Information Notice 1986-60, Unanalyzed Post-LOCA Release Paths

Unanalyzed Post-LOCA Release Paths

ML031250042
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:	07/28/1986
From:	Jordan E NRC/IE
To:
References
IN-86-060, NUDOCS 8607240023
Download: ML031250042 (5)

L lSSINS No.: 6835 IN 86-60

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 July 28, 1986 IE INFORMATION NOTICE NO. 86-60: UNANALYZED POST-LOCA RELEASE PATHS

Addressees

All nuclear power reactor facilities holding an operating license or a

construction permit.

Purpose

This information notice is being provided to alert recipients to a potentially

significant problem pertaining to substantial possible leakage of radioactive

water flowing in pipes outside containment after a loss-of-coolant accident

(LOCA). The NRC expects that recipients will review this notice for applica- bility to their facilities. Suggestions contained in this notice do not

constitute NRC requirements; therefore, no specific action or written response

is required.

Reference:

NUREG-0737: "Clarification of TMI Action Plan Requirements,"

November 1980. Item III.0.1.1: Integrity of Systems Outside

Containment Likely to Contain Radioactive Material for Pressurized- Water Reactors and Boiling-Water Reactors.

Description of Circumstances

On August 2, 1985, the licensee at Haddam Neck Nuclear Power Plant reported to

the NRC that two potential post-LOCA release paths from containment had been

identified:

1. The following potential post-accident release path resulted from TMI

Action Plan modifications completed in 1981. The release path can come

about in two ways (Figure 1):

a. When the charging system is running and normally aligned, borated

water is injected from the volume control tank (VCT) to the reactor

coolant pump (RCP) seals past the thermal barrier and into the

reactor cooling system (RCS). Some of the seal injection water flows

through the Number 1 seal and returns through a filter and the seal

water heat exchanger to the charging pump suction. Because a charg- ing pump is operating, the seal water return header does not pressur- ize. In the post-LOCA situation, the system operates essentially the

8607240023

IN 86-60

July 28, 1986 same except the injection water is drawn from the refueling water

storage tank (RWST) rather than the VCT and the charging pumps will

automatically start only if normal power is available. To preserve

for the operator the option of running the RCPs after an accident, the licensee removed automatic safety injection and containment

isolation signals to the isolation valves for the RCP auxiliaries

[i.e., seal water (valve A in Figure 1), thermal barrier, and oil

cooler returns]. These isolation valves remain remotely operable

from the control room.

Under post-accident conditions, if offsite power is lost, the charg- ing pumps stop and are not automatically restarted. With no operator

action, the unisolated RCP seal water return line will pressurize

from the seal leakage that is normally routed to the charging pump

suction. This line relieves to the VCT at 140 psig; eventually the

VCT will overflow to the waste treatment system. If no action is

taken to stop the seal water leakage, a flow path for highly radioac- tive fission products to the plant stack would eventually exist

through the waste treatment system. Manual isolation of the seal

water return header (closure of valve A in Figure 1) to the VCT or

manual start of a charging pump would terminate the scenario.

b. At some time after a LOCA when 100,000 gallons have been pumped from

the RWST, the ECCS will take suction from the containment sump

(recirculation mode). If the RCS pressure exceeds the shutoff head

of the residual heat removal (RHR) pumps, the charging system will be"->

manually aligned to take a suction on the RHR system and discharge to

the RCS at a higher pressure. In this mode of operation, if the seal

return header isolation valve (valve B in Figure 1) downstream of the

relief valve to the VCT were to be manually closed or to fail closed

(for example, on loss of control air), the seal water return header

would again pressurize to the point of safety relief at 140 psig.

The licensee informed plant operators of these potential post-accident release

pathways, of expected indications, and appropriate actions to stop the leakage

(either start a charging pump or isolate the return line, based on operator

judgment).

2. The second release path is related to the post-LOCA recirculation mode.

The licensee had considered only RHR system leakage outside containment as

a source of radioactive release during sump recirculation. Because the

charging system may also be used in this recirculation, it could be moving

highly radioactive water outside containment. Previously, the licensee

was monitoring RHR system leakage to assure that it was below the Techni- cal Specification, but not the charging system leakage. The licensee has

now expanded its surveillance to include both systems.

I

IN 86-60

July 28, 1986 Discussion:

These release paths are associated with low frequency events, but because the

associated offsite doses may be significant, licensees may want to consider

these release paths and other release paths that may be unique to their plants

in post-LOCA analyses. Such release paths are related to the referenced TMI

Action Plan item for a program to reduce to as-low-as-reasonably-achievable

(ALARA) levels the leakage from systems outside containment that would or could

contain highly radioactive fluids during a serious transient or accident.

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.

wa . an, Director

Divi n of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Vern Hodge, IE

(301) 492-7275 Attachments:

1. Figure 1

2. List of Recently Issued IE Information Notices

F- RELIEF VALVE

CHECK VALVE

PIC

75 fWAStE

NORMALLY OPEN - TREATMENT

SYSTEM

-*4- NORMALLY CLOSED

SIS-- SAFETY INJECTION SIGNAL 140 PSIG

4<1- AIR-OPERATED VALVE9 V)

C MOTOR-OPERATED VALVE )

FILTER 3SIS TO

CLOSE

1. 1 SEAL WATER RETURN

A __7 SEAL WATER

SIS TO HEATEXCHANGER

CLOSE

Il SEAL NRCP

LEAKOFF

_CHAGlNG RECIRCULATION

CHARGI/G RHR HEAT

EXCHANGER

INSIDE CONTAINMENT

TO OTHER OUTSIDE CONTAINMENT RWST

THROTTLE L OPS

VALVE CHARGING OPEN

PUMP

SEAL WATER C+C+

FLOW CONTROL < co b

VALVE co 0 3

• OaD

Figure 1 Chemical and Volume Control System Seal Water Supply (SImpIlfled-

Attachment 2 IN 86-60

July 28, 1986 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

86-31 Unauthorized Transfer And 7/14/86 All NRC general

Sup. 1 Loss Of Control Of Industrial licensees that possess

Nuclear Gauges and use industrial

nuclear gauges

86-59 Increased Monitoring Of 7/14/86 All NRC licensees

Certain Patients With authorized to use

Implanted Coratomic, Inc. nuclear-powered

Model C-100 and C-101 cardiac pacemakers

Nuclear-Powered Cardiac

Pacemakers

86-58 Dropped Fuel Assembly 7/11/86 All power reactor

facilities holding

an OL or CP

86-57 Operating Problems With 7/11/86 All power reactor

Solenoid Operated Valves At facilities holding

Nuclear Power Plants an OL or CP

86-56 Reliability Of Main Steam 7/10/86 All PWR facilities

Safety Valves holding an OL or CP

86-55 Delayed Access To Safety- 7/10/86 All power reactor

Related Areas And Equipment facilities holding

During Plant Emergencies an OL or CP

86-54 Criminal Prosecution Of A 6/27/86 All holders of NRC

Former Radiation Safety license authorizing

Officer Who Willfully Directed the possession of

An Unqualified Individual To byproduct, source, Perform Radiography or special nuclear

material

86-53 Improper Installation Of Heat 6/26/86 All power reactor

Shrinkable Tubing facilities holding

an OL or CP

86-52 Conductor Insulation Degrada- 6/26/86 All power reactor

tion On Foxboro Model E facilities holding

Controllers an OL or CP

OL = Operating License

CP = Construction Permit