Information Notice 1997-40, Potential Nitrogen Accumulation Resulting from Backleakage from Safety Injection Tanks

Potential Nitrogen Accumulation Resulting from Backleakage from Safety Injection Tanks

ML031050497
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
Issue date:	06/26/1997
From:	Slosson M Office of Nuclear Reactor Regulation
To:
References
IN-97-040, NUDOCS 9706230168
Download: ML031050497 (12)

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, DC 20555-0001 June 26, 1997 NRC INFORMATION NOTICE 97-40: POTENTIAL NITROGEN ACCUMULATION

RESULTING FROM BACKLEAKAGE FROM SAFETY

INJECTION TANKS

Addressees

All holders of operating licenses or construction permits for pressurized-water reactors.

Purpose

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

addressees to potential nitrogen accumulation in interfacing systems resulting from

backleakage from safety injection tanks (SITs). 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

Waterford

On November 19 and 21, 1996, Waterford Generating Station, Unit 3, experienced

waterhammer events on the low-pressure safety injection (LPSI) B train. On November 19,

1996, the control room pressure gauge was observed to spike to approximately 3.55 MPa

[500 psig] (normal operating pressure is approximately 1.2 MPa [160 psig]). On

November 21, 1996, the train B piping was vented, and a strip chart recorder was installed to

monitor pressure. A pressure of 4.65 MPa [660 psig] was observed following the start of the

pump. Shortly thereafter, the LPSI train B flow control valve was found partially open

because of a valve mispositioning error by the operations crew. The valve was closed, and

the pump started without a pressure transient. Apparently no structural damage resulted

from the waterhammer events.

On December 13, 1996, LPSI train A experienced a waterhammer event. During a routine

surveillance run of LPSI pump A, the pressure spiked to approximately 2.3 MPa [317 psig].

The licensee's investigation after this event utilized ultrasonic testing (UT) to inspect high

points in the LPSI piping. The licensee identified gas voiding in the horizontal run of the two

A train injection lines of 30.5 cm [12 inches] and 35.5 cm [14 inches) of arc. The injection

lines are 20 cm [8 inches] in diameter. The gas was sampled and found to be approximately

97 percent nitrogen. The licensee concluded that nitrogen-saturated water from the SIT (the

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IN 9740

June 26, 1997 The gas was vented from the A train of LPSI, and LPSI was declared operable on

December 14, 1996. On December 18, 1996, voiding was found in LPSI train B piping, with

arcs of 28 cm (11 inchesl and 25.4 cm [10 inches]. Because of the location of these gas

pockets, the licensee was unable to vent these lines. The licensee performed an operability

evaluation and concluded that the B train remained operable but instituted a UT surveillance

program to inspect the voids every 3 days and identified acceptance criteria for an

acceptable arc length. Furthermore, the licensee was pursuing a design modification to

install high-point vents.

In February 1997, the licensee noted that one of its SITs was experiencing a lowering in

level. Upon investigation, the licensee found that a LPSI system containment isolation valve

was off its shut seat. The licensee surmised that water was leaking from the SIT past check

valves and the partially open isolation valve in the LPSI to the refueling water storage pool

(RWSP). On February 20, 1997, the licensee conducted testing on the isolation valve to

investigate why the valve was not shut. The licensee cycled the valve several times during

the course of this testing. At the completion of the testing, the licensee performed UT of the

A LPSI injection line to check for voiding.

The licensee found that the high horizontal run of piping was dry and that a void extended

203 cm [80 inches) down the vertical run of piping. In response to the large void, the

licensee used a vacuum pump to draw water into the line until the voiding was reduced to a

12.7-cm [5-inch] arc. The reduced arc was within the licensee's acceptance criteria for this

line, and LPSI was declared operable.

