Information Notice 1996-49, Thermally Induced Pressurization of Nuclear Power Facility Piping

Thermally Induced Pressurization of Nuclear Power Facility Piping
	ML031060096
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	08/20/1996
From:	Martin T; Office of Nuclear Reactor Regulation
To:	;
References
	IN-96-049, NUDOCS 9608190050
	Download: ML031060096 (7)
	v • d • e

4 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 August 20, 1996 NRC INFORMATION NOTICE 96-49: THERMALLY INDUCED PRESSURIZATION OF NUCLEAR

POWER FACILITY PIPING

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice to alert addressees to a number of scenarios reported by licensees that

involve thermal expansion of fluid in closed piping that could lead to

overpressurization of the piping and either degraded operability or loss of

function of safety systems. It is expected that recipients will review the

information for applicability to their facilities and consider actions. as

appropriate, to avoid similar problems. However, suggestions contained in

this information notice are not NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

Licensees have reported actual and postulated situations in which the thermal

expansion of water in piping systems within containment could produce

undesirable consequences. Two situations are presented in this notice to

illustrate the range of scenarios, the postulated consequences, and the

corrective actions taken. Each situation involves the heating of a section of

water-filled piping between two closed block or isolation valves. Although

the examples involve piping inside containment, this condition could arise

elsewhere in the facility.

Beaver Valley Unit 1 The first scenario was reported by the licensee for the Beaver Valley facility

in a notification dated July 3. 1996. During surveillance testing of a motor- operated butterfly valve located in the component cooling water inlet line to

the residual heat removal heat exchanger, it was observed that the valve which

was located inside containment would not open. The licensee investigation

revealed that pressure in the piping section between this valve and a closed

manual butterfly valve located outside containment was measured as being

slightly higher than the system design pressure. After the pressure was

relieved by the opening of a drain valve, the remotely operated valve was

opened. The pressurization was caused by an increase in trapped water

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IN 96-49 August 20, 1996 temperature due to an increase in ambient temperatures from the conditions

that existed in the Spring. when the valves were closed, to those that existed

after plant heatup to mode 1 with a summer temperature of about 32 degrees C

[90 degrees F]. This could potentially jeopardize the structural integrity of

the containment penetration. Immediate corrective actions for this and other

piping sections without thermal relief included draining fluid from piping

sections and opening the inboard valve to provide access to relief protection.

The identified root cause was inadequate design reviews relating to contain- ment penetration relief protection.

Maine Yankee

The second scenario was reported by the licensee for the Maine Yankee facility

in a notification dated July 19. 1996. The primary component cooling water

system at Maine Yankee has a nonsafety-related subdivision that serves the

containment air coolers. and a safety-related subdivision that serves the

emergency core cooling system equipment. The nonsafety subdivision of the

piping has a swing-check valve at the containment inlet (supply) penetration.

and an air-operated valve at the containment outlet (return) penetration. In

a postulated accident scenario (a loss-of-coolantaccident), the containment

isolation logic would initiate closure of the outlet valve, thereby causing

water flow to cease. Heat from the containment environment would cause the

water in the fan coolers between the inlet check valve and closed outlet valve

to expand. potentially causing a rupture in the system. The rupture would

depressurize the isolated portion of the system and reestablish water flow

from the operating safety-related portion located outside containment through

the inlet check valve. The water would spill from the rupture and deplete the

surge tank, thereby causing failure from overheating of safety-related

equipment served by the remainder of the system. Upon identifying this

postulated scenario, the licensee promptly shut down the facility. Other

closed systems and containment penetrations were evaluated. As a result, the

licensee took corrective action which included the installation of a pressure

relief valve on each of the six containment air cooler branch lines.

Discussion

Because of thermal expansion. water heated while trapped in closed piping is

capable of producing extremely high pressures. This phenomenon is typically a

design consideration. Piping design codes as far back as USAS B31.1 have

required consideration of fluid pressure caused by heating of fluid trapped

between two valves. The potential for thermally induced expansion of fluid

trapped in valve bonnets was one reason for issuing Generic Letter 95-07,

"Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate

Valves." In addition, several information notices have been issued discussing

pressurization of water trapped in valve bonnets.

The potential for failure of systems to perform their safety functions as a

result of thermally-induced overpressurization is dependent on many factors.

These factors include leak-tightness of valve seats, bonnets, packing glands

and flange gaskets: piping and component material properties, location and

geometry: ambient and post-accident temperature response: pipe fracture

mechanisms: fan coastdown characteristics and the effect of fan operation on

IN 96-49 August 20, 1996 water in the associated fan cooling system; relief valves and their settings:

and system isolation logic and setpoints. Engineering design and modification

evaluations, which include systematic evaluation of heat input to systems and

components with consideration of factors such as those above, can detect

conditions which may influence system operability under normal operations, operational transients and accident conditions.

Please also note that under the "single-failure concept," thermal over- pressurization is a consequence of the event and is not considered to be an

independent active or passive failure. Active or passive failures must also

be considered in the same and other systems in evaluating plant response to a

postulated accident. If relief valves are installed to prevent overpressure

conditions, consideration must be given to the effects of a stuck-open relief

valve and consequent diversion of system flow, associated environmental

flooding and radiation hazards.

This information notice requires no specific action or written response. If

you have any questions about information in this notice, please contact one of

the technical contacts listed below or the appropriate Office of Nuclear

Reactor Regulation project manager.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Jerry Carter. NRR

(301) 415-1153 Email: tjc@nrc.gov

Bill Long, NRR

(301) 415-3026 Email: wol@nrc.gov

Attachmen ist f Recently Issued NRC Information Notices

'el H '. e

Attachment

IN 96-49 August 20. 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-48 Motor-Operated Valve 08/21/96 All holders of OLs or CPs

Performance Issues for nuclear power reactors

96-47 Recordkeeping, Decommis- 08/19/96 All U.S. Nuclear Regulatory

sioning Notifications for Commission licensees

Disposals of Radioactive

Waste by Land Burial

Authorized Under Former

10 CFR 20.304. 20.302, and Current 20.2002

96-46 Zinc Plating of Hardened 08/12/96 All holders of OLs or CPs

Metal Parts and Removal for nuclear power reactors

of Protective Coatings

in Refurbished Circuit

Breakers

96-45 Potential Common-Mode 8/12/96 All holders of OLs or CPs

Post-Accident Failure of for nuclear power reactors

Containment Coolers

96-44 Failure of Reactor 8/05/96 All holders of OLs or CPs

Trip Breaker from Cracking for nuclear power reactors

of Phenolic Material in

secondary contact assembly

96-43 Failures of General 08/02/96 All holders of OLs or CPs

Electric Magne-Blast for nuclear power reactors

Circuit Breakers

96-42 Unexpected Opening of 08/05/96 All holders of OLs or CPs

Multiple Safety Relief for nuclear power reactors

Valves

96-41 Effects of a Decrease in 07/26/96 All holders of OLs or CPs

Feedwater Temperature on for pressurized water

Nuclear Instrumentation reactors

96-40 Deficiencies in Material 07/25/96 All holders of OLs or CPs

Dedication and Procurement for nuclear power reactors

Practices and in Audits of

Vendors

OL = Operating License

CP = Construction Permit

%~IN 96-49 August 20, 1996 water in the associated fan cooling system; relief valves and their settings: