Information Notice 1990-05, Inter-System Discharge of Reactor Coolant

Inter-System Discharge of Reactor Coolant

ML031130342
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	01/29/1990
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-90-005, NUDOCS 9001230126
Download: ML031130342 (8)

UK

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 January 29, 1990

NRC INFORMATION NOTICE NO. 90-05: INTER-SYSTEM DISCHARGE OF REACTOR COOLANT

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is intended to. alert addressees to a potentially

system

significant problem in identifying and terminating reactor coolant will

leakage in operating modes 4 and 5. It is expected that licenseesconsider

review the information for applicability to their facilities and

actions, as appropriate, to avoid similar problems. However, suggestions

contained in this information notice do not constitute NRC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

On December 1, 1989, Braidwood Unit 1 experienced the unplanned inter-system

discharge of approximately 68,000 gallons of water. The discharge was caused

by the inadvertent opening of a residual heat removal (RHR) system suction

relief valve. The valve failed to reclose, allowing an open flow path from

the reactor vessel, through the RHR system, into the unit's two recycle hold-up

tanks (HUTs).

The unit, which had been in a refueling outage since September 2, 1989,4.wasThe

heating up in operational mode 5, preparing to enter operational mode

plant was solid and in the process of drawing a bubble in the pressurizer. The

RHR train "A" pump was in operation and, although the "BO pump was not running, the "B" train was unisolated and available. The reactor coolant system (RCS)

0

was at a pressure of 350 psig .and a temperature of 175 F. Charging flow to the

vessel was being provided by the "A" charging pump. Pressurizer heaters were

on. The "B" charging pump was Isolated and tagged out of service. (Technical

Specifications governing cold overpressure protection require that only one

injection

charging pump be available. The other charging pump and the safety removed).

pumps are required to be tagged out of service, with power supplies

To protect against a pressure switch failure and the subsequent automatic

isolation of the RHR system, the train "A" RHR suction isolation valve was

open and tagged out of service.

90130126 Z#

IN 90-05 January 29, 1990 At 1:42 a.m., operators throttled the charging flow and maximized

flow in preparation for drawing a bubble in the pressurizer. The the letdown

was 404 psig and the pressurizer level was off scale, high. At RCS pressure

1:44 a.m., a

rapid reduction in the pressurizer level occurred, with the pressurizer

off scale, low, at 1:52 a.m. Approximately 14,000 gallons of water level

from the pressurizer and the pressurizer surge line; however, the drained

level instrumentation system indicated that the vessel level remainedreactor vessel

percent. At 1:49 a.m., the charging flow was increased and the at 100

suction was switched from the volume control tank to the refueling charging pump

tank (RWST). water storage

About 30 to 50 gallons of water were observed on the floor of the

building in proximity to the RHR train "AN suction relief valve, auxiliary

personnel to believe that this valve had lifted. At 1:53 a.m., leading plant

flow was reduced to minimum and charging was maximized. The RHR the letdown

switched from "A" to EB", the "A" pump was stopped, and the isolationtrains were

"A" train was initiated. At 1:59 a.m., one of the two running of the

pumps (RCPs) was stopped because of low RCS pressure. reactor coolant

A second charging pump, NBN, was started following completion of

the formal pro- cedure for tagout removal. At 2:35 a.m., the "A RHR suction isolation

was returned to service and closed, completing the isolation of valve

of the RHR system. The pressurizer level began to recover and the the "A" train

increased slightly, giving operators the impression that the discharge RCS pressure

isolated. The *B" charging pump was therefore secured at 2:45 had been

surizer level, however, did not recover. At 2:54 a.m., the ABN a.m. The pres- charging

was restarted. At 3:49 a.m., the inter-system discharge was terminated pump

the RHR train WA" pump was started, the "B pump shut down, and when

the "8' train

was isolated. The level indication for the HUTs stabilized and

the pressurizer

level began to recover at 3:52 a.m.

By 5:06 a.m., the pressurizer level had fully recovered and the

unit was sta- bilized at 360 psi and 1750F. Approximately 68,000 gallons of water

discharged from the reactor vessel to the HUTs. (The total amount had been

was composed of 14,000 gallons of initial pressurizer inventory of water

gallons of makeup water). and 54,000

Following the event, it was determined that the RHR MB" train

suction

valve had lifted at 411 psi. The lift setpoint for the valve should relief

450 psi. The valve should have reclosed on reducing pressure but have been

so. The premature opening of the valve was attributed to the failed to do

material lodged between the valve spindle and the spindle guide. presence of foreign

material either prohibited the correct adjustment of the valve This foreign

or affected the

valve's lift setpoint. The valve's failure to reclose was attributed

proper nozzle ring adjustment. The reset pressure is strongly to im- influenced by

the dynamic forces created by the nozzle ring. If the ring is

located too high

on the nozzle, it may result in an inadequate ventilation area

nozzle. Undesirable forces will develop which may cause a much just above the

pressure. lower reseat

The water found near the RHR train "A" suction relief valve had

leaked from

a weep hole on a relief valve in a radwaste evaporator line connected

to the

IN 90-05 January 29, 1990 common discharge header of the train "A" and "B" suction relief valves. Con- trary to original assumptions, there was no evidence that the OA" train suction

relief valve had lifted. The root cause of the problem with the relief valve

on the evaporation line is under investigation but is thought to be unrelated

to the failure of the 'BM suction relief valve.

