ML18218A501
| ML18218A501 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/02/2018 |
| From: | Thomas Wengert Plant Licensing Branch IV |
| To: | Pyle S Entergy Nuclear Operations |
| References | |
| L-2018-LLA-0047 | |
| Download: ML18218A501 (8) | |
Text
NRR-DMPSPEm Resource From: Wengert, Thomas Sent: Thursday, August 2, 2018 1:36 PM To: PYLE, STEPHENIE L Cc: BICE, DAVID B (ANO); Pascarelli, Robert
Subject:
ANO Final RAI RE: License Amendment Request to Adopt TSTF-425, Revision 3 (EPID L-2018-LLA-0047)
Attachments: ANO Final PRA RAI Regarding TSTF-425.pdf On July 18, 2018, the U.S. Nuclear Regulatory Commission (NRC) staff sent Entergy Operations, Inc. (the licensee) the draft Request for Additional Information (RAI) identified below. This RAI relates to the license amendment request to adopt Technical Specifications Task Force (TSTF)-425, Revision 3, at Arkansas Nuclear One, Unit 2, as described below.
On August 2, 2018, the NRC staff held a conference call with the licensee staff to clarify this request. During the call, the NRC staff agreed to modify the RAI by changing STI calculation to STI application in several places. [Following the call, the NRC staff made some additional editorial changes for clarity.] At the conclusion of the call, the licensee agreed to provide a response to this RAI within 45 days of this correspondence. A publicly available version of this final RAI (attached with Draft removed) will be placed in the NRCs Agencywide Documents Access and Management System (ADAMS).
From: Wengert, Thomas Sent: Wednesday, July 18, 2018 4:40 PM To: 'PYLE, STEPHENIE L' Cc: 'BICE, DAVID B (ANO)' ; Pascarelli, Robert
Subject:
ANO Draft RAI RE: License Amendment Request to Adopt TSTF-425, Revision 3 (EPID L-2018-LLA-0047)
By letter dated February 6, 2018 (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML18038B354), as supplemented by letter dated March 26, 2018 (ADAMS Accession No. ML18085A816), Entergy Operations, Inc. (Entergy) requested changes to the Technical Specifications (TSs) for the Arkansas Nuclear One, Unit 2 (ANO-2). The proposed change would modify the ANO-2 TSs by relocating specific surveillance frequencies to a licensee-controlled program, with the adoption of Technical Specifications Task Force (TSTF)-425, Revision 3, Relocate Surveillance Frequencies to Licensee Control -
Risk Informed Technical Specifications Task Force (RITSTF) Initiative 5b.
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the submittals and determined that additional information is required in order to complete the review. The staffs draft request for additional information (RAI) is provided as an attachment to this email. Please review and let me know if Entergy would like to have a conference call with the NRC staff to clarify this request. Also, lets discuss the timing for your response to this RAI.
Tom Wengert Project Manager - Arkansas Nuclear One NRR/DORL/LPL4 (301) 415-4037 1
Hearing Identifier: NRR_DMPS Email Number: 506 Mail Envelope Properties (Thomas.Wengert@nrc.gov20180802133600)
Subject:
ANO Final RAI RE: License Amendment Request to Adopt TSTF-425, Revision 3 (EPID L-2018-LLA-0047)
Sent Date: 8/2/2018 1:36:24 PM Received Date: 8/2/2018 1:36:00 PM From: Wengert, Thomas Created By: Thomas.Wengert@nrc.gov Recipients:
"BICE, DAVID B (ANO)" <DBICE@entergy.com>
Tracking Status: None "Pascarelli, Robert" <Robert.Pascarelli@nrc.gov>
Tracking Status: None "PYLE, STEPHENIE L" <SPYLE@entergy.com>
Tracking Status: None Post Office:
Files Size Date & Time MESSAGE 2455 8/2/2018 1:36:00 PM ANO Final PRA RAI Regarding TSTF-425.pdf 166673 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received:
REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO RELOCATE SPECIFIC SURVEILLANCE FREQUENCIES TO LICENSEE CONTROL ENTERGY ARKANSAS, INC.
ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368 By letter dated February 6, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18038B354), as supplemented by letter dated March 26, 2018 (ADAMS Accession No. ML18085A816), Entergy Operations, Inc., (Entergy), submitted a license amendment request (LAR) to relocate specific surveillance requirement frequencies to a licensee-controlled program with the adoption of Technical Specifications Task Force (TSTF)-425, Revision 3, Relocate Surveillance Frequencies to Licensee Control - Risk Informed Technical Specifications Task Force (RITSTF) Initiative 5b, for Arkansas Nuclear One, Unit 2 (ANO-2).
The U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is required to complete its review, as discussed below.
Background
The guidelines for technical adequacy of probabilistic risk assessment (PRA) models used in risk-informed applications is provided in Regulatory Guide (RG) 1.200, Revision 2, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities (ADAMS Accession No. ML090410014), on PRA technical adequacy. RG 1.200 describes a peer review process utilizing American Society of Mechanical Engineers/American Nuclear Society (ASME/ANS) PRA standard RA-Sa-2009, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications, Addendum A to RA-S-2008, as one acceptable approach for determining the technical adequacy of the PRA once acceptable consensus approaches or models have been established for evaluations that could influence the regulatory decision.
In its application, the licensee stated that it ANO-2 intends to follow the guidance provided in NEI 04-10, Risk-Informed Technical Specification Initiative 5B, Risk-Informed Method for Control of Surveillance Frequencies, Revision 1, in evaluating proposed surveillance test interval (STI) changes (also referred as surveillance frequency changes).
Request for Additional Information (RAI)
RAI-PRA Facts and Observations (F&Os) Closure Process - Internal Event Findings Section 4.2 of RG 1.200 states, in part, that the LAR should include, [a] discussion of the resolution of the peer review findings and observations that are applicable to the parts of the PRA required for the application.
1 of the LAR, Documentation of PRA Technical Adequacy, provides finding-level F&Os for internal events that are still open. For a number of F&O dispositions, there is insufficient information in the application for NRC staff to conclude that the F&O is sufficiently resolved for this application.
F&O SY-B15-01 regarding assessment of Systems, Structures, and Components (SSCs) operating beyond environmental qualifications of the LAR (page 16) indicates that this finding applies to PRA supporting requirement (SR) SY-B15 of the PRA standard. SR SY-B15 of the 2009 ASME/ANS PRA standard requires that the PRA [i]nclude operator interface dependencies across systems or trains, where applicable. The finding presented in the LAR against this SR discusses the lack of environmental qualification for SSCs in three systems, which seems more applicable to SR SY-B14. SR SY-B14 requires identification of SSCs that need to operate beyond their environmental qualification and requires inclusion of failures in the PRA that result from operation in adverse conditions (seven example adverse conditions are then listed). The disposition to this F&O states that the documentation for the Revision 6 PRA model will be updated to discuss: 1) walkdowns of credited equipment that were performed to identify potential susceptibility to flooding, spray, and a steam environment due to a pipe break, and 2) evaluation of the ability of systems to operate after loss of heating, ventilation, and air conditioning (HVAC). It is not clear from the response whether the environmental qualification concerns for SSCs in the three systems from the originating finding were resolved.
Provide a detailed description confirming that all of the required degraded environments listed in SY-B14 have been analyzed for the cited SSCs or explain how the exclusion of the degraded environment analysis does not impact the STI application.
RAI-PRA F&Os Closure Process - Internal Flooding - Open/Partially Open Internal Flooding Findings in the Process of Being Resolved Section 4.2 of RG 1.200 states, in part, that the LAR should include, [a] discussion of the resolution of the peer review findings and observations that are applicable to the parts of the PRA required for the application. This decision should take the following forms:
x A discussion of how the PRA model has been changed x A justification in the form of a sensitivity study that demonstrates the accident sequences or contributors significant to the application decision were not adversely impacted (remained the same) by the particular issue.
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a) F&O IFEV-A7 (MCR A2-5859) regarding internal flood scenario screening (Page 31 of Attachment 2 to the LAR)
This finding description states, [m]aintenance event screening is currently documented as a
~1E-05/yr [year] frequency, and concludes that the quantitative screening criteria is not met.
The disposition for this finding states that resolution of the F&O is only a documentation issue and that additional discussion of potential maintenance-related flooding mechanisms will be added to the documentation. It not clear to the NRC staff how the disposition addressed the F&O, given that the basis for screening maintenance-induced flooding is not provided. In light of these observations, address the following:
- i. Describe the basis for applying the screening value of ~1E-05/yr frequency.
ii. Clarify whether all maintenance-induced flooding events above the ASME/ANS screening threshold have been incorporated into the internal flooding model of record.
b) F&O 19-5 regarding internal flooding operator action execution steps (Page 32 of Attachment 2 to the LAR)
The finding cites several issues related to the calculation of human error probabilities (HEPs).
