Information Notice 1989-58, Disablement of Turbine-Driven Auxiliary Feedwater Pump Due to Closure of One of the Parallel Steam Supply Valves

Disablement of Turbine-Driven Auxiliary Feedwater Pump Due to Closure of One of the Parallel Steam Supply Valves

ML031180715
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
Issue date:	08/03/1989
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-89-058, NUDOCS 8907280169
Download: ML031180715 (7)

U-

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 August 3, 1989 NRC INFORMATION NOTICE NO. 89-58: DISABLEMENT OF TURBINE-DRIVEN AUXILIARY

FEEDWATER PUMP DUE TO CLOSURE OF ONE OF

THE PARALLEL STEAM SUPPLY VALVES

Addressees

All holders of operating licenses or construction permits for pressurized water

reactors.

Purpose

This information notice is being provided to alert-addressees to the potential

for causing the turbine-driven auxiliary feedwater pump to be incapable of com- pletely performing its intended safety function by closing one of the turbine's

two parallel steam supply valves. 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 do not constitute NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

On January 17, 1989, Diablo Canyon plant personnel closed one of the two

parallel steam supply valves to the turbine-driven auxiliary feedwater pump

without realizing that this would make the auxiliary feedwater system incapable

of meeting the condition assumed in the plant's accident analysis; that is, that the auxiliary feedwater system would supply water to at least two steam

generators.

Steam to the turbine-driven auxiliary feedwater pump is normally provided from

two of the unit's four steam generators, as illustrated in the enclosed figure

of the auxiliary feedwater system. The operators considered operation with

one steam supply available to the auxiliary feedwater pump turbine acceptable

because the technical specification covering the turbine-driven auxiliary

feedwater pump does not specify two sources of steam. It refers only to "an

operable steam supply system" for the auxiliary feedwater pump turbine. The

operators believed that the flow path through one steam supply system satisfied

this requirement.

4i

-r 9: i

IN 89-58 August 3, 1989 Discussion:

The assumption that the auxiliary feedwater system supplies water to at least

two steam generators in the event of a main feedwater line break was not made

in the original Diablo Canyon main feedwater line break analysis. However, the results of this analysis.indicated that the pressurizer would fill and

vent liquid coolant for a significant period of time. After the TMI accident

in which liquid coolant venting from the pressurizer was believed to have

contributed to the accident, the Diablo Canyon main feedwater line break

analysis was redone. Among the major assumptions made in the new analysis

was the assumption that auxiliary feedwater would be supplied to two steam

generators. As a consequence, the new analysis predicted that the reactor

coolant system would sustain the transient without filling the pressurizer.

As shown in the figure, the auxiliary feedwater system has one turbine-driven

pump, which supplies water to all four steam generators, and two motor-driven

pumps, each of which supplies water to a pair of steam generators. In keeping

with the single-failure criterion, the main feedwater line break analysis

assumes that, in addition to the line break, one of the motor-driven pumps

fails. The unacceptability of operation with one of the auxiliary feedwater

pump turbine steam supplies isolated becomes apparent when the broken line is

assumed to be the line feeding the steam generator that provides the remaining

steam supply to the turbine, and the failed pump is assumed to be the one

feeding the remaining pair of unaffected steam generators. Since the steam

generator with the broken feed line rapidly vents all of its coolant, it

cannot supply steam to the pump turbine; with the other steam supply isolated, the turbine-driven auxiliary feedwater pump is lost also. The one remaining

auxiliary feedwater pump feeds the pair of steam generators that includes the

one with the broken feed line. This pump's output will be vented through the

broken line until this line is isolated. After this, the pump can supply water

to only one steam generator. Thus, the assumption in the analysis that two

steam generators will be supplied by auxiliary feedwater cannot be satisfied.

Pacific Gas and Electric Company has revised the procedures at Diablo Canyon

to make it clear to the operators that isolation of one of the auxiliary feed- water pump turbine steam supplies does cause the turbine-driven pump to be

inoperable with respect to the emergency requirements. It should be noted, however, that auxiliary feedwater systems having turbine-driven pumps vary

significantly from plant to plant, even among Westinghouse-supplied plants.

Therefore, isolation of one of the auxiliary feedwater pump turbine steam

supplies at a particular plant might not be contrary to the assumptions in

the safety analyses for that particular plant. Nevertheless, the second

steam supply is an important enhancement in regard to the reliability of

the turbine-driven pump. Regardless of the effect on the safety analysis, it is not likely that one of the steam supplies can be isolated without

significantly reducing the margin of safety for any plant.

IN 89-58 August 3, 1989 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate NRC

regional office.

es E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

J. Wermiel, NRR

(301) 492-0870

Attachments:

1. Figure 1, Diablo Canyon Auxiliary Feedwater System

2. List of Recently Issued NRC Information Notices

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motor

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D ri av

Pumps W2) g l r Main fu

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FIGURE 1. DIABLO CANYON AUXILIARY FEEDWATER SYSTEM

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Attachment 2 IN 89-58 August 3, 1989 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

Qor7 II-I 11.- - - _

Uof-G

uflqualilTlea LiectricaI J/Z6/89 All holders of OLs

Splices in Vendor-Supplied or CPs for nuclear

Environmentally Qualified power reactors.

Equipment

89-56 Questionable Certification 7/20/89 All holders of OLs

of Material Supplied to the or CPs for nuclear

Defense Department by Nuclear power reactors.

Suppliers

89-45, Metalclad, Low-Voltage 7/6/89 All holders of OLs

Supp. 1 Power Circuit Breakers or CPs for nuclear

Refurbished With Substandard power reactors.

Parts

89-55 Degradation of Containment 6/30/89 All holders of OLs

Isolation Capability by a or CPs for nuclear

High-Energy Line Break power reactors.

89-54 Potential Overpressurization 6/23/89 All holders of OLs

of the Component Cooling or CPs for nuclear

Water System power reactors.

89-53 Rupture of Extraction 6/13/89 All holders of OLs

Steam Line on High or CPs for nuclear

Pressure Turbine power reactors.

88-46, Licensee Report of 6/8/89 All holders of OLs

Supp. 3 Defective Refurbished or CPs for nuclear

Circuit Breakers power reactors.

89-52 Potential Fire Damper 6/8/89 All holders of OLs

Operational Problems or CPs for nuclear

power reactors.

89-51 Potential Loss of Required 5/31/89 All holders of OLs

Shutdown Margin During or CPs for nuclear

Refueling Operations power reactors.

88-88, Degradation of Westinghouse 5/31/89 All holders of OLs

Supp. 1 ARD Relays or CPs for nuclear

power reactors.

OL = Operating License

CP = Construction Permit

IN 89-58 August 3, 1989 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate NRC

regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

J. Wermiel, NRR

(301) 492-0870

Attachments:

1. Figure 1, Diablo Canyon Auxiliary Feedwater System

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS PAGE FOR CONCURRENCE

• OGCB:DOEA:NRR *SPLB:DEST:NRR *RPB:ARM *C/OGCB:DOEA:NRR

DCKirkpatrick JWermiel TechEd CHBerlinger

07/25/89 07/25/89 07/21/89 07/24/89

IN 89-XX

July xx, 1989 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate NRC

regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

J. Wermiel, NRR

(301) 492-0870

Attachment: List of Recently Issued NRC Information Notices

OGCB:DOEA:NRR SPLB:DESt:NRR RPB:ARM C/OG .DOEA:NRR D/DOEA:NRR

DCKirkpac JWermiel TechEd)WM CHBerlinger CERossi

07/;Z3-/89gW$ 07/.X789 07/at/89 07#//89 07/ /89