Information Notice 1993-67, Bursting of High Pressure Coolant Injection Steam Line Rupture Discs Injures Plant Personnel

Bursting of High Pressure Coolant Injection Steam Line Rupture Discs Injures Plant Personnel

ML031070135
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, 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, 05000349, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	08/16/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-93-067, NUDOCS 9308100248
Download: ML031070135 (14)

U

-AU

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

August 16, 1993

NRC INFORMATION NOTICE 93-67:

BURSTING OF HIGH PRESSURE COOLANT INJECTION

STEAM LINE RUPTURE DISCS INJURES PLANT

PERSONNEL

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 remind addressees of the hazards associated with steam driven

coolant injection systems such as the high pressure coolant injection (HPCI)

system and the reactor core isolation cooling (RCIC) system at BWRs and the

auxiliary feedwater system at PWRs. 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

X

contained in this information notice are not NRC requirements; therefore, no

specific action or written response is required.

Background

The purpose of HPCI steam exhaust rupture discs is to protect the HPCI turbine

casing and associated exhaust piping from an overpressure event if the normal

exhaust path to the suppression pool becomes blocked.

At Quad Cities Station, two 40.6-cm [16-inch] stainless steel discs are installed in series with a

6.4-cm [2.5-inch] spacer between them to allow for a pressure sensor

instrumentation line. The pressure sensor, while serving no control function, actuates an alarm in the control room at 68.9 kPa [10 psig] to alert the

operators that the inner disc is leaking.

The normal range of the HPCI

exhaust steam pressure is 172 to 207 kPa [25 to 30 psig].- The HPCI high

exhaust pressure turbine trip setpoint is 689 kPa [100 psig] and is sensed by

pressure sensors located downstream from where the section of piping

containing the rupture discs branches off from the exhaust piping. The

section of piping containing the rupture discs is mounted vertically over the

turbine exhaust and vents directly to the HPCI room.

Pressure greater than

1034 kPa [150 psig] in the exhaust line will cause the inner disc to rupture

and impact the outer disc, releasing steam into the HPCI room.

Description of Circumstances

During a quarterly inservice test of the HPCI pump at the Commonwealth Edison

Quad Cities Station, Unit 1, on June 9, 1993, the exhaust steam line rupture

9308100248 F

QrRi

IN 93-67 August 16, 1993 discs burst, releasing steam into the HPCI room, burning, and slightly

contaminating, five workers.

The rupture discs burst within one second after

the turbine was started.

Fire doors between the Unit 1 and Unit 2 HPCI rooms

were blown off their hinges into the Unit 2 HPCI room.

Both sets of double

doors that are part of the secondary containment boundary were also blown

open.

The floor latch on the inner containment door was bent; the outer doors

were also slightly damaged, but were repaired, closed and sealed approximately

35 minutes after the event. The steam release was terminated by automatic

isolation of the steam supply line on high HPCI turbine area temperature about

20 seconds into the event.

Discussion

Upon investigating the event, the licensee determined that water had

accumulated in the turbine casing because the drain system level switches for

the Unit 1 HPCI system had failed. In April 1992, the licensee performed a

reliability-centered maintenance study which recommended the level switches be

included in the preventive maintenance program but the recommendation had not

been acted on at the time of the event. The Unit 2 HPCI drain system level

switches were also found to be inoperable.

The slug of water created during the HPCI turbine roll passed from the turbine

casing to the vertical exhaust line and compressed the air in the 40.6 cm

[16 inch] line containing the rupture discs.

The resulting pressure pulse

caused the inner rupture disc to burst, which impacted the outer disc as

designed and caused it to burst as well.

The exhaust line pressure sensors, located in the horizontal 61 cm [24 inch] exhaust line that tees off from the

vertical 40.6 cm [16 inch] rupture disc line, did not detect a high pressure

(see Figure 1).

The pressure switches were within tolerance and should have

immediately isolated the steam supply upon sensing a high exhaust pressure

before the rupture discs burst.

