Information Notice 1989-67, Loss of Residual Heat Removal Caused by Accumulator Nitrogen Injection

Loss of Residual Heat Removal Caused by Accumulator Nitrogen Injection

ML031180745
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
Issue date:	09/13/1989
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-89-067, NUDOCS 8909070043
Download: ML031180745 (7)

• - .

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 September 13, 1989 NRC INFORMATION NOTICE NO. 89-67: LOSS OF RESIDUAL HEAT REMOVAL CAUSED

.:BY ACCUMULATOR NITROGEN INJECTION

Addressees

'.: -

All holders of operating licenses or construction permits forLpre~surized water

reactors (PWRs).

Purpose

. '. . .  ;

This information notice is intended to alert addressees to potential problems

resulting from the loss of residual heat removal (RHR) cauied'by the injection

of nitrogen from an accumulator.into the reactor coolantisystemi (RCS). It is

expected that recipients will review the information f6r applicability to'their

facilities and consider actions, as appropriate,'to'avoid'tsimilai problems.

However, suggestions contained in thislinformation notice do' not constitute

NRC requirements; therefore:,-no specific'action or written response is required.

Description of Circumstances

Salem Unit 1 lost both RHR pumps for about 50 minutes'6n:May 20, 1989, as a

result of an injection of nitrogen from an accumulator into the RCS'and, sub- sequently, into the:RHR system. This injection'occurred while the licensee

was conducting full-flow testing of the accumulator check yalves' The reactor

was in Mode 5 (cold shutdown) after-a recent refueling with the reactor.head

installed. .The RCS was filled to a cold calibrated pressurizer level of

10 percent withiair contained;in.the reactor vessel 'head and in'the steam

generator U-tubes. All accumulators were filled to normal operating level

and were pressurized to approximately 600 psig.

At.9:25 a.m., while performing a post-maintenance full-flow test of the check

valves for accumulator 13, the accumulator isolttion valve remained open'for

about 70 seconds as a result of an operator error. During this time, approxi- mately 1800 cubic feet of nitrogen at about 62 psig entered the RCS. As the

nitrogen expanded into the RCS, the pressurizer level went off-scale high, and

the reactor pressure rose from 14 psig to about 51 psig. The operator, not

realizing that nitrogen had been injected-into the RCS, initiated pressurizer

level ,restoration by draining the RCS to the refueling water storage tank

(RWST). At 9:35 a.m., the operator observed zero RHR flow and a reduction

of the pump motor current from 44 amps to about 21 amps.

K 890907004) A

r

IN 89-67 September 13, 1989 The operator, assuming that the pump was'mechanfically damaged, secured the pump

and started the second RHR pump, When this pump exhibited the same character- istics as the other pump, the operator real'zed that the pumps were gas bound

and started venting the RHR system. Venting was slow because of the size of

the vent lines and .an RHR. system qonfiguration that allowed air entrapment.

Operators also had dIfficulty-in locating one vent and drain valve; when it

was located,-an-installed cap had to be removed. Slow venting continued until

10:18 a.m. when the operators initiated filling of the RHR system, using gravity

feed from the RWST. At this time, the core exit temperature had increased to.

1221F from a pre-event value of 920F. At 10:23 a.m., the RHR system was filled, and RHR pump 11 was successfully started. At 10:37 a.m.,.RHR pump 12 was placed

in'service, and RHR pump 11 was secured to'return the system to normal operation.

Because of an inadequate abnormal operating procedure and emergency classifi- cation guide, a 10 CFR 50.72 report for this loss of RHR pumps was not made.

until May 22, 1989.

Discussion: < i

An assessment of this loss-of-RHR-pump event at S'alem'Unit I identified the

folloWing'concernis' ' .' Uni 1 i the

1. 'IThe operators appeaied to believe that nitrogen i~njection lntQ the RCS

'-

was not possible'dui-ng the full-flow test of'the accumulator check valves.

This mindset caused the operators to drain the RCS when the pressurizer

level kept increasing due to the expansion of tnj'ected.nitrogen.'

2. The abnormal operat'in" procedures and the memrge'ncy classification guide

did not adequately address the potentiay' for loss of RHR cooling. The

symptom-oriented procedures did not address the reactor parameters during

a loss of shutdown cooling while in Modes 5 and 6..'Consequently, the

event was nbot r'eporteddfmmediitely under 10 CFR 50.72.

3. The operators were not adequqte ly trained, to differenitiate gas binding of

• theRHR pumps from methanical damage'. Thi s caused the operators to.start

RHR pump 11 when they erroneously' concluded that RHR pump 1Z was mechani- cally damaged. .

4. Elevation differences-f'the RHR suction pipe, the difficulty in locating

one vent and drain' vialve;aid the $ize'of the vent lines caused'the venting

I:opdration to be extrenely-slow. Iaddition, complete system yenting was

not possible because "as was trapped in the high pointsfof the RHR system.

5. .:The appropriateness oif performing-a full-flow test of the accumulator

check valves with fuel in the reactor vessel had not been fully assessed.

An event similar to the one described in this information notice would.

not occur to this extent if this test'had been conducted while the core

was off-loaded. Furthermore, if this test had been performed with either

reduced accumulator nitrogen pressure or with the reactor vessel head

removed, the effects of nitrogen injection into the RCS would have been

minimized.

IN 89-67 September 13, 1989 Ituis important to note that if the accumulator check valve full-flow tests had

been conductedlwhen'they.are more commonly performed, during the shutdown prior

to refueling, and an event similar to the one described in this information

notice had occurred, the consequences could have been much'more significant.

