ML17269A203

LLC Response to NRC Request for Additional Information No. 109 (Erai No. 8949) on the NuScale Design Certification Application

ML17269A203
Person / Time
Site:	NuScale
Issue date:	09/26/2017
From:	Rad Z NuScale
To:	Document Control Desk, Office of New Reactors
References
RAIO-0917-56211
Download: ML17269A203 (8)

Text

RAIO-0917-56211 September 26, 2017 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 Response to NRC Request for Additional Information No.

109 (eRAI No. 8949) on the NuScale Design Certification Application

REFERENCE:

U.S. Nuclear Regulatory Commission, "Request for Additional Information No.

109 (eRAI No. 8949)," dated July 29, 2017 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) response to the referenced NRC Request for Additional Information (RAI).

The Enclosure to this letter contains NuScale's response to the following RAI Question from NRC eRAI No. 8949:

21.0-1 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 Steven Mirsky at 240-833-3001 or at smirsky@nuscalepower.com.

Sincerely, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8G9A Samuel Lee, NRC, OWFN-8G9A Prosanta Chowdhury NRC, OWFN-8G9A : NuScale Response to NRC Request for Additional Information eRAI No. 8949 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

RAIO-0917-56211 :

NuScale Response to NRC Request for Additional Information eRAI No. 8949 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.: 8949 Date of RAI Issue: 07/29/2017 NRC Question No.: 21.0-1 10 CFR 52.47(c)(3) states that [a]n application for certification of a modular nuclear power reactor design must describe and analyze the possible operating configurations of the reactor modules with common systems, interface requirements, and system interactions. 10 CFR 50 Appendix A General Design Criteria 5Sharing of structures, systems, and components states that Structures, systems, and components important to safety shall not be shared among nuclear power units unless it can be shown that such sharing will not significantly impair their ability to perform their safety functions, including, in the event of an accident in one unit, an orderly shutdown and cooldown of the remaining units.

NuScale Design Certification Application (DCA), Final Safety Analysis Report (FSAR) Tier 2, Chapter 9, Section 9.4.2, Reactor Building and Spent Fuel Pool Area Ventilation System, identifies a presence of an Annex Building HVAC System (ANBVS) and, NuScale document ER-P070-3938, Shared System Hazards Analysis, Revision 0, which was provided for staff audit, identified ANBVS as serving 12 nuclear power modules. However, NuScale DCA, FSAR Tier 2, Chapter 21, Multi-Module Design Considerations, does not identify ANBVS as a shared system.

Staff requests that NuScale update Chapter 21 to include and describe ANBVS, or justify why it is not necessary.

NuScale Response:

The Annex Building HVAC System (ABVS) is a shared system, supporting 12 NPMs, that provides heating, ventilation, and air conditioning for the annex building. A fault in this system does not contribute to any initiating event frequency. An initiator is not modeled because the equipment in the annex building is not relied on for plant operations nor does it serve a role in accident mitigation.

Tier 2, FSAR Table 21-1: Shared Systems not Associated with Design Basis Event Initiators has been updated to include this system.

NuScale Nonproprietary

Impact on DCA:

FSAR Section 9.4.2 and FSAR Table 21-1 have 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 Air Conditioning, Heating, Cooling, and Ventilation Systems 9.4.2 Reactor Building and Spent Fuel Pool Area Ventilation System The Reactor Building (RXB) contains a single air volume encompassing the reactor pool, the refueling pool, spent fuel pool (SFP), dry dock, new fuel storage, the NuScale Power Modules (NPMs) and their handling equipment. The Reactor Building HVAC system (RBVS) is designed to maintain acceptable ambient conditions in the RXB to support personnel and equipment, and to control airborne radioactivity in the area during normal operation and following events that have the potential to release radioactivity in the RXB, such as a fuel handling accident.

