05000369/LER-1982-007, Forwards LER 82-007/03L-0.Detailed Event Analysis Encl

Forwards LER 82-007/03L-0.Detailed Event Analysis Encl

ML20071H412
Person / Time
Site:	McGuire
Issue date:	02/16/1982
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20071H414	List: 05000369/LER-1982-007, Forwards LER 82-007/03L-0.Detailed Event Analysis Encl 05000369/LER-1982-007-03, /03L-0:on 820111,many Instrument Lines Froze W/ Instruments Declared Inoperable Leading to Inadvertent Actuation of ESF Causing Safety Injection,Steamline Isolation & Reactor Trips.Caused by Cold Weather
References
TAC-48049, NUDOCS 8203080407
Download: ML20071H412 (7)

LER-1982-007, Forwards LER 82-007/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691982007R00 - NRC Website

text

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DUKE POWER COMI%NY Powen llun.nswo

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422 SouTu Cnencu STREET, CnAHwTTE, N. C. 28242 $ ' '

!i February 16, 1982

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v.c r p....or.a Setaw Pnoovction 373-4083 Mr. J. P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission m

Region II c3 101 Marietta Street, Suite 3100 g

Atlanta, Georgia 30303

..I h,5CElygn

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'f4tg Re: McGuire Nuclear Station Unit 1 I982h 'Il Docket No. 50-369 Nj

Dear Mr. O'Reilly:

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Please find attached Reportable Occurrence Report R0-369/82-07. This report concerns T.S.3.3.2, "The Engineered Safety Feature Actuation System (ESFAS) instrumentation channels and interlocks shown in Table 3.3-3 shall be oper-able...".

This incident was considered to be of no significance with respect to the health and safety of the public.

A report will be submitted pursuant to T.S.6.9.2 in fulfillment of the special report provision of T.S.3.5.2(action b) concerning the inadvertent safety a

injection, by April 9, 1982.

V truly yours, b._..,

ce,

.N William O. Parker, Jr.

PBN/j fw Attachments cc: Director Records Center Office of Management and Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C.

20555 Atlanta, Georgia 30339 Mr. P. R. Bemis Senior Resident Inspector-NRC McGuire Nuclear Station npy1CIM 82030B0407 020216 4

PDR ADOCK 05000369 e4e S

PDR

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DUKE POWER COMPANY McGUIRE NUCLEAR STATION REPORTABLE OCCURRENCE REPORT NO. 82-07 REPORT DATE: February 16, 1982 FACILITY: McGuire Unit 1, Cornelius, NC IDENTIFICATION: Engineered Safety Features Actuation and Reactor Trip Resulting from Extreme Cold Weather DISCUSSIqd: On January 11, 1982, while at 75% reactor power, Unit 1 experienced an inadvertent actuation of Engineered Safety Features (ESF) causing safety injec-tion (SI), steamline isolation, and reactor and turbine trips. ESF was automat-ically actuated as a result of a two-out-of-three low pressure coincidence trip of steam generator (S/G) "A" pressure instrumentation channels. Both channels tripped when pressure was released from their impluse lines through manually cracked open test connections.

In the progress of this event, abnormal efforts were employed to maintain power production. Extremely cold weather was being experienced throughout the South-east, and record peak power demands were predicted for Monday morning, January 11.

With several major power units off-line, it was considered essential to keep McGuire Unit 1 operating.

Exposure to the cold conditions began to cause errors in Unit 1 parameter measure-ment on January 10.

When frozer; impluse lines disabled automatic feedwater control, efforts to prevent instrument lines from freezing were initiated by installing portable heaters in the exterior doghouse. During the day the effects of the cold escalated (see " Sequence of Events").

By about 2200, when safety related instrument lines began to freeze, there were ten to twelve technicians continuously working to thaw instrument lines and warm the doghouse. Propane burners were used on the instrument lines, und a variety of heat producing devices including smudge pots were brought in to warm the area. Workers attempted to place a plactic covering over the open-topped doghouse to retain heat; however, the material shattered due to the cold before it could be installed.

l At approximately 0900 on January 11, test connections on S/G pressure transmitter l

serving S/G's "A" and "D" (a total of six) in the penetration room were manually cracked open to provide flow in the associated impulse lines. This measure was intended to prevent further freezing by drawing warm steam line condensate through the lines. This method appeared successful for nearly three hours; so, personnel, who had been involved in heating instrument lines, abandoned the effort. At 1155 the impulse line to SMPT-5080, S/G "A" pressure transmitter (Channel I) either emptied of condensate, or froze providing a freeze seal line on the line. Pressure bled from the transmitter through the test connection and the channel tripped.

