Information Notice 1994-46, Nonconservative Reactor Coolant System Leakage Calculation

Nonconservative Reactor Coolant System Leakage Calculation

ML031070006
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:	06/20/1994
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-94-046, NUDOCS 9406130222
Download: ML031070006 (10)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 June 20, 1994 NRC INFORMATION NOTICE 94-46: NONCONSERVATIVE REACTOR COOLANT SYSTEM LEAKAGE

CALCULATION

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 the potential for water from sources other than

the reactor to be routed to closed system tanks inside the containment and

thus cause a nonconservative evaluation of unidentified reactor coolant system

leakage. 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

McGuire Nuclear Station. On December 7, 1993, during review of the leakage

inputs into the reactor coolant drain tank, the licensee, Duke Power Company, determined that several valve stem leakoff lines other than those associated

with the reactor coolant system or the chemical and volume control system were

connected to the tank. In particular, leakoff water from the cold leg

accumulators and the refueling water storage tank was collected in the reactor

coolant drain tank. The connected cold leg accumulator leakoff lines included

the four nominal 10 in. discharge isolation valves, four nominal 1 in. fill

isolation valves, and seventeen nominal I in. or 1 in. isolation valves

associated with the test header for cold leg accumulator and safety injection

check valves. In addition, a discharge line from a relief valve on a flush

line to the regenerative heat exchanger was connected to the reactor coolant

drain tank. Leakoff from these sources incorrectly increased the value of

identified RCS leakage, resulting in a nonconservative value of unidentified

leakage from the reactor coolant system (Licensee Event Report (LER)

50-369/94-01).

Upon discovery, the licensee conservatively labeled the measured total reactor

coolant system leakage as unidentified. At that time, total leakage was

calculated to be less than 3.8 1/min [1 gal/min]; therefore, the technical

specification limit of 3.8 1/min [1 gal/min] for unidentified leakage was not

exceeded. At each unit, the licensee redirected these leakoff lines to the

containment sump and reevaluated unidentified leakage for the current

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IN 94-46 June 20, 1994 Page 2 OF 3 operating cycle. The licensee found the unidentified leakage to be no greater

than 4.9 1/min [1.3 gal/min] greater than previously evaluated. The licensee

concluded that some leakoff from the non-reactor sources had drained into the

reactor coolant drain tank at each unit and that the technical specification

limit for unidentified leakage had been exceeded several times during the

current operating cycle for Unit 2.

Catawba Nuclear Station. In a similar review, the licensee, also Duke Power

Company, determined that the leakoff lines from the four nominal 10-in. cold

leg accumulator discharge isolation valves were connected to the reactor

coolant drain tank. The licensee redirected these lines to the containment

sump, reevaluated operability, and determined that the technical specification

unidentified leakage limit had not been exceeded during the current operating

cycle.

Discussion

In a pressurized water reactor (PWR), reactor coolant system leakage inside

containment is typically classified as "identified" or "unidentified."

Identified leakage includes the coolant leakage directed into closed system

tanks, such as the leakoff systems for the reactor coolant pumps or valves

routed to the reactor coolant drain tank and the leakoff systems for

pressurizer safety and relief valves routed to the pressurizer relief tank.

All other leakage is labeled "unidentified."

The licensee assigned the cause of the McGuire event to failure in the

original design of the computer program for calculating reactor coolant system

leakage to recognize inputs of water from other systems to the reactor coolant

drain tank. Most PWR leakage detection calculations use measurements of

changes in the reactor coolant system inventory over a specified time period.

The total leakage is obtained from the sum of subsidiary inventory changes, such as changes in the inventories of the volume control tank and of the

pressurizer. The identified leakage component is determined from changes in

the closed system inventory, and the unidentified component is then determined

by subtracting the identified leakage from the total leakage. Typical

technical specifications for PWRs, as is the case here, set the limiting

condition for operation for unidentified leakage at 3.8 I/min [1 gal/min] and

stipulate periodic determinations of this leakage.

IN 94-46 June 20, 1994 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: George F. Maxwell, RII

(704) 875-1681 John Zeiler, RII

(803) 831-2963 Garry A. Harris, RII

(704) 875-1682 Attachment:

List of Recently Issued NRC Information Notices

A tachment

IN 94-46 June 20, 1994 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

94-45 Potential Common-Mode 06/17/94 All holders of OLs or CPs

Failure Mechanism for for nuclear power reactors.

Large Vertical Pumps

94-44 Main Steam Isolation 06/16/94 All holders of OLs or CPs

Valve Failure to Close for nuclear power reactors.

on Demand because of

Inadequate Maintenance

and Testing

94-43 Determination of Primary- 06/10/94 All holders of OLs or CPs

to-Secondary Steam for pressurized water

Generator Leak Rate reactors.

94-42 Cracking in the Lower 06/07/94 All holders of OLs or CPs

Region of the Core for boiling-water reactors

Shroud in Boiling-Water (BWRs).

Reactors

94-41 Problems with General 06/07/94 All holders of OLs or CPs

Electric Type CR124 for nuclear power reactors.

Overload Relay Ambient

Compensation

94-40 Failure of a Rod Control 05/26/94 All holders of OLs or CPs

Cluster Assembly to Fully for pressurized-water

Insert Following a Reactor reactors (PWRs).

Trip at Braidwood Unit 2

94-39 Identified Problems in 05/31/94 All U.S. Nuclear Regulatory

Gamma Stereotactic Commission Teletherapy

Radiosurgery Medical Licensees.

94-38 Results of a Special NRC 05/27/94 All holders of OLs or CPs

Inspection at Dresden for NPRs and all fuel cycle

Nuclear Power Station and materials licensees

Unit 1 Following a Rupture authorized to possess spent

of Service Water Inside fuel.

Containment

OL = Operating License

CP = Construction Permit

IN 94-46 June 20, 1994 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: George F. Maxwell, RII

(704) 875-1681 John Zeiler, RII

(803) 831-2963 Garry A. Harris, RII

(704) 875-1682 Attachment:

List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

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IN 94-XX

June xx, 1994 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical Contacts: George F. Maxwell, RII

(704) 875-1681 John Zeiler, RII

(803) 831-2963 Garry A. Harris, RII

(704) 875-1682 Attachment:

List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

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NAME CVHodge MMejac GFMaxwell JZeiler GAHarris

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June xx, 1994 Page 3 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical Contacts: George F. Maxwell, RII

(704) 875-1681 John Zeiler, RII

(803) 831-2963 Garry A. Harris, RII

(704) 875-1682 Attachment: List of Recently Issued NRC Information Notices

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical Contacts: George F. Maxwell, RII

(704) 875-1681 John Zeiler, RII

(803) 831-2963 Garry A. Harris, RII

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March xx, 1994 Page 3 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical Contacts: George F. Maxwell, RII

(704) 875-1681 John Zeiler, RII

(803) 831-2963 Gary A. Harris, RII

(704) 875-1682 Attachment: List of Recently Issued NRC Information Notices

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