The licensee also postulated that the shutdown cooling heat exchanger isolation valves may

be susceptible to waterhammer-induced pressure locking. The isolation valves had been

previously evaluated for a trapped bonnet pressure of 2.2 MPa [300 psig] and found to be

operable. However, there is no assurance that bonnet pressure would not exceed 2.2 MPa

[300 psig] when subjected to a waterhammer pressure surge. There is no evidence that this

pressure locking has occurred in the past, and the licensee believes that this scenario is

unlikely. However, the postulated phenomenon could result in common-mode failure of the

heat exchangers, and the licensee has installed bonnet pressure relief devices.

Sequoyah

In January 1995, during a Sequoyah Unit I scheduled quarterly residual heat removal (RHR)

pump test, a loud metallic noise was heard and movement of the refueling water storage tank

(RWST) suction piping was observed. At the time when the noise was heard and pipe

movement observed, personnel were performing a walkdown of a previously identified

damaged RHR pipe hanger. The RHR system piping was subsequently inspected for gas

voids and approximately .23 cubic meters (8 cubic feet] of gas was identified. A sample

taken of the vented gas determined the gas to be approximately 98 percent nitrogen. The

license believed that the source of the gas was one or more of the Emergency Core Cooling

System (ECCS) Cold Leg Accumulators (CLA) and that there were two potential leakage

IN 97-40

June 26, 1997 paths that water could travel from the CLAs to the RHR injection piping where the nitrogen

gas came out of solution: through the Safety Injection System (SIS) test header and/or

through the secondary check valves on the RHR cold leg Injection lines to the Reactor

Coolant System (RCS). The licensee performed an operability evaluation which determined

that the gas did not affect operability of the RHR system either in normal or accident

conditions.

Over the course of the next several months the licensee periodically vented the RHR piping, monitored the rate of gas accumulation and calculated the gas volume in the RHR piping, and tracked the level decrease of the CLAs. To date, the licensee has not been successful

in identifying and correcting leaking isolation valves in the SIS test header. The Sequoyah

RHR system design and layout may have contributed to the gas accumulation due to the lack

of high point vents in the RHR system and the difficult accessibility of those vents which

were available. In November 1996, the licensee installed a manual vent in the Unit 1 A train

RHR system in a 49 meter 1160 footl section of piping which previously was not completely

ventable.

In October 1996, an analysis of the Unit 1 RHR piping system was performed to determine

the imposed forces resulting from system operation with various volumes of gas in the piping

system. The analysis concluded that the hydraulic forces built up are higher with increasing

volumes of gas but level off when the gas volumes go beyond more than .28 cubic meters

[10 cubic feet). The measured volumes of gas in the Unit 1 RHR system have varied from

approximately .23 cubic meters [8 cubic feet] to .4 cubic meters [14 cubic feet]. The licensee

also calculated that for each gallon of water released from the CLAs, approximately 2.1 liters

[0.073 cubic feet] of gas is released.

Discussion

If SITs or CLAs lose water level, nitrogen gas accumulation could be occurring in interfacing

systems. The presence of large amounts of gas in discharge piping creates the possibility of

waterhammer with potentially significant consequences. Waterhammer of sufficient magni- tude can cause common-mode failure of safety injection trains. Structural failure of the

discharge piping could create a containment bypass release path in addition to preventing

safety injection flow. Additionally, a waterhammer event could potentially cause pressure

locking in some valves. A plant's susceptibility to nitrogen accumulation in the ECCS lines is

dependent on a number of plant-specific factors, including operating pressure of the SITs or

CLAs, elevations and orientation of ECCS injection lines, and the elevation of the RWSP or

RWST. Licensees may wish to evaluate the possibility and effect of gas accumulation on

potentially susceptible systems. Licensees may also wish to evaluate the design of these

systems to ensure adequate venting capability.

IN 97-40

June 26, 1997 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.

