ML19119A348

LLC Supplemental Response to NRC Request for Additional Information No. 366 (Erai No. 9292) on the NuScale Design Certification Application

ML19119A348
Person / Time
Site:	NuScale
Issue date:	04/29/2019
From:	Rad Z NuScale
To:	Document Control Desk, Office of New Reactors
References
RAIO-0419-65366
Download: ML19119A348 (7)

Text

RAIO-0419-65366 April 29, 2019 Docket No.52-048 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

NuScale Power, LLC Supplemental Response to NRC Request for Additional Information No. 366 (eRAI No. 9292) on the NuScale Design Certification Application

REFERENCES:

1. U.S. Nuclear Regulatory Commission, "Request for Additional Information No. 366 (eRAI No. 9292)," dated February 08, 2018

2. NuScale Power, LLC Response to NRC "Request for Additional Information No. 366 (eRAI No.9292)," dated April 09, 2018

3. NuScale Power, LLC Supplemental Response to NRC "Request for Additional Information No. 366 (eRAI No. 9292)," dated November 15, 2018 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) supplemental response to the referenced NRC Request for Additional Information (RAI).

The Enclosure to this letter contains NuScale's supplemental response to the following RAI Question from NRC eRAI No. 9292:

12.03-43 This letter and the enclosed response make no new regulatory commitments and no revisions to any existing regulatory commitments.

If you have any questions on this response, please contact Carrie Fosaaen at 541-452-7126 or at cfosaaen@nuscalepower.com.

Sincerely, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8H12 Samuel Lee, NRC, OWFN-8H12 Getachew Tesfaye, NRC, OWFN-8H12 Enclosure 1: NuScale Supplemental Response to NRC Request for Additional Information eRAI No.

9292 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

RAIO-0419-65366 :

NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 9292 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

Response to Request for Additional Information Docket No.52-048 eRAI No.: 9292 Date of RAI Issue: 02/08/2018 NRC Question No.: 12.03-43 Regulatory Basis Appendix A to 10 CFR Part 50 General Design Criteria for Nuclear Power Plants, Criterion (GDC) 61 Fuel Storage and Handling and Radioactivity Control, requires that new and spent fuel storage facilities include provisions for inspection and the provision for testing are important to verify that there is no corrosion of the spent fuel pool liner.

10 CFR 52.47(a)(6) requires compliance with the requirements of 10 CFR 20.1406 Minimization of contamination, which requires a description in the DCD how facility design and procedures for operation will minimize, to the extent practicable, contamination of the facility and the environment, facilitate eventual decommissioning, and minimize, to the extent practicable, the generation of radioactive waste.

10 CFR 20.1406 requires applicants to describe in the application how facility design and procedures for operation will minimize, to the extent practicable, contamination of the facility and the environment, facilitate eventual decommissioning, and minimize, to the extent practicable, the generation of radioactive waste. The acceptance criteria of NuScale DSRS Section 12.3-12.4, Radiation Protection Design Features, state that the applicant is to describe how facility design addresses the requirements of 10 CFR 20.1406.

10 CFR 20.1101(b) and 10 CFR 20.1003, require the use of engineering controls to maintain exposures to radiation as far below the dose limits in 10 CFR Part 20 as is practical. The guidance provided in NuScale DSRS Section 12.3-12.4 Radiation Protection Design Features, and Standard Review Plan (SRP) Section 9.1.2 New and Spent Fuel Storage, are consistent with and support the review of the design features provided for satisfy these regulatory requirements.

NuScale Nonproprietary

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Background===

Information contained in DCD Tier 2 Revision 0, and in the response to RAI 8963 Question 03.08.05 Question 23, dated October 17 2017, (RAI-8963-03.08.05-23) indicates that portions of the pool liner may not be covered by the pool leakage detection system (PLDS). Based on the information contained within the RAI response and the DCD, it is not clear to the staff how the applicant intends to meet the regulatory requirements for providing at an early stage of the design, sufficient information that demonstrates the capability of the PLDS to detect low leakage rates from structures containing pool water.

The Liquid Radioactive Release Task Force Final Report (ADAMS Accession No. ML062650312,) documents that radioisotopes have been released from spent fuel pools, including fission products. The report further noted that the potential exists for unplanned and unmonitored releases of radioactive liquids to migrate offsite undetected, including those portions of spent fuel pools not visible to operators. Leakage (and the resultant contamination) that enters the ground below the plant may be undetected. Radioactive contamination in groundwater onsite may migrate offsite undetected. One of the main components resulting in ground water contamination identified by the Task Force was leakage from spent fuel pools.

Key Issue 1 The NuScale response states that FSAR Tier 2, Section 9.1.3.2.5 describes the pool leakage detection system (PLDS). Per this section, the PLDS consists of floor leakage channels, perimeter leakage channels, channel drainage lines, leak collection headers, leakage rate measuring lines, and valves. The floor leakage channels are embedded in the concrete beneath the field welded seams of the pool floor liner plates in the UHS pools and the dry dock. A perimeter channel is embedded in concrete at the wall and floor liner joint area. Based on the staff interpretation of this response and information contained in the DCD, it appears that the NuScale design only monitors for leakage from welds located on the base mat and at the juncture of the walls and the base mat.

However, the guidance in SRP Section 9.1.2 does not make a distinction between those sections of the pool liner located on the wall, and those sections of the liner located on the base mat.

