05000440/LER-1917-002, Regarding Loss of Safety Function Due to Main Turbine Bypass Valve Opening

Regarding Loss of Safety Function Due to Main Turbine Bypass Valve Opening

ML17179A208
Person / Time
Site:	Perry
Issue date:	06/27/2017
From:	Hamilton D FirstEnergy Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-17-207 LER 17-002-00
Download: ML17179A208 (6)

LER-1917-002, Regarding Loss of Safety Function Due to Main Turbine Bypass Valve Opening

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
4401917002R00 - NRC Website

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FENOC Perry Nuclear Power Plant P.O. Box 97 10 Center Road FirstEnergy Nuclear Operating Company Perry' Ohio 44081 David B. Hamilton 440-280-5382 Vice President June 27, 2017 L-17-207 10CFR50.73(a)(2)(v)(A) 10CFR50.73(a)(2)(v)(D)

ATTN:

Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001

SUBJECT:

Perry Nuclear Power Plant Docket No. 50-440, License No. NPF-58 Licensee Event Report Submittal Enclosed is Licensee Event Report (LER) 2017-002, "Loss of Safety Function Due to Main Turbine Bypass Valve Opening".

There are no regulatory commitments contained in this submittal.

If there are any questions or if additional information is required, please contact Mr. Nicola Conicella, Manager - Regulatory Compliance, at (440) 280-5415.

David B. Hamilton Vice President

Enclosure:

LER 2017-002 cc:

NRC Project Manager NRC Resident Inspector NRC Region III

Enclosure L-17-207 LER 2017-002

NRC FORM 366 (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

(See Page 2 for required number of digits/characters for each block)

(See NUREG-1022, R.3 for instruction and guidance for completing this form http:/A/vww.nrc.qov/readinq-rm/doc-collections/nuregs/staff/sr1022/r3/

APPROVED BY OMB:

NO. 3150-0104 EXPIRES:

3/31/2020 Estimated burden per response to comply with this mandatory collection request:

80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.

Reported lessons learned are incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S.

Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.

Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503.

If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME Perry Nuclear Power Plant

2. DOCKET NUMBER 05000-440

3. PAGE 1

OF

4. TITLE:

Loss of Safety Function Due to Main Turbine Bypass Valve Opening

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.

MONTH FACILITY NAME DOCKET NUMBER 05000 04 30 2017 2017 002 00 06 27 2017 FACILITY NAME DOCKET NUMBER 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §:

(Check all that apply) 20.2201 (b) 20.2201 (d) 20.2203(a)(1) 20.2203(a)(2)(i) 20.2203(a)(3)(i) 20.2203(a)(3)(ii) 20.2203(a)(4) 50.36(c)(1)(i)(A) 50.73(a)(2)(ii)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(iii) 50.73(a)(2)(iv)(A) 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(ix)(A) 50.73(a)(2)(x)

10. POWER LEVEL 100 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71 (a)(4) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(B) 73.71 (a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 73.77(a)(2)(i) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)

OTHER Specify in Abstract below or in To mitigate pressurization transient effects of a main turbine trip the EOC-RPT must trip the recirculation pumps from fast speed operation after initiation of initial closure movement of either the TSVs or the TCVs.

The combined effects of this trip and a scram reduce fuel bundle power more rapidly than does a scram alone, resulting in an increased margin to the Minimum Critical Power Ratio (MCPR) safety limit.

The EOC-RPT function is automatically disabled when turbine first stage pressure is less than 38 percent power.

To consider this function operable, the turbine bypass valves must remain shut at power greater than or equal to 38 percent.

Rod Withdrawal Limiter (RWU -TS 3.3.2.1:

The RWL is designed to prevent violation of the MCPR safety limit and the cladding 1

percent plastic strain fuel design limit that may result from a single control rod withdrawal error (RWE) event.

The RWL is assumed to mitigate the consequences of an RWE event when operating greater than 33.3 percent power.

With any bypass valve open both channels of the listed functions are inoperable resulting in a loss of safety function.

During the transient the following TS action statements were entered: TS 3.3.1.1 conditions A, B and C, 3.3.2.1 condition A and 3.3.4.1 conditions A and B.

The required action for TS 3.3.1.1 C.1 requires restoration of RPS trip capability within 1

hour.

TS 3.3.2.1 Action A.1 requires immediate suspension of control rod withdrawal and verification of no rod motion by 2 licensed operators.

3.3.4.1 Action B.1 requires restoration of EOC-RPT capability within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

On April 30, 2017, at 1910 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.26755e-4 months <br />, the action statements for TS 3.3.1.1, 3.3.2.1, and 3.3.4.1 were exited following confirmation of bypass valve closure.

On May 3, 2017, at 1259 hours0.0146 days <br />0.35 hours <br />0.00208 weeks <br />4.790495e-4 months <br /> event notification 52727 was made to the NRC Operations Center in accordance with 10CFR50.72(b)(3)(v)(A) and 10CFR50.72(b)(3)(v)(D) for the loss of safety function.

CAUSE

The direct cause of the bypass valve opening was degradation of the Primary Low Value Gate (PLVG) card in the main turbine speed control circuit [SC].

The problem solving team assembled for this issue evaluated monitoring equipment attached to the speed control portion of the Electro-Hydraulic system in order to determine the source of the inadvertent opening of the bypass valve. The failure mode was narrowed down to the turbine speed control portion of the circuitry based upon the alarms received during the transient.

The decision was made to replace the Primary Low Value Gate and the Primary Frequency to Voltage Converter Speed Control cards.

After the replacement was completed, the turbine was re-synchronized to the electrical grid. The installed monitoring equipment showed no evidence of an issue within the Electro-Hydraulic control systems and there were no further openings of the bypass valves.

The analysis of the removed cards is not yet completed, and if a change to the primary cause is warranted a LER revision will be submitted.

Preliminary testing found a degradation of the PLVG card. During bench checks of the card it was discovered that an intermittent varying output signal was created with no changes to the input of the card. This intermittent change in output of the card would have caused the opening of the bypass valve.

The second card that was replaced was the Primary Frequency to Voltage Converter card although initial analysis has identified no issues with this card.

EVENT ANALYSIS

The event is of small safety significance from the Probabilistic Risk Assessment (PRA) perspective as no PRA related mitigative components or strategies were affected by this event.

While the corresponding functions were declared inoperable from a Technical Specification perspective, functionality was maintained and the plant was correspondingly controlled via proper actions to reduce power.

The event did not result in an automatic trip.

With no transient and no impact to any PRA related components or functions, there would be no corresponding change (delta) in core damage frequency (CDF), and no corresponding change (delta) in the large early release frequency (LERF).

The delta CDF and delta LERF values would therefore be well below the acceptable thresholds of 1.0E-06/yr and 1.0E-07/yr, respectively, as discussed in Regulatory Guide 1.174.

The risk of this event is therefore considered small in accordance with the Regulatory Guidance.

During the transient, the sensed reactor pressure at the turbine first stage did not drop low enough to impede the ability for the listed parameters to perform their function, therefore, this is not considered a safety system functional failure.

CORRECTIVE ACTIONS

The PLVG card was replaced following discovery of the failure.

No other issues have been noted since replacement.

In addition to the card replacement, the mitigation strategy for the control system will be reviewed.

PREVIOUS SIMILAR EVENTS

A review of LERs and the corrective action database for the past three years identified no similar events.

COMMITMENTS

There are no regulatory commitments contained in this report. Actions described in this document represent intended or planned actions, are described for the NRC's information, and are not regulatory commitments.(06-2016)