The fact that a high exhaust line pressure

was not detected indicates two possible causes for the disc rupture.

Either

the inner rupture disc was degraded and burst at lower-than-design pressure, or the pressure pulse actually exceeded the design pressure and caused the

disc to burst, relieving the exhaust line pressure before the downstream

pressure sensors detected a high pressure condition.

While inspection of the rupture discs did not reveal any degradation from

corrosion or aging, the vendor, Black Sivalls & Bryson, Inc, stated that the

discs are warranted for one year of service under normal conditions.

The HPCI

and RCIC rupture discs at Quad Cities Station had been in service for 20 years

and were not part of any scheduled inspection or preventive maintenance

program.

When consulted about the event, the vendor advised against using the

spare discs in the plant storeroom because they were purchased at the same

time as the failed discs. The licensee later replaced the failed discs with

new units.

Before this event, the licensee recently replaced a HPCI rupture

disc during a refueling outage at the Dresden Station, a plant similar to Quad

Cities, after finding a crack in the disc during an inspection.

The rupture

discs were inspected at the Dresden station as part of an enhancement to the

preventive maintenance program that was recommended by a reliability-centered

analysis.

I

I

IN 93-67 August 16, 1993 The steam injured five workers, four of whom were participating in the HPCI

pump surveillance test. The fifth, and m6st severely. injured worker was a

health physics technician in the room on routine rounds, who was not aware of

the danger posed by the surveillance test.

The test procedure contained no

specific guidance on room occupancy.

Interviews with the workers revealed

that they had performed the surveillance in the past and were familiar with

the process.

This familiarity may have led to a relaxed attitude toward

personal safety.

The workers stated that during previous surveillances they

sometimes evacuated the room before rolling the turbine, or stood near the

doors to be ready to escape. The licensee made no routine announcement over

the plant paging system to alert plant personnel before the HPCI-turbine

start, and the workers were not prepared for the turbine to start.

A lack of constant communication between the workersand the control room may

have contributed to the personnel injuries. If a control room operator had

been in contact with the workers in the HPCI room during the turbine roll, the

workers would have been aware of the impending turbine start and, after start, the steam supply might have been manually-isolated or the turbine manually

tripped before the automatic isolation caused by the high area temperatureoin

the HPCI room.

When the Unit 1 HPCI rupture disc failure caused the fire doors to be blown

off their hinges and into the Unit 2 HPCI room, one of the doors impacted a

pipe hanger in the room and moved it 5.1 centimeters [2 inches].

If the steam

release had resulted from a high energy line break from the inlet side of the

HPCI steam line instead of the exhaust line, the damage to the Unit 2 HPCI

system could have been more severe.

While high energy line breaks have been

analyzed for safety systems at all plants, the doors to rooms containing high

energy steam lines may not have been included in the analysis.

For example, at Duane Arnold Energy Center, the licensee discovered that while the HPCI and

RCIC rooms were qualified for pressures of 26.2 kPa [3.8 psig], the doors

between these rooms and the reactor building would yield at 6.9 kPa [1 psig].

The licensee for the Quad Cities Station will implement a preventive

maintenance schedule for both the HPCI and RCIC rupture discs and the level

switches. The licensee will review the surveillance test procedure and

evaluate the missile hazard created by the fire doors. The licensee replaced

the rupture discs for the Unit 2 HPCI and RCIC systems with new ones after the

event at Unit 1 and is considering burst testing the removed discs to

determine if they are degraded.

