IR 05000336/2021012

Temporary Instruction 2515/194 Inspection Report 05000336/2021012 and 05000423/2021012

ML21076A411
Person / Time
Site:	Millstone
Issue date:	03/17/2021
From:	Glenn Dentel Engineering Region 1 Branch 2
To:	Stoddard D Dominion Energy
Dentel G
References
IR 2021012
Download: ML21076A411 (8)

Text

March 17, 2021

SUBJECT:

MILLSTONE POWER STATION, UNITS 2 AND 3 - TEMPORARY INSTRUCTION 2515/194 INSPECTION REPORT 05000336/2021012 AND 05000423/2021012

Dear Mr. Stoddard:

On March 4, 2021, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Millstone Power Station, Units 2 and 3 and discussed the results of this inspection with Mr. John Daugherty, Site Vice President and other members of your staff. The results of this inspection are documented in the enclosed report.

No findings or violations of more than minor significance were identified during this inspection.

This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.

Sincerely, X /RA/

Signed by: Glenn T. Dentel Glenn T. Dentel, Chief Engineering Branch 2 Division of Reactor Safety Docket Nos. 05000336 and 05000423 License Nos. DPR-65 and NPF-49

Enclosure:

As stated

Inspection Report

Docket Numbers: 05000336 and 05000423 License Numbers: DPR-65 and NPF-49 Report Numbers: 05000336/2021012 and 05000423/2021012 Enterprise Identifier: I-2021-012-0004 Licensee: Dominion Energy Nuclear Connecticut, Inc.

Facility: Millstone Power Station, Units 2 and 3 Location: Waterford, CT 06385 Inspection Dates: March 1, 2021 to March 4, 2021 Inspectors: L. Dumont, Reactor Inspector D. Werkheiser, Senior Reactor Analyst Approved By: Glenn T. Dentel, Chief Engineering Branch 2 Division of Reactor Safety Enclosure

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting a Temporary Instruction 2515/194 Inspection at Millstone Power Station, Units 2 and 3, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors. Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.

List of Findings and Violations

No findings or violations of more than minor significance were identified.

Additional Tracking Items

None.

INSPECTION SCOPES

Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.

Starting on March 20, 2020, in response to the National Emergency declared by the President of the United States on the public health risks of the coronavirus (COVID-19), inspectors were directed to begin telework. In addition, regional baseline inspections were evaluated to determine if all or portion of the objectives and requirements stated in the IP could be performed remotely. If the inspections could be performed remotely, they were conducted per the applicable IP. In some cases, portions of an IP were completed remotely and on site. The inspections documented below met the objectives and requirements for completion of the IP.

OTHER ACTIVITIES

- TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL 2515/194 - Inspection of the Licensees Implementation of Industry Initiative Associated with the Open Phase Condition Design Vulnerabilities In Electric Power Systems (NRC Bulletin 2012-01)

(1 Sample)

(1) Dominion Energy Nuclear Connecticut, Inc., selected the open phase detection system designed and manufactured by Power System Sentinel Technologies, LLC, (PSSTech) as the design vendor for the open phase condition (OPC) system at Millstone Power Station. The open phase protection system is designed to protect the offsite power sources from a loss of phase condition.

The offsite electrical distribution system is functionally the same for both Millstone Unit 2 and Unit 3. At each unit the offsite power system includes the transmission system and the 345-kV switchyard. Included in the system are main generator step-up transformers (GSUs) and the reserve station service transformers (RSSTs) of both Unit 2 and Unit 3.

The PSSTechs were in the "Detect" mode of operation. The trip function was bypassed and will remain disabled on Unit 2 transformers and was not installed on the Unit 3 transformers. Dominion Energy Nuclear Connecticut, Inc. uses the risk-informed method, which utilizes manual actions for protective action measures for Unit 2 and Unit 3, to comply with the open phase detection initiative. At the end of this inspection the PSSTech system was monitoring and would alarm the control room if a loss of one- or two-phase conditions is detected.

INSPECTION RESULTS

Observation: Temporary Instruction 2515/194-03.01 - Voluntary Industry 2515/194 Initiative Based on discussions with Dominion staff, review of design and testing documentation, and walkdowns of installed equipment, the inspectors had reasonable assurance that Dominion is appropriately implementing, with a noted exception discussed below, the voluntary industry initiative at Millstone Power Station, Units 2 and 3. The inspectors verified the following criteria:

Detection, Alarms and General Criteria 1. [03.01(a)(1)] Open phase conditions are detected and alarmed in the control room.

2. [03.01(a)(2)] Detection circuits are sensitive enough to identify an open phase condition for credited loaded conditions (i.e. high and low loading).

3. [03.01(a)(4)] No Class 1E circuits were being replaced with non-Class 1E circuits in this design.

