Information Notice 1990-22, Unanticipated Equipment Actuations Following Restoration of Power to Rosemount Transmitter Trip Units

Unanticipated Equipment Actuations Following Restoration of Power to Rosemount Transmitter Trip Units

ML031140237
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:	03/23/1990
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-90-022, NUDOCS 9003190349
Download: ML031140237 (8)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 March 23, 1990

NRC INFORMATION NOTICE NO. 90-22: UNANTICIPATED EQUIPMENT ACTUATIONS

FOLLOWING RESTORATION OF POWER TO

ROSEMOUNT TRANSMITTER TRIP UNITS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is intended to alert addressees to potential problems

resulting from the reenergization of Rosemount transmitter trip units. 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

The River Bend Station was operating at 100-percent power on February 11, 1990.

While maintenance was being performed on a division 2 battery charger, a sudden

increase in dc bus voltage occurred when the battery charger was placed in the

equalize mode of operation. The voltage increase had a magnitude of less than

10-percent above the nominal voltage while in the equalize mode. However, this

voltage was sufficient to cause the automatic shutdown of a Topaz inverter con- nected to the battery bus that was being energized by the charger. In turn, the Topaz inverter deenergized a number of Rosemount transmitter trip units.

The licensee was aware of the potential for unwanted equipment actuations upon

restoration of power to the transmitter trip units and removed what was believed

to be the affected equipment from service. The battery charger voltage was then

lowered to allow the inverter to reset. Upon resetting the inverter, unexpected

trip signals occurred that resulted in a number of unanticipated equipment

actuations. The most notable of these actuations was the opening of the low- pressure coolant injection (LPCI) valves while the plant was at full power.

The unanticipated trip signals and actuations occurred because the operators

did not have procedures and/or a load list available and could not predict all

components that were affected.

Topaz inverters have an automatic reset feature that operates when the supply

voltage returns to normal. When the battery charger voltage was lowered, the

90031904Z

IN 90-22 March 23, 1990 Rosemount trip units powered by the inverter were immediately reenergized. The

transmitters required several additional milliseconds to completely reenergize.

The transmitter inputs to the trip units decrease to zero on loss of power, and

therefore the inputs were equal to zero when power was restored.

Those trip units that actuate on a decreasing input (i.e., a trip occurs when

the input goes below the setpoint value) reenergized in the tripped condition, even though the actual value of the monitored variable was above the trip set- point. In the first few milliseconds after the inverter reset, the trip units

detected "low" reactor vessel water level which satisfied the LPCI initiation

logic, and "low" reactor pressure which satisfied the low pressure permissive

required to open the LPCI valves. These signals caused the division 2 (trains

B and C) LPCI valves to automatically open as well as numerous other actuations.

This resulted in a single check valve isolation of the high-pressure reactor

coolant system from the low-pressure residual heat removal (RHR) system. Failure

of the single check valve would have overpressurized the RHR piping and could

have resulted in loss of reactor coolant, fbr example, through the failure of

RHR pump seals or other components.

On January 3, 1984, and February 23, 1985, Grand Gulf experienced nearly identi- cal events. In both instances, the plant was at cold shutdown and low-pressure

coolant injection occurred. As in the event at River Bend, a higher than ex- pected voltage occurred when the battery charger was placed in equalize, causing

the Topaz inverters to trip. When the bus voltage was lowered, the inverters

reset and reenergized the Rosemount transmitter trip units.

A similar event occurred at Hope Creek on April 14, 1989. The licensee reported

that while attempting to restore the Topaz inverter, a voltage transient caused

a loss-of-coolant accident initiation signal. The high-pressure coolant

injection system was secured before water was injected into the reactor vessel;

at the time, the plant was at 100-percent power.

Discussion:

The effects of restoration of power to safety-related equipment that is normally

energized are typically not as thoroughly analyzed as the effects of losses of

power. Since the potential for serious consequences exists from unanticipated

component actuations, careful consideration of the effects of restoration of

power to Rosemount transmitter trip units is warranted. The potential may also

exist for unanticipated plant response to restoration of power to similar equip- ment from other manufacturers. Awareness of the potential consequences of

rendering numerous safety-related components inoperable during power operation

to prevent equipment from actuating upon restoration of power is also important.

Degraded transient and accident response capability and the potential for human

errors during these operations are of particular concern.

\-/ IN 90-22 March 23, 1990 The NRC-approved design described in NEDO 21617, "Analog Transmitter Trip

Unit System for Engineered Safeguard Sensor Trip Inputs", includes a redundant

voltage converter leading to the trip units. The voltage converters are auc- tioneered so if one is lost, the other voltage converter supplies power. The

use of the redundant voltage converter would decrease the probability of de- energizing the transmitter trip units. However, other power supply failures

upstream of the voltage converters may also produce events similar to those

described above.

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 1i1 sted below or the appropriate NRR project

manager.

Charles E. Rossi, D rector'

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: P. C. Wagner, RIV

(817) 860-8127 A. Mattson, NRR

(301) 492-1177 R. Kendall, NRR

(301) 492-1192 Attachment: List of Recently Issued NRC Information Notices

Attachh.S

IN 90-22 March 23 1990

Page I of I

LIST OF RECENTLY ISSUED

NRCINFORMATION NOTICES

1lrnt e t~n .

UsIE UT

llntice Mno (,,h 4..

