Information Notice 1994-52, Inadvertent Containment Spray and Reactor Vessel Draindown at Millstone Unit 1

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Inadvertent Containment Spray and Reactor Vessel Draindown at Millstone Unit 1
ML031060587
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant  Entergy icon.png
Issue date: 07/15/1994
From: Grimes B
Office of Nuclear Reactor Regulation
To:
References
IN-94-052, NUDOCS 9407080145
Download: ML031060587 (10)
v • d • e


UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 July 15, 1994 NRC INFORMATION NOTICE 94-52: INADVERTENT CONTAINMENT SPRAY AND REACTOR

VESSEL DRAINDOWN AT MILLSTONE UNIT 1

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice to alert addressees to the potential for inadvertent containment spray

and reactor vessel draindown as a result of valve misalignment caused by

inadequate procedures. It is expected that recipients will review the

information for applicability to their facilities and consider actions, as

appropriate, to avoid similar problems. However, suggestions contained in

this information notice are not NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

Millstone Unit 1 was shut down in January 1994 for refueling. During the

outage, the licensee planned to test the low-pressure coolant injection (LPCI)

logic system. The LPCI logic system functional test procedure, which had been

performed numerous times in the past, had been revised recently to permit the

licensee to test system valves and the two-thirds core height LPCI/drywell

spray interlock at the same time. This interlock permits manual initiation of

drywell spray via the LPCI system after adequate core cooling has been

achieved. When the event began, both recirculation pumps were running, both

trains of shutdown cooling were operating, and LPCI was not operating (see

Figure 1). The water level in the reactor vessel was 85 inches. Much of the

equipment previously taken out of service during the outage had been restored

to operable status and the licensee considered the shutdown risk from this

test to be low. However, the test procedure included steps to rack out the

breakers for the LPCI pumps and to place the control switch for the core spray

pump in the "pull-to-lock" position, rendering these pumps incapable of

automatically starting in response to a low water level in the reactor vessel.

Most boiling-water reactors use the same pumps for the shutdown cooling and

LPCI functions, but Millstone Unit 1 has separate pumps. The licensee

intended to functionally test the LPCI system valves without flow. While

performing the test on April 10, 1994, the licensee opened the lOB valve,

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IN 94-52 July 15, 1994 pressurizing LPCI loop B and, through the normally open 8A valve, LPCI loop A.

Continuing the procedure, the licensee opened the 15A and 16A valves in the

LPCI system, opening a flow path from LPCI loop A to the drywell spray header.

This alignment allowed approximately 9500 liters per minute (2500 gpm) from

the discharge of the shutdown cooling pumps to be diverted from the reactor

vessel to the drywell (see Figure 2).

The licensee did not realize that the test procedure had established this flow

path. Within about two minutes a high-level alarm for the drywell sump was

received. Approximately two minutes later a control room operator closed the

drywell spray valves, isolating the flow path. The water level in the reactor

vessel decreased approximately 180 cm (70 inches), and a corresponding volume

of water (approximately 46,000 liters [12,000 gallons]) was sprayed into the

drywell. Shutdown cooling continued during the event. If the operator had

not closed the drywell spray valves, the shutdown cooling discharge and

suction valves would have started to close automatically about 30 seconds

later. These shutdown cooling valves would have closed in less than

48 seconds, ending the event. The level instrumentation that initiates this

automatic closure is independent of the instrumentation being tested by the

two-thirds core height interlock logic test.

Normally, if the water level in the reactor vessel had decreased further, LPCI

and the core spray system would have initiated automatically to restore the

level in the reactor vessel. However, the breakers for the LPCI pumps were

racked out for the test, and the core spray pump control switch was in "pull- to-lock," so an operator would have had to start the system.

Discussion

The root cause of this event was the failure of the licensee to adequately

review the procedure. The revised procedure had formal concurrence, including

a determination that integrated review was not required. The combined

procedure was primarily the product of the instrumentation and control staff.

