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NRC Inspection of the Licensees Implementation of Industry Initiative Associated with the Open Phase Condition Design... - Inspection Report Nos 05000528/2018010, 05000529/2018010, and 05000530/2018010
	ML18103A157
Person / Time
Site:	Palo Verde
Issue date:	04/13/2018
From:	Greg Werner; NRC/RGN-IV/DRS/EB-2
To:	Bement R; Arizona Public Service Co
	Werner G
References
	IR 2018010
	Download: ML18103A157 (38)
	v • d • e

April 13, 2018

SUBJECT:

PALO VERDE NUCLEAR GENERATING STATION - NRC INSPECTION OF THE LICENSEES IMPLEMENTATION OF INDUSTRY INITIATIVE ASSOCIATED WITH THE OPEN PHASE CONDITION DESIGN VULNERABILITIES IN ELECTRIC POWER SYSTEMS - INSPECTION REPORT 05000528/2018010, 05000529/2018010, AND 05000530/2018010

Dear Mr. Bement:

On March 22, 2018, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at the Palo Verde Nuclear Generating Station. On March 22, 2018, the inspectors discussed the results of this inspection with Ms. M. Lacal, Senior Vice President Regulatory and Oversight, and other members of your staff. The results of this inspection are documented in the enclosed report.

The NRC inspectors did not identify any findings or violations of more than minor significance.

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 10 CFR 2.390, Public Inspections, Exemptions, Requests for Withholding.

Sincerely,

/RA James Drake Acting for/

Gregory E. Werner, Chief Engineering Branch 2 Division of Reactor Safety

Docket Nos. 50-528, 50-529, and 50-530 License Nos. NPF-41, NPF-51, and NPF-74

Enclosure:

Inspection Report 05000528/2018010, 05000529/2018010, and 05000530/2018010 w/ Attachments: 1. Table 1 - Information Gathered for TI 2515/194 2. TI 2515/194 Inspection Documentation Request

Enclosure

U.S. NUCLEAR REGULATORY COMMISSION

Inspection Report

Docket Number(s):

05000528, 05000529, 05000530

License Number(s):

NPF-41, NPF-51, NPF-74

Report Number(s):

05000528/2018010, 05000529/2018010, and 05000530/2018010

Enterprise Identifier: I-2018-010-0018

Licensee:

Arizona Public Service Company

Facility:

Palo Verde Nuclear Generating Station

Location:

Tonopah, Arizona

Inspection Dates:

March 19, 2018, to March 22, 2018

Inspectors:

S. Graves, Team Lead, Senior Reactor Inspector, Region IV

B. Correll, Reactor Inspector, Region IV

Accompanying

K. Nguyen, Electrical Engineer, NRR/DE/EEOB

Personnel:

I. Kafeez, Reactor Inspector, Region III/DRS/EB3

H. Kodali, Electrical Engineer, NRR/DE/EEOB

J. Quichocho, Chief, NRR/DE/EEOB

Approved By:

G. Werner, Branch Chief, Engineering Branch 2

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) continued monitoring licensees performance by conducting Temporary Instruction 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), at Palo Verde Nuclear Generating Station, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the Nuclear Regulatory Commission 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

None.

Additional Tracking Items

None.

INSPECTION SCOPE

This inspection was conducted using Temporary Instruction 2515/194 (ADAMS Accession No. ML17137A416), dated October 31, 2017. The inspectors reviewed the licensees implementation of Nuclear Energy Institute Voluntary Industry Initiative in compliance with Commission guidance. The team discussed the licensees open phase condition system design and ongoing implementation plans with plant staff and vendor staff. The team reviewed licensee and vendor documentation, and performed system walkdowns to verify that the installed equipment was supported by the design documentation. The team verified that the licensee had completed the installation and testing of equipment (with the exception of the tripping functions), installed and tested alarming circuits both local and in the control room, and analyzed potential impacts associated with the design implementation on the current licensing basis.

OTHER ACTIVITIES

- TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL

Temporary Instruction 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)

The objective of Temporary Instruction 2515/194, is to verify that licensees have appropriately implemented the Nuclear Energy Institute Voluntary Industry Initiative including updating their licensing basis to reflect the need to protect against open phase conditions, and to gather the information necessary for Office of Nuclear Reactor Regulation staff to determine whether the licensees have adequately addressed potential open phase conditions.

