ML17272A341

Deficiency Rept Involving Primary Containment Penetration Weld Design Error,Causing Thermal Stress During Operation. Penetration X69D Will Not Be Used for Sampling Line

ML17272A341
Person / Time
Site:	Columbia
Issue date:	02/22/1979
From:	WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:
Shared Package
ML17272A339	List: ML17272A340 ML17272A341
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 7903220033
Download: ML17272A341 (2)

Text

. Reportable Deficiency and Corrective Action WPPSS NUCLEAR PROJECT NO. 2 Possible Violation of Primary Containment After a Penetration Weld Failure WASHINGTON PUBLIC POWER SUPPLY SYSTEM DOCKET NO. 50-397 License No. CPPR-93 Descri tion of Deviation The design of all Primary Containment instrument penetrations consists of stainless steel instrument piping penetrating one inch thick carbon steel penetration end caps. Fillet welds are provided between the piping and the end cap on both sides of the end cap. Due to the differ-ence in thermal expansion between stainless and carbon steel, the pene-trations will experience thermal stresses during operation, the magnitude of which is proportional to penetration temperature..

Fatigue analyses have been performed on all instrument penetrations.

All but one will experience less fatigue cycles than the code allowable over the 40 year plant design life. The one remaining penetration

'X69D) contains the RPV sample line. It is anticipated that this line will be in constant intermittant use (sampling at least once per day over the 40 year plant design life), and thus the number of thermal

. cycles under "Normal" desi'gn conditions will exceed the fatigue life permitted by code. Meld failure is postulated thus causing a breach in Containment which could lead to an increase in the radiation dose to the public beyond the levels estimated in the event of a LOCA.

Safet Im lication As stated, the postulated failure of the penetration weld would cause a breach of Containment and an increase in the radiation dose to the public in the event of a LOCA. The potential increase in dose was considered to be a substantial safety hazard.

Corrective Action Penetration X69D will not be used for the RPV Sampling Line. A pene-tration capable of withstanding the expected number of thermal cycles over the forty year life will be designed and installed.