The operations staff was not involved in preparing the procedure or in the

subsequent training, but gave approval to perform the test. The test

procedure gave directions to open not only the drywell spray valves but also

the torus spray valves (13A and 14A) and the valves in a test line to the

torus (43A and 44A). Any of these flow paths would have drained the vessel.

However, during the test one of the torus spray valves was inoperable and was

not opened, so the torus spray flow path was not established. The test flow

path to the torus was not established because the test procedure was stopped

as soon as the drywell spray event occurred.

This event demonstrates the importance of rigorously reviewing procedures for

potential systems interactions and of avoiding inadvertent system lineups that

have the potential to drain the reactor vessel.

IN 94-52 July 15, 1994 Related Generic Communications

Inventory in Boiling Water Reactors During Shutdown and Startup," dated

November 16, 1984

of Misalignment of RHR Valves," dated August 20, 1986

Between Operations and Maintenance Personnel During Valve Testing and

Manipulations," dated June 27, 1991

Instrumentation in BWRs," dated May 28, 1993 This information notice requires no specific action or written response. If

you have any questions regarding the information in this notice, please

contact the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

an K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: Amy Cubbage, NRR

(301) 504-2875 Attachments:

1. Figure 1, System Alignment Prior to the Test

2. Figure 2, System Alignment During the Test

3. List of Recently Issued NRC Information Notices

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>< VALVE OPEN

" VALVE CLOSED

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FROM LPCI 'A' LOOP PUMPS

LOOP PUMPS

Figure 1 System Alignment Prior to the Test

Do VALVE OPEN

" VALVE CLOSED

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FROM LPCI 'B' 4:-

FROM LP.i 'A

LOOP PUMPS

LOOP PUMPS

Figure 2 System Alignment During the Test

Attachment 3 IN 94-52 July 15, 1994 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

94-51 Inappropriate Greasing 07/15/94 All holders of OLs or CPs

of Double Shielded Motor for nuclear power reactors.

Bearings

94-50 Failure of General 07/14/94 All holders of OLs or CPs

Electric Contactors for nuclear power reactors.

to Pull in at the

Required Voltage

94-49 Failure of Torque 07/06/94 All holders of OLs or CPs

Switch Roll Pins for nuclear power reactors.

94-48 Snubber Lubricant 06/30/94 All holders of OLs or CPs

Degradation in High- for nuclear power reactors.

Temperature Environments

94-13, Unanticipated and Unin- 06/28/94 All holders of OLs or CPs

Supp. 1 tended Movement of Fuel for nuclear power reactors.

Assemblies and other

Components due to Improper

Operation of Refueling

Equipment

94-47 Accuracy of Information 06/21/94 All U.S. Nuclear Regulatory

Provided to NRC during Commission Material

the Licensing Process Licensees.

94-46 NonConservative Reactor 06/20/94 All holders of OLs or CPs

Coolant System Leakage for nuclear power reactors.

Calculation

94-45 Potential Common-Mode 06/17/94 All holders of OLs or CPs

Failure Mechanism for for nuclear power reactors.

Large Vertical Pumps

94-44 Main Steam Isolation 06/16/94 All holders of OLs or CPs

Valve Failure to Close for nuclear power reactors.

on Demand because of

Inadequate Maintenance

and Testing

OL = Operating License

CP = Construction Permit

IN 94-52 July 15, 1994 Related Generic Communications

Inventory in Boiling Water Reactors During Shutdown and Startup," dated

November 16, 1984

of Misalignment of RHR Valves," dated August 20, 1986

Between Operations and Maintenance Personnel During Valve Testing and

Manipulations," dated June 27, 1991

Instrumentation in BWRs," dated May 28, 1993 This information notice requires no specific action or written response. If

you have any questions regarding the information in this notice, please

contact the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

oijginl signed by

Wan K. Gfimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: Amy Cubbage, NRR

(301) 504-2875 Attachments:

