ML19084A178

Summary of Category 1 Public Teleconference with NuScale Power, LLC, to Discuss the NuScale Turbine Missile Analysis

ML19084A178
Person / Time
Site:	NuScale
Issue date:	04/16/2019
From:	Vera M NRC/NRO/DLSE/LB1
To:	Samson Lee NRC/NRO/DLSE/LB1
Vera A
References
Download: ML19084A178 (6)

Text

April 16, 2019 MEMORANDUM TO: Samuel S. Lee, Chief Licensing Branch 1 Division of Licensing, Siting, and Environmental Analysis Office of New Reactors FROM: Marieliz Vera, Project Manager /RA/

Licensing Branch 1 Division of Licensing, Siting, and Environmental Analysis Office of New Reactors

SUMMARY

OF THE MARCH 19, 2019, CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC, TO DISCUSS NUSCALES ANALYSIS FOR TURBINE MISSILE EVENTS The U.S. Nuclear Regulatory Commission (NRC) held a Category 1 public teleconference on March 19, 2019, to discuss the approach for protecting structures, systems, and components (SSCs) important to safety against turbine missile (TM) events. Participants included personnel from NuScale and NRC staff.

The public meeting notice can be found in the Agencywide Documents Access and Management System (ADAMS) under Accession No. ML19077A035. This meeting notice was also posted on the NRC public website.

The Meeting Agenda and List of Participants can be found in Enclosures 1 and 2, respectively.

On March 19, 2019, the NRC staff conducted a public teleconference to gain a better understanding of NuScales turbine missile barrier analysis. Specifically, the staff requested to focus the discussion on the following:

• With respect to materials engineering, previous discussions included a spectrum of missiles to be considered from a single turbine blade to the last stage of the rotor.

o What are the types of turbine missiles considered in the analysis?

o What are the obstacles considered in the path of the missiles prior to impacting the barrier?

CONTACT: Marieliz Vera, NRO/DLSE 301-415-5861

S. Lee

• With respect to structural engineering.

o Are there any potential obstacles before the barrier protecting the SSCs being considered in this evaluation?

o Which is the barrier that will protect the SSC?

o What data was used to bench mark the analysis methodology to demonstrate its effectiveness in capturing the physics of missile impact for both deformable and hard missile-target combinations?

o What was the adopted performance criteria for the barrier?

o How was this performance criteria included in the barrier analysis?

During the teleconference, NuScale referenced its response to RAI 9058, dated June 25, 2018 (ADAMS Accession No. ML18176A394), in which the essential SSCs identified in Regulatory Guide 1.115, are protected by barriers alone. The credited barrier for the essential SSCs in the NuScale design is the concrete reactor building wall. Other barriers available but not credited in the analysis are the turbine casing and the turbine building. NuScales contractor, Structural Integrity Associates, Inc., performed the finite element analysis of penetration depth of a rigid and deformable turbine blade. For each turbine blade type, the analysis showed that the blade did not perforate the reactor building wall. During the discussion, NuScale clarified that the safety-related SSCs in the control building are below grade level. The turbine building is at or above grade level and is more likely to penetrate the SSCs in the reactor building at grade level.

In addition, the NuScale contractor noted that the finite element analysis (FEA) was benchmarked against military and other research test data. To summarize, the NuScale turbine missile analysis considered the following missile types: a turbine blade, a turbine blade with a chunk of the rotor attached, a turbine blade with half of the rotor attached, and a turbine blade in the casing (not credited).

The staff noted its concerns from a recent January 28, 2019, audit in which the FEA reports showed results that need additional discussion and justification to understand some apparent anomalies. Penetration for higher energy impact is lower than that for the lower energy impact (penetration for 180 percent overspeed is larger than that for 200 percent overspeed).

• Penetration for 32 lb. blade is larger than that for 52 lb. blade.

• Penetration depths shown in the figures and tables are not consistent.

• FEA computer program is not validated for scabbing and spalling in the concrete.