The acceptance criteria of DSRS Section 12.3-12.4 states that the acceptability of the design features described in the application will be based on the guidance contained in RG 4.21 and Appendix 12.3-12.4-A Evaluation and Scoping information for Structures, Systems, and Components 10 CFR 20.1406 Design Review. Attachment A of DSRS 12.3-12.4 Appendix NuScale Nonproprietary

12.3-12.4-A, specifically identifies structures, systems and components, such as spent fuel pools, separated from the environment by a single barrier, or with below grade concrete-to-concrete joints (such as the Ultimate Heat Sink pool in the NuScale Reactor Building). Appendix 12.3- 12.4-A Attachment B Examples of Structures, Systems, and Components for 20.1406 Review, specifically identifies the spent fuel pool as an area for the staff to review.

Question 1

a. Please discuss how the proposed NuScale design is consistent with the requirements of GDC 61 and 10 CFR 20.1406.

b. Alternatively, revise the DCD to include sufficient information to describe any features to address potential-leakage monitoring for all walls in contact with the pool water, including the Ultimate Heat Sink, the fuel storage area, the dry dock area and the refueling area.

OR Provide the specific alternative approaches used and the associated justification.

NuScale Response:

Background:

On a clarification call held April 2, 2019, the NRC provided the following question for discussion:

In the supplemental response to RAI 9292, Question 12.3-43, the staff noted two terms which the staff believes are typos or inadvertent use of terminology.

a. Issue 1: In the supplemental response NuScale states the following (emphasis added): Leak channels have been added to the walls behind seam welds protecting the UHS by directing leakage to the wall collection channel in the floor.

i. The problem with this term is that seam welding is an industry term for a resistance welded lap joint. This sort of weldment design would be particularly bad for the UHS liner because seam welds are prone to failure when stressed perpendicular to the plates (i.e. the hydrostatic load of the UHS). The staff believes that this statement is supposed to apply to the wall welds regardless of the weld joint design. The staff suggests modifying to wording to behind the butt NuScale Nonproprietary

joint welds (the weld design that would be expected for this application) or simply behind seam welds.

b. Issue 2: The FSAR revision associated with this RAI response adds the following sentence (emphasis added): Additional leakage channels are attached behind the wall liner plate seal welds.

i. The term used here is seal welds which does not match the RAI response.

Seal welds are used in the NuScale UHS design, but they are used on the collection channels. Verbatim compliance would require leak channels to be backed up by an additional leak channel. The same modifications as mentioned above would be acceptable: modifying to wording to wall liner plate butt joint welds (the weld design that would be expected for this application) or simply wall liner plate seam welds.

During the call, NuScale concurred with the NRC's concern and agreed to remove the terms "seam" and "seal" from the RAI response and FSAR.

The following response revises the supplemental response with the weld type removed from the text.

Supplemental Response:

NuScale has elected to change the PLDS design in the pool walls to be similar to strategies implemented by the operating fleet. Leak channels have been added to the walls behind liner welds, protecting the structural concrete of the RXB by directing leakage from the wall to a collection channel that can be inspected and cleaned. The welds and the leak channels are permanent physical features that will protect the structural concrete of the RXB from borated water during the life of the plant.

The modified NuScale liner wall design is described in the revised DCA pages accompanying this response.

Impact on DCA:

FSAR Section 9.1.3 has been revised as described in the response above and as shown in the markup provided in this response.

NuScale Nonproprietary

NuScale Final Safety Analysis Report Fuel Storage and Handling RAI 12.03-43, RAI 12.03-43S1, RAI 12.03-43S2 The PLDS consists of floor and wall leakage channels, perimeter leakage channels, channel drainage lines, leak collection headers, leakage rate measuring lines, and valves. The valves are used to isolate each channel drainage line and leakage rate measuring line. System components with the potential for contact with borated water are stainless steel. The floor leakage channels are embedded in the concrete beneath field welded seams of the pool floor liner plates in the UHS pools and dry dock that cannot be fully inspected on both sides. Additional leakage channels are attached behind the wall liner plate welds. The wall liner plates are erected prior to concrete placement. Wall liner welds are inspected on both sides of the plate before pouring concrete that covers the welds. A perimeter channel is embedded in concrete at the wall and floor liner joint area. The channels collect leakage from the pool wall and floor liner plates and direct it to a sump or to collection header piping leading to a sump in the radioactive waste drain system (RWDS). The leakage collected in the RWDS sumps is routed to the LRWS for further processing.

The PLDS will be accompanied by monitoring and surveillance by plant personnel (see COL Item 12.3-7). Section 3.2 provides the safety and seismic classifications for the system and identifies the applicable QA requirements.

Each zone of the pool leak chase system in the PLDS consists of one or more leakage channels that are interconnected to flow to one RWDS sump. The chase system segregates the PLDS into zones under the pool liner plates. Active leakage into a sump can be followed back to identify a leakage channel with flow. Leakage channels, channel drainage lines, and leak collection headers are accessible for inspection and cleaning.

As described in Section 9.3.3, the sumps in the RWDS are monitored for level. The RWDS supports the leakage detection function of the PLDS by providing local and control room indication and associated alarms when the leakage rate from the PLDS reaches a predetermined level.

9.1.3.3 Safety Evaluation The pool support systems have sufficient capacity to perform their intended functions for normal operating conditions. The ability of the SFPCS and RPCS to transfer heat from the SFAs and the NPMs for normal operations is described further below. The ability of the DWS to provide normal makeup for pool water evaporation ensures sufficient shielding for the SFAs and NPMs for normal operations. As nonsafety-related systems, the continued performance of these active functions for cooling and shielding by these systems is not credited for accident conditions.

To ensure adequate safety under accident conditions when these active systems are assumed to not operate, the UHS provides a cooling water source as described in Section 9.2.5.

General Design Criteria 2, 4, 5, 61, and 63 were considered in the design of the structures that perform the function of cooling and shielding the stored SFAs for accident conditions. Section 9.2.5 describes how the UHS conforms to these GDC and meets Regulatory Guides 1.13, 1.26, and 1.29.

Tier 2 9.1-35 Draft Revision 3