ML20234A242

NRR E-mail Capture - Diablo Canyon Additional Request for Additional Information: Exigent License Amendment Request for Application to Provide a New Technical Specification 3.7.5, Auxiliary Feedwater System, Condition G EPID: L-2020-LLA-017

ML20234A242
Person / Time
Site:	Diablo Canyon
Issue date:	08/20/2020
From:	Samson Lee NRC/NRR/DORL/LPL4
To:	Richardson M Pacific Gas & Electric Co
References
L-2020-LLA-017
Download: ML20234A242 (3)

Text

From: Lee, Samson Sent: Thursday, August 20, 2020 2:28 PM To: Richardson, Michael

Subject:

Diablo Canyon additional request for additional information: Exigent License Amendment Request for application to provide a new Technical Specification 3.7.5, Auxiliary Feedwater System, Condition G (EPID: L-2020-LLA-0176)

By letter dated August 12, 2020 (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML20225A303), Pacific Gas and Electric Company (PG&E or the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License Nos. DPR 80 and DPR-

82) for the Diablo Canyon Nuclear Power Plant (Diablo Canyon), Units 1 and 2. The proposed amendments would avoid an unnecessary plant shutdown during the expected time needed to perform potential repairs to the Unit 1 auxiliary feedwater system (AFW) piping that PG&E conservatively anticipates may be identified during Diablo Canyon, Unit 1, Cycle 22, planned upcoming inspections to the AFW system. The NRC staff has reviewed the license amendment request (LAR) and determined that additional information is required to complete the review. The NRC staff has sent requests for additional information (RAIs) on August 14, 2020, and August 17, 2020. The NRC staffs additional RAI is listed below. The staff may have additional RAIs. The staff sent the draft additional RAI to the PG&E staff and had a clarification conference call on August 19, 2020. The PG&E staff requested, and NRC agreed, to a RAI response by August 20, 2020.

The NRC staff considers that timely responses to RAIs help ensure sufficient time is available for staff review and contribute toward the NRCs goal of efficient and effective use of staff resources. Please note that if you do not respond to this request by the agreed-upon date or provide an acceptable alternate date, we may deny your application for amendment under the provisions of Title 10 of the Code of Federal Regulations, Section 2.108. If circumstances result in the need to revise the agreed upon response date, please contact me at (301) 415-3168 or via e-mail Samson.Lee@nrc.gov.

Background:

When in proposed Condition G in Technical Specification (TS) 3.7.5, steam generator (SG) 1-2 will be isolated from AFW, but the SG 1-2 will continue to be used for power generation. The accident analysis for Steam Generator Tube Rupture (SGTR) is addressed in Updated Final Safety Analysis Report (UFSAR)

Section 15.4.3. An important consideration in the accident consequence analysis is to identify the SG with the ruptured SG and isolate that SG. The analysis states that in the event of an SGTR, the plant must diagnose the SGTR and perform the required recovery actions to stabilize the plant and terminate the primary to secondary leakage. The major operator actions include identification and isolation of the ruptured SG , cool down and depressurization of the RCS to restore inventory, and termination of safety injection to stop primary to secondary leakage. The specific actions for detection are described in Item (1), which partially states: The AFW flow will begin to refill the SGs, distributing equal flow to the SGs.

Since primary to secondary leakage adds additional liquid inventory to the ruptured SG, the water level will return to narrow range earlier in that SG and will continue to increase more rapidly. This response, as indicated by the SG water level instrumentation, provides confirmation of an SGTR event and also identifies the ruptured SG.

RAI:

When in proposed Condition G of TS 3.7.5, if a SGTR were to occur in the isolated SG, provide a discussion of the impact on the SGTR accident analysis in UFSAR Section 15.4.3, with emphasis on how operator actions to detect and isolate the SG may change.

Hearing Identifier: NRR_DRMA Email Number: 744 Mail Envelope Properties (DM8PR09MB61836DFDE4DFAA75603799F49A5A0)

Subject:

Diablo Canyon additional request for additional information: Exigent License Amendment Request for application to provide a new Technical Specification 3.7.5, Auxiliary Feedwater System, Condition G (EPID: L-2020-LLA-0176)

Sent Date: 8/20/2020 2:28:10 PM Received Date: 8/20/2020 2:28:10 PM From: Lee, Samson Created By: Samson.Lee@nrc.gov Recipients:

"Richardson, Michael" <MJRm@pge.com>

Tracking Status: None Post Office: DM8PR09MB6183.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 3504 8/20/2020 2:28:10 PM Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date: