ML21137A308
| ML21137A308 | |
| Person / Time | |
|---|---|
| Issue date: | 05/25/2021 |
| From: | Louise Lund NRC/RES/DE |
| To: | Joseph Donoghue NRC/NRR/DSS |
| J Wallace | |
| Shared Package | |
| ML21137A307 | List: |
| References | |
| Download: ML21137A308 (3) | |
Text
CONTACT:
Jay Wallace, RES/DE/CIB (301) 415-2418 MEMORANDUM TO:
Joe Donoghue, Director Division of Safety Systems Office of Nuclear Reactor Regulation FROM:
Louise Lund, Director Division of Engineering Office of Nuclear Regulatory Research
SUBJECT:
IMPENDING PUBLICATION OF TECHNICAL LETTER REPORTS CALCULATIONAL METHODS FOR REACTOR PRESSURE VESSEL FLUENCE IN EXTENDED BELTLINE LOCATIONS, (TLR-RES/DE/CIB-2021-08) AND REACTOR PRESSURE VESSEL FLUENCE, DPA, AND UNCERTAINTY QUANTIFICATION IN EXTENDED BELTLINE LOCATIONS (TLR-RES/DE/CIB-2021-09)
The Office of Nuclear Regulatory Research (RES) has completed technical letter reports (TLRs) entitled Calculational Methods for Reactor Pressure Vessel Fluence in Extended Beltline Locations and Reactor Pressure Vessel Fluence, DPA, and Uncertainty Quantification in Extended Beltline Locations produced under contract with Oak Ridge National Laboratory (ORNL). These TLRs document a portion of the work performed under the user need request NRR-2015-002, Reactor Pressure Vessel Fluence Evaluation Methodology Guidance.
Neutron fluence estimates for reactor vessel locations above and below the core and for reactor vessel internal (RVI) components, such as core barrels and upper support structures, are used by NRC licensees and applicants to determine the appropriate aging management activities necessary for renewed operating licenses pursuant to the requirements of 10 CFR Part 54.
However, the regulatory guidance in RG 1.190 does not apply to methods and calculations for estimates of neutron fluence outside of the traditional beltline region.
The first TLR, Calculational Methods for Reactor Pressure Vessel Fluence in Extended Beltline Locations, provides an overview of radiation transport calculational methods and details the results of sensitivity studies of parameters that can affect neutron fluence determinations in the extended beltline. Special emphasis was placed on the effect of discrete ordinates quadrature selection in fluence determination. The results from these studies provide insights into where modifications in analysis methodology may be necessary to obtain calculational uncertainty in the extended beltline region that is comparable to that specified for traditional beltline fluence analyses.
May 25, 2021 Bowen, Jeremy signing on behalf of Lund, Louise on 05/25/21
J. Donoghue The second TLR, Reactor Pressure Vessel Fluence, DPA, and Uncertainty Quantification in Extended Beltline Locations, evaluates the effects of using multigroup (MG) cross-section libraries on neutron fluence evaluation and neutron displacement per atom (dpa) rates, both inside the traditional beltline region and in the extended beltline region. In addition, the TLR documents the effect of the scattering cross section expansion order, PN, on calculated fast flux levels and dpa rates in the extended beltline region, and the effects that the selections of an MG library and scattering order play in dosimetry reaction rates. Finally, there is a discussion of uncertainty estimation techniques for combining fluence estimates.
The capability to estimate neutron fluence in the extended beltline region, including reactor vessel internal (RVI) components and nozzles, was not addressed in RG 1.190 when it was published in 2002. The results from the parametric and sensitivity studies presented in these two TLRs provide a technical basis for determining the applicability of RG 1.190 for evaluating neutron fluence in the extended beltline region and help inform decisions about changes to calculational methodology guidance that may be needed.
Staff representatives from the Division of Safety Systems in the Office of Nuclear Reactor Regulation have reviewed drafts of these TLRs and did not find issues with either of the TLRs.
Nonetheless, please feel free to notify the responsible RES contact if you have any questions concerning the impending public release of these TLRs.
RES has established an online quality survey to collect feedback from user offices on the usefulness of RES products and services. This survey can be found online at the hyperlink:
RES Quality Survey. I would appreciate the responsible manager completing this short survey within the next 10 working days to present your offices views of the delivered RES product. Please share any concerns with me or the Division of Engineering contact listed below, so that they may be addressed.
If additional information is required, please contact Jay Wallace of my staff at 301-415-2418 or Jay.Wallace@nrc.gov.
Enclosures:
1.
TLR-RES/DE/CIB-2021-08, Calculational Methods for Reactor Pressure Vessel Fluence in Extended Beltline Locations 2.
TLR-RES/DE/CIB-2021-09, Reactor Pressure Vessel Fluence, DPA, and Uncertainty Quantification in Extended Beltline Locations
ML21137A307; ML21137A308 OFFICE RES/DE/CIB RES/DE/CIB RES/DE NAME JWallace RIyengar LLund JBowen for DATE May 24, 2021 May 24, 2021 May 25, 2021