05000440/LER-2017-006

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LER-2017-006, Loss of Safety Function due to the Inoperability of Both Trains of Motor Control Center Ventilation
Perry Nuclear Power Plant
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material

10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat

10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
Initial Reporting
ENS 53000 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material
4402017006R00 - NRC Website
LER 17-006-00 for Perry Nuclear Power Plant Regarding Loss of Safety Function due to the Inoperability of Both Trains of Motor Control Center Ventilation
ML17335A065
Person / Time
Site: Perry FirstEnergy icon.png
Issue date: 12/01/2017
From: Hamilton D B
FirstEnergy Nuclear Operating Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
L-17-0318
Download: ML17335A065 (5)


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 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.

- 006 - 00 05000-440 YEAR 2017 Energy Industry Identification System (EIIS) codes are identified in the text as [XX].

INTRODUCTION

On October 4, 2017, at

0155 hours
0.00179 days
0.0431 hours
2.562831e-4 weeks
5.89775e-5 months

, while in Mode 1 and 100 percent rated thermal power, inoperability of both trains of Motor Control Center, Switchgear, and Miscellaneous Electrical Equipment Areas Heating, Ventilation, and Air Conditioning System and Battery Rooms Exhaust System (M23/24) occurred. This resulted in a loss of safety function.

This event is being reported in accordance with 10CFR50.73(a)(2)(v)(B), 10CFR50.73(a)(2)(v)(C), and 10CFR50.73(a)(2)(v)(D) as an event or condition that prevented the fulfilment of a safety function.

EVENT DESCRIPTION

On October 4, 2017 at

0155 hours
0.00179 days
0.0431 hours
2.562831e-4 weeks
5.89775e-5 months

, with the plant in Mode 1 and at 100 percent rated thermal power, M23/24 Train A was shutdown and declared inoperable due to a report of excessive drive belt noise and malfunctioning belts on the A supply fan [AHU]. Concurrently, Control Complex Chilled Water (CCCW) Chiller B [KM] was out of service for planned maintenance resulting in Train B of M23/24 being inoperable. This combination resulted in a loss of safety function due to the impact to Division 1,2, and 3 electrical switchgear. At

0200 hours
0.00231 days
0.0556 hours
3.306878e-4 weeks
7.61e-5 months

, M23/24 was shifted from train A to train B. CCCW Chiller C was already running and had been started at

2225 hours
0.0258 days
0.618 hours
0.00368 weeks
8.466125e-4 months

on 10/03/17. Cooling to the affected areas through the B train of M23/24 was maintained through use of the nonsafety related CCCW Chiller C, which is able to supply either train with chilled water.

Due to the inoperability of both trains of M23/24, actions were taken in LCO 3.8.7 for Alternating Current (AC) [EA] and Direct Current (DC) [EJ] Distribution Systems, LCO 3.8.4 for DC Sources, LCO 3.8.1 for AC Sources, and the associated support systems. The High Pressure Core Spray System (HPCS) [BC] was also declared inoperable, which is a single train safety system, and therefore an additional loss of safety function.

On October 04, 2017 at

0553 hours
0.0064 days
0.154 hours
9.143518e-4 weeks
2.104165e-4 months

, event notification EN# 53000 was made to the NRC Operations Center in accordance with 50.72(b)(2)(i) & 50.72(b)(3)(v)(D) for initiation of plant shutdown and loss of safety function. Train A of M23/24 was declared operable at 0620, following belt replacement, and TS 3.0.3 was exited. The plant was restored to 100 percent rated thermal power at

0804 hours
0.00931 days
0.223 hours
0.00133 weeks
3.05922e-4 months

. At

0926 hours
0.0107 days
0.257 hours
0.00153 weeks
3.52343e-4 months

, the event notification reporting requirements were updated to include 50.72(b)(3)(v)(B) and 50.72(b)(3)(v)(C), in addition to 50.72(b)(3)(v)(D).

CAUSE

With the B train of the M23 system out of service for maintenance, the belt malfunction on the A train supply fan resulted in a loss of safety function and entry into Technical Specification 3.0.3. It was determined that two V-belts on the M23 A supply fan malfunctioned due to inadequate tensioning. The cause was determined to be inadequate procedural guidance in that the "general tensioning" method supplied in plant maintenance procedure, V-belt and Sheave Maintenance, which requires only a visual check of belt sag, is insufficient for restoring components utilizing V- belts to a reliable operating condition.

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

- 006 - 00 Perry Nuclear Power Plant Unit 1 05000-440 YEAR 2017

EVENT ANALYSIS

A Probabilistic Risk Assessment (PRA) evaluation was performed. The analysis indicates that the event resulted in a very small change to overall plant risk with a change (delta) in core damage frequency (CDF) of 1.78E-09/yr, and a change (delta) in the large early release frequency (LERF) of 1.11E-09/yr. The delta CDF and delta LERF values are well below the acceptable thresholds of 1.0E-06/yr and 1.0E-07/yr, respectively, as discussed in Regulatory Guide 1.174. Therefore, the safety significance of this event is considered to be very small.

CORRECTIVE ACTIONS

Corrective actions in response to the event include: revising the maintenance procedure to use the Force Deflection Method for tensioning of the belts; replacing the M23 A supply fan drive belts and restoring M23/24 to operable; and performing an additional check of belt tension on the same train exhaust fan along with the opposite train supply and exhaust fans. Additionally, the belts for the Auxiliary Building ventilation EVE] exhaust fans will be checked.

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.