Hampering operators' efforts throughout this event was the lack of an appro- priate emergency operating procedure (EOP) to detect coolant leaks while in

operating modes 4 and 5. However, the operators were able to combine two

related abnormal operating procedures for guidance during this event. One

of the procedures is designed to locate system leaks while in modes 3 and 4.

The other provides guidance for the restoration of the RHR system following

its loss during conditions in which the reactor vessel inventory is at a

reduced level.

Discussion:

The event at Braidwood 1 is significant because it underscores the need to

have EOPs available for use in other than 'at power" operating modes. The

fact that over 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> were required to locate the stuck-open valve, to

terminate the discharge, and to begin refilling the pressurizer highlights

the need to provide personnel with adequate tools to perform their tasks.

Relying on ad hoc procedures during significant events places an unnecessary

burden on operating personnel. The lack of adequate EOPs could handicap the

most competent operators in their efforts to address significant operational

problems.

Also illustrated by this event Is the need for procedures to assure that

adequate RCS makeup capability and cooling options are available in a timely

fashion during shutdown. The discharge through the stuck-open relief valve

exceeded the capability of a single charging pump. Starting a second charging

pump required that formal procedures for tag removal be conducted. This effort

necessitated a considerable amount of time, which may not be available should a

similar event occur while the RCS is at a higher temperature.

The severity of this event could have been increased if greater decay heat were

present in the reactor vessel or if a gross failure of the relief valve discharge

header had occurred. Greater decay heat would have increased the potential for

voiding in the core. Also, because the header discharges to the HUTs which are

located outside containment, a piping failure could have resulted in all or a

portion of the RCS water being discharged to the building floor. This event

would have necessitated a major cleanup effort and increased the potential for

personnel contamination.

If this event had occurred at one of the nuclear plants that has a single

suction line from the RCS to the RHR system, all shutdown cooling would

have been lost as a result of isolating the failed suction relief valve.

An alternate heat sink would likely have been required; however, in mode 5, an alternate heat sink may not be readily available.

IN 90-05 January 29, 1990 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 NRR project manager.

arl E. ss, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Nick Fields, NRR

(301) 492-1173 Julian Hinds, RIII

(315) 388-5575 Attachment: List of Recently Issued NRC Information Notices

Attachment

IN 90-05 January 29, 1990 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice-No.. Subject - Issuance Issued to- el 90-04 Cracking of the Upper Shell- 1/26/90 All holders of OLs

to-Transition Cone Girth or CPs for Westinghouse- Welds in Steam Generators designed and Combustion

Engineering-designed

nuclear power reactors.

90-03 Malfunction of Borg-Warner 1/23/90 All holders of OLs

Bolted Bonnet Check Valves or CPs for nuclear

Caused by Failure of the power reactors.

Swing Arm

90-02 Potential Degradation of 1/22/90 All holders of OLs

Secondary Containment or CPs for BWRs.

90-01 Importance of Proper 1/12/90 All holders of NRC

Response to Self-Identified materials licenses.

Violations by Licensees

89-90 Pressurizer Safety Valve 12/28/89 All holders of OLs

Lift Setpoint Shift or CPs for PWRs.

89-89 Event Notification 12/26/89 All holders of OLs

Worksheets or CPs for nuclear

power reactors.

89-88 Recent NRC-Sponsored 12/26/89 All holders of OLs

Testing of Motor-Operated or CPs for nuclear

Valves power reactors.

89-87 Disabling of Emergency 12/19/89 All holders of OLs

Diesel Generators. by or CPs for nuclear

Their Neutral Ground-Fault power reactors.

Protection Circuitry

89-45, Metalclad, Low-Voltage 12/15/89 All holders of OLs

Supp. 2 Power Circuit Breakers or CPs for nuclear

Refurbished with power reactors.

Substandard Parts

89-86 Type HK Circuit Breakers 12/15/89 All holders of OLs

Missing Close Latch Anti- or CPs for nuclear

Shock Springs. power reactors.

OL = Operating License

CP = Construction Permit

IN 90-05 January 29, 1990 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 NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Nick Fields, NRR

(301) 492-1173 Julian Hinds, RIII

(315) 388-5575 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS PAGE FOR CONCURRENCE

• EAB:NRR *TECH:EDITOR *EAB:NRR *C:EAB:NRR *C:OGCB:NRR

NFields:db DCFischer CJHaughney CHBerlinger Ross

1/12/90 1/14/90 1/16/90 1/18/90 1/22 /90 11/.AY9O

. - ; IN 90-

January , 1990 No specific action or written response is required by this information

notice. If you have any questions about this matter, please contact one of

the technical contacts listed below or the Regional Administrator of the

appropriate regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Nick Fields, NRR

(301) 492-1173 Julian Hinds,RIII

(315) 388-5575 Attachment: List of Recently Issued Information Notices

JJV m

I'Ins ofi w coY

EAB:NRR TECH:EDITOR EAB:NRR C: EB:NRR C:OGCB:NRR D:DOEA:NRR

NFields:db DCFischer CJHaughney CHBerlinger CERossi

/ /,1-90 1 /*t/90 1/ i190 I As/90 I/.090 / /90