NG-75-2010, AO 50-261/75-17:on 751101,both Containment Personnel Air Lock Doors Opened Simultaneously W/Rcs Temp Above 200 F, Violating Tech Spec 3.6.1.a.Caused by Broken Rod,Bearing & Cam Follower on Outer Door Mechanism

AO 50-261/75-17:on 751101,both Containment Personnel Air Lock Doors Opened Simultaneously W/Rcs Temp Above 200 F, Violating Tech Spec 3.6.1.a.Caused by Broken Rod,Bearing & Cam Follower on Outer Door Mechanism

ML20086F534
Person / Time
Site:	Robinson
Issue date:	11/12/1975
From:	Bessac N CAROLINA POWER & LIGHT CO.
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20086F538	List: ML20086F540 NG-75-2010, AO 50-261/75-17:on 751101,both Containment Personnel Air Lock Doors Opened Simultaneously W/Rcs Temp Above 200 F, Violating Tech Spec 3.6.1.a.Caused by Broken Rod,Bearing & Cam Follower on Outer Door Mechanism
References
AO-50-261-75-17, NG-75-2010, NUDOCS 8401030383
Download: ML20086F534 (5)

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(,h,y Carolina Power & Light Company November 12, 1975 FILE: NG-3513 (R)

SERIAL: NG-75-2010 i

Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Commission Region II, Suite 818 230 Peachtree Street, N. W.

Atlanta, Georgia 30303

Dear Mr. Moseley:

H. B. ROBINSON UNIT NO. 2 LICENSE NO. DPR-23 VIOLATION OF CONTAINMENT INTEGRITY In accordance with 6.6.2.a of the Technical Specifications for

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H. B. Robinson Unit No. 2, the attached Abnormal Occurrence Report is submitted for your information. This report fulfills the requirement for a written report within ten days of an Abnormal Occurrence and is in accordance with the format set forth in Regulatory Guideline 1.16, Revision 1.

Yours very truly, B.

essac Manager Nuclear Generation DBW:cs Attachment cc: Messrs. D. C. Knuth W. C. Mcdonald 8401030383 751112

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PDR ADOCK 05000261 S

PDR 6 Fayetteville Stree:. P O ox 1551. Raleigh, N. C. 27602

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ABNCRMAL OCCURRENCE REPORT 1.

Report No.

50-261/75-17 2a.

Report Date November 6, 1975 2b.

Occurrence Date November 1, 1975 3

Facility H. B. Robinson Unit No. 2 i

Hartsville, South Carolina P9550 4.

Identification of Occurrence Both containment personnel air lock doors were opened simultaneously with the Reactor Coolant System temperature above 200 F which is in violation of Technical Specification 3.6.1.a.

This constitutes an abnormal occurrence as defined by facility Technical Specification paragraph 1.8.b.

5 Conditions Prior to Occurrence The plant was in hot shutdown condition with primary system cooldown in progress. Personnel were in containment making preparations for outage work.

H. P. personnel had exited containment and experienced some difficulty in closing the outer door. Three people remained inside working on the r,efueling cavity lighting and the manipulator crane.

6.

Descriotion of Occurrence At approximately 1430 hrs. one of the people inside the C.V. attempted to exit through the personnel air lock but the inner personnel door would not open. An unsuccessful attempt to close the outer door to m ;r-isterlock v.; cJ ':w the innor door to opeu we made. Personnel 2taide the containment then attempted to open the outer door to enter the access hatch for determination of the interlock problem. The outer

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2 loor became jammed approximately two (2) inches open and would not open further or ree?ose. Access to the door interlocks was therefore not possible from the outside.

Due to the time remaining until cold shutdown conditions could be met and problems experienced with the electrical distribution system, ths personnel'in containment decided to remove.the inner door operating 7

mechanism pins and open the inner door. This was accomplished at approximately 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br />. Following entry into the air lock, the door was held closed by hand until it could be properly secured. This sas accomplished at approximately 1555 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.916775e-4 months <br />. Personnel then released the outer door from within the access hatch and exited. The containment integrity was thus violated for the brief period of time during which the inner and outer doors were open.

7.

Designation of Apparent Cause of Occurrence I

Investigation revealed a broken rod and bearing and cam follower on the outer door operating mechanism causing the door to jam.

an intermediate position.

Personnel inside the containment then made the decision to violate containment integrity and defeated the' inner door interlock in order-to exit the containment.

8.

Analysis of Occurrence There were no personal injuries, nor was. there. anyl release of radio-active materials involved in this occurrence ;which would jeopardize :

the paulic heelth rr 29fety.

s A containment purge was in progress at the -time both doors were;open allowingairflowintothecontainmentthroughithe[doorsrather?than-outward. -In'.the event of a. containment pressurization and ventilation ~

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s isolation the inner door would have been closed and secured due to the pressure differential across the access hatch.

9.

Corrective Action The broken rod and bearing and cam follower were replaced on the outer door operating mechanism and the outer door secured. The inner door operating mechanism pins were then replaced and both doors and interlocks tested satisfactorily.

Further investiga-tion will be made into the need for periodic inspection of operat-ing mechanisms.

The integrity violation was a consequence of the mechanical door 1

mechanism failure, but was a direct result of the decision to open the inner door. As stated above, the plant was in hot shut-down condition and a purge was in process.

The safety implication l

was negligible.

Entrance to the air lock from outside had been attempted with no success, making it apparent that proper repairs would require access from the inside to prevent further damage to t

f the door mechanism. It is believed that the decision was justified under the existing conditions, since the personnel involved had complete cognizance of plant conditions and the consequences of j

the violation of containment integrity. No administrative action is deemed necessary.

l 10.

Failure Data October 31, 1972 Can track bearing on inner door operating mechanism failed and decision was made to violate integrity to permit personnel to

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exit containment to minimize exposure. time.

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1-M. Donald C. Knuth, Director I

Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 1

Washington, D. C.

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