Marylee M. Slosson, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Robert D. Starkey, RII Christopher Jackson, NRR

(423) 842-8001 301-415-2947 E-mail: drs@nrc.gov E-mail: cpj@nrc.gov

Phillip Harrell, RIV John Tappert, NRR

(817) 860-8250 301415-1167 E-mail: phhenrc.gov E-mail: jrt@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

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Attachment

IN 97-40

June 26, 1997 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

97-39 Inadequate 10 CFR 72.48 06/26/97 All holders of OLs or CPs

Safety Evaluations of for nuclear power reactors.

Independent Spent Fuel All holders of licenses for

Storage Installations independent spent fuel

storage installations

97-38 Level-Sensing System 06/24/97 All holders of OLs or CPs

Initiates Common-Mode for nuclear power reactors

Failure of High-Pressure- Injection Pumps

96-53, Retrofit to Amersham 660 06/23/97 All industrial radiography

Supp. 1 Posilock Radiography licensees

Camera to Correct Incon- sistency in 10 CFR Part 34 Compatibility

97-37 Main Transformer Fault 06/20/97 All holders of OLs or CPs

with Ensuing Oil Spill for nuclear power reactors

into Turbine Building

97-36 Unplanned Intakes by 06/20/97 All holders of OLs and CPs

Worker of Transuranic permits. All licensees of

Airborne Radioactive of nuclear power reactors

Materials and External in the decommissioning

Exposure Due to Inadequate stage and fuel cycle

Control of Work

97-35 Retrofit to Industrial 06/18/97 All industrial radiography

Nuclear Company (INC) licensees

IR100 Radiography Camera

to Correct Inconsistency

in 10 CFR Part 34 Compatibility

OL = Operating License

CP = Construction Permit

..

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IN 97-40

June 26, 1997 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.

original signed by S. H. Weiss for

Marylee M. Slosson, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Robert D. Starkey, RII Christopher Jackson, NRR

(423) 842-8001 301-415-2947 E-mail: drs@nrc.gov E-mail: cpj@nrc.gov

Phillip Harrell, RIV John Tappert, NRR

(817) 860-8250 301-415-1167 E-mail: phh@nrc.gov E-mail: jrt@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

Tech Editor reviewed 3131/97 DOCUMENT NAME: 97-40.IN

OFFICE Contacts C/SRXB:DSSA C/PECB:DRPM (A)DIDRPM

NAME RStarkey JLyons* AChaffee* MSlosson

CJackson* lu I

PHarrell* fa

_ _ JTappert*

DATE 04/22/87 05/11/97 06/04/97 06t097 Official Rec ord Copy

IN 97-xx

June xx, 1997 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.

Marylee M. Slosson, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Robert D. Starkey, Ril Christopher Jackson, NRR

(423) 842-8001 301-415-2947 E-mail: drs@nrc.gov E-mail: cpj@nrc.gov

Phillip Harrell, RIV John Tappert, NRR

(817) 8604250 301415-1 167 E-mail: phh@nrc.gov E-mail: jrtenrc.gov

Attachment: List of Recently Issued NRC Information Notices

Tech Editor reviewed 3/31/97 DOCUMENT NAME: G:URT1N2VOID.IN

OFFICE Contacts C/SRXB:DSSA CIPECB:DRPM (A)D/DRPM

NAME RStarkey JLyons* AChaffee MSlosson

CJackson*

PHarrell*

_ JTappert2 05111/97 5/____51_/97 DAE 04/22/87 105/11/97 5/ /97 15/ /97 _J

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K2 IN 97-xx

May xx, 1997 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.