RAI 21.0-1 The RBVS includes three subsystems: the supply subsystem, the general area exhaust subsystem, and the SFP exhaust subsystem. During normal operation, the RBVS provides conditioned and filtered outside air to the RXB, high-efficiency particulate air (HEPA)-

exhaust from RXB, and HEPA-filtered exhaust from the SFP area. The two exhaust subsystems deliver air to the plant exhaust stack for discharge from the plant. In addition to air from the RXB, the RBVS general area exhaust subsystem receives and filters air from the Radioactive Waste Building HVAC system (RWBVS) and the Annex Building HVAC system (ANBVS).

9.4.2.1 Design Bases This section identifies the RBVS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure the functions are fulfilled. Together, this information represents the design bases, defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).

The RBVS serves no safety-related function, is not credited for mitigation of design basis accidents, and has no safe shutdown functionfunction. It is credited as a passive vent path for high energy line breaks in the Reactor Building. General Design Criteria (GDC) 2, 3, and 5 were considered in the design of the RBVS. Components of the RBVS whose structural failure could affect the operability of safety-related SSC are designed as Seismic Category II. The remainder of the RBVS is Seismic Category III (nonseismic).

Consistent with GDC 3, the RBVS is designed to limit hydrogen concentration in battery rooms in accordance with Regulatory Position 6.1.7 of Regulatory Guide (RG) 1.189 by using guidance in section 52.3.6 of NFPA 1. Consistent with GDC 5, the RBVS is common for the NPMs and is designed to operate during an accident on one unit without significantly affecting the capability to conduct a safe and orderly shutdown and cooldown on the remaining units. See Section 9.4.2.3 for the safety evaluation.

The RBVS is designed to remove radioactive contaminants from the exhaust streams of RXB general area, the radioactive waste building general area, and the annex building (ANB). The exhaust from the RBVS is monitored for radioactive contamination consistent with GDC 60. The RBVS includes air filtration and utilizes automatic realignment of the SFP area subsystem to limit release of airborne radioactive contaminants to the environment consistent with GDC 61. Consistent with GDC 64, RBVS exhaust paths are monitored for radioactive releases.

Tier 2 9.4-22 Draft Revision 1

NuScale Final Safety Analysis Report Air Conditioning, Heating, Cooling, and Ventilation Systems

• reactor pool area

• SFP area

• dry dock area

• new fuel area

• battery, battery equipment, and input and output rooms

• galleries

• telecommunications rooms

• hot lab

• remote shutdown station

• elevator machine room The supply subsystem includes four main supply air handling units (AHUs), AHUs for the input and output rooms, battery room, and battery charger rooms (two per operating NPM), and two remote shutdown station AHUs. There are ten telecommunications rooms, each of which is served by two fan coil units (FCUs). The elevator machine room is served by two FCUs. The reactor pool area also includes two supplemental recirculation AHUs that provide the additional cooling capacity to meet the heat loads in this area.

The general area exhaust subsystem includes HEPA filter units and exhaust fans. The SFP exhaust subsystem includes two charcoal and HEPA filter units and exhaust fans.

Both the general area and SFP exhaust subsystems have a standby fan and filter set, and each fan and filter set has isolation dampers that can be closed to isolate the equipment for inspection, testing, and maintenance while the remaining sets are in operation. Airflow through each exhaust filter is limited to approximately 30,000 cfm to ensure reliable in-place testing in accordance with RG 1.140. The RBVS filters all exhaust air in order to reduce radioactivity release to the environment.

RAI 21.0-1 The general area exhaust subsystem collects exhaust air from all areas of the RXB. The exhaust ducts are routed and connected to a main exhaust duct. Exhaust from the RWBVS (Section 9.4.3) then joins exhaust from the RBVS and the ANBVS, and the combined flow enters the RBVS exhaust filter units, and exits the plant through the plant exhaust stack.

The SFP exhaust subsystem draws air through vents located just above the water level around most of the SFP perimeter. This exhaust is ducted to one of two HEPA filtration units with associated exhaust fans. The fan and filter units operate in a lead and stand-by arrangement in which one unit is in operation and the redundant unit is in stand-by.