They include: (1) lack of operator verifications to ensure as-built, as-operated Human Factor Events (HFEs) are modeled, (2) inconsistent timings assumptions that can affect HEP values, and (3) the use of non-proceduralized recovery actions for execution steps. The disposition states, adjustments to some flooding HFE timing will be implemented. The disposition further states that these adjustments are not expected to impact flooding results, but are expected to be assessed in case-by-case STI evaluations.
- i. Confirm whether the model of record (MOR) incorporates the updated HEP analysis and explain how the adjustment to the HEP updates do not impact the STI application.
ii. If the licensee has not incorporated the updated HEP analysis and cannot conclude there is no impact to the STI program, propose a mechanism to ensure the updates for the cited HEPs are completed and implemented in the PRA model used for STI applications prior to program implementation.
c) F&O 20-9 regarding dependency analysis seeding value (Page 35 of Attachment 2 to LAR)
The finding states that it appears that the HFE values in the dependency analysis was not seeded with high enough values to ensure inclusion of all relative combinations. The disposition states, [t]he impacted HFEs will be updated as needed in the Internal Flooding Assessment (IFA) model and documentation. It further states that the HEP seed values are expected to have minimal or no impact on the flooding results, but are expected to be assessed in case-by-case STI evaluations.
Explain how the process used to ensure the appropriate seeding value is implemented in the PRA model used for STI applications prior to program implementation.
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RAI-PRA Identifying Key Assumptions and Uncertainties (Internal Events and Internal Flooding) that could impact the Application Section 4.2 of RG 1.200 states, in part, that for licensee submittal documentation, [i]dentification of the key assumptions and approximations relevant to the results used in the decision-making process, is to be provided.
Step 5 of NEI 04-10, states, in part, that identified sources of key uncertainty serve as inputs to identifying appropriate sensitivity cases in Step 14.
Two of the F&Os presented in Attachment 2 of the LAR pertain to identification of key assumptions and uncertainty. The dispositions to these F&Os provide insufficient information for NRC staff to conclude that the F&O is sufficiently resolved for this application.
F&O QU-F4-01 and 20-4 pertains to model assumptions and uncertainties. (Pages 27 and 34 of to the LAR)
The disposition for internal events F&O (i.e., QU-F4-01) states in part that, Appendix 1 of the Sensitivity and Uncertainty includes a review of the sources of uncertainty using EPRI [Electric Power Research Institute] 1016737. The disposition for the internal flooding F&O (i.e., 20-4) states, is a documentation issue [and] will be included in the IFA documentation. In light of these observations, address the following:
- i. Describe the process used to determine the key assumption and sources of uncertainty for the internal events and internal flooding PRAs. The description should contain sufficient detail to identify: (1) whether all assumptions and sources of uncertainty related to all aspects of the PRA analysis were evaluated to determine whether they were key, and (2) the criteria that were used to determine whether the modeling assumptions and sources of uncertainty were considered key.
ii. Also, explain how the approach adequately resolves the concerns raised in F&Os QU-F4-01 and 20-4.
RAI-PRA Fire HRA Methodology Revision a) F&O HR-G7-01 pertains to joint human error probability (Page 77 of Attachment 2 to LAR)
The finding states, in part, that the dependency approach does not consider availability of resources. The disposition states, [a] review was performed of the most challenging scenario with respect to manpower requirements, control room abandonment, which confirmed that available manpower is sufficient to support multiple HEPs (HFEs) in a cutset for the control room abandonment cutsets. The disposition also states that the Human Reliability Analysis (HRA) methodology was updated using NUREG-1921, EPRI/NRC-RES Fire Human Reliability Analysis Guidelines. It is not clear to the NRC staff how reviewing the resources associated with one scenario (albeit the most challenging) for adequate availability resources substitutes not considering the availability of resources in the dependency analysis.
The NRC staff notes that manpower limitations can occur for HFEs that have overlapping execution windows.
