ML21033A702

Pre-submitting for Planned LAR for Standby Liquid Control Tank Volume Increase

ML21033A702
Person / Time
Site:	Brunswick
Issue date:	02/03/2021
From:	Andrew Hon Plant Licensing Branch II
To:	Krakuszeski J Duke Energy Progress
Hon A
References
EPID L-2021-LRM-0010
Download: ML21033A702 (9)

Text

Pre-Submittal Meeting - February 3, 2021 Standby Liquid Control Tank Volume Increase

SLC Tank Volume Increase Duke Attendees Steve Evans - Brunswick Nuclear Design Brad Lambert - Manager - Brunswick/Oconee Nuclear Design Mike Blom - Director - Fuel Management and Design Mark Turkal - Licensing Engineer Art Zaremba - Director - Nuclear Fleet Licensing Purpose Brief the NRC on scope and purpose of change Obtain NRC feedback prior to formal submittal 2

SLC Tank Volume Increase

Background

To comply with 10 CFR 50.62, BSEP uses a sodium pentaborate (SPB) solution with boron enriched to 92 atom-percent with boron-10 (B-10) isotope.

The current volume versus concentration limits in Figure 3.1.7 1 are established to ensure that the SLC system injects a quantity of boron which produces a concentration of 720 ppm equivalent of natural boron in the reactor coolant at 70°F with normal reactor vessel water level.

Purpose of LAR To accommodate core reload flexibility, the assumed 720 ppm equivalent of natural boron is being increased to 925 ppm.

Lower gadolinia loading The proposed change increases the minimum boron solution storage tank volume requirements of Figure 3.1.7-1.

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SLC Tank Volume Increase 4

SLC Tank Volume Increase The minimum allowable SPB volume from Figure 3.1.7-1 defines the equivalent concentration of natural boron used in reload SLC shutdown margin analysis.

Reactor coolant inventory at 70 deg F and normal vessel level SPB volume increased by 25% to allow for imperfect mixing, leakage and additional water volume found in small piping connected to reactor vessel No changes to B-10 enrichment, SPB concentration range OR reactor coolant inventory Increase in SPB volume is directly proportional to the increase in the natural boron concentration Proposed change is more restrictive than current Acceptable region in Figure 3.1.7-1 No plant changes are required based on recent SLC tank volume surveillances (SR 3.1.7.1) 5

SLC Tank Volume Increase The SLC System satisfies 10 CFR 50.62 (ATWS) requirements Compliance based on equivalency equation in Section 9.3.4.6 of BSEP UFSAR Proposed change does not effect equation variables 10 CFR 50.62 satisfied with same margin established with approval of MELLLA+ LAR The SLC System is also credited in the LOCA dose analysis to maintain suppression pool pH level above 7 Ensures iodine will be retained in the suppression pool water Additional SPB volume will increase suppression pool pH providing additional margin 6

SLC Tank Volume Increase Summary Increases core design flexibility and provides additional shutdown margin Does not increase range of previously approved concentration and volume combinations No impact on 10 CFR 50.62 compliance No adverse impact on ability to maintain suppression pool pH at or above 7.0 7

SLC Tank Volume Increase LAR Content BSEP 1 and 2 Tech Spec Markups (Figure 3.1.7-1)

BSEP 1 and 2 Revised Tech Spec Pages BSEP 1 Tech Spec Bases Markup For information only Schedule Planned submittal February 2021 Request approval March 2022 Required to support Unit 1 fuel cycle following spring refuel outage 8

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