It is also important to'note that operator training provided in response to

NRC Generic Letter 88-17, "Loss of Decay Heat Removal," did assist the operators

in restoring the RHR system once gas binding of the system was recognized.

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.

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Daniel Prochnow, NRR

(301.) 492-1166 Warren Lyon, NRR' - -

.. (301) 492-0891 .

Attachment: List of Recently Issued NRC Information'Notices

..

- .'_... .. _. .

ih aunt

Septesber 13, 1989 Page 1 of I

LIST Of RECENTLY ISSUED

XRC INFORMATION NOTICES

Itotice No SubJect u.Lw or"

issuance Issued to

89-66 Qualification Life of 9/11/89 All holders of OLs

Solenoid Valves or CPs for nuclear

power reactors.

88-41* Licensee Report of 9/11/83 All holders of OLs

Supp. 4 Defective Refurbished or CPs for nuclear

Circuit Breakers power reactors.

89-65 Potential for Stress 9/8/89 All holders of OLE

Corrosion Cracking in or CPs for PURs.

Steen Generator Tube

Plugs Supplied by

Babcock and Wilcox

89-64 Electrical Bus Bar Failures 9/7/89 All holders of OLs

or CPs for nuclear

power reactors.

89-63 Possible Subaurgence of 9/1/89 All holders of OLs

Electrical Circuits Located or CPs for nuclear

Above the Flood Level Because power reactors.

of Water Intrusion and Lack

of Drainage

89-62 Malfunction of Borg-Warner 8/31/89 All holders of OLE

Pressure Seal Bonnet Check or CPs for nuclear

Valves Caused By Vertical. pcwer reactors.

Misalignment of Disk

89-61 Failure of Borg-Warner Gate 8/30/89 All holders of OLs

valves to Close Against or CPs for nuclear

Differential Pressure power reactors.

s8-48, Licensee Report of Defective 8/22/89 All holders of OLE

Supp. 2 Refurbished Valves or CPs for nuclear

power reactor.

89-60 Maintenance of Teletherapy 8/18/89 All NRC Medical

__ _ - Unit _t

T ii1verag-ticense eas

OL

• Operating License

CP

• Construction Permit

UNITED STATES FRT CLASS MAI

NUCLEAR REGULATORY COMMISSION POSTAGE

• FEES PAID

WASHINGTON, D.C. 20555 USNRAC

PERMIT No. 0-w

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. $300

IN 89-67 September 13, 1989 It is important to note that if the accumulator check valve full-flow tests had

been conducted when they are more commonly performed, during the shutdown prior

to refueling, and an event similar to the one described in this information

notice had occurred, the consequences could have been much more significant.

It is also important to note that operator training provided in response to

NRC Generic Letter 88-17, "Loss of Decay Heat Removal," did assist the operators

in restoring the RHR system once gas binding of the system was recognized.

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: Daniel Prochnow, NRR

(301) 492-1166 Warren Lyon, NRR

(301) 492-0891 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

• C/OGCB:DOEA:NRII *RPB:ARM

CHBerlinger TechEd

9/f/89 9/6/89 9/01/89

• OGCB:DOEA:NRR*SRXB:DEST:NRR *C/SRXB:DEST:NRR *SAD/DEST:NRR *D/DEST:NRR

DProchnow WLyon MHodges AThadani JRichardson

8/16/89 8/16/89 8/18/89 8/20/89 8/20/89

.: I. 'a

IN 89-xx

September xx, 1989 It is important to note that if the accumulator check valve full-flow tests had

been conducted when they are more commonly performed, during the shutdown prior

to fuel refueling, and an event similar to the one described in this informa- tion notice had occurred, the consequences could have been much more signifi- cant. It is also important to note that operator training provided in response

to NRC Generic Letter 88-17, "Loss of Decay Heat Removal," did assist the

operators in restoring the RHR system once gas binding of the system was

recognized.

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

you have any questions about the information in this notice, please contact 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: Daniel Prochnow, NRR

(301) 492-1166 Warren Lyon, NRR

(301) 492-0891 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

D/DOEA:NRR C/OGC *RPB:ARM

CERosSi CHBerlin etI TechEd

9/ /89 9/ /89 9/01/89

• OGCB:DOEA:NRR*SRXB:DEST:NRR *C/SRXB:DEST:NRR *SAt/DEST:NRR *D/DEST:NRR

DProchnow WLyon MHodges AThadani JRichardson

8/16/89 8/16/89 8/18/89 8/20/89 8/20/89

IN 89-xx

August xx, 1989 It is also important to note that this event indicated that operator training

provided in response to NRC Generic Letter 88-17 (Loss of Decay Heat Removal)

did assist the operators in restoring the RHR system once gas binding of the

system was recognized.

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

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

the technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Daniel Prochnow, NRR

(301) 492-1166 Warren Lyon, NRR

(301) 492-0891 Attachment: List of Recently Issued NRC Information Notices

OGCB:DOEA:NRR RXB:DEST:NRR C:S DEST: NRR SAD:DEST:NRR f DEST:NRR

DProchnow W8/o/8 MHod es AThadani 'Richardson

8/i1 /89 8/Y6/89 8/l1F/89 - 8/ V4/89 8/2A /89 VSRPM:ARM C:OGCB:DOEA:NRR D:DOEA:NRR

Tech Ed CHBerlinger CERossi

X1 1/89 8/ /89 8/ /89