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Explain how the other fire scenarios that include both internal events and fire operator actions are not impacted by resource limitations, as defined by NUREG-1921.
b) F&O CF-A1-01, ES-C1-01, ES-D1-01, ES-D1-02, HRA-A2-01, HRA-A4-02, PRM-B2-01, PRM-B9-01, and HR-G3-01 pertain to revised HRA methodology (Pages 43, 44, 52, 54, 55, 64, 66, 69, 70, and 76 of Attachment 2 to the LAR)
The licensee stated that, for these F&Os, the HRA methodology was revised to follow the guidance of NUREG-1921, EPRI/NRC-RES Fire Human Reliability Analysis Guidelines.
- i. Justify that the HRA revision to NUREG-1921 does not constitute an ASME/ANS PRA Upgrade. Include a description of the HRA methodology originally used in the ANO-2 PRA models and how it was changed to be in alignment with guidance in NUREG-1921.
ii. If the HRA methodology update is determined to meet the definition of a PRA upgrade per the ASME/ANS 2009 PRA standard, clarify that a focused-scope peer review has been conducted on HRA updates determined to be PRA upgrades and that all resulting findings along with their dispositions have been provided with this LAR.
RAI-PRA External Hazards , Section 3.5 of the LAR does not explain how the risk from external hazards evaluated in the ANO-2 Individual Plant Examination of External Events was updated to reflect new information when used in performing a qualitative or bounding analysis in support of STI extension evaluations in accordance with NEI 04-10, Section 4, Step 10.
Describe the process for monitoring for and incorporating new information into the qualitative or bounding analyses performed for external hazards. Include justification that this process is sufficient to support the Surveillance Frequency Control Program (SFCP) and reflect the as-built, as-operated plant configuration. Specifically, describe monitoring for and incorporating new information for the high winds and tornado, hurricane, external flooding, and seismic hazards analyses, such as the need to update the site-specific ground motion response spectra.
RAI-PRA Very Early Warning Fire Detection Systems (VEWFDS) utilized in the PRA In the LAR, the licensee implied that the fire PRA that will be used to support the Initiative 5b calculations will be the same fire PRA that was determined to be acceptable for the National Fire Protection Association Standard 805 (NFPA 805) transition and future self-approval.
As discussed in the February 18, 2015 (ADAMS Accession No. ML14356A227), safety evaluation on the amendment to transition the fire protection program to Section 50.48(c) of Title 10 of the Code of Federal Regulations (10 CFR), ANO-2 used the guidance in frequently asked question (FAQ) 08-0046, Closure of National Fire Protection Association 805 Frequently Asked Question 08-0046 Incipient Fire Detection Systems to incorporate its very early warning fire detection system (VEWFDS) into the fire PRA. When FAQ 08-0046 was released, there was limited test data and PRA experience available for in-cabinet applications. In December 2016, the NRC staff published new guidance on modeling VEWFDS in NUREG-2180, Determining the Effectiveness, Limitations, and Operator Response for Very Early Warning Fire Detection Systems in Nuclear Facilities, (Delores-VEWFIRE), which resulted from a confirmatory research program (including 5
the evaluation of recent operating experience) to advance the state of knowledge for in-cabinet applications. The research program was unable to confirm several key assumptions from FAQ 08-0046 that were used in the calculation of risk. Upon further evaluation of operating experience and the results of recent testing, the program determined that the risk reduction available for cabinet fires that are monitored by a VEWFDS system using the new assumptions was significantly reduced. The method provided in NUREG-2180 is more robust and technically justifiable. The methodology in NUREG-2180 is currently the best available guidance and replaces the guidance in FAQ 08-0046, which has been retired.
By letter dated November 17, 2016 (ADAMS Accession No. ML16253A111), the NRC staff informed the industry that, [i]f a licensee is performing a periodic or interim PRA update, performing a fire risk evaluation in support of self-approval, or submitting a future risk-informed license amendment request, the staffs expectation is that they will assess the impact of new operating experience and information [e.g., NUREG-2180] on their PRA analyses and incorporate the change as appropriate per Regulatory Guide 1.200, Revision 2.
- i. Explain when the guidance in NUREG-2180 will be fully incorporated into the PRA modeling or provide justification that the exclusion of the updated VEWFDS methodology has no impact on the STI evaluations.
ii. If the licensee identifies that this change will impact the STI application, then propose a mechanism that ensures the VEWFDS methodology will be updated to the PRA model used for STI calculations prior to program implementation.
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