L-16-016, Response to NRC Rais Regarding Generic Letter 2016-01

Response to NRC Rais Regarding Generic Letter 2016-01

ML18151B046
Person / Time
Site:	Vogtle
Issue date:	05/31/2018
From:	Gayheart C Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GL-16-016, NL-18-0688
Download: ML18151B046 (4)

Text

• Southern Nuclear May 31, 2018 Docket Nos.: 50-424 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Regulatory Affairs Vogtle Electric Generating Plant-Unit 1 Response to NRC RAis Regarding Generic Letter 2016-01 Ladies and Gentlemen:

40 Inverness Center Parkway Post Office Box 1295 Birmingham, AL 35242 205 992 5000 tel 205 992 7601 fax NL-18-0688 By letter dated November 2, 2016, Southern Nuclear Operating Company (SNC) provided a response to Nuclear Regulatory Commission (NRC) Generic Letter (GL) 2016-01, "Monitoring of Neutron Absorbing Materials in Spent Fuel Pools" for Vogtle Electric Generating Plant, Unit 1.

By letter dated November 7, 2017, the NRC requested supplemental information to complete its review.

Enclosed is the SNC response.

This letter contains no NRC commitments. If you have any questions, please contact Jamie Coleman at (205) 992-6611.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on May 31, 2018.

efb/scm

Enclosure:

Response to NRC RAis Regarding Generic Letter 2016-01 cc:

NRC Regional Administrator, Region II NRC NRR Project Manager-Vogtle NRC Senior Resident Inspector-Vogtle SNC Records RTYPE: CVC7000

Vogtle Electric Generating Plant Unit 1 Enclosure Response to NRC RAis Regarding Generic Letter 2016-01

Enclosure to NL-18-0688 SNC Response to GL 2016-01 RAis - Vogtle Unit 1 NRC Request for Supplemental Information Generic Bora/

For licensees that utilize neutron-absorbing materials (NAM) in the Spent Fuel Pool (SFP), the 10B areal density (AD) of the NAM must be verified so that the assumption for the 10B minimum AD in the SFP criticality analysis is supported. The NRC staff needs to ensure the programs are in place to monitor the condition of NAM in the SFP are appropriate for their intended purpose. In addition, the condition of the NAM must be considered in the SFP nuclear criticality analysis (NCS) analysis of record (AOR). To verify that the potential reactivity changes due to degradation of physical changes to the NAM are accounted for in the SFP NCS AOR, the following information is requested. This includes any changes that would affect the neutron spectrum for the SFP in addition to any loss of neutron attenuation capability.

Industry operating experience, as described in Information Notices 2009-26, "Degradation of Neutron Absorbing Materials in the Spent Fuel Pool," (ML092440545) and 1983-29, "Fuel Binding Caused by Fuel Rack Deformation," (ML14043A291) has demonstrated that certain manufacturing processes and plant conditions (dose, chemistry, length of time installed, and installed configuration) have resulted in material deformation as a result of blisters or bulging associated with Bora/.

Vogtle Electric Generating Plant (VEGP) does not appear to have a site-specific monitoring program and, consequently, SNC is relying on general operating experience as a surrogate for the condition of the Bora/ installed in the spent fuel pool.

Vogtle-RAI-1. Please describe how industry operating experience bounds the condition of the Bora/ at VEGP, thereby providing assurance that any degradation or deformation that may affect the Bora/ at VEGP is identified.

SNC Response Through its Nuclear Safety Culture, procedures, and processes, VEGP systematically and effectively collects, evaluates, and implements relevant internal and external operating experience (OE) in a timely manner. Issues emerging from the use of Boral in the spent fuel racks are monitored through the VEGP OE Program and Corrective Action Program. As indicated in the original Generic Letter response for VEGP, the site will continue to monitor industry OE related to Boral, which includes ongoing participation in the EPRI Neutron Absorber Users Group (NAUG) and its related programs (e.g., industrywide learning aging management).

Industry-wide, to date, there have been no indications of a loss of Boral material of a nature that diminished the neutron-absorbing capability of the Bora I. (See EPRI Report 1021052: Overview of BORAL Performance Based Upon Surveillance Coupon Measurements.) VEGP follows the EPRI Water Chemistry Control Program guidelines and there has been no indications of a loss of Boral neutron-absorbing capabilities at a plant following these guidelines. In addition, to date, there are no plant-specific operating conditions or rack design attributes that would merit concern that the VEGP spent fuel racks or SFP environment are not bounded by the industry-wide OE. Finally, EPRI Report 3002013119 documents that observed or foreseen degradation or deformation of the Boral has an insignificant impact on SFP criticality. (See EPRI Report 3002013119: Evaluation of the Impact of Neutron Absorber Material Blistering and Pitting on Page E-1

Enclosure to NL-18-0688 SNC Response to GL 2016-01 RAis - Vogtle Unit 1 Spent Fuel Pool Reactivity.) Consequently, the industry OE aligns with the VEGP licensing basis.

The NAUG, through EPRI, is currently developing an industrywide program/database to aid in monitoring indications of potential Boral degradation and deformation. Over 70,000 water chemistry data points have been collected to date, from over 30 SFPs, for this program.

Surveillance data from 50 coupons across 25 SFPs has also been collected to date. The program, supported by EPRI NAUG and industry participants, is described in EPRI Report 3002013122 and includes insights and feedback received from numerous communications with the NRC. (See EPRI Report 3002013122: Roadmap for the lndustrywide Learning Aging Management Program (i-LAMP) For Neutron Absorber Materials in Spent Fuel Pools.) Relevant issues emerging from this industry effort will be monitored through the VEGP OE Program and Corrective Action Program.

Vogtle-RAI-2. Please discuss the criticality impact due to relevant material deformation identified in general industry operating experience, and how it can be accommodated by the nuclear criticality safety analysis of record for VEGP without exceeding NRC subcriticality requirements.

SNC Response To date, the industry OE has revealed no instances of an impact on SFP criticality due to observed Boral deformation (e.g. blistering) or degradation (e.g. pitting). The NAUG, through EPRI, has recently completed a study which analyzes the criticality impact of blisters and pits on Boral. (See EPRI Report 3002013119: Evaluation of the Impact of Neutron Absorber Material Blistering and Pitting on Spent Fuel Pool Reactivity.) Simulations were performed for varying enrichment, burnup, areal density values, at unborated conditions (0 ppm), which is conservative for Pressurized Water Reactors such as VEGP. The study results demonstrate that pitting and blistering, on a scale much larger than any that has been observed in the industry OE, has an insignificant impact on SFP criticality. Therefore, the SFP criticality safety analysis of record remains applicable.

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