Information Notice 1995-10, Potential for Loss of Automatic Engineered Safety Features Actuation

Potential for Loss of Automatic Engineered Safety Features Actuation
	ML031060352
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:	02/03/1995
From:	Grimes B; Office of Nuclear Reactor Regulation
To:	;
References
	IN-95-010, NUDOCS 9502030313
	Download: ML031060352 (8)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 February 3, 1995 NRC INFORMATION NOTICE 95-10: POTENTIAL FOR LOSS OF AUTOMATIC ENGINEERED

SAFETY FEATURES ACTUATION

Addressees

nuclear power

All holders of operating licenses or construction permits for

reactors.

PurDose

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

notice to alert addressees to the potential for loss of the automatic

actuation function of engineered safety features (ESF) as a result of

expected that

electrical faults in some non-class 1E input signals. Ittoistheir facilities

recipients will review the information for applicabilityproblems. However, and consider actions, as appropriate, to avoid similar not NRC requirements;

suggestions contained in this information notice are

therefore, no specific action or written response is required.

Description of Circumstances

On February 2, 1995, the licensee for the Diablo Canyon facility reported to

of

the NRC a condition that could result in the failuresteamline one train of their

break in the

solid state protection system (SSPS) during a main The licensee postulated

turbine building (10 CFR 50.72 report number 28318). in the turbine building.

a break of a main steamline at the turbine stop valve approximately 10

If the steamline breaks completely, it is free to rotate

could result in the steam

degrees. The 10-degree rotation of the steamline Junction box. The

jet from the faulted steamline striking an electrical signals to the SSPS,

Junction box contains terminations for non-safety input

circuits, two circuits for each

turbine stop valve position indication (four

train).

The force of the steam jet impinging on the Junction box is postulated to

destroy the box and result in electrical faults in the affected non-safety

inputs to the SSPS. The high current resulting from the electrical faults

would cause 15-ampere fuses to open, interrupting 120-V ac power supply to the

faulted circuits. Since dc power supplies for SSPS logic and ESF train

actuation relays are supplied by the same 15-ampere fuses, opening of the

fuses would also interrupt power to the SSPS logic one channels and possibly one

ESF train actuation relay bank. This would render SSPS train inoperable.

If a single failure of the other SSPS train is considered, as is required in

PD/2 Z4.I-1otc 9e-0lo 7~o2I 3

9502030313 Pi( oil ' 1

V<-- IN 95-10

February 3, 1995 the high energy line break analysis methodology, both trains of the SSPS would

be rendered inoperable and no ESF actuations would be The automatically available

reactor trip

to mitigate the consequences of the steamline break. trip. Manual action

circuitry would be de-energized resulting in a reactor

could be initiated to operate individual pieces of equipment.

that provide input

NRC inspectors determined that other non-class IE circuits include turbine auto

to the SSPS were not properly isolated. These circuits class lE standard),

stop oil (three circuits), seismic trip (constructed tocoolant pump breaker

12-kV undervoltage, 12-kV underfrequency, and reactor of these circuits could cause

position indication. An electrical fault in anyway described above.

loss of power to SSPS logic circuit in the same

only one SSPS train

Although a single main steamline break would likely render depending upon the

inoperable, either train could be rendered inoperable the ESF portion of the

location of the steamline break. The licensee declared Technical Specification

solid state protection system inoperable and entered Technical Specification 3.3.2 for inoperable ESF instrumentation and thenshutdown of both units within

3.0.3 limiting condition for operation to start

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

On February 1, 1995, the licensee for the Salem facility notified the NRC that

the SSPS at its facility was similar

it had been determined that the design of report number 28321). The

to that at the Diablo Canyon facility (10 CFR 50.72 have the same

Salem licensee concluded that a main steamline breakatcould the Diablo Canyon

effect on non-class 1E circuits as that postulated

concluded that a seismic event could

facility. In addition, the licensee associated with both

challenge both trains of SSPS since both junction boxes

Canyon licensee

trains of SSPS are located in the turbine building (the Diablo of these non-class

is continuing to evaluate seismic and other vulnerabilities

IE circuits). The circuits that are potentially affected at Salem include

turbine stop valve position indication, auto-stop oil pressure switches, and

reactor coolant pump breaker position indication. could The circuit faults

initiated by the steamline break or seismic event result in loss of

the Diablo Canyon

power to SSPS logic circuitry similar to that postulated byor total loss of the

licensee. The resulting impact would be either a partial trip circuitry would be

automatic actuation function of the SSPS. The reactor would be required to

de-energized, resulting in a reactor trip. Manual action The licensee

mitigate the consequences of a main steamline breakofevent.Unit I as required by

declared the SSPS inoperable and began a shutdown

Technical Specifications. (Unit 2 was already shut down.)

