ML19308A868

Abnormal Occurrence AO-269/73-03:on 730613,during Test Preparations Reactor Bldg Leak Test Pressurization Line Was Open to Atmosphere.Caused by Inadequate Procedures.Preheatup Checklist of Operating Procedure OP1102/01 Revised

ML19308A868
Person / Time
Site:	Oconee
Issue date:	07/10/1973
From:	DUKE POWER CO.
To:
Shared Package
ML19308A865	List: ML19308A864 ML19308A868 ML19308A873
References
NUDOCS 7912120657
Download: ML19308A868 (3)

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. e DUKE POWER COMPANY OCONEE NUCLEAR STATION - UNIT I ABNORMAL OCCURRENCE PIPORT A0-269/73-3 FAILURE TO MAINTAIN CONTAINMENT INTEGRITY Introduction On June 13, 1973, during preparations for oconee Unit 2 Reactor Building Structural Integrity and Leak Rate Test, it was discovered that the Unit 1 Reactor Building Leak Test Pressurization Line was open to the atmosphere.

This opening results in an abnormal occurrence as defined in Technical Specification 1.8b, " Exceeds a limiting condition for operation as estus-11shed in the Technical Specifications." Technical Specification 3.6.1 requires that containment integrity be maintained when the reactor coolant system is greater than 300 psig pressure, 200*F temperature, and nuclear fuel is in the core. Containment integrity, as defined in Technical l l

Specification definition 1.7c was not established. 1 Containment integrity was established immediately. The station superinten-dent was absent from the plant at that time and was not informed of the incident until several days later. He notified Regulatory Operations Region II Office in Atlanta, Georgia, on June 25, 1973.

1 Description of the Incident l l

On June 13, 1973, it was discovered that station air was not being supplied to the penumatic operators for isolation valves in the Unit 1 Reactor Building Leak Rate Test Pressurization Line. This pressurization line is an 8" nominal pipe size and is the route for air from the air compressors used for leak rate testing into the reactor building. Outside of the building, two air-operated diaphragm valves in series with a 6" vent line between them provide reactor building isolation. The operators were aware that there was a provision to install a blank flange inside the reactor building. Figure 1 is a diagram of t'..is portion of the Reactor Building Leak Rate Test Pressuri-zation System. The isolation valves LRT-15, -16 and -17 require air to close, p 12120 6 7

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s s Upon discovery, air pressure was icsediately supplied to the valves to close them, thereby providing the required double isolation. A reactor trip was experienced on June 14, 1973 following which a check was made inside the reactor building to determine if the blank flange was installed on the terminal end of the pressurization line. It was found that the blank flange was not on the line, and therefore restart of the reactor was delayed until it could be installed.

Corrective Action To preclude recurrence, the Preheatup Checklist of Operating Procedure OP1102/01, " Controlling Procedure for Unit Startup," has been revised to include checks to assure that the flange on the terminal end of the pressuri-zation line is in place and valve LRT-17, the common valve in the line outside the reactor building is closed. Since this line is rarely used (only for testing at 3-1/2 year intervals), it was inadvertantly omitted from routine penetration checklists. A thorough review of the reactor building penetrations has been initiated to assure that no other penetrations which could affect containment integrity have been omitted from the checklist. Furthermore, a station problem report has been initiated to change the control of the pneumatic operators of the isolation valves to require air to open rather than close.

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Safety Analysis i

Due to the short time of operation at low power level, activity in the reactor building was practically zero during the time that the valves were open. Further, there was no significant pressure differential between inside and outside the building that would cause ai exchange. Therefore, this failure to establish containment did not result in the release of any detectable amounts of activity 1 to the atmosphere. However, it is realized that this failure to fully estab-lish containment integrity required by the technical specifications is a serious matter and that it provided a potential path for the release of activity i from the reactor building.

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" LRT-16 e m I

8 1 i i \ Compressors g 4 a 1 / _

LRT-17 LRT-15 Reactor Building 1

. Figure 1 Leak Rate Test Pressurization System -

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