ML18017B141

NRC Slides for Jan 18, 2018, Public Meeting to Discuss Licensee Methods of Accounting for Seismic Risk in 10 CFR 50.69 Applications Without Using a Seismic Probabilistic Risk Assessment

ML18017B141
Person / Time
Issue date:	01/17/2018
From:	Ed Miller Special Projects and Process Branch
To:	Ed Miller Special Projects and Process Branch
References
Download: ML18017B141 (16)

Text

NRR-DMPSPEm Resource From: Miller, Ed Sent: Wednesday, January 17, 2018 12:27 PM To: Miller, Ed

Subject:

NRC Slides for Jan 18, 2018, Public Meeting on 10 CFR 50.69 Attachments: Jan18_2018_public meeting 10 CFR 50_69 NRC Slides.pdf Slides for the subject meeting are attached.

1

Hearing Identifier: NRR_DMPS Email Number: 98 Mail Envelope Properties (DM5PR0901MB23928383CA83D58F33AA3C61E9E90)

Subject:

NRC Slides for Jan 18, 2018, Public Meeting on 10 CFR 50.69 Sent Date: 1/17/2018 12:26:31 PM Received Date: 1/17/2018 12:26:33 PM From: Miller, Ed Created By: Ed.Miller@nrc.gov Recipients:

"Miller, Ed" <Ed.Miller@nrc.gov>

Tracking Status: None Post Office: DM5PR0901MB2392.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 48 1/17/2018 12:26:33 PM Jan18_2018_public meeting 10 CFR 50_69 NRC Slides.pdf 430025 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

50.69 LARs NRC Observations January 18, 2018 public meeting Steve Dinsmore/ Mihaela Biro Division of Risk Assessment Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission

Topics

• Status

• Categorization Process Description

• PRA Quality Issues

• F&O Dispositions

• PRA Model Uncertainties

• External Hazards

• Passive Categorization

• Conclusions 2

Status

• Pilot submitted August 2012, issued December 2014

• Draft NEI template provided for NRC comment August 2016

- Template differed from pilot LAR

- Formal NRC review not requested, not performed

• Public meetings August 2016, January 2017, June 2017, October 2017.

• As of January 18, 2017, 9 LARs based on template in house, many more LARs expected 3

Categorization Process Description - Pilot

• The Pilot LAR included a detailed description of the process for categorization

- Procedures governing process

- Observation of trial IDP deliberations

- Observation of results of two systems categorizations

• The Pilot LAR included explanation of how the process was consistent with process endorsed in NEI 00-04

• The pilot review revealed the categorization process is fairly complex and flexible 4

Categorization Process Description - Template

• 10 CFR 50.69 (b)(2)(i) requires a description of the categorization process in LARs

• Template LAR provides no description of process

- states that the categorization process will be "in accordance with NEI 00-04"

- followed by deviations and clarifications

• Previous staff comments on LAR template

- Text in template descriptive of required information, not boilerplate

- LAR should address plant specific implementation and procedures

• Template should be revised to provide the required plant specific process description 5

Categorization Process Description - Current LARs

• NEI 00-04 contains a number of steps performed in certain order

- Changing the steps or the order could impact the results presented to the IDP and thus the categorization

• Staff has developed an RAI requesting a summary description of the process, e.g.,

- sequence of steps

- when IDP can re-assign preliminary HSS components

- component vs. function categorization

- how the passive categorization integrates in the overall process

• Expectation is that future LARs will include a plant specific summary description of process that will be implemented at the pant 6

Categorization Process Description - Plant Specific 7

PRA Quality Issues

• Adequate PRA quality needed

• Need the peer and F&O review history up to the date of the LAR

• PRA models need to reflect the current as-built, as operated plant

• All unclosed F&Os need to be reported in the LAR and dispositioned for this application

• General statement that only methods acceptable to NRC are used could help minimize RAIs about fire and seismic methods

- Summary about how this conclusion was reached should be added to the LARs

- F&Os should be consistent with this observation 8

F&O Dispositions

• F&O Disposition should either:

- justify why the F&O has no impact on the categorization, either with a reasonable technical discussion or a sensitivity study, or

- summarize an acceptable change to the PRA and commit to implementing it, followed by a focused scope peer review if it was an upgrade

• Insufficient to state that the impact of resolving F&O will be evaluated and fixed if it could affect categorization 9

PRA Model Uncertainties

• NEI 00-04 discusses [A]pplicable sensitivity studies identified in the characterization of PRA adequacy

• RG 1.201, interprets this as dealing with uncertainties associated with the licensees choice of specific models and assumptions

• NUREG-1855 discusses identifying key sources of uncertainty and assumptions

• Includes any not commonly accepted methods and assumptions

• Like F&O resolution, disposition for each important model uncertainty is PRA model specific and should be reported in the LAR 10

External Hazards

• Fire - PRA, updated FIVE (screening) in NEI 00-04; Safe Shutdown list proposal under review

• Seismic - PRA, updated SMA (screening) in NEI 00-04; generic alternative proposal part of this meeting

• Other screening (e.g., meets the SRP or low CDF) which assigns nothing to HSS based on low risk does not meet the guidance in NEI 00-04

• hazards of less magnitude but higher frequency not automatically low risk

• SSCs that cause low CDF/LERF might be HSS

• Step in Fig. 5-6 asks if removal of SSC could result in screened scenario becoming unscreened 11

External Hazards (contd)

• Figure 5-6 in Section 5.4 of NEI 00-04 summarizes the process that begins with the SSC selected for categorization and then proceeds through the flow chart for each external hazard 12

Passive Categorization

• ANO-2 passive categorization methodology excludes all Class 1 pressure boundary components

• Code Case N-660 allows including the following Class 1 components, but includes additional steps

i. breaks small enough for makeup provided by the reactor coolant makeup system; or ii. The component is or can be automatically isolated from the reactor coolant system by two valves in series

• RG 1.147, referenced in RG 1.201, accepted Code Class N-660 with limitation that it must be applied to only Code Class 2 and 3, and non-code

• Deviation from ANO-2 or accepted N-660 is not a short term solution 13

Conclusions

• LARs need to include categorization process summary description

• RG 1.200 PRA quality guidelines apply

• Any deviations should be minimized

• Methods not accepted by NRC should be avoided

• Consistency with Figure 5-6 should be demonstrated in LAR

• Passive categorization should not deviate from accepted methods in LARs 14