• FEA computer program is not benchmarked or validated for rigid and deformable missiles against relevant test results applicable to mass and velocity parameters considered for turbine missiles.

In addition, the staff noted that the barrier penetration depth for deformable blade is 1/3 of that due to rigid blade. The significant reduction in penetration depth is remarkable. The staff does not have a clear understanding of the benchmarking and validation of the model and the methodology used. The staff discussed its concern with the use of an industry equation for a

S. Lee rigid missile and the consideration of uncertainties in the test data used for benchmarking.

NuScale indicated that the verification and validation (V&V) report may address these concerns.

In addition, NuScale will follow-up on the resolution to the concerns that the staff identified during the audit.

The staff noted that this issue does not appear to have a clear path forward. The staff identified actions during the meeting (see below) that NuScale should address to support a clear path forward and closure of this item.

In addition, the staff requested NuScale to discuss what additional structures would prevent a missile from hitting safety related equipment. NuScale clarified that the safety-related equipment is attached to the module which is protected by a wall, all of which are housed in the reactor building. NuScale also noted that between this module wall and the reactor building wall, there are some safety-related equipment. This discussion prompted the staff to note the benefits of a diagram depicting the layout of structures and the safety related equipment that were considered in the turbine missile analysis to communicate with the staff who were not present.

At the end of the discussion, NuScale indicated that it would consider providing more information on the analysis considerations in its application. The staff requested, at a minimum, the considerations, including those not credited in the analysis, be summarized and made available for the staff to audit.

Below are the action items resulting from the discussion:

1. The staff will work with NuScale to determine the mechanism to view the test data used in benchmarking the analysis.

2. The staff will work with NuScale to determine the mechanism to view the V&V report.

3. NuScale will provide a status of the concerns identified by the staff in a recent audit.

4. NuScale will consider developing a plan and schedule to support the closure of this issue.

5. NuScale will provide a diagram depicting the layout of structures and safety-related equipment considered in the turbine missile analysis.

6. NuScale will summarize the analysis considerations, including those considerations not credited in the analysis, and make this information available for the staff to audit.

7. The staff and NuScale will reach an agreement to have a level of granularity in the information in the application that can support a reasonable assurance of safety conclusion.

Docket No.52-048

Enclosures:

As stated cc w/encls.: DC NuScale Power, LLC Listserv

ML19084A178 *via email NRC-002 OFFICE NRO/DLSE/LB1: PM NRO/DLSE/LB1: LA NRO/DNRL/LB1: PM NAME CLauron CSmith MVera DATE 03/25/2019 03/27/2019 04/16/2019 U.S. NUCLEAR REGULATORY COMMISSION CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC TO DISCUSS NUSCALES ANALYSIS FOR TURBINE MISSILE EVENTS March 19, 2019 1:00 p.m. - 2:00 p.m.

Meeting Agenda Time Topic 1:00 p.m. - 1:15 p.m. Welcome and Introductions 1:15 p.m. - 2:00 p.m. Technical discussion 2:00 p.m. - 2:15 p.m. Public - Questions and Comments 2:15 p.m. Adjourn Enclosure 1

U.S. NUCLEAR REGULATORY COMMISSION CATEGORY 1 PUBLIC TELECONFERENCE WITH NUSCALE POWER, LLC TO DISCUSS NUSCALES ANALYSIS FOR TURBINE MISSILE EVENTS March 19, 2019 List of Attendees NAME AFFILIATION B. P. Jain U.S. Nuclear Regulatory Commission (NRC)

Carolyn Lauron NRC Matthew A. Mitchell NRC Sujit Samaddar NRC Angelo Stubbs NRC Robert M. Taylor NRC Amber Berger NuScale Power, LLC (NuScale)

Martin Bryan NuScale Mark Chitty NuScale Josh Parker NuScale Michael Melton NuScale Keith Kubischta Structural Integrity Associates, Inc.

Derrick Watkins Structural Integrity Associates, Inc.

Enclosure 2