05000237/LER-2002-003, Manual Valve Failures Prevent the Cooling Water Flow to Control Room Refrigeration Condensing Unit

Manual Valve Failures Prevent the Cooling Water Flow to Control Room Refrigeration Condensing Unit

ML021970570
Person / Time
Site:	Dresden
Issue date:	07/08/2002
From:	Hovey R Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RHLTR: #02-0049 LER 02-003-00
Download: ML021970570 (5)

LER-2002-003, Manual Valve Failures Prevent the Cooling Water Flow to Control Room Refrigeration Condensing Unit

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
2372002003R00 - NRC Website

text

Exelo n.

Exelon Generation www.exeloncorp.com Nuclear Dresden Generating Station 6500 North Dresden Road Morris, IL 60450-9765 Tel 815-942-2920 10 CFR 50.73 July 8, 2002 RHLTR: #02-0049 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 2 Facility Operating License No. DPR-1 9 NRC Docket No. 50-237

Subject:

Licensee Event Report 2002-003-00, "Manual Valve Failures Prevent the Cooling Water Flow to Control Room Refrigeration Condensing Unit" Enclosed is Licensee Event Report 2002-003-00, "Manual Valve Failures Prevent the Cooling Water Flow to Control Room Refrigeration Condensing Unit," for the Dresden Nuclear Power Station (DNPS). This event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(D),

"Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident."

Corrective Actions include:

A temporary modification was implemented to remove the internals of the two valves, restoring flow to the heat exchangers.

The valves, 2/3-3999-332 and 2/3-3999-334 will be replaced with stainless steel valves.

Valves that are susceptible to conditions identified in the root cause in both the Diesel Generator Cooling Water and Control Room Train 'B' Heating Ventilation and Air Conditioning systems will be inspected to determine if similar conditions exist. The conditions observed during the inspection of these valves will be evaluated to verify that the appropriate corrective measures are in place to prevent recurrence.

July 8, 2002 U.S. Nuclear Regulatory Commission Page 2 If you have any questions, please contact Bob Rybak, Regulatory Assurance Manager at (815) 416-2800.

Respectfully, I#1 R. J. Hovey Site Vice President Dresden Nuclear Power Station Enclosure cc:

Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station

Abstract

On May 9, 2002, while performing the monthly surveillance requirement for the control room heating, ventilation and air conditioning (HVAC) system, the refrigeration condensing unit (RCU) compressor tripped due to high discharge pressure.

A review of the system operating parameters by Operations determined that there was no cooling water flow through the RCU heat exchanger. Troubleshooting of the system determined that the disk from manual valve 2/3-3999-334 (inlet) was separated from the stem and became stuck in the closed position preventing any cooling flow to the Control Room Train B HVAC RCU heat exchanger. Additional investigation determined that manual valve 2/3-3999-332 (outlet) was also found separated from stem but did not block the flowpath. The failed disks of the valves were evaluated and found to be corroded over the entire surfaces. The cause of this event was determined to be a combination of using carbon steel material and frequently exercising the valves in a Service Water environment. Frequent exercising of the valves caused the protective corrosion layer on the ears to be removed, which accelerated the rate of corrosion. The valve internals were removed in accordance with a temporary modification, which allows flow to the heat exchanger. The valves will be replaced with stainless steel valves. The non-safety related Control Room HVAC System "A" Train was available and started during the unavailability of the "B" Train HVAC System RCU. The heat removal capability of the "A" Train System is equivalent to the "B" Train. At no time did this condition compromise the health and safety of the public.

- U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 COMMISSION EXPIRES 0713112004 (7-2001)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

FACILITY NAME (1)

DOCKET NUMBER (2)

ER NUMBER 6 PAGE (3)

YEAR SEQUENTIAL REVISION Dresden Nuclear Power Station Unit 2 05000237 NUMBER NUMBER 2002 003 00 2 of 3 (If more space is required, use additional copies of NRC Form 366A)(17)

A.

Plant Conditions Prior to Event:

Unit: 02 (03)

Event Date: 05-09-2002 Event Time: 1750 CDT Reactor Mode: 1 (1)

Mode Name: Run (Run)

Power Level: 97 (100) percent Reactor Coolant System Pressure: 1005 (1002) psig B.

Description of Event

This event is being reported in accordance with 10 CFR 50.73 (a)(2)(v)(D), which requires reporting "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident."

On May 9, 2002, while performing the Control Room train "B" HVAC and Air Filtration [VI] Surveillance for normal operability run, the refrigeration condensing unit (RCU) compressor tripped due to high discharge pressure. The "B" train of Control Room HVAC system was secured and the "A" train started in accordance with station procedures. A review of the system operating parameters by Operations determined that there was no cooling water flow through the RCU heat exchanger. Troubleshooting of the system determined that the disk from manual valve 2/3-3999-334 (inlet) was separated from the stem and became stuck in the closed position preventing any cooling flow to the Control Room Train B HVAC RCU heat exchanger. Additional investigation determined that manual valve 2/3-3999-332 (outlet) was also found separated from stem but did not block the flowpath. The failed disks of the manual valves were evaluated and found to be corroded over the entire surfaces. A temporary modification was implemented that removed the valve internals, which restored flow to the RCU.

C.

Cause of Event

The root cause of this event was determined to be the combination of using carbon steel material and frequently exercising the valves in a Service Water [BI] environment. (NRC Cause Code E)

Frequent exercising of the valves caused the protective corrosion layer on the ears to be removed, which accelerated the rate of corrosion. The immediate corrective actions were to remove the valve internals in accordance with a temporary modification, which allowed flow to the heat exchanger. Extent of condition revealed similar valves in the Diesel Generator Cooling Water System and the Control Room Train B HVAC RCU system.

Corrective actions are in place to disassemble and inspect these valves.

D.

SafetV AnalVsis:

The non-safety related Control Room HVAC System "A" train was available and started during the unavailability of the "B" train HVAC system RCU. The "A" train system is the normal supply for the control room. The heat removal capability of the "A" train system is equivalent to the "B" train and the "A" train system can be used if "B" train fails to perform its design function. Station procedures provide instructions to power the "A" Train system via an alternate power source if required, in the event of a loss of offsite power. At no time did this condition compromise the health and safety of the public.U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 COMMISSION EXPIRES 0713112004 (7-2001)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISION Dresden Nuclear Power Station Unit 2 05000237 NUMBER NUMBER 2002 003 00 3 of 3 (If more space is required, use additional copies of NRC Form 366A)(17)

E.

Corrective Actions

A temporary configuration control package was implemented to remove the 2/3-3999-332 and 2/3-3999-334 valve internals, which restored flow to the heat exchangers.

Valves 2/3-3999-332 and 2/3-3999-334 will be replaced with stainless steel valves.

Valves that are susceptible to conditions identified in the root cause in both the Diesel Generator Cooling Water and Control Room Train 'B' Heating Ventilation and Air Conditioning systems will be inspected to determine if similar conditions exist. The conditions observed during the inspection of these valves will be evaluated to verify that the appropriate corrective measures are in place to prevent recurrence.

F.

Previous Occurrences

None G.

Component Failure Data

Manufacturer Nomenclature:

Model Number:

Manufacture Part Number:

Nuclear Valve Div. / Borg-Warner 402HBD4-001 N/A