Information Notice 1991-63, Natural Gas Hazards at Fort St. Vrain Nuclear Generating Station

Natural Gas Hazards at Fort St. Vrain Nuclear Generating Station
	ML031190130
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:	10/03/1991
From:	Rossi C; Office of Nuclear Reactor Regulation
To:	;
References
	FOIA/PA-2015-0150 IN-91-063, NUDOCS 9109270123
	Download: ML031190130 (8)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 October 3, 1991 NRC INFORMATION NOTICE 91-63: NATURAL GAS HAZARDS AT FORT ST. VRAIN

NUCLEAR GENERATING STATION

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 problems that could result from the presence of natural

gas at nuclear facilities. It is expected that recipients will review the

information for applicability to their facilities and consider actions, as

appropriate, to avoid similar problems. Although this notice specifically

describes hazards associated with natural gas, licensees should note that

similar hazards may be imposed by other toxic, flammable, or explosive mate- rials which may be brought into close proximity to licensee's facilities.

However, suggestions contained in this information notice are not new NRC

requirements; therefore, no specific action or written response is required.

Background

When the Fort St. Vrain facility was licensed'in 1973, no natural gas pipelines.

were located nearby; thus, neither the licensee's final safety analysis report'

nor the NRC staff's safety evaluation report addressed the hazards associated

with natural gas present in geological-formations in the area. In 1974, a'

16-inch low pressure natural gas collection pipeline was constructed'nearby by

a natural gas company. This pipeline crossed a corner of the licensee's

property about 0.9 mile from the reactor building. At its closest point, this

pipeline came within 0.85 mile of the reactor building. Although the pipeline

was not constructed by the Public Service Company of Colorado (PSC), the '

Fort St. Vrain licensee, PSC was informed of its construction.

Between 1981 and 1983,-12 natural gas wells were installed within about one

mile of the Fort St. Vrain reactor building. Seven of these wells were drilled

on land owned by the-Fort St. Vrain licensee by a company that had acquired the

mineral rights from the licensee.' Some of these wells were located within the

Exclusion Area Boundary, but all were outside'of the protected area. Nine of

these wells were connected to the 16-inch'collection pipeline by.a 6-inch

pipeline. The closest well was located 1524 feet from the reactor building,;

and the 6-inch pipe passed within 1340 feet'of the reactor building. Personnel

involved in the drilling of these wells and the licensee's manager of nuclear

production concluded that possible accidents at the well sites would not

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IN 91-63 October 3, 1991 produce adverse effects further than 300 feet from the weliheads.

did not prepare any written analyses for any of the wells or pipelines. The licensee

Late in 1987, PSC allowed the drilling of a gas well within 1184 Fort St. {rain reactor building, which was within the Exclusion feet of the

Area Boundary

and 300 feet from the protected area fence. The pipeline associated

well passed within 560 feet of the Fort St. Vrain switchyard. PSC with this

10 CFR 50.59 safety evaluation that concluded that in the event prepared a

fire caused by a blow out, the area affected both by the fire and of a well

needed to control it would not be larger than the existing drillsite the equipment

The licensee also concluded that the air temperature beyond a radius location.

200 feet would not be elevated above the ambient temperature and of

construction and operation of the closest well did not create the therefore, the

of a new type of reactor plant accident or constitute an unreviewed possibility

question. The safety analysis did not evaluate the consequences safety

of

of either the 6-inch or 16-inch pipeline and did not postulate the a rupture

cloud of natural gas which might drift toward safety-related structuresrelease of a

equipment and ignite and either burn or detonate. or

Description of Circumstances

On August 18, 1989, the licensee shut down the Fort St. Vrain facility

letter of August 29, 1989, informed the NRC that the plant would and, by

permanently. In November 1990, the licensee submitted a proposed be shut down

decommission- ing-plan. While-reviewing the-proposed-deconnissioning- an-,th9NRC-became_

concerned that plans to introduce natural gas at Fort St. Vrain

as part of a

proposed repowering of the facility could lead to an accident that

reviewed. During this review, the NRC further determined that the had not been

not adequately addressed the natural gas already on site. The licensee licensee had

sponded by preparing analyses that addressed the limiting failures re- natural gas pipelines existing on site. Before completing these of all

analyses, the

licensee took prompt corrective actions to limit the amount of natural

could be released from a large rupture of the 6-inch collection gas that

These actions consisted of closing a 6-inch valve and opening a pipeline.

bypass valve in the line that carried gas from the wells to the 1 1/2-inch

16-inch collec- tion pipeline. This configuration would reduce the gas leakage

in the 6-inch pipeline by reducing the flow of gas back from the from a rupture

pipeline. 16-inch

The NRC staff reviewed the licensee's analyses including those

flammability and explosive hazards associated with the gas cloudregarding

that could be

released by a postulated-worst-case rupture of a wellhead or pipelines.

the licensee and the NRC determined that, with the compensatory Both

postulated accidents associated with the natural gas on site wouldmeasures taken, the safe storage of spent fuel or other radioactive components in not affect

building. After reaching this conclusion, the NRC issued the Fort the reactor

possession only license (POL) amendment on May 21, 1991. The POL St. Vrain

included a license condition that requires the licensee to obtain amendment

approval before making changes to the collection system that would the NRC's

permanently opening the 6-inch valve. involve

IN 91-63 October 3, 1991 In August 1991, the licensee completed additional analyses which indicated that

postulated explosions or deflagrations resulting from natural gas line ruptures

with the 6-inch line open would not have resulted in unacceptable consequences

at the Fort St. Vrain reactor building or at the switchyard. Nevertheless, PSC

indicated that redundant check valves would be installed in the 6-inch pipeline

to reduce the possibility that natural gas could flow back from the 16-inch

pipeline, if the 6-inch line ruptured.