A technician was dispatched to shut the test connection on the instrument line, but before pressure could be recovered and the channel reset, a second channel tripped by the same mechanism.

The recovery from inadvertent SI and reactor trip was accomplished without incident and the unit was soon stabilized at normal hot standby conditions.

D Report No. 82-07 Page 2 SEQUENCE OF EVENTS: The sequence of events presents the major consequences of the cold weather experienced at the station.

1/10/82 0724 "S/G A flow mismatch lo, CF flow alert", CF (Main Feedwater) flow on Channel I failed low.

0830 S/G in manual (feedwater control) due to CF flow instruments freezing.

Technicians installing heaters (in the doghouse area where the impnise lines are located).

1035 EMF-33 (Process Radiation Monitoring System) declared inoperable due to loss of sample flow.

Sample line frozen.

1135 The CF flow detectors experienced fluctuations due to freezing of the instrument lines. Outside temperature N19 F.

FWST (Refueling Water Storage Tank) temperature had reached the lo lo setpoint. All heaters on; FW pump was on recirculate.

1345 EMF-31 declared inoperable due to loss of f?nw.

1514 An RF (Fire Protection System) sprinkler head burst on the tuto.ne building mezzanine floor. The leak was isolated by shutting RF 135.

1535 All steam generator level control (feedwater flow) returned to the automatic mode.

1656 An RF sprinkler header on the southeast corner of Unit 1 Turbine Building was frozen and burst. The header was isolated.

1930

" Low Condensate Booster Pump Suction Pressure" alarm. The pressure switches on the impulse line had been blown off. The pump did not trip (as designated).

Suspect the pressure switches had frozen. The impulse line was reinstalled.

1958 The RF header ruptured in the area around "G" feedwater heaters.

2034 An RF line of the turbine floor ruptured.

It was isolated by shutting RF-421.

2056 S/G "D" auxiliary feedwater flow insturment, CAP 5120 frozen; declared inoperable.

2148 Main steam pressure decreasing rapidly.

Computer point for "A" S/G indicating 1500 lbs. (actual N1000 lbs).

Found SV-19, power operated relief valve for S/G "A" open.

Isolated the valve.

2152 CFPT-5680, S/G "A" feedwater pressure transmitter, is off scale high; suspected frozen.

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Report No. 82-07 Page 3 2159 CAFT-5090, S/G "A" auxiliary feedwater flow, failed high; declared

'noperable.

2205 SMPT-5080 and -5100, S/G "A" pressure transmitters, failing high; suspected frozen; declared inoperable.

2235 CFPT-565, S/G "D" feedwater pressure failed high.

Isolated SV-1, PORV for S/G "D".

2300 Commenced unit shutdown, reducing the load.

1/11/82 0054 CFPT-5000 and -5010, Channel I and Channel II, S/G "A" feedflow. transmitters failed low; S/G "A" feedwater flow control valve in manual.

0130 SMPT-5090, S/G "A" pressure transmitter failing high.

0145 SMPT-5080 operating properly; declared operable.

0220 SMPT-5180, S/G "D" pressure transmitter, failing high; declared inoperable, and placed the channel (I) in the tripped condition.

0300 SMPT-5100 frozen; declared inoperable, and placed the channel (III) in the tripped condition.

0302 SMPT-5090 operating properly; declared the instrument operable, and secured the load reduction.

0318 SMPT-5180 operating properly; declared operable, and returned to operation.

t 0320 Comme'nced increasing reactor power to 75%; only Channel III of S/G "A" pressure instrumentation remains in the tripped condition.

0330 Returned S/G "A" feedwater control to the automatic mode.

1 0531 SMPI-5100 operating properly; declared operable and returned to operation.

0723 SMPT15180 failing high;fdsclared* inoperable,'and placed, the'dhannel'(I) in the tripped condition.

0820 SMPT-5100 declared inoperable; placed the channel (III) in the tripped condition.

0825 SMPT-5100 operating properly; declared operable, and' returned to operation.

0830 SMPT-5180 operating properly; declared operable and returned to operation.

SMPT-5090 declared inoperable; placed the channel (II) in the tripped condition.

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Report No. 82-07 Page 4 40900 Flow was established in S/G pressure transmitter impulse lines by bleeding test connections.

0930 SKPT-5090 operating properly; declared operable and returned to operation.

1155 SMPT-5080 failed low, tripping channel (I); the instrument tas declared inoperable.

1206 Pressure at SMPT-5100 dropped below the trip setpoint due to instrument line bleed.

S/G "A" pressure channel III subsequently tripped in coin-cidence with the already present channel I trip. ESF actuation and subsequent reactor and trubine trips ensued.