Marylee M. Slosson, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Robert D. Starkey, RII Christopher Jackson, NRR

(423) 842-8001 (301) 415-2947 E-mail: drs@nrc.gov E-mail: cpj@nrc.gov

Phillip Harrell, RIV John Tappert, NRR

(817) 860-8250 (301) 415-1167 E-mail: phh@nrc.gov E-mail: jrt@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

Tech Editor reviewed 3131/97 DOCUMENT NAME: G:VRTN2VOID.IN

OFFICE Contacts C/SRXB:DSSA C/PECB:DRPM (A)D/DRPM

NAME RStarkey JLyons*AChaffee MSlosson

CJackson*

PHarrell*

JTappert* _

DATE 04/22/87 05111/97 5/ 197 5/ 197 Official Record Copy Ad

IN 97-xx

May xx, 1997 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 manage

Marylee M. Slosson, Acting Direor

Division of Reactor Program nagement

Office of Nuclear Reactor gulation

Technical contacts: Robert D. Starkey, RII Christopher Jac on, NRR

(423) 842-8001 (301) 415-29 E-mail: drs@nrc.gov E-mail: cpj nrc.gov

Phillip Harrell, RIV John appert, NRR

(817) 860-8250 (30 415-1167 E-mail: phh@nrc.gov E ail: jrt@nrc.gov

Attachment: List of Recently Issued NRC Inform tion Notices

Tech Editor reviewed 3/3147 DOCUMENT NAME: G: ThN2VOID.IN

OFFICE Contacts / CISRXB:DSSA C/PECB:DRPM (A)DIDRPM

NAME RStarkey JLyons* AChaffee MSlosson

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IN 97-xx

May xx, 1997 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 age

Marylee M. Slosson, Acting irector

Division of Reactor ProgrT Management

Office of Nuclear Rea r Regulation

Technical contacts: Robert D. Starkey, RII Christophe ackson, NRR

(423) 842-8001 (301) 41 -2947 E-mail: drs@nrc.gov E-maillcpjnrc.gov

Phillip Harrell, RIV ohn Tappert, NRR

(817) 860-8250 (301) 415-1167 E-mail: phh@nrc.gov E-mail: jrt@nrc.gov

Attachment: List of Recently Issued NR nformation Notices

Tech Editor revie ed 3/31/97 DOCUMENT N ME: G:URTRN2VOID.IN

OFFICE I ntacts C/SRXB:DSSA CIPECB:DRPM D/DRPM

NAME /RStarkey JLyons* AChaffee TMartin

CJackson*

/ PHarreli*

JTappert*

DATE 04/22/87 05111/97 Official Record Co

3W4497

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J K> IN 97-xx

May xx, 1997 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.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Robert D. Starkey, Region II Christopher Jackson, NRR

(423) 842-8001 (301) 415-2947 E-mail: drs@nrc.gov E-mail: cpjenrc.gov

Phillip Harrell, Region IV John Tappert, NRR

(817) 860-8250 (301) 415-1167 E-mail: phhenrc.gov E-mail: jrtenrc.gov

Attachment: List of Recently Issued NRC Information Notices

Tech Editor reviewed 3131/97 DOCUMENT NAME: G:AJRTNN2VOID.IN

OFFICE Contacts C/SRXB:DSSA CIPECB:DRPM DIDRPM

NAME RStarkey JLyons* AChaffee TMartin

CJackson*

PHarrell*

JTappert*

DATE 04122/87 05/11/97 'J13 I

Official Record Copy

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IN 97-xx

April xx, 1997 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.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Robert D. Starkey, Region II Christopher Jackson, NRR

(423) 842-8001 (301) 415-2947 E-mail: drs@nrc.gov E-mail: cpj@nrc.gov

Phillip Harrell, Region IV John Tappert, NRR

(817) 860-8250 (301) 415-1167 E-mail: phh@nrc.gov E-mail: jrt@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

Tech Editor reviewed 3/31/97 DOCUMENT NAME: G:\JRT\N2VOID.IN

OFFICE Contacts C/SRXB:DSSA C/PECB: DRPM D/DRPM

NAME RStarkey -$1YA'J'JLo4 I L144 AChaffee TMartin

CJacksonV elII

PHarrel ^1A X

JTappert __ __I_ _ _ _

DATE . Copy

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