Discussion of Safety Significance

The natural gas pipelines and wells completed between 1973 and 1983 introduced

additional unanalyzed external hazards that could have affected the safe

operation of the Fort St. Vrain facility. These additional hazards were not

evaluated by the licensee prior to their introduction to the site to determine

the impacts on the safe operation of the plant and whether these hazards

exceeded those evaluated during the initial licensing-of the facility. For the

gas well drilled in 1987, the licensee's 10 CFR 50.59 evaluation was too

narrowly focused and did not consider additional possible malfunctions before

concluding that an unreviewed safety question was not involved.

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 project. manager. .

Charles E. Rossi, Director

// Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: Richard Dudley, Jr., NRR

(301) 492-1116 Stephen Koscielny, NRR

(301) 492-0726 Attachment:

List of Recently Issued NRC Information Notices: 4

2 C

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00

~0 Attachment

IN 91-63 October 3, 1991 CI Page I of I

l aw LIST OFRECENTLY ISSUED

52 NRCINFORMATION NOTICES

I"

Information

Notice No. Date of

Subject Issuance Issued to

91-6z Diesel Engine Damage

Caused by Hydraulic

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-

Issued t

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All holders of OLs or CPs

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Lockup Resulting from for nuclear power reactors.

Fluid Leakage Into

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91-61 Preliminary Results of 09/30/91 Validation Testing of All holders of OLs or CPs

Motor-Operated Valve for nuclear power reactors

Diagnostic Equipment and motor-operated valve

(MOV)diagnostic equipment

vendors identified herein.

91 -60 False Alarms of Alarm 09/24/91 All Nuclear Regulatory Com- Ratemeters Because of

Radiofrequency Inter- mission (NRC) licensees

ference authorized to use sealed

sources for industrial

radiography.

91-59 Problems with Access 09/23/91 All holders of OLs or CPs

Authorization Programs

for nuclear power reactors.

91-58 Dependency of Offset 09/20/91 All holders of OLs or CPs

Disc Butterfly Valve's

Operation on Orientation for nuclear power reactors.

with Respect to Flow

91-57 Operational Experience 09/19/91 C

on Bus Transfers All holders of OLs or CPs

for nuclear power reactors.

91 -56 Potential Radioactive 09/19/91 All holders of OLs or CPs

Leakage to Tank Vented

to Atmosphere for nuclear power reactors.

91-55 Failures Caused by An 09/16/91 All holders of OLs or CPs

Improperly Adjusted Test

Link In 4.16 KV General for nuclear power reactors.

Electric Switchgear

IOL Operating License

Qta CP- Construction Permit

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IN 91-63 October 3, 1991 In August 1991, the licensee completed additional analyses which indicated that

postulated explosions or deflagrations resulting from natural gas line ruptures

with the 6-inch line open would not have resulted in unacceptable consequences

at the Fort St. Vrain reactor building or at the switchyard. Nevertheless, PSC

indicated that redundant check valves would be installed in the 6-inch pipeline

to reduce the possibility that natural gas could flow back from the 16-inch

pipeline, if the 6-inch line ruptured.

Discussion of Safety Significance

The natural gas pipelines and wells completed between 1973 and 1983 introduced

additional unanalyzed external hazards that could have affected the safe

operation Rf the Fort St. Vrain facility. These additional hazards were not

evaluated by the licensee prior to their introduction to the site to determine

the impacts on the safe operation of the plant and whether these hazards

exceeded those evaluated during the initial licensing of the facility. For the

gas well drilled in 1987, the licensee's 10 CFR 50.59 evaluation was too

narrowly focused and did not consider additional possible malfunctions before

concluding that an unreviewed safety question was not involved.

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 project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contacts: Richard Dudley, Jr., NRR

(301) 492-1116 Stephen Koscielny, NRR

(301) 492-0726 Attachment:

List of Recently Issued NRC Information Notices

SEE PREVIOUS CONCURRENCES

D/DOEA:NRR

CERossi(CB for)

09/27/91

C/SPLB:DST:NRR*D/DST:NRR *OGC *RPB:ADM *C/OGCB:DOEA:NRR

CMcCracken ACThadani LJChandler TechEd CHBerlinger

09/16/91 09/20/91 09/04/91 09/05/91 09/27/91

D/DET:NRR *C/ESGB:DET:NlIR*C/EMCB:DET:NRR*EMCB:DET:NRR *D/DAR:NRR

JERichardson GBagchi CYCheng SSKoscielny DCrutchfield

09/13/91 09/12/91 09/12/91 09/12/91 09/12/91

OGCB:DOEA:NRR *PDNP:DAR:NRR *PDNP:DAR:NRR *PDNP:DAR:NRR *D/PDNP:DAR:NRR

RJKiessel EHylton RErickson RDudley SWeiss

09/05/91 06/20/91 06/19/91 09/07/91 09/07/91 DOCUMENT NAME: IN 91-63

IN 91-XX

September xx, 1991 In August 1991, the licensee completed additional analyses which indicated that