ML19196A302
| ML19196A302 | |
| Person / Time | |
|---|---|
| Site: | Nuclear Energy Institute, 99902028 |
| Issue date: | 07/19/2019 |
| From: | Office of Nuclear Reactor Regulation |
| To: | Nuclear Energy Institute |
| Shared Package | |
| ML19168A097 | List: |
| References | |
| 3002010613, 3002010614 | |
| Download: ML19196A302 (8) | |
Text
Disposition Table for NEI and EPRI Comments Draft Safety Evaluations for EPRI Depletion TRs 3002010613 and 3002010614 Technical and editorial comments are listed in Table A-2-1 and Table A-2-2, respectively.
Table A-2-1: Technical comments on Draft SER, Revision 2 Page # Line # Comments Staff Disposition The Kopp memo interpretation in the ISG only includes uncertainty The language in the SER was in the isotopic content as stated in item i (line 30-33). The reported removed because it was related bias and uncertainties in the EPRI depletion benchmarks cover not to criticality code cross-section only isotopics but also the cross sections, numerical approximations, uncertainty (part of criticality etc. The comment in the SER acknowledges this fact; however, it is code validation), which is a not reflected in the main text of the draft SER. To avoid confusion separate and different topic for future applicants and reviewers, we recommend this point be from cross-section related clarified in the text. uncertainties present during depletion calculations. The comment on the language removal is focused on criticality code validation considerations.
3 48 The NRC believes that the existing SER language already includes what is being asked to be added:
In DSS-ISG-2010-01, it states that the NRC staff should interpret depletion uncertainty as the uncertainty in the isotopic number densities generated during the depletion simulations. The
uncertainty in the isotopic number densities can arise from uncertainty associated with the depletion code (i.e., based on chosen models and methods) and the underlying nuclear data used by the depletion code
- this also includes how the nuclear data is implemented by the depletion code. Both of these uncertainty components can have a significant impact on the isotopic number densities output by the depletion code.
The bold text already acknowledges that the EPRI benchmarks account for cross-section related uncertainties present during depletion calculations.
Footnote 8 also already includes the requested language:
This k-infinity change represents a means to estimate the net effect of all sources of depletion code
uncertainty - for example, uncertainty introduced by nuclear data, manufacturing tolerances, thermal hydraulic conditions, etc. - as long as measurement uncertainties are properly accounted for or shown to be insignificant.
The following text, additional study may be warranted for other fuel When using an approved topical designs over a range of BA types and loadings," might be confusing report, all limitations and to an applicant as it could be interpreted as a requirement for conditions (L&C) must be additional analysis by the applicant to demonstrate applicability for addressed by licensees. In this all PWR fuel types. The next page acknowledge that these issues case, L&C 1 provides the were addressed via RAI responses and the applicability was necessary clarification. The demonstrated. Therefore, we recommend clarifying the original text NRC does not see any to avoid confusion. One option could be to re-state this item in a disconnect from the discussion way that the SER clearly states that this concern was raised during in question and L&C 1.
the NRC review and addressed by EPRI and described in the following section?
The SER also quotes the utilization report RAI 7 response 10 47-49 clarifying analysts responsibility, which the NRC agrees with:
The General Response to
[the EPRI utilization report]
RAIs provides a similarity analysis to a range of rack and fuel designs and shows excellent agreement with non-flux trap racks designs and good agreement with flux trap designs with low burnup fuel.
The criticality safety analyst can rely on the similarity
analysis given in the general response and only needs to do further analysis if the rack or fuel is significantly different than current racks and fuel. If there is a new rack or fuel design significantly different [than] the current generation racks or fuels then the analyst should confirm similarity or use alternate methods to establish a bias and uncertainty for burned fuel in the spent fuel rack.
"For other fuel types, BAs, or other SFP storage conditions This comment is handled by additional analysis may be needed to demonstrate that results of the L&C 1. Regardless of the EPRI benchmark report are applicable to a given application." phrasing, the licensee is responsible for stating why the Same as the previous comment. The statement is vague and open approved methodology is ended, which could lead to confusion and delay on the part of applicable to their fuel (i.e., in applicants and reviewers thinking that additional analysis is needed scope). Based on the deviation for current designs. If the goal is to include considerations for any from the norm, the NRC future potential exotic designs and ensure exclusions of those exotic reviewer will need to make a 13 28-30 designs, perhaps that should be clearly stated? Instead of stating judgment call on whether the For other fuel types, perhaps should state For any other future, licensees justification is non-standard, exotic fuel types, .... adequate or not and whether or not additional analysis is needed. Bottom-line: Some judgment calls will be needed by both the licensee and the NRC reviewer. If the wording is changed to the proposed, ambiguity still remains anyhow.
That is, how to interpret non-standard and exotic?