4. [03.01(a)(5)] The Final Safety Analysis Report was updated to discuss the design features and analyses related to the effects of any open phase condition design vulnerability.

5. [03.01(a)(6)] The open phase condition detection and alarm components are maintained in accordance with Dominions procedures or maintenance program, and periodic tests, calibrations setpoint verifications or inspections (as applicable) have been established.

Use of Risk-Informed Evaluation Method 1. [03.01(c)(1)] The plant configuration matched the changes made to the probabilistic risk assessment model to address an open phase condition, and the logic of the probabilistic risk assessment model changes is sound. One exception was noted by the inspectors and documented in a separate observation.

2. [03.01(c)(2)] The procedures which validate that the open phase condition alarm would identify the proper indication to validate the open phase conditions at all possible locations.

3. [03.01(c)(3)] Observations associated with procedure(s) and operator actions required to respond to an open phase condition alarm and potential equipment trip match the Human Reliability

4. [03.01(c)(4)] Assumptions listed in the NEI 19-02 Appendix A evaluation and the

sensitivity analyses listed in Section 5 of the evaluation were verified.

5. [03.01(c)(5)] Assumptions, procedures, operator actions and Dominions analyses specified above are consistent with the plant-specific design and licensing basis, including:

a. Initiating events considered in the analysis b. Boundary conditions specified in Attachment 1 of the NEI Voluntary Industry Initiative, Revision 3 c. Operating procedures for steps taken to recover equipment assumed tripped/locked out or damaged due to the open phase conditions (or use of alternate equipment)

Observation: Use of Risk-Informed Evaluation Method Exception 2515/194 Use of Risk-Informed Evaluation Method Exception - [03.01(c)(1)] The plant configuration matched the changes made to the probabilistic risk assessment model to address an open phase condition, and the logic of the probabilistic risk assessment model changes is sound.

Dominion's NEI 19-02 evaluation selected an OPC initiating event frequency and probability based on accepted industry data per guidance in NEI 19-02, Section 4.2. However, Dominion, in their analysis, modified this frequency and apportioned (divided by the number of potentially impacted transformer locations) it to different response models, thereby reducing the initiating event frequency for each response by this factor. In Millstone Unit 2 and Unit 3 cases the inspectors noted the initiating event frequency was divided by two and allotted to both locations for each response case evaluated.

During discussions with Dominion, the licensee referenced assumptions and the use of apportionment in an NRC Preliminary Risk Estimate on the Impact of Open Phase Condition documented in 2017 (ADAMS Accession ML17234A631). Inspector discussions with NRC subject matter expert staff indicate that the apportionment was required in the noted example risk estimate due to the multiple line feeders to the offsite power source and is not the configuration for Millstone.

The methodology the inspectors observed Dominion implement regarding OPC initiating event frequency and probability in their analysis, based on discussions with NRC subject matter expert staff, is not consistent with the guidance and methods described in NEI 19-02. This may affect the assessment of the change in risk as measured by delta core damage frequency (CDF) and delta large early release frequency (LERF) and other related results. This applies to both Millstone Units 2 and 3 and potentially other Dominion sites, based on discussions with Millstone staff.

Inspector review and assessment of Millstone's NEI 19-02 analysis Section 5.0 results and sensitivity studies indicate that delta CDF and delta LERF results would be near 1E-6/yr and less than 1E-7/yr respectively, and that the CDF ceiling criteria would still be met (<1E-5/yr)even if the current results were doubled.

EXIT MEETINGS AND DEBRIEFS

The inspectors verified no proprietary information was retained or documented in this report.

• On March 4, 2021, the inspectors presented the Temporary Instruction 2515/194 inspection results to Mr. John Daugherty, Site Vice President and other members of the licensee staff.

DOCUMENTS REVIEWED

Inspection Type Designation Description or Title Revision or

Procedure Date

2515/194 Calculations MP2-ENG-EMTP- MP2 Open Phase Condition EMTP Time Delay Limit Analysis 3

04447E2

MP3-ENG-EMTP- MP3 Open Phase Condition Time Delay Limit Analysis 3

0454 7E3

Drawings 25203-39150 RSST Open Phase Cabinet C549-A Schematic 0

Engineering MP2-17-00156 MP2 Open Phase Condition Detection System (Protection 9

Changes Phase)

MP3-17-00157 MP3 Open Phase Condition Detection System (Protection 10

Phase)

Engineering MP3-ENG-EMTP- MP3 Open Phase Detection Modeling and Analysis 2

Evaluations 04548E3

NOTEBK-PRA- Open Phase Mitigation Risk Evaluation 1

MPS2-RA.031

NOTEBK-PRA- Open Phase Mitigation Risk Evaluation 1

MPS3-RA.024

Procedures EOP 2525 Standard Post Trip Actions 29

EOP 35 E0 Emergency Operating Procedure 34

Work Orders 53203264248

203264249

203264250

203264251

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