, - ... -.. IUS;gfNc Issued to

90-21 Potential Failure of Motor- 3/22/90 All holders of OLs

Operated Butterfly Valves or CPs for nuclear

to Operate Because Valve power reactors.

Seat Friction was Under- estimated

90-20 Personnel Injuries Resulting 3/22/90 All NRClicensees

from Improper Operation of who process or

Radwaste Incinerators Incinerate radio- active waste.

90-19 Potential Loss of Effective 3/14/90 All holders of OLs

Volume for Containment or CPs for PWRs.

Recirculation Spray at

PWRFacilities

90-18 Potential Problems with 3/9/90 All holders of OLs

Crosby Safety Relief Valves or CPs for nuclear

Used on Diesel Generator power reactors.

Air Start Receiver Tanks

90-17 Weight and Center of 3/8/90 All holders of OLs

Gravity Discrepancies or CPs for nuclear

for Copes-Vulcan Valves power reactors.

89-59. Suppliers of Potentially 3/7/90 All holders of OLs

Supp. 2 Misrepresented Fasteners ,. I or CPs for nuclear

power reactors.

90-16 Compliance with New 3/7/90 All materials licensees.

Decommissioning Rule

90-15 Reciprocity: Notification 3/7/90 All holders of NRC

of Agreement State Radiation materials licenses

Control Directors Before which authorize use

Beginning Work in Agreement of radioactive

States material at temporary

job sites.

90-14 Accidental Disposal of 3/6/90 All U.S. tRCbyproduct

Radioactivt Matertils- fiateria'Ticensees.

OL * Operating License

C * Construction Permit

UNITED STATES

FIRST CLASS MAIL

NUCLEAR REGULATORY COMMISSION POSTAGE b FEES PAID

WASHINGTON, D.C. 20555 USNRC

PERMIT No. 0o67 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, $300

i %a

IN 90-22 March 23, 1990 The NRC-approved design described in NEDO 21617, "Analog Transmitter Trip

Unit System for Engineered Safeguard Sensor Trip Inputs", includes a redundant

voltage converter leading to the trip units. The voltage converters are auc- tioneered so if one is lost, the other voltage converter supplies power. The

use of the redundant voltage converter would decrease the probability of de- energizing the transmitter trip units. However, other power supply failures

upstream of the voltage converters may also produce events similar to those

described above.

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 NRR project

manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: P. C. Wagner, RIV

(817) 860-8127 A. Mattson, NRR

(301) 492-1177 R. Kendall, NRR

(301) 492-1192 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence.

• RIV *EAB:NRR *EAB:NRR *EAB:NRR *AC:OEAB:NRR *RPB:ADM *C:OGCB:NRR

TStetke AMattson RKendall PBaranowsky PBaranowsky TechEd CHBerlinger

3/15/90 3/15/90 3/16/90 3/16/90 3/16/90 3/5/90 3/16/90

3/fl/90

Region IV concurrence 3/15/90 per telcon PWB with TStetke.

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IN 90-XX

March xx, 1990 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 NRR project

manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: P. C. Wagner, RIV

(817) 860-8127 A. Mattson, NRR

(301) 492-1177 R. Kendall, NRR

(301) 492-1192 Attachment: List of Recently Issued NRC Information Notices

• See previous concurrence.

EA 4 AC: gNRR *RPB:ADM *C:OGCU'NRR

RIP

TStetke

3/15/90

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CHBerlinger

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Region IV concurrence 3/15/90 per telcon PW'B with TStetke.

IN 90-XX

March xx, 1990 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 NRR project

manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: P. C. Wagner, RIV

(817) 860-8127 A. Mattson, NRR

(301) 492-1177 R. Kendall, NRR

(301) 492-1192 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES i*D

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-2- The licensee was aware of the potential for unwanted equipment actuation upon

restoration of power to the trip units and had attempted to remove the

affected equipment from service before restoration. Actions taken to

deliberately render safety-related equipment inoperable during power operation

are undesirable because of the degraded transient and accident response

capability and because of the potential for human errors.

Similar Events:

On January 3, 1984 and February 23, 1985, Grand Gulf experienced

nearly identical events. In both instances, the plant was at cold shutdown

and LPCI injection occurred. As in the events at River Bend a higher than

expected voltage occurred when the battery charger was placed into the equalize

mode, causing the Topaz inverters to trip. When the bus voltage was lowered, the inverters reset and reenergized the Rosemount transmitter trip units.

A similar event occurred at Hope Creek on April 14, 1989. The licensee

reported that while attempting to restore the Topaz inverter, a voltage

transient caused a LOCA initation signal. The high pressure coolant injection

system was secured before water was injected into the reactor vessel; at the

time, the plant was at 100 percent power.

Discussion:

The NRC-approved design described in NEDO 21617 includes a redundant voltage

converter leading to the trip units. These voltage converters are

auctioneered so that in the loss of one, the other voltage converter supplies

power. The use of the redundant voltage converter would decrease the

probability of deenergizing the transmitter trip units, and would avoid the

problems encountered with reenergization of the transmitter trip units.

No specific action or written response is required by this information

notice. If you have any questions about this matter, please contact one of

the technical contacts listed below or the Regional Administrator of the

appropriate regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: P. C. Wagner, RIV

(817) 860-8127 A.- Mattson, NRR

(301) 492-1177 R. Kendall, NRR

(301) 492-1192 Attachment: List of Recently Issued NRC Information Notices

OFC :EAB:NPR :EAB:NPP :TC -E :C:OGCB:NRR :D:DOEA:NRR

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