IN 93-67 August 16, 1993 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 Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grim s, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts:

Clark Vanderniet, RIII

(708) 790-5594

David Skeen, NRR

(301) 504-1174 Attachments:

1. Figure 1, "Simplified Layout of Quad Cities

Station HPCI Turbine Exhaust Steam Line"

2. List of Recently Issued NRC Information Notices

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SUPPRESSION

POOL

1 OUTER RUPTURE DISC

_____

CLOSABLE

CHECK

CHECK VALVE

VALVE

I

INNER RUPTURE DISC

[1 In]

2

40.6 cm

[16 in]

VENT TO

HPCI ROOM

STEAM INLET LINE

FROM "B" MAIN

STEAM LINE

LOCKED

OPEN

I

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RX BLDG

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50.8 cm

[20 In]

61 cm

[24 In]

HPCI ROOM

25 cm

[10 In]

D

NOTES:

1. PRESSURE SWITCH ACTUATES ALARM IN CONTROL ROOM WHEN PRESSURE BETWEEN THE INNER RUPTURE DISC AND OUTER

RUPTURE DISC IS GREATER THAN 68.9 kPa [10 psig]. ALARM IS FOR INNER RUPTURE DISC LEAK DETECTION.

2. REDUNDANT PRESSURE SWITCHES IN EXHAUST STEAM LINE TRIP THE HPCI TURBINE IF PRESSURE IS GREATER THAN 689 kPa [100 psig].

3. RUPTURE DISC MAXIMUM DESIGN BURST PRESSURE IS 1034 kPa [150 psig].

Figure 1 - Simplified Layout of Quad Cities Station HPCI Turbine Exhaust Steam Line

Attachment 2

IN 93-67

August 16, 1993 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

93-66

93-65

93-64

93-63

93-62

93-61

93-60

93-59

93-58 Switchover to Hot-Leg

Injection Following

A Loss-of-Coolant

Accident in Pres- surized Water Reactors

Reactor Trips Caused

by Breaker Testing

with Fault Protection

Bypassed

Periodic Testing and

Preventive Maintenance

of Molded Case Circuit

Breakers

Improper Use of Soluble

Weld Purge Dam Material

Thermal Stratification

of Water in BWR Reactor

Vessels

Excessive Reactor Coolant

Leakage Following A Seal

Failure in A Reactor

Coolant Pump or Reactor

Recirculation Pump

Reporting Fuel Cycle and

Materials Events to the

NRC Operations Center

Unexpected Opening of

Both Doors in An

Airlock

Nonconservatism in Low-

Temperature Overpressure

Protection for Pressurized-

Water Reactors

08/16/93

08/13/93-

08/12/93

08/11/93

08/10/93

08/09/93

08/04/93

07/26/93

07/26/93

All holders of OLs or CPs

for pressurized water

reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for boiling water reactors.

All holders of OLs or CPs

for nuclear power reactors.

All fuel cycle and materials

licensees.

All holders of OLs or CPs

for nuclear power reactors.

All holders of OLs or CPs

for pressurized-water

reactors.

OL = Operating License

CP = Construction Permit

l

IN 93-67 August 16, 1993 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 Office of Nuclear

Reactor Regulation (NRR) project manager.

orig /s/'d by CIGrimes/for

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts:

Clark Vanderniet, RIII

(708) 790-5594

David Skeen, NRR

(301) 504-1174 Attachments:

1. Figure 1, "Simplified Layout of Quad Cities

Station HPCI Turbine Exhaust Steam Line"

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE.

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IN 93-XX

July XX,

1993 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 Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Clark Vanderniet, RIII

(708) 790-5594 David

(301)

Skeen, NRR

504-1174 Attachment:

List of Recently Issued NRC Information Notices

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IN 93-XX

July xx, 1993 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 Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts:

Clark Vanderniet, R-III

(708) 790-5594 David Skeen, NRR

(301) 504-1174 Attachment:

List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

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July xx, 1993 This information notice requires no specific action or written response. If

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one of the technical contacts 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 contacts:

Clark

(708)

Vanderniet, R-III

790-5594

David Skeen, NRR

(301) 504-1174 Attachment:

List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

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the technical contact listed below or the appropriate Office of Nuclear

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Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts:

Clark

(708)

Vanderniet, R-III

790-5594

David Skeen, NRR

(301) 504-1174 Attachment:

List of Recently Issued NRC Information Notices

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