ML23059A228

NRR E-mail Capture - Draft RAIs for Containment Buffer Change to Natb (L-2022-LLA-0162)

ML23059A228
Person / Time
Site:	North Anna
Issue date:	02/28/2023
From:	Ed Miller Plant Licensing Branch II
To:	Sinha S Dominion Generation
References
L-2022-LLA-0162
Download: ML23059A228 (6)

Text

From: Ed Miller Sent: Tuesday, February 28, 2023 10:30 AM To: Shayan.Sinha@dominionenergy.com

Subject:

Draft RAIs for Containment Buffer Change to NaTB (L-2022-LLA-0162)

Attachments: North Anna NaTB LAR Draft RAI R3.docx Mr. Sinha, Attached is the NRC staffs draft RAI for the subject request. The questions are being transmitted to you to determine 1) If the questions clearly convey the NRC information needs, 2)

Whether the regulatory basis for the questions are clear, and 3) If the information has already been provided in existing docketed correspondence. Additionally, review of the draft question will allow you to determine what response time you can support. After youve had a chance to review, please let me know if you would like to have a clarification call or public meeting to discuss. Thank you.

Ed Miller (301) 415-2481

Hearing Identifier: NRR_DRMA Email Number: 1964 Mail Envelope Properties (SA1PR09MB7487E39E1D5C11FC9A6BB58BE9AC9)

Subject:

Draft RAIs for Containment Buffer Change to NaTB (L-2022-LLA-0162)

Sent Date: 2/28/2023 10:30:09 AM Received Date: 2/28/2023 10:30:00 AM From: Ed Miller Created By: Ed.Miller@nrc.gov Recipients:

"Shayan.Sinha@dominionenergy.com" <Shayan.Sinha@dominionenergy.com>

Tracking Status: None Post Office: SA1PR09MB7487.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 644 2/28/2023 10:30:00 AM North Anna NaTB LAR Draft RAI R3.docx 37006 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION LICENSE AMENDMENT REQUEST (LAR) TO REVISE TECHNICAL SPECIFICATION (TS) 3.6.8 LIMITING CONDITION FOR OPERATION TO REMOVE THE REFUELING WATER CHEMICAL ADDITION TANK AND REPLACETHE CONTAINMENT SUMP BUFFER NORTH ANNA POWER STATION, UNITS 1 AND 2 NRC DOCKET NOS. 50-338 and 50-339 (L-2022-LLA-0162)

By Letter dated November 3, 2022 (Agencywide Documents Access Management System (ADAMS) Accession No. ML22307A317), Virginia Electric and Power Company (Dominion Energy Virginia, the licensee) requested amendments to North Anna Power Station (NAPS),

Units 1 and 2, Renewed Facility Operating License Numbers NPF-4 and NPF-7, respectively.

The proposed amendment would revise the NAPS, Units 1 and 2, TS to eliminate the Refueling Water Chemical Addition Tank (CAT) and allow the use of sodium tetraborate decahydrate (NaTB) to replace sodium hydroxide (NaOH) as a chemical additive (buffer) for Containment sump pH control.

The NRC staff has reviewed the LAR. As a result of its review, the NRC staff has determined that the following additional information is needed to complete its review of the LAR.

ELTB RAI - 1 The regulations in 10 CFR 50.49, Environmental qualification of electric equipment important to safety for nuclear power plants, requires, in part, licensees to establish a program for qualifying electric equipment important to safety as defined in 50.49(b). The regulation in 50.49(e) requires that the electric equipment qualification program must include and be based on the following parameters: temperature and pressure, humidity, chemical effects, radiation, aging, submergence, synergistic effects, and margins.

Section 3.1.6, Environmental Qualification (EQ) of Equipment, of the submittal dated November 3, 2022, provides the licensees evaluation of the impact the proposed changes have on the chemical parameters for equipment subject to 10 CFR 50.49. It is not apparent, however, that the licensee discussed the impact of the proposed changes on other environmental parameters that affect EQ of electric equipment such as temperature, pressure, radiation, etc.

Provide a discussion on the impact of the proposed changes on the other environmental parameters specified in 10 CFR 50.49(e).

NCSG RAI - 1 Page 14 of 26 in attachment 1 of the submittal dated November 3, 2022, states that each of the 8 empty baskets weighs 1,456lbs. The weight of each basket when loaded with sodium tetraborate is stated to be approximately 4,450lbs. Subtracting the weight of the empty basket from the total loaded weight results in 2,985lbs of sodium tetraborate per basket. The combined weight of sodium tetraborate for 8 baskets would be 23,880lbs. This amount exceeds the proposed TS limit for maximum mass of sodium tetraborate which is stated as 22,192 lbs.

Explain how the maximum TS value for sodium tetraborate will not be exceeded given the design parameters of a fully loaded basket described above.

SNSB RAI - 1 The following General Design Criteria of Title 10 of Code of Federal Regulations (CFR), Part 50, Appendix A, whose conformity is discussed in Chapter 3 of the North Anna UFSAR, are applicable for containment design:

Criterion 16Containment design. Reactor containment and associated systems shall be provided to establish an essentially leak-tight barrier against the uncontrolled release of radioactivity to the environment and to assure that the containment design conditions important to safety are not exceeded for as long as postulated accident conditions require.

Criterion 38Containment heat removal. A system to remove heat from the reactor containment shall be provided. The system safety function shall be to reduce rapidly, consistent with the functioning of other associated systems, the containment pressure and temperature following any loss-of-coolant accident and maintain them at acceptably low levels.