Temporary Instruction 2515/194-03.01 - Voluntary Industry Initiative (Part 1)

Palo Verde Nuclear Generating Station selected the open phase detection system designed and manufactured by Power System Sentinel Technologies, LLC, as the design vendor for their open phase condition system. At the end of this inspection the power system sentinel technologies system was still in the monitoring mode of operation to facilitate continued data gathering of grid perturbations for evaluation of alarm and trip setpoints. The open phase condition equipment was installed on the startup transformers (SUTs) AE-NAN-X01, AE-NAN-X02, and AE-NAN-X03 which provide power to station busses, including the stations six engineered safety feature (ESF) busses. The licensee is scheduled to transition the power system sentinel technologies system to full implementation (tripping functions enabled) in December 2018. The licensee was preparing design modifications and associated documentation for this transition, however they were not available for review at the time of inspection.

Section 03.01 of the Temporary Instruction required the determination of whether the licensee appropriately implemented the voluntary industry initiative, dated March 16, 2015 (ADAMS Accession No. ML15075A454), by verifying the following:

a. Detection, Alarms and General Criteria

1. Either open phase conditions are detected and alarmed in the control room, or

(a) The licensee has demonstrated that open phase conditions do not prevent the functioning of important-to-safety systems, structures, and components,

(b) Open phase condition detection will occur within a reasonably short period of time (e.g., 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months ), and

(c) The licensee has established appropriate documentation regarding open phase condition detection and correction.

2. Either detection circuits are sensitive enough to identify an open phase condition for

credited loading conditions (i.e., high and low loading), or if automatic detection may not be possible in very low or no loading conditions when offsite power transformers are in standby mode, automatic detection must happen as soon as loads are transferred to this standby source. Additionally, the licensee has established appropriate shiftly surveillance requirements to look for evidence of open phase conditions.

3. Open phase condition design/protective schemes minimize misoperation or spurious

action in the range of voltage unbalance normally expected in the transmission system that could cause separation from an operable offsite power source.

Licensees have demonstrated that the actuation circuit design does not result in lower overall plant operation reliability.

4. New non-Class-1E circuits are not used to replace existing Class-1E circuits.

5. The Updated Final Safety Analysis Report (UFSAR) has been updated to discuss the

design features and analyses related to the effects of, and protection for, any open phase condition design vulnerability.

b. Protective Actions

1. If the licensee determines there is no single credible failure that could cause an open

phase condition, then verify that the licensee has developed and issued a full engineering evaluation to document the basis for open phase condition as a non-credited event. The Bruce Power and Forsmark operating experience must be considered as part of this analysis.

2. With open phase condition occurrence and no accident condition signal present,

either an open phase condition does not adversely affect the function of important-to-safety system, structures, and components, or,

(a) Technical Specification Limiting Condition of Operations (LCOs) are maintained or the technical specification actions are met without entry into Technical Specification Limiting Condition of Operation 3.0.3 (or equivalent),and

(b) Important-to-safety equipment is not damaged by the open phase condition, and

(c) Shutdown safety is not compromised.

3. With open phase condition occurrence and an accident condition signal present,

automatic detection and actuation will transfer loads required to mitigate postulated accidents to an alternate source and ensure that safety functions are preserved, as required by the current licensing bases, or the licensee has shown that all design basis accident acceptance criteria are met with the open phase condition, given other plant design features. Accident assumptions must include licensing provisions associated with single failures. Typically, licensing bases will not permit consideration of the open phase condition as the single failure since this failure is in a non-safety system.

4. Periodic tests, calibrations, setpoint verifications, or inspections (as applicable)

have been established for any new protective features. The surveillance requirements have been added to the plant Technical Specifications if necessary to meet the provisions of 10 CFR 50.36.

Temporary Instruction 2515/194-03.02 - Information Gathering for Voluntary Industry Initiative Assessment (Part 2)

Section 03.02 of the Temporary Instruction required information gathering as part of the initial inspections to enable the Nuclear Reactor Regulation staff to determine whether the modifications implemented by the licensee of each unique open phase condition system design for the voluntary industry initiative adequately address potential open phase conditions. The information gathered for this section is tabulated in attachment, Table 1 - Information Gathered for TI 2515/194, to this report.

INSPECTION RESULTS

Based on interviews and discussions with the licensee and the vendor, review of available design, testing, grid data trending results documentation, and walkdowns of installed equipment, the team had reasonable assurance the licensee appropriately implemented, with noted exceptions discussed below, the voluntary industry initiative.

TI 2515/194-03.01 - Voluntary Industry Initiative (Part 1)

a. Detection, Alarms and General Criteria

(1) The team determined by walkdowns and observation that open phase conditions will be detected and alarmed in the control room for each unit.

(2) The team determined that detection circuits were sensitive enough to identify an open phase condition for all credited loading conditions.

(3) No Class-1E circuits were replaced with non-Class 1E circuits in the design.

b. Protective Actions Criteria

(1) The team determined the licensee identified they were susceptible to an open phase condition and were implementing design changes to mitigate the effects.