EVALUATION: All instrument lines affected by the cold were associated with S/G's "A" and "D".

The unit 1 exterior doghouse serves as a containment penetration foom for "A" and "D" secondary systems, while the interior doghouse provides for S/G's "B" and "C".

Impulse line systems taps are made in the piping runs through the doghouses.

The doghouses are concrete structures providing physical security and support for the secondary systems piping. Their atmospheres are uncontrolled and they are mostly open

• the top for natural ventilation, and to provide for the release of steam should a Oteam line break occur.

Because of the relative location of those structures, the wind has a greater effect on the dissipation of heat from the exterior doghouse due to its exposure.

Inspection of site environmental data showed that, prior to the SI event, the temperature had remained below freezing for a 41 hour4.74537e-4 days <br />0.0114 hours <br />6.779101e-5 weeks <br />1.56005e-5 months <br /> period. The most critical cold times were at approximately 1000 on January 10 and at 0700 on January 11 0

when the chill factored equivalent temperature was -28 F.

It is considered sig-nificant that the wind direction during the period was from the northwestern and southwestern quadrants, providing maximum ventilation of the exterior doghouse.

In this event the instrument lines in the exterior doghouse proved to be the more susceptible to the consequences of cold environmental conditions. However, more severe conditions might produce similar results in the interior doghouse.

The instrument lines in neither structure are insulated and some lengths are anchored to and are in direct contact with the structural concrete walls.

At 2205 on January 10, two S/G "A" pressure channels began to freeze, and were declared inoperable. Since both channels could not be tripped (results in SI actuation), technicians attempted to restore the channels by clearing the instrument lines of ice. At 2300 control room operators began shutting down the plant by reducing power. The conditions, for continuing plant operation, of Technical Specification 3.3.2 could not be met, b

Report No. 82-07 Page 5 The only remaining operable S/G "A" pressure channel exhibited signs of freezing (fluctuating high indication) at 0130, January 11.

However, by 0302 two channels were c1 cared, the third channel was manually tripped, and the load reduction was stopped. Having satisfied the conditions of Technical Specification 3.3.2, power escalation was initiated at 0320.

During the period from 2205, January'10 until 0302, January 11 the automatic ESF actuation capability of S/G "A" pressure channels was completely lost.

The freeze seals on the impulse lines caused the instruments to fail high (in the unconserva-tive direction). Except for the first hour in this condition, during which efforts to clear the known problem were ongoing, progress toward reactor shutdown was continual.

Under normal circumstances conservative operating pr 1ctice would have dictated initiation of shutdown procedures at the time of the failure of the first two S/G pressure channels. Although continued operation was challenging to the allowable limits of Technical Specifications, the action taken is considered justified and no violation occurred.

At approximately 0900, the test connections on the S/G pressure transmitter impulse lines were cracked open. This action could have allowed the lines to void of fluid; but, through interview, it was assured that only a drip was established at all the test connections.

Therefore, it can reasonably be assumed that freeze seals were established on the impulse lines of the channels that tripped. The freeze seals allowed depressurization of the lines at the pressure transmitters through the test connections.

Several technicians had worked throughout the night thawing instrument lines; so, when the test connection flow appeared to solve the problem, they were assured that continued effort was no longer necessary. After the doghouse was left unmanned the lines froze again.

SAFETY ANALYSIS

The purpose of the pressure instrumentation involved is to initiate ESF actuation and reactor trip in the event of a steam line break. The reactor trip is anticipatory to degraded primary system parameters which would follow a steam line break inciden.. Had a steam line break occurred in the S/G "A" associated subsystem while the instrumentation was disabled, a slightly delayed l

trip would have occurred when primary system parameters were affected. A steam j

line break in itself present no radiaiton-hazard to the public.

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CORRECTIVE ACTION

As immediate corrective action, heat tracing has been applied to instrument lines in the doghouse. The doghouse-enciesed equipment has been covered to prevent loss of heat until freezing is no longer a potential problem.

Luke Power Company is currently analyzing several potential permanent solutions, l

including permanent heat tracing; a comprehensive cold weather procedure; or l

providing adjustable dampers on the doghouses, f

Report No. 82-07 Page 6 The interim measures now in effect are expected to be effective for the remainder of the season. The event, however, took place under unusual conditions.

Permanent solutions will be analyzed for conditions as severe with an appropriate margin for safety.