Criterion 50Containment design basis. The reactor containment structure, including access openings, penetrations, and the containment heat removal system shall be designed so that the containment structure and its internal compartments can accommodate, without exceeding the design leakage rate and with sufficient margin, the calculated pressure and temperature conditions resulting from any loss-of-coolant accident. This margin shall reflect consideration of (1) the effects of potential energy sources which have not been included in the determination of the peak conditions, such as energy in steam generators and as required by § 50.44 energy from metal-water and other chemical reactions that may result from degradation but not total failure of emergency core cooling functioning, (2) the limited experience and experimental data available for defining accident phenomena and containment responses, and (3) the conservatism of the calculational model and input parameters.

In its letter dated November 3, 2022, Attachment 1, Section 4.1, Applicable Regulatory Requirements/Criteria, states that the ability of the quench spray (QS) and recirculation spray (RS) subsystems to cool the reactor core and return the containment to subatmospheric pressure and maintain it at subatmospheric pressure is not affected by the proposed change. It also states that the proposed change will not impact the ability of NAPS to comply with the requirements of Criterion 38. It is not, however, apparent that a technical evaluation of these results is provided in Section 3.0, Technical Evaluation.

Based on the proposed change, the combined effect of parameters given below could impact the loss-of-coolant accident (LOCA) containment response.

• The reduction of containment free volume from the addition of NaTB baskets.

• Removal of NaOH from the refueling water storage tank (RWST) water in the analysis of record (AOR) would affect its density and, therefore, impact the QS pump performance and flow rate.

• Addition of NaTB and removal of NaOH from the sump water in the AOR would affect its density and, therefore, impact RS pump performance and flow rate during the LOCA recirculation phase.

• Change in the performance of the RS cooler due to change in flow rate and its overall heat transfer coefficient.

• Change in the properties of the QS and RS droplets.

Due to the combined effect of the changes in above parameters and/or any other, provide a discussion of changes and impact on the following:

(a) LOCA containment pressure and temperature response AOR results.

(b) Net positive suction head (NPSH) AOR results for the pumps that draw water from the sump during LOCA recirculation phase.

ESEB RAI 1

Background:

The following General Design Criteria of Title 10 of Code of Federal Regulations (CFR), Part 50, Appendix A, whose conformity is discussed in Chapter 3 of the North Anna UFSAR, are applicable for containment design:

10 CFR 50, Appendix A, General Design Criterion (GDC) 1, Quality standards and records, with respect to ensuring that the structures important to safety other than containment are designed, fabricated, erected, constructed, tested, and inspected to quality standards commensurate with the safety function to be performed.

10 CFR Part 50, Appendix A, GDC 2, Design bases for protection against natural phenomena, as it relates to the design of seismic Category I structures, systems, and components (SSCs),

requires, in part, that the SSCs important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, floods, tsunami, and seiches without loss of capability to perform their safety functions.

In its letter dated November 3, 2022, (ADAMS Accession No. ML23017A317), the licensee states in Subsection 3.2.1, NaTB Basket Design,:

The baskets are classified as Non-safety Quality (NSQ) based on not being functionally safety-related, but are required to be seismically anchored to prevent damage to nearby safety-related equipment. The baskets are also required to remainfunctional (i.e., some of or all their passive functions must remain intact) during and/or after a Design Basis Event (DBE). Therefore, the baskets are designed to meet Seismic II/I requirements and maintain their structural integrity during a DBE.

The design loads for the baskets are generated by combining the unfactored load effects of dead loading, chemical pressure loading, and seismic loading. The NaTB baskets were evaluated to maintain their structural integrity during an Earthquake DBE concurrent with post-LOCA elevated temperature conditions.

The basket members and connections are analyzed to meet applicable licensing and design basis requirements in the NAPS Updated Final Safety Analysis Report (UFSAR) for Unit 1 and Unit 2 and Dominion Energy Nuclear Engineering Standard (DNES)

DNES-VA-CE-0046, American Institute of Steel Construction (AISC) 9th Edition, "Manual of Steel Construction" [Reference 12].

Issue/Request:

a) Although, the NaTB is placed in granular form in baskets, it is not apparent whether additional forces or moments can result from movement of the NaTB within the baskets during seismic events and/or due to eccentric or non-uniform loading of the NaTB and may affect the walls or anchorage of the baskets. Discuss whether the forces generated from movement and/or eccentric/non-uniform loading of the NaTB within the baskets were considered in the seismic analysis.

b) It is not apparent whether the anchorage patterns of the NaTB baskets can be placed at the sites as qualified in the analytical report(s). Discuss whether the anchorage patterns of the NaTB baskets, as qualified in the analytical report(s), can be placed with acceptable engineering tolerances during the installation process at the sites.

c) It is not apparent whether prying effects on the anchor loads were considered in qualifying the anchors and associated baseplates. Describe whether the anchor loadings include prying effects to qualify the anchors and associated base plates. If not, describe why prying effect on anchors were not considered.

d) It is not apparent whether the material compositions of the NaTB basket and its anchorage system may be vulnerable to or could cause dissimilar-metal corrosion that could degrade the structural integrity of anchorages over the remaining period of the renewed facility operating license. Describe whether dissimilar-material condition exists between the NaTB basket and the anchorage system, and whether there would be a condition of dissimilar-metal corrosion. Describe whether a plant periodic condition monitoring program (new or existing) will be initiated to ensure the structural integrity of basket anchorages during the extended period of operation.

e) The application did not provide engineering/fabrication drawings of the basket and refer to any associated analytical report(s) in the application. Provide engineering/fabrication drawings and analytical report(s) of the NaTB basket(s).