(2) The team determined that with an open phase condition present and no accident condition signal, the power system sentinel technologies system would not adversely affect the function of important-to-safety systems, structures, and components. The licensees open phase condition design solution added a set of additional tripping inputs in parallel to the existing transformer isolation controls. This addition added a new tripping condition (open phase) to the electrical faults which result in loss of one preferred source of power to one train of ESF loads. The credited plant response would be the same regardless of the conditions that generated the isolation of the transformer.

No findings were identified, however the team identified the following exceptions to the Temporary Instruction criteria resulting from the incomplete design modifications:

c. Detection, Alarms and General Criteria Exceptions

(1) The licensees design was operating in the monitoring mode with vendor recommended setpoints enabled, to gather data to ensure the open phase condition design and protective schemes would minimize misoperation, or spurious actions in the range of voltage unbalance normally expected in the transmission system.

Because actual demonstration of this criterion requires the system to be in operation with final trip setpoints established, the team was not able to fully verify this criterion.

After discussions with licensee and vendor staff, design document and test results reviews, and historical monitoring date reviews, the team had reasonable assurance that the actuation circuit design would not result in lower overall plant operation reliability. The team did not identify any issues of concern.

(2) The Final Safety Analysis Report had not been updated to include information related to open phase conditions at the conclusion of the onsite inspection. The licensee provided and the team reviewed proposed changes to the licensing basis that discussed the design features and analyses related to the effects of, and protection for, any open phase condition design vulnerability. The team verified the proposed changes had been entered into the corrective action program as Condition Report CR NON 18-04437 to track the completion of the Updated Final Safety Analysis Report. The team did not identify any issues of concern.

d. Protective Actions Criteria Exceptions

(1) The licensees open phase condition design solution used the existing isolation and power scheme for safety-related accident loads; only a new tripping condition (open phase) had been added to the electrical faults which result in loss of one preferred source of power to one train of ESF loads. A loss of voltage, including a loss of voltage caused by isolation of the preferred source due to an open phase condition, on the affected ESF bus results in the affected train loading being automatically transferred to the onsite emergency power source, if available (single failure), or manually to a different SUT. While no changes to this configuration were planned due to the inclusion of the power system sentinel technologies system, actual demonstration of this criterion requires the system to be in full operation.

Through review of available design documents and discussions with plant and vendor staff, the team had reasonable assurance that with an open phase condition present and an accident condition signal, the power system sentinel technologies system automatic detection and actuation would isolate the affected transformer.

Due to the configuration of Palo Verde Nuclear Generating Stations electrical distribution system, a loss of a SUT would only affect one train of equipment, and loads required to mitigate postulated accidents would be available on the non-affected train ensuring that safety functions are preserved as required by the current licensing bases. The team did not identify any issues of concern.

(2) The licensee had not finalized documentation for periodic tests, calibrations, setpoint verifications, or inspection procedures for open phase condition-related components at the time of this inspection. The team held discussions with licensee and vendor staff and identified that the vendor guidance, including periodic tests, setpoint verification, and equipment maintenance and inspection would be integrated into plant procedures and processes.

The licensee had existing Condition Report CR-17-12228 which was written to establish maintenance strategies for the open phase protection equipment.

The licensee updated this condition report to develop additional strategies for the transformer neutral cables which are an integral part of the power system sentinel technologies system. The licensee created Condition Report CR-18-04542 to add additional inspection criteria to existing outside area operator log procedures for visual inspection of the transformer neutral cable, neutral bushing, and ground connection integrity. The team also held discussions about the licensees plans to include open phase condition-related components into the Maintenance Rule (10 CFR 50.65) program. The licensee generated Condition Report CR NON 18-04442 to create an enhancement action item which tracked the scoping process for inclusion into their maintenance rule program. Existing plant equipment will continue to be maintained according to the licensees current preventative maintenance program. The team did not identify any issues of concern.

EXIT MEETINGS AND DEBRIEFS

On March 22, 2018, the team presented the Temporary Instruction 2515/194 inspection results to Ms. M. Lacal, Senior Vice President Regulatory and Oversight, and other members of the licensee staff.

The inspectors verified no proprietary information was retained, however some material used by the team to document compliance was characterized as proprietary by the vendor.

DOCUMENTS REVIEWED

Inspection Procedure TI 2515/194

Condition Reports

18-04439

NON 18-04437*

18-04442*

NON 18-04542*

Issued as a result of inspection activities.

Drawings Number

Title

Revision

A0-E-NAB-008

Elementary Diagram 13.8 kV Non-Class 1E Power