ML16337A332

Request for Additional Information Regarding License Amendment Request for Electrical Power System Alignments for Shared Systems

ML16337A332
Person / Time
Site:	Catawba
Issue date:	01/12/2017
From:	Michael Mahoney Plant Licensing Branch II
To:	Henderson K Duke Energy Carolinas
Orenak M, NRR/DORL/LPL2-1
References
CAC MF7748, CAC MF7749
Download: ML16337A332 (6)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 12, 2017 Mr. Kelvin Henderson Vice President Catawba Nuclear Station Duke Energy 4800 Concord Road I CN01VP York, NC 29745

SUBJECT:

CATAWBA NUCLEAR STATION, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST FOR ELECTRICAL POWER SYSTEMS ALIGNMENTS FOR SHARED SYSTEMS (CAC NOS. MF7748 AND MF7749)

Dear Mr. Henderson:

By letter dated May 26, 2016 (Agencywide Documents Access and Management System Accession No. ML16147A105), Duke Energy, Inc. (the licensee) requested approval for an updated final safety analysis report (UFSAR) change for the Catawba Nuclear Station (CNS),

Units 1 and 2. CNS proposes to add descriptions to several sections of the UFSAR to clarify how a shutdown unit supplying either its normal or emergency power source may be credited for operability of shared components supporting the operating unit.

The U.S. Nuclear Regulatory Commission staff has reviewed the licensee's submittal and determined that additional information is needed in order to complete its review. Please provide your response to the enclosed request for additional information within 30 days of the date of this letter.

If you have any questions, please contact me at 301-415-3867 or by e-mail to Michael.Mahoney@nrc.gov.

!&A

~chael Mahoney, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-413 and 50-414

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO REVISE THE UPDATED FINAL SAFETY ANALYSIS REPORT TO REFLECT ELECTRICAL POWER SYSTEMS ALIGNMENTS FOR SHARED SYSTEMS DUKE ENERGY CAROLINAS. LLC CATAWBA NUCLEAR STATION, UNITS 1 AND 2 DOCKET NOS. 50-413 AND 50-414 By letter dated May 26, 2016 (Agencywide Documents Access and Management System Accession No. ML16147A105), Duke Energy, Inc. (the licensee) requested approval for an updated final safety analysis report (UFSAR) change for the Catawba Nuclear Station (CNS),

Units 1 and 2. CNS proposes to add descriptions to several sections of the UFSAR to clarify how a shutdown unit supplying either its normal or emergency power source may be credited for operability of shared components supporting the operating unit.

The U.S. Nuclear Regulatory Commission staff needs the following additional information to complete its review of the license amendment request (LAR).

Request for Additional Information (RAI) 5 With a single line diagram, please explain how the electrical systems for each unit (power sources (both alternating current (ac) and direct current (de), ac medium voltage buses and switchgears, distribution panels, load centers, motor control centers, and shared loads) are configured. For the following operating configurations, please identify (1) the applicable electrical-related technical specification (TS) requirements for each unit; (2) the operability of each shared structure, system, and component (SSC) (i.e., nuclear service water system (NSWS), control room area ventilation system (CRAVS), control room area chilled water system (CRACWS), and the auxiliary building filtered ventilation exhaust system (ABFVES)); and (3) the applicable TS required actions:

a. When both units are in Modes 1-4;

b. When both units are in Modes 1-4 and Train A of one unit is undergoing engineered safety feature (ESF) testing;

c. When both units are in Modes 1-4 and Train A of both units is undergoing ESF testing, if performed;

d. When one unit (Unit 1) is in Modes 1-4 and the other unit is in Modes 5-6; and Enclosure

e. When one unit (Unit 1) is in Modes 1-4 and the other unit is in Modes 5-6 and undergoing ESF testing.

The regulation at Title 10 of the Code of Federal Regulations (1 O CFR) 50.36(c)(2)(ii)(C),

"Criterion 3," states that a TS Limiting Condition for Operation (LCO) must be established for:

A structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier.

(1) Please review the following scenarios as an example:

a. Both units are in Mode 1 requiring all four emergency diesel generators (EDGs) to be OPERABLE to meet TS 3.8.1 for each unit. CNS, Unit 2, suffers a loss of coolant accident (LOCA) and both units suffer a loss of offsite power (LOOP).

CNS, Unit 2, needs at least one CNS, Unit 1, EOG (either 1A or 1B) and the distribution systems to mitigate the LOCA, assuming a single failure of either 2A or 2B EDGs.