The SFP exhaust filter units utilize HEPA filters and charcoal adsorbers to minimize radioactivity contained in the SFP exhaust. The exhaust is normally filtered through the HEPA filters, but also passes though charcoal adsorbers if high radiation is detected upstream of the SFP filter unit. The SFP exhaust proceeds directly to the plant exhaust Tier 2 9.4-24 Draft Revision 1

NuScale Final Safety Analysis Report Air Conditioning, Heating, Cooling, and Ventilation Systems Plant Exhaust Stack The plant exhaust stack is located in the northwest corner of the RWB. The minimum stack height is set in accordance with criteria in RG 1.194, Section 3.2.2.

Per the Department of Energy Nuclear Air Cleaning Handbook (Reference 9.4.2-20),

Section 5.5.2, the stack is designed to maintain a minimum stack exit velocity of 3,000 fpm to prevent downwash from winds up to 22 mph, to keep rain out, and to prevent condensation from draining down the stack. The plant exhaust stack is designed in accordance with ASME-STS-1 (Reference 9.4.2-19) and Reference 9.4.2-3, Section AA.

9.4.2.2.2 System Operation 9.4.2.2.2.1 Normal Operation RAI 21.0-1 During normal plant operation, the RBVS main supply AHUs, the general exhaust, and the SFP exhaust units are active and servicing the RXB general area, the reactor pool area, the fuel handling area, and the equipment galleries.

In addition, RBVS filters exhaust from the ANBVS and the RWBVS via the general exhaust subsystem.

The main supply AHUs and general exhaust filter units operate continuously and provide sufficient ventilation and air conditioning to maintain personnel comfort and equipment reliability. One of the general area fans and one of the filter units is in standby mode allowing flexibility for maintenance activities.

The general exhaust system also serves the battery rooms to maintain hydrogen concentrations to less than one percent by volume.

The SFP exhaust subsystem draws air near the surface of the SFP through vents located along the long sides of the SFP and the refueling dock pool. The SFP exhaust air bypasses the charcoal adsorbers of the filter units during normal operation. One of the two SFP exhaust fans and filter units is in service and the remaining exhaust fan and filter unit is in standby.

The recirculating cooling subsystem, located in the SFP area, is normally in operation, as are the AHUs servicing the input and output rooms, battery rooms, and battery charger rooms, the remote shutdown AHU, and the FCUs servicing the telecommunications rooms and the elevator machine room.

9.4.2.2.2.2 Off-normal Operation High Radiation Alarm in Plant Exhaust Stack A high radiation signal from the sensor in the plant exhaust stack provides an alarm in the main control room (MCR), but results in no automatic actions. The operating staff takes action to determine the source of the contamination and isolate it. In general, this does not include shutting down RBVS supply and Tier 2 9.4-29 Draft Revision 1

NuScale Final Safety Analysis Report MULTI-MODULE DESIGN CONSIDERATIONS RAI 21.0-1 Table 21-1: Shared Systems not Associated with Design Basis Event Initiators Shared System NPMs Supported Ground and lightning protection system 12 Plant lighting system 12 Fixed area radiation monitoring system 12 Health physics network 12 Meteorological and environmental monitoring system 12 Communication system 12 Seismic monitoring system 12 Plant wide video monitoring system 12 Balance-of-plant drains system 6 Site drainage system 12 Solid radioactive waste system 12 Radioactive waste drain system 12 Radioactive Waste Building heating ventilation and air conditioning (HVAC) system 12 Diesel Generator Building HVAC system 12 Turbine Building HVAC system 6 Potable water system 12 Utility water system 12 New fuel storage 12 Spent fuel storage 12 Cathodic protection system 12 Service air system 12 Backup power supply system 12 Condensate polishing system 6 Feedwater treatment system 6 Annex Building heating ventilation and air conditioning system (HVAC) 12 Tier 2 21-9 Draft Revision 1