ML19347A394
| ML19347A394 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/13/2019 |
| From: | NRC |
| To: | NRC/NRR/DNRL |
| References | |
| Download: ML19347A394 (14) | |
Text
From: Rankin, Jennivine Sent: Friday, December 13, 2019 8:17 AM To: Vogtle PEmails
Subject:
Vogtle 3&4: Request for Tech Exchange Regarding CMT Boron Concentration Surveillance Attachments: LAR-231 NRC Technical Exchange.pdf Slidedeck for the Vogtle 3 and 4 public meeting on 12/19/2019.
From: Henderson, Ryan Donald <RDHENDER@SOUTHERNCO.COM>
Sent: Thursday, December 12, 2019 6:17 PM To: Rankin, Jennivine <Jennivine.Rankin@nrc.gov>
Cc: Patel, Chandu <Chandu.Patel@nrc.gov>; Santos, Cayetano <Cayetano.Santos@nrc.gov>; Humphrey, Mark Phillips <MPHUMPHR@southernco.com>; Byers, Jerri D. <JDBYERS@southernco.com>;
Chamberlain, Amy Christine <ACCHAMBE@southernco.com>
Subject:
[External_Sender] RE: Vogtle 3&4: Request for Tech Exchange Regarding CMT Boron Concentration Surveillance
- Jennie, See attached for the slides for next weeks meeting. As a reminder, we plan to participate via conference call. Please let me know if you have any questions.
- Thanks, Ryan Henderson Licensing Office: 205-992-6426 Cell: 205-613-0342
Hearing Identifier: Vogtle_COL_Docs_Public Email Number: 512 Mail Envelope Properties (BY5PR09MB4818D0037E2CBCBBC8D85A5998540)
Subject:
Vogtle 3&4: Request for Tech Exchange Regarding CMT Boron Concentration Surveillance Sent Date: 12/13/2019 8:16:59 AM Received Date: 12/13/2019 8:17:05 AM From: Rankin, Jennivine Created By: Jennivine.Rankin@nrc.gov Recipients:
"Vogtle PEmails" <Vogtle.PEmails@nrc.gov>
Tracking Status: None Post Office: BY5PR09MB4818.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 851 12/13/2019 8:17:05 AM LAR-231 NRC Technical Exchange.pdf 462071 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Core Makeup Tank Boron Concentration Surveillance Requirement (WEC LAR 231)
Technical Exchange Meeting 12/19/2019
Agenda
- Background
- Problem Statement
- Proposed Path Forward
- Core Makeup Tank (CMT) Conditional Sampling
- Questions/Discussion
Background
- CMTs provide sufficient borated water to assure Reactor Coolant System (RCS) reactivity and inventory control for all design basis accidents (DBAs).
- The CMTs are in open communication with the RCS cold legs via a balance line.
- During operation, current Technical Specification Surveillance Requirements verify every 7 days that the boron concentration in each CMT is within the required limits.
- The sampling is performed utilizing the Primary Sampling System which has sampling taps at the top and bottom of the CMTs. Prior to collection of the sample, the sample lines are purged with liquid from the CMT to provide a representative sample. The purging flow is routed to the effluent holdup tank.
Problem Statement
- The frequent sampling, which involves the purging flow, results in the removal of borated water from the CMT which is replaced by RCS water via the balance line. RCS water is typically at a more dilute boron concentration; therefore, the CMT is diluted by the makeup from the RCS at each sampling.
- Over the course of an 18 month operating period there is the possibility that the sampling alone could directly cause the CMT boron concentration to fall to a point which would trigger the need for borated makeup (or multiple makeups) to the CMT.
This is undesirable because it forces water in the balance line back into the RCS cold leg.
Proposed Path Forward
- Increase the upper limit of the boron concentration for the CMT
- Increase the weight of trisodium phosphate (TSP) provided for post-accident floodup pH adjustment
- Provide conditional sampling of the CMT
Supporting Technical Information
- Increasing the upper limit of the boron concentration is evaluated to not require revision to safety analyses for shutdown margin since those evaluations utilize the lower limit. The revision to the upper limit allows CMT makeup to come from undiluted Boric Acid Storage Tank (BAST) contents; therefore, the initial boron concentration of the CMTs is assumed to be at the nominal BAST concentration. The increase in boron is negligible for the purposes of boron precipitation margin.
pH Adjustment Markup LCO 3.6.8 The pH adjustment baskets shall contain 25,92026,460 lbs of trisodium phosphate (TSP).
SURVEILLANCE FREQUENCY SR 3.6.8.1 Verify the pH adjustment baskets contain 24 months 25,92026,460 lbs of TSP.
CMT Boron Concentration Markup SURVEILLANCE FREQUENCY SR 3.5.2.5 Verify the boron concentration in each CMT is 3400 7 days ppm, and 37004500 ppm. See next slide
Conditional CMT Boron Sampling
- For the frequency of the surveillance, we are proposing to monitor various indications of potential CMT dilution (e.g. from leakage or sampling) which would then cause the need to sample.
- Potential leak paths out of the CMT are through various instrumentation lines, CMT outlet valve leakage into the RCS, or sample/drain lines.
- Potential sources of makeup into the CMT are from the balance lines or from the makeup lines.
- Most leak paths out of the CMTs would be detectable as RCS LEAKAGE via other TS requirements.
- Leak paths from the CMTs into RCS would be detectable as impacts on reactivity.
Conditional CMT Boron Sampling (cont)
- By sampling less frequently, CMT boron dilution is made less likely.
- By providing bounding analysis, conservatively assumed leak paths from the CMT can be detected via monitoring and trigger a sample verification of the boron concentration before the leak can cause inoperability of the CMT via diluting the boron concentration.
Applicable Regulatory Requirements
- 10 CFR 50.36, Technical specifications.
- General Design Criteria (GDC) 4, Environmental and dynamic effects design bases
- GDC 27, Combined reactivity control systems capability.
- GDC 35, Emergency core cooling
- GDC 37, Testing of emergency core cooling system
- RG 1.45, Rev. 0, Reactor Coolant Pressure Boundary Leakage Detection Systems
Questions / Discussion