1. Figure 1, System Alignment Prior to the Test

2. Figure 2, System Alignment During the Test

3. List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCES

Tk- a4to C". Doci~Atnt Tnenortnr and thp PM havp rpvitewad this IN

OFFICE RPB:ADM* OGCB:DORS* RI* OEAB:DORS* SRXB:DSSA*

NAME TechEd AJKugler LTDoerflein TJCarter AECubbage

DATE 06/10/94 06/13/94 06/24/94 06/1 394 06/13/94 OFFICE AC/SRXB:DSSA* AD/DSSA* AC/OGCB:DORS* _DAx

NAME TECollins MJVirgilio RLDennig _ ___es

DATE 06/15/94 06/17/94 06/24/94 07/9 /94 DOCUMENT NAME: 94-52.IN

IN 94-XX

June XX, 1994 Related Generic Communications

Inventory in Boiling Water Reactors During Shutdown and Startup," dated

November 16, 1984

of Misalignment of RHR Valves," dated August 20, 1986

Between Operations and Maintenance Personnel During Valve Testing and

Manipulations," dated June 27, 1991

Instrumentation in BWRs," dated May 28, 1993 This information notice requires no specific action or written response. If

you have any questions regarding the information in this notice, please

contact the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical Contact:

Amy Cubbage, NRR

(301) 504-2875 Attachments:

1. Figure 1, System Alignment Prior to the Test

2. Figure 2, System Alignment During the Test

3. List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCES

Tho cita Sr Resident TnsnActor and the PM have reviewed this IN

OFFICE RPB:ADM* OGCB:DORS* RI* OEAB:DORS* SRXB:DSSA*

NAME TechEd AJKugler LTDoerflein TJCarter AECubbage

DATE 06/10/94 06/13/94 06/24/94 06/13/94 06/13/94 OFFICE AC/SRXB:DSSA* AD/DSSA* AC kNR D/DORS

NAME TECollins MJVirgilio Rg ly BKGrimes

DATE 06/15/94 06/17/94 06/14 /94 06/ /94 DOCUMENT NAME: G:\ANDY\MILLSTON.IN

, .

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IN 94-XX

June XX, 1994 Related Generic Communications

Inventory in Boiling Water Reactors During Shutdown and Startup"

of Misalignment of RHR Valves"

Between Operations and Maintenance Personnel During Valve Testing and

Manipulations"

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

you have any questions regarding the information in this notice, please

contact the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical Contact:

Amy Cubbage, NRR

(301) 504-2875 Attachments:

1. Figure 1, System Alignment Prior to the Test

2. Figure 2, System Alignment During the Test

3. List of Recently Issued NRC Information Notices

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OFFICE RPB:ADM OGCB:DORS RI OEAB:DORSSS

NAME TechEd AJKugler

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DATE 06/10/94 06/l>/94 06/2A4/94 06/ /94 06/45/94 OFFICE AC/SRXB:DSSA AC/OGCB:DORS D/DORS

NAME TECollins MJVirgyfi o RLDennig BKGrimes

DATE 06/1/994 06/ /94 06/ /94 DOCUMENT NAME: G:\ANDY\MILLTONFIN

IN 94-XX

June XX, 1994 Related Generic Communications

Inventory in Boiling Water Reactors During Shutdown and Startup"

of Misalignment of RHR Valves"

Between Operations and Maintenance Personnel During Valve Testing and

Manipulations"

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

you have any questions regarding the information in this notice, please

contact the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical Contact:

Amy Cubbage, NRR

(301) 504-2875 Attachments:

1. Figure 1, System Alignment Prior to the Test

2. Figure 2, System Alignment During the Test

3. List of Recently Issued NRC Information Notices

  • SFF PRFVIOUS CONCURRENCES

OFFICE RPB:ADM OGCB:DORS RI 0 ORSSRXB:DSSA

NAME TechEd AJKugler t EMKelly Vrter AECubbage

DATE 06/10/94 06/11/94 06/ /94 06//3/94 06/ /94 OFFICE AC/SRXB:DSSA AD/DSSA AC/OGCB:DORS D/DORS

NAME TECollins MJVirgilio RLDennig BKGrimes l

DATE 06/ /94 06/ /94 06/ /94 06/ /94 _ _ _ _

DOCUMENT NAME: G:\ANDY\MILLSTON.IN


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