However, TS 3.8.1 for CNS, Unit 2, does not include the CNS, Unit 1, EDGs (i.e., TS 3.8.1 does not require all four EDGs), nor does TS 3.8.9 for CNS, Unit 2, include the CNS, Unit 1, power distribution systems. Even without postulating a single failure (i.e., EOG failure), CNS, Unit 2, still needs at least one of the CNS, Unit 1, EDGs to mitigate the LOCA.

Please explain how compliance with 10 CFR 50.36(c)(2)(ii)(C) is achieved in this scenario considering that a CNS, Unit 1, EOG is required to mitigate a CNS, Unit 2, LOCA, or provide proposed TS changes.

b. CNS, Unit 1, is in Mode 5 with 1A EOG inoperable and meets TS 3.8.2. CNS, Unit 2, is in Mode 1 and meets TS 3.8.1 and TS 3.8.9. Neither unit is in a TS ACTION statement.

CNS, Unit 2, suffers a LOCA and both units suffer a LOOP. The 2B EOG fails, leaving only the 1B and 2A EDGs OPERABLE.

Depending on the lineup of the current power supply (both medium and low voltage buses) and valve lineup of the shared systems (NSWS, CRAVS, CRACWS, and ABFVES), CNS, Unit 2, may need the 1B EOG and associated distribution systems to mitigate the LOCA. However, TS 3.8.1 does not include the CNS, Unit 1, EDGs; TS 3.8.9 does not include any CNS, Unit 1, power distribution systems; nor are any required conditions for the shared systems in the CNS, Unit 2, TS.

Please explain how compliance with 10 CFR 50.36(c)(2)(ii)(C) is achieved in this scenario considering that a CNS, Unit 1, EOG is required to mitigate a CNS, Unit 2, LOCA, or provide proposed TS changes.

(2) Please provide a discussion of why the existing CNS TSs for electric systems (both ac and de) are conservative to support dual unit operation considering the operability requirements for shared systems when a CNS unit is operating or provide proposed TS changes in accordance with (10 CFR) 50.36(c)(2)(ii)(C).

RAI 7

UFSAR Section 8.3.1.1.2.3.2, "Periodic Testing," states, in part:

The normal and emergency AC [alternating current] power distribution systems for both units at Catawba are separate during normal operation. During testing on Unit 2, the power systems on Unit 1 will be lined up in their normal operating configurations, which will assure that cross-ties are not present which could affect availability of emergency power to Unit 1 during testing on Unit 2.

a. Please clarify whether there are any cross-tie between CNS, Unit 1, and CNS, Unit 2, and between divisions within each unit. If cross-ties exist, explain how CNS meets 10 CFR Part 50, Appendix A, "General Design Criteria for Nuclear Power Plants," Criterion 5, "Sharing of structures, systems, and components."

b. Please explain, with a diagram, how the above UFSAR statement is met during normal operation with ESF testing and also when one unit's emergency diesel generator (EOG) is inoperable.

During Train A load sequence testing, please state which shutdown unit's diesel generator would be credited as OPERABLE to support Train A equipment to satisfy the following proposed UFSAR statement:

The credited offsite power circuit and emergency diesel generator associated with the shutdown unit meet applicable TS 3.8.1 requirements ...

Please describe how this statement would avoid an "unnecessary TS 3.0.3 entry" if a Train B component was discovered inoperable on the operating unit.

Is CNS LCO 3.0.9 ever applied to the CNS safety related-electrical systems? If yes, please describe the circumstances.

RAI 10

The TS bases for the NSWS, CRAVS, CRACWS, and ABFVES currently state, in part,

A shutdown unit supplying its associated emergency source (1 EMXG/2EMXH) cannot be credited for OPERABILITY of components supporting the operating unit.

According the supplemental letter dated November 10, 2016 (ADAMS Accession No. ML16315A411), the licensee plans to remove the above statement from the TS bases upon approval of the LAR.

Please identify and discuss the reasons and intent for the TS bases statement above that does not allow crediting a shutdown unit supplying its associated emergency source (1 EMXG/2EMXH) to be credited for OPERABILITY of components supporting the operating unit.

ML16337A332 *Via Email OFFICE NRR/DORL/LPL2-1 /PM NRR/DORL/LPL2-1 /LA NRR/DE/EEEB/BC NRR/DORL/LPL2-1 /BC NAME MMahoney KGoldstein JZimmerman* MMarkley DATE 01/11/17 01/11/17 11/22/16 01/12/17 OFFICE NRR/DORL/LPL2-1 /PM NAME MMahoney DATE 01/12/17