Discussion

The electrical

The licensees are undertaking similar corrective actions.

from a point electrically

supply to the SSPS dc power supplies will be taken This modification will

upstream of the 15-ampere fuse referred to above. in the non-class IE

ensure that opening of the fuse, because of faults IE dc power supplies.

circuits, does not cause a loss of power to the class condition of a single

as-found

Figure 1 is a one-line diagram illustrating the four channels

of are

channel of the SSPS at Diablo Canyon. Two out

<J IN 95-10

February 3, 1995 potentially affected in SSPS Train A and two out of four channels are

potentially affected in SSPS Train B.

a formal

The Diablo Canyon licensee plan for repairs includes draftingjunction boxes, modification procedure, curtailing work near the vulnerable the modificatidn

deferring train-related maintenance and surveillance during a mock-up, period, maintaining constant power level, testing the procedure on(the reactor

de-energizing one channel at a time while modifying that channel

trip bypass breaker will be closed during the modification), training

operators on safety considerations during the repairs, and postmodification

frequency

testing. The licensee estimated that the increase in core damage licensee repair

during the repair period would be less than 2E-7. (The Salem

plan was not available when this information notice was prepared.)

This information notice requires no specific action or writtenpleaseresponse. If

in this notice, contact

you have any questions about the information Office of

one of the technical contacts listed below or the appropriate

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: E. Nick Fields, NRR

(301) 415-1173 Cliff Doutt, NRR

(301) 415-2847 Attachments:

1. Figure 1

2. List of Recently Issued NRC Information Notices

Char

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KPtachment 2 IN 95-10

February 3, 1995 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

95-09 Use of Inappropriate 01/31/95 All holders of OLs or CPs

Guidelines and Criteria for nuclear power reactors.

for Nuclear Piping and

Pipe Support Evaluation

and Design

95-08 Inaccurate Data Obtained 01/30/95 All holders of OLs or CPs

with Clamp-On Ultrasonic for nuclear power reactors.

Flow Measurement Instruments

95-07 Radiopharmaceutical Vial 01/27/95 All USNRC medical licensees

Breakage during Preparation authorized to use byproduct

material for diagnostic

procedures.

95-06 Potential Blockage of 01/25/95 All holders of OLs or CPs

Safety-Related Strainers for nuclear power reactors.

by Material Brought Inside

Containment

95-05 Undervoltage Protection 01/20/95 All holders of Construction

Relay Settings Out of Permits for nuclear power

Tolerance Due to Test reactors.

Equipment Harmonics

95-04 Excessive Cooldown and 01/19/95 All holders of OLs or CPs

Depressurization of the for nuclear power reactors.

Reactor Coolant System

Following a Loss of

Offsite Power

95-03 Loss of Reactor Coolant 01/18/95 All holders of Ols or CPs

Inventory and Potential for nuclear power reactors.

Loss of Emergency Mitiga- tion Functions While in

a Shutdown Condition

OL = Operating License

CP - Construction Permit

IN 95-10

February 3, 1995 potentially affected in SSPS Train A and two out of four channels are

potentially affected in SSPS Train B.

The Diablo Canyon licensee plan for repairs includes drafting a formal

modification procedure, curtailing work near the vulnerable Junction boxes, deferring train-related maintenance and surveillance during the modification

period, maintaining constant power level, testing the procedure on a mock-up, de-energizing one channel at a time while modifying that channel (the reactor

trip bypass breaker will be closed during the modification), training

operators on safety considerations during the repairs, and postmodification

testing. The licensee estimated that the increase in core damage frequency

during the repair period would be less than 2E-7. (The Salem licensee repair

plan was not available when this information notice was prepared.)

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 Project Support

Office of Nuclear Reactor Regulation

Technical contacts: E. Nick Fields, NRR

(301) 415-1173 Cliff Doutt, NRR

(301) 415-2847 Attachments:

1. Figure 1

2. List of Recently Issued NRC Information Notices

DOCUMENT NAME: 95-10.IN

See revious concurrence

OFC OECB:DOPS SC/OECB:DOPS PUB:ADM C/OECB:DOPS

NAME NFields* EGoodwin* Tech Ed* AChaffee*

DATE 02/03/95 02/03/95 02/03/95 02/03/95 OFC HICB:DRCH C/HICB:DRCH D/DRCH

NAME CDoutt4' JWermiel o BBoger+ ___________

DATE 02/03/95 02/03/95 02/03/95 02/ 3!/95 OFFICIAL RECORD COPY

IN 95-XX

February xx, 1995 potentially affected in SSPS Train A and two out of four channels are

potentially affected in SSPS Train B.

The Diablo Canyon licensee plan for repairs includes drafting a formal

modification procedure, curtailing work near the vulnerable junction boxes, deferring train-related maintenance and surveillance during the modification