Information Notice 1986-40, Degraded Ability to Isolate the Reactor Coolant System from Low-Pressure Coolant Systems in BWRs

Degraded Ability to Isolate the Reactor Coolant System from Low-Pressure Coolant Systems in BWRs

ML031250039
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	06/05/1986
From:	Jordan E NRC/IE
To:
References
IN-86-040, NUDOCS 8606030014
Download: ML031250039 (5)

LIS ORIGINALNo: 6835 R E C E IVE D

UNITED STATES Bart D. Withers

NUCLEAR REGULATORY COMMISSION Vice Presdent. Nuclear

OFFICE OF INSPECTION AND ENFORCEMENT *JlJjfi131986 WASHINGTON, D.C. 20555 Route To: .. 'eL _

June 5, 1986 IE INFORMATION NOTICE NO. 86-40: DEGRADED ABILITY TO ISOLATE THE REACTOR

COOLANT SYSTEM FROM LOW-PRESSURE COOLANT

SYSTEMS IN BWRS

Addressees

All nuclear power reactor facilities holding an operating license (OL) or a

construction permit (CP).

Purpose

This notice is provided as a supplement to Information Notice (IN)84-74 on

interfacing systems loss-of-coolant accidents (LOCA) in boiling water reactors

(BWRs) which would bypass primary containment. Two recent events are described

where the high-pressure reactor coolant system could not be fully isolated from

low-pressure piping systems outside of primary containment.

It is expected that recipients will review the information for applicability to

their facilities and consider actions, if appropriate, to preclude similar

problems from occurring at their facilities. However, suggestions contained in

this information notice do not constitute NRC requirements; therefore, no

specific action or written response is required.

Description of Circumstances

Pilgrim

On February 13, 1986, Pilgrim experienced a "design pressure" alarm on the B

loop of the residual heat removal (RHR) system because of leakage through a

check valve (1001-68B) and a motor-operated Isolation valve (1001-288, the

outboard, normally closed, isolation valve) in the line (see Figure 1). The

RHR system has a design pressure of 450 psig compared with a 1250 psig design

pressure of the reactor coolant system. In addition to design pressure alarms, the piping up to the 288 valve had become warm. Several design pressure alarms

had occurred during the preceding several weeks. The licensee's prior correc- tive action had been to vent the lines. On February 13, the licensee closed

the normally open 1001-29B valve and opened the 288 valve to isolate the

system. The licensee planned to operate in this configuration until a sched- uled refueling and maintenance outage in September 1986.

Copies to: YWethers, Yundt, Lentsch, Orser, Steele, E. Burton, E. Jordan, A. Holm,

-.LIS,'C. A. Olmstead, S. Hoag, S. Sautter, TNP:GOV REL F:NRC CHRONO,

TNP:GOV REL F:NRC IE Information Notice 86-40

PGE OAR Action - M. H. Malmros (Due 9/12/86)

NSRD Action - M. H. Malmros

I ,,' :,

IN 86-40

June 5, 1986 29B valve began leaking. Several high

On April 11 and 12, 1986, the closed licensee bled off the line to reduce

pressure alarms were reported. The but within a short period of time, the

pressure and began an orderly shutdown, The 28B valve was closed, but the

high pressure alarm was again received. rate was then increased until the unit

leakage problem continued. The shutdown An NRC augmented inspection team was

scrammed because of other problems. these RHR valve problems and two problems

dispatched to the site to investigate

in other systems.

Duane Arnold

for an outage, Duane Arnold reported

On March 15, 1986, while reducing power coolant injection mode of RHR) isola- closing the outboard LPCI (low-pressure the inboard isolation valve MO-2003 tion valve MO-2004 due to leakage through

(see Figure 2).

small, the ap across the check valve

Because the leakage flow was relatively not high enough to seat the check valve.

inside of containment (CV-2002) was was noted that the pressure controllers on

The problem was discovered when it a pressure of 450 psig rather than the

the RHR heat exchangers were indicating at or

valves had lifted to keep pressure

normal 70 psig. RHR system relief valve stopped the leakage, but because the

below 450 psig. Closing the MO-2004 loops of LPCI were rendered inoperable.

plant has loop selection logic, both and reached cold shutdown on March

16.

The plant continued its planned shutdown the outage.

s_ The leaking valves were repaired during

Discussion:

inac- is leaking valves, one of which is

The underlying cause of this problemPossible solutions include increased sur- cessible with the plant at power. and reliability-based replacement. Other

veillance, preventive maintenance, similar problems include but are not limited

BWR systems that can be subject to injection system (see IE Information Notice

to core spray, high pressure coolant

cooling.

84-74), and reactor core isolation

a low

possible for leakage to exist from the reactor coolant system to safety

It is high pressure alarm or lifting of

pressure system without causing a For example, for the preceding events, if

valves in the low pressure system. one of the RHR pumps is leaking, the

the check valve at the discharge of pool. Hence, slowly increasing

reactor coolhnt will flow to the suppression

indication that there is leakage from

the

level in the suppression pool is one pressure RHR system, and degradation

of the

reactor coolant system to the low If leakage through the degraded valves

were

reactor coolant pressure boundary. could result, as described in the

to increase suddenly, a severe accident

should be noted that such leakage

does not

following paragraph. Further, it criteria 14, 30, and 54 of Appendix A to 10

meet the intent of general design

CFR Part 50.

IN 86-40

. June 5, 1986 The leaking of primary coolant into RHR lines that were never meant to contain

fluid at that temperature and pressure can cause a number of incidents:

over-pressurization with possible faulting of the low pressure line and a LOCA,

steam binding of one or more of the RHR pumps, and waterhammer. The safety

significance of these events is the increased probability of core melt and

releases in excess of 10 CFR 100 limits. The Office of Nuclear Reactor Regula- tions has designated this topic Generic Issue number 105, "Interfacing Systems

LOCA at Boiling Water Reactors," and has given it a "high" priority. A generic

letter concerning staff actions relating to this topic is being considered.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

Divisio oEmrnc epre n Xs

and Engineeri g Response

Office of Inspection and Enforcement

Mary S. Wegner

(301) 492-4511 Attachments:

1. Simplified RHR Diagrams

2. List of Recently Issued IE Information Notices

.4.

Attachment 1 IN 86-40

June 5, 1986 SIMPLIFIED RHR DIAGRAMS

Figure 1 (Original Condition)

Figure 2 (Original Condition) RHR Pump

IP-229C Exchanger A

Attachment 2 IN 86-40

June 5, 1986 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

86-39 Failures Of RHR Pump Motors 5/20/86 All power reactor

And Pump Internals facilities holding

an OL or CP

86-38 Deficient Opera; 'r Actions 5/20/86 All power reactor

Following Dual Function Valve facilities holding

Failures an OL or CP

86-37 Degradation Of Station 5/16/8r All power reactor

Batteries facilities holding

an OL or CP

86-36 Change In NRC Practice 5/16/86 All power reactor

Regarding Issuance Of facilities holding

Confirming Letters To an OL or CP

Principal Contractors

86-35 Fire In Compressible Material 5/15/86 All power reactor

At Dresden Unit 3 facilities holding

an OL or CP

86-34 Improper Assembly, Material 5/13/86 All power reactor

Selection, And Test Of Valves facilities holding

And Their Actuators an OL.or CP

86-33 Information For Licensee 5/6/86 Fuel cycle licensees

Regarding The Chernobyl and Priority 1 material

Nuclear Plant Accident licensees

86-32 Request For Collection Of 5/2/86 All power reactor

Licensee Radioactivity facilities holding

Measurements Attributed To an OL or CP

The Chernobyl Nuclear Plant

Accident

86-31 Unauthorized Transfer and 5/6/86 All power reactor

Loss of Control of facilities holding

Industrial Nuclear Gauges an OL or a CP

OL = Operating License

CP = Construction Permit