Table 1 should be replaced with the agreed-upon changes, All suggestions have been specifically, with the Table included in the letter. Based on the incorporated.
agreements during December 20, 2018 public meeting, EPRI is providing this table to the NRC as part of this package, as Attachment 1. It is recommended to remove confirmatory NRC/PNNL Bias and Uncertainty from Table 1 of draft SER-Rev2 to avoid confusion by the applicant given Appendix C was only for 18 26-27 confirmatory purposes and new bias is for additional NRC safety margins. Also recommending to address uncertainty and bias for the values that are between the values listed in Table. For that purpose, suggest adding a statement similar to Linear interpolation between the burnup values, listed in Table 1, is acceptable to calculate the corresponding EPRI uncertainty and additional NRC bias for specific fuel assembly burnups to avoid ambiguity for the user.
Based on the discussions during the December 20, 2018 public The paragraph was kept. The meeting and to avoid confusion, recommend deleting this paragraph. staff has determined that it provides context for Appendix 19 17-24 C. Editorially it was moved up a few paragraphs to better fit with the narrative.
Based on the discussions during the December 20, 2018 public The whole paragraph was meeting and to avoid any confusion, it is recommended to delete deleted.
"Specifically, the net effect of EPRI-derived biases and uncertainties were found to be slightly non-conservative at higher burnups exceeding approximately 30 GWd/MTU."
19 26-31 If NRC plans to keep Appendix C, this whole paragraph can be re- This was the basis for keeping worded to state that NRC staff performed a confirmatory analysis, as the paragraph in question in the presented in Appendix C, and additional discussions with EPRI were preceding comment. Discussion conducted (ML number for public meeting) to further discuss the has been added in the reasons behind the observed discrepancies. Based on these paragraph directly preceding discussions, NRC added additional safety margins for the Bias Table 1.
calculations, as shown in Table 1.
Given the new agreed upon numbers, suggest adding the NRC bias This text was updated to fit with 20 3--5 in this item. Note the text states 430 GWD (typo), which should be preceding changes.
changed to 30.
Similar to first comment, SER needs to spell out that bias and See NRC response to the first 20 11--14 uncertainty values cover not only isotopic but cross sections, etc. comment.
Given the revised numbers and plans for utilization report revisions, This text was updated to fit with the last sentence should be changed to reflect the change. "There preceding changes.
20 26 is no need for an end user to account for this bias" is not true anymore.
Based on the agreed numbers from the December 20, 2018 public This text was updated to fit with 23 41--46 meeting and revised Table 1, this paragraph should be deleted or preceding changes.
updated to reflect these changes. ;
Not sure of the purpose of Appendix A and B. If Appendix C is going The purpose of Appendices A to be included in the final SER, we recommend revising the chosen and B are to document the example based on the discussions from the December 20, 2018 NRCs confirmatory analysis of Appendix public meeting. The observations should be revised to reflect the EPRIs statistical analysis and A-C agreed upon changes. Need to make clear that Appendix C is for was originally requested to be confirmatory purposes and not for applicant use. included by NEI. The Appendices support NRC
review conclusions in the SER body. I.e., they are inherently regulatory review tools, not guidance or modifications to the methods being reviewed.
Licensees who adopt topical reports into their licensing bases generally understand the mechanics of using them in licensing applications. I.e.,
L&Cs are used to clarify or modify how the approved methods are to be used. In this case the L&Cs make no mention of the Appendices, therefore there should be no confusion as to whether or not a licensee should use them.
Nonetheless, the requested clarification was added in Footnote 20.
Table A-2-2: Editorial comments on Draft SER, Revision 2 Page # Line # Comments Staff Disposition 1 10 Suggest revising "(McCullum, 2013)" to "NEI, 2013" All suggestions have been incorporated.
Suggest revising "(Smith et al., 2011; Smith et al., 2017)" to All suggestions have been incorporated.
Suggest revising "(Akkurt and Cummings 2018)" to "(EPRI All suggestions have been incorporated.
2 10 2018)"
Suggest revising "(Smith et al., 2017; Akkurt and All suggestions have been incorporated.
3 5 Cummings, 20172018)" to "(EPRI 2017, EPRI 2018)"
Suggest revising "(Akkurt and Cummings, 2018)" to "(EPRI All suggestions have been incorporated.
20 38 2018)"
Per EPRI guidelines, citation should be changed to: All suggestions have been incorporated.
EPRI, 2018, Utilization of the EPRI Depletion Benchmarks 24 38-40 for Burnup Credit Validation - Revision 1. EPRI, Palo Alto, CA: 2018. 3002010614. ADAMS Accession No. ML18088B395.
Per EPRI guidelines, citation should be changed to: All suggestions have been incorporated.
26 35-37 EPRI, 2011, Benchmarks for Quantifying Fuel Reactivity Depletion Uncertainty. EPRI, Palo Alto, CA: 2011.
1022909. ADAMS Accession No. ML12165A457.
Per EPRI guidelines, citation should be changed to: All suggestions have been incorporated.
27 1--3 EPRI, 2017, Benchmarks for Quantifying Fuel Reactivity Depletion Uncertainty Revision 1. EPRI, Palo Alto, CA:
2017. 3002010613. ADAMS Accession No. ML18088B397.