technical Letter Report PNNL-27120 to PNNL-27120 Rev. 1.
This type treatment does not build public confidence in the technical review of age management programs, particularly as operating license extensions become more and more extreme.