Information Notice 1987-46, Undetected Loss of Reactor Coolant

Undetected Loss of Reactor Coolant

ML031130322
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:	09/30/1987
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-87-046, NUDOCS 8709240315
Download: ML031130322 (9)

SSINS No.: 6835

- IN 87-46 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 September 30, 1987, NRC INFORMATION NOTICE NO. 87-46: UNDETECTED LOSS OF REACTOR COOLANT

Addressees

All pressurized water reactor facilities holding an operating license or a

construction permit.

Purpose

.*

This Information notice iss provided to alert recipients to potentially serious

operational errors that may result in the inadvertent loss of reactor coolant

system (RCS) inventory during abnormal system conditions. It is expected that

recipients will review this information for applicability to their reactor

facilities and consider actions, if appropriate, to prevent similar problems.

Suggestions contained In.this notice do not constitute NRC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

On.June 21,. 1987, the North Anna Unit 1 operators discovered that approximately

17,000 gallons of reactor coolant had been lost from the RCS while the unit was

in cold shutdown. The delay in discovering.the inventory loss resulted from

1 the use of pressurizer level as an indication of reactor coolant inventory,

2 failure to use all available indications, (3) and failure to perform a mass

inventory balance.

On June 17, 1987, while making preparations to start up North Anna Unit 1 following a refueling outage, a problem developed with a reactor coolant pump

motor, requiring removal of the motor. When the problem was discovered, the

unit was at approximately 1950F, 325 psig, with a bubble in the pressurizer.

In order to establish plant conditions for removal of the motor (which may

involve leakage from the RCS), the plant would normally have been (1)cooled to

less than 1400F, (2)drained to mid-nozzle, and.(3) placed on the residual heat

removal system. In order to expedite the work, the plant was cooled to 110*F.,

and the pressurizer was cooled by filling the pressurizer while venting via the

power-operated relief valves (PORVs). The pressurizer level was lowered to 80%

with the PORVs open. The PORVs were then shut because the vapor space tempera- ture led the operators to believe a bubble still existed, and the level was

further lowered to 20%. This was done using a procedure that was not specifi- cally intended for draining the system. The operators did not realize that

lowering the level with the PORVs shut -- and subsequently cooling the pressur- izer -- caused a vacuum to form in the pressurizer, essentially holding the

pressurizer level at 20%.

IN 87-46 September 30, 1987 On June 18, 1987, the pump'motor was uncoupled and a small amount of expected

leakage (estimated 2 gallons-per minute) up the pump shaft was encountered.

This leakage was relatively clean water from the seal injection line past the

pump seals, which did not provide a tight seal when the motor was uncoupled.

Makeup to the RCS was from the volume control tank (VCT). The VCT level was

maintained with VCT pressure greater than reactor pressure. The operators

believed that maintaining the pressurizer level and VCT'level would maintain

the reactor coolant inventory by making up for any losses by flow from the VCT

to the RCS. Voids consisting of non-condensable gases and vapor formed in the

RCS and collected in the system high points (reactor vessel head and steam

generator tubes). The voids were not indicated by any decrease of the pressur- izer level.

On June 21, 1987, a decision was made to reduce the pump shaft leakage by

raising the pressurizer level, cycling the PORVs to vent the pressure,' and, then lowering the pressurizer level to draw a slight vacuum in the pressurizer.

This was a condition that already existed, but'the operators were unaware of

it. When the PORVs were cycled, the pressurizer relief tank pressure dropped, as well as the pressurizer level, indicating that a vacuum already existed in

the pressurizer. The reactor vessel level indicating system (RVLIS) indication

at this time was 79%; however, the operators were not monitoring this indica- tion because the system had been modified during the previous outage and the

operators thought it unreliable. Because of the recorder scale and the time

span visible on the RVLIS trend recorder, the change in the level indication

would-onl-yav&-been noticed (lLwtth aseparatelel -plotor

(2) by rolling

the chart back 12 to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to compare it with the present indTcatf-or. Wh3en- -

the condition was discovered, the operators took action to make up to the RCS

and vent the reactor vessel head, as well as to check other available informa- tion to account for the system inventory. A total of 17,000 gallons of borated

water was required to reestablish the RCS inventory.

Discussion:

The principal error associated with this event is that the operator used only

pressurizer level as an indication of RCS inventory. The operator relied on

this single indication of inventory for an extended period with a known but

unquantified leak from the RCS, rather 'than using other available indications

to confirm reactor inventory.

The RYLIS level was available but was not used, as discussed previously. This

system was not reQuired to be operable while the reactor was shut down.

Recorded RVLIS readings in the recorder viewing window did not show a downward

trend in vessel level until the paper was removed from the recorder and evalu- ated for an extended period, because the level decrease was very gradual.

Also, several work request stickers on the RVLIS display had not been removed

following the modifications made during'the outage. In addition, an inventory

balance was not maintained to show how much water was being collected from the

leak compared with the amount of water being added to the system.

IN 87-46 September 30, 1987 The plant procedures were;not adequate for monitoring'the reactor coolant

inventory. The procedure used to establish plant conditions for removing the

motor did not contain appropriate instructions for monitoring and maintaining

RCS inventory..

The licensee is changing the procedure to require (1) a review of reactor

coolant system inventory and (2)routine surveillance of all available level

indication, including RYLIS.

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.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: R. Croteau, RII

(404) 242-4668 Sam MacKay, NRR

(301) 492-8394 Attachment: List of Recently Issued NRC Information NIotices -.- .  ; - . -,

Attachment

1K 87-46 Septembr 30, 1987 LIST OF RECEIILY ISSUEO

INFOPHATION NOTICES1987 Infrmteton Date of

NoticeNo. Subiect Issuance Issued to

57-45 RecentSefetytRelatiId 9/n5/57 All RRClicensees, Violations ef PC - autorized to poses

Requiremnts by Ift 1strial and use sealed sources

Radiograpy Licernsa is for industrlal radio.

graphy.

87.44 Thimble Tube Thimini qg In 3/16/57 All PWRfacilities

Wetinghou Reactop ts emplaying a M nuclear

$teem supplyfsystoi

holding in OLor CP.

87-43 CpS ton Neutron-AbSCereing M87 'All npcleai per

Material IN mgh.bof r41ty reactor fac1ities

Spent Fuel Storage bchS holding an OL or CP.

87.42 Ofesl Generetor Fus a 9/4/67 All nuclea ruer

Contacts reactor fac1 ities

holding an OL or CP.

87.41 el luree f Certaiw Seal 8131/87 All nuclear poWer

evenr Electric Cirevit reactor facilities

Breakers holdingas OL or CP.

87-40 Bachkseeting Volv& Iboutlnely B/31/87 - All n"ulea posr '

to Prevnt Pecking LLekage reactor facilities

holding so OL or CP.

87-31 Control of Not Perti cle 3/21/87 All nuclear poar

Contamination at Ng leer reactor facilities

PaverPlants and spent fuel

storage facilities

holdingan we

licenseor CP.

57-38 Inadequate or Inadve rtept 8/17/P All ,nucler1 cwer

8l1cking of Valvo Mevest reactor factitie

hol1ingao tL or CP.

OL* Opetig1conse

a Constrtin Permit

- -- ..4.A- . ___ - -

UNITED STATES FIRST CLASS MAIL

NUCLEAR REGULATORY COMMISSION POSTAGE 6 FENS PAID

USNRC

WASHINGTON, D.C. 2055 PERMIT No. O-II

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. $300

IN 87-46 September 30, 1987 The plant procedures were not adequate for monitoring the reactor coolant

inventory. The procedure used to establish plant conditions for removing the

motor did not contain appropriate instructions for monitoring and maintaining

RCS inventory.

The licensee is changing the procedure to require (1) a review of reactor

coolant system inventory and (2) routine surveillance of all available level

indication, including RYLIS.

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.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: R. Croteau, RII

(404) 242-4668 Sam MacKay, NRR

(301) 492-8394 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

• C/OGCB:DOEA:NRR *PPMB:ARM *OGCB:DOEA:NRR *RI I

CHBerlinger TechEd SDMacKay MErnst

09/21/87 08/28/87 08/27/87 07/28/87

• RII *RII *RII *RII *RII

RCroteau FCantrell TPeebles VBrownlee LReyes

07/22/87 07/24/87 07/24/87 07/24/87 07/24/87

IN 87-XX

September xx, 1987 The plant procedures were not adequate for monitoring the reactor coolant

inventory. The procedure used to establish plant conditions for removing the

motor did not contain appropriate instructions for monitoring and maintaining

RCS inventory.

The licensee is changing the procedure to require (1) a review of reactor

coolant system inventory and (2) routine surveillance of all available level

indication, including RVLIS.

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

you have any questions about this matter, please contact the Regional Adminis- trator of the appropriate regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: R. Croteau, RIT

(404) 242-4668 Sam MacKay, NRR

(301) 492-8394 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

D/DOEA:NRR C/OGCB:DOEt;jRR_ *PPMB:ARM *OGCB:DOEA:NRR *RI I

CERossi CHBerl ing:e( TechEd t' SDMacKay MErnst

09/ /87 09/X//87 oWN/T qjiI 08/27/87 07/28/87

• RII *RII *RII *RII *RII

RCroteau FCantrell TPeebles VBrownlee LReyes

07/22/87 807/24/87 07/24/87 07/24/87 07/24/87 e"-j

PN'y"c

IN 87-XX

September xx, 1987 situation degraded, RHR suction may have been lost. Had water level decreased

below the nozzles, the water In the pressurizer may have burped out to the

vessel, providing water for the RHR suction and indicating to the operators

that a problem existed.

The RVLIS level was available but was not used, as discussed previously. This

system was not required to be operable in modes 4, 5, and 6 by the Technical

Specifications. Recorded RVLIS readings in the recorder viewing window did not

show a downward trend in vessel level until the paper was removed from the

recorder and evaluated for an extended period since the level decrease was very

gradual. Also, several work requbtt stickers on the RVLIS display had not been

removed following the modifications made during the outage.

In addition, an inventory balance was not maintained that showed how much water

was being collected from the leak compared to the amount of water being added to

the system.

The procedure used to establish plant conditions for removing the motor was not

adequate and did not contain appropriate instructions for monitoring and

maintaining RCS inventory. The procedure was not written to establish the

conditions for which it was used in this case. Pressurizer level was the sole

means being used by the operators for RCS inventory indication.

The licensee is changing the procedure to require (1) a review of reactor

coolant system inventory and (2) routine surveillance of all available level

indication, including RVLIS. As stated in IN-87-23, the NRC is currently

considering generic action on the issue of loss of decay heat removal during

reduced water level operations.

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

you have any questions about this matter, please contact the Regional Adminis- trator of the appropriate regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: R. Croteau, RIU

(404) 242-4668 Sam MacKay, NRR

(301) 492-8394 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

D/DOEA:NRR C/OGCB:DOEA:NRR *PPMB:ARM *OGCB:DOEA:NRR RII

gay PA'oAuel CERossi CHBerlinger TechEd SDMacKay JNGrace

08/ /87 08/ /87 08/28/87 08/27/87 08/ /87

• RIiS{ *RII *RII *RII *RII *RII

RCroteau FCantrell TPeebles VBrownlee LReyes MErnst

7/22/87 7/24/87 7/24/87 7/24/87 7/24/87 7/28/87

IN 87-XX

August xx, 1987 lost. Had water level decreased below the nozzles, the water in the pressur- izer may have burped out to the vessel providing water for RHR suction and

indication to the operators that a problem existed.

RVLIS level was available but not used as discussed previously. This system

was not required to be operable in modes 4, 5, and 6 by the Technical Specifi- cations. Recorded RVLIS readings in the recorder viewing window did not show a

downward trend in vessel level until the paper was removed from the recorder

and evaluated for an extended period since the level decrease was very gradual.

Also, several work request stickers on the RVLIS display had not been removed

following the modifications made during the outage.

In addition, an inventory balance was not maintained showing how much water was

being collected from the leak compared to the amount of water being added to

the system.

The procedure used to establish plant conditions for removing the motor was not

adequate and did not contain appropriate instructions for monitoring and

maintaining reactor coolant system inventory. The procedure utilized was not

written to establish the conditions for which it was used in this case.

Pressurizer level was the sole means being used by the operators for reactor

coolant system inventory indication.

The licensee is changing the procedure to require (1) a review of reactor

coolant system inventory and (2) routine surveillance of all available level

indication including RVLIS. As stated in IN-87-23, the NRC is currently

considering generic action on the issue of loss of decay heat removal during

reduced water level operations.

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

you have any questions about this matter, please contact the Regional Adminis- trator of the appropriate regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: R. Croteau, RII

(404) 242-4668 Sam MacKay, NRR

(301) 492-8394 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

D/DOEA:NRR C/OGCB:DOEA:NRR PPMB:AjM OGCB:DOEA:NRR RII

CERossi CHBerlinger Techw SDftacKay5' JNGrace

08/ /87 08/ /87 08/$A87 08/z7/87 08/ /87

• RII *RII *RII *RII *RII *RII

RCroteau FCantrell TPeebles VBrownlee LReyes MErnst

7/22/87 7/24/87 7/24/87 7/24/87 7/24/87 7/28/87

N

v 3 RMLIS level was available but not used as discussed previously. This system

was not required to be operable in modes 4, 5, and 6 by the Technical

Specifications. Recorded RVLIS readings in the recorder viewing window did not

show a downward trend in vessel level until the paper was removed from the

recorder and evaluated for an extended period since the level decrease was very

gradual. Also, several work request stickers on the RVLIS display had not been

removed following the modifications made during the outage.

In addition, an inventory balance was not maintained showing how much water was

being collected from the leak compared to the amount of water being added to

the system.

The procedure used to establish plant conditions for removing the motor was not

adequate and did not contain appropriate instructions for monitoring and

maintaining reactor coolant system inventory. The procedure utilized was not

written to establish the conditions for which it was used in this case.

Pressurizer level was the sole means being used by the operators for reactor

coolant system inventory indication.

Following this event, the licensee is changing the procedure used to require (1)

a review of reactor coolant system makeup and loss inventory and (2) routine

surveillance of all available level indication including RVLIS. As stated in

IN-87-23, the NRC is currently considering generic action on the issue of loss

of decay heat removal during reduced level evolutions.

This Information Notice requires no specific action or written response. If

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

Administrator of the appropriate Regional Office or this office.

Charles E. Rossi, Director

Division of Operational Events

Assessment

Office of Nuclear Reactor Regulation

Technical Contacts:

Attachment:

List of Recently Issued NRC X

Information Notices

I RII RII RII RI RII RII

roteau:jt Reantrell Tzeebles lJwniee yes JN e

V87 e7/j%/87 7/xy/87 7 /87

/7