ML20085B474

Ao:On 720226,leak Discovered in Socket Weld Upstream of Charging Pump Discharge Shutoff Valve P-55A.Caused by Piping Configuration & Vibration Induced by Positive Displacement Pumps.Welds Tested & Safety Analysis Performed

ML20085B474
Person / Time
Site:	Palisades
Issue date:	03/06/1972
From:	Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085B477	List: ML20085B474
References
NUDOCS 8307080154
Download: ML20085B474 (2)

Text

-

O 4(*

,i , 6 Mag j F3  % ConSumBIS

c -

eh b 9

$ Power

%;A i, aw6' 8  % Company yf&[ ?y .(Q v

f'h Df v U oen. . ore.ce.: 2,2 w. r u.cn%.n Avenue. secason. u.cmg.n 4o201. A,e Code 517 7R8-0550 March 6, 1972 Dr. Peter A. Morris, Director Re: Docket No 50-255 Division of Reactor Licensing Licere No DPR-20 United States Atomic Energy Commission Washington, DC 20545

Dear Dr. Morris:

On February 26, 1972, while the Palisades Plant was in a hot shutdown condition, a leak was discovered in a socket veld just upstream of the P-55A charging pump discharge shutoff valve. At the time the leak occurred, the primary system pressure was 2100 psia, primary system tem-perature was 532 F and boron concentration was 1580 ppm.

In order to make repairs to the weld, it was necessary to iso-late the normal primary coolant system charging path and drain the affected portion of the line. In preparation for the repairs, the pressurizer was filled to an 80% level and an alternate makeup path to the primary coolant system was established through the P-550 pump and MO-3072 to the redundant safety injection header. It was estimated that existing primary system known leakage would result in a pressurizer level drop of about 6% per hour. This would allow about eight hours to accomplish the repair before requiring makeup to the primary system. Although an alternate makeup path was available, it was not used because the piping vibrations would inter-fere with welding performed during the repair.

Normal primary coolant system charging and letdown were secured at 0255 hours0.00295 days <br />0.0708 hours <br />4.21627e-4 weeks <br />9.70275e-5 months <br />. The repair was completed at 0715 hours0.00828 days <br />0.199 hours <br />0.00118 weeks <br />2.720575e-4 months <br /> and normal charging and letdown was reestablished at 0848 hours0.00981 days <br />0.236 hours <br />0.0014 weeks <br />3.22664e-4 months <br />.

Later the same day at 1408 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.35744e-4 months <br />, another slight leak was dis-covered in the cap on the check valve in the discharge line of the P-55A charging pump. This leak was easily isolated because it was between the pump discharge and discharge shutoff valve. Because the charging system 39 vibration makes welding repairs difficult, the pressurizer level was raised to 60% and primary coolant system charging and letdown was secured. The alternate flow path through the redundant high-pressure safety injection header was established for use if required. The repair was completed and charging and letdown flow reestablished at 1840 hours0.0213 days <br />0.511 hours <br />0.00304 weeks <br />7.0012e-4 months <br />.

,)

e307080154 720306 9Q((uJ v

A b' PDR ADOCK 05000255 b s PDR The-h COPY SENT REC ONID

f c.,

• O

• ' Di . Peter A. Morris O 2 Iiocket No 50-255 March 6, 1972-The cause of the difficulties with the welds in the charging system pump discharge piping is due to the vibration induced by the posi-

' tive displacement pumps and compounded by the present piping configura-tion. The leaks experienced in this system have first appeared as a fine crack in the outer surface of the weldment on socket-welded pipe fittings.

The leakage first appears as a fine mist, which allows it to be readily detectable. This leakage is solely from the charging system output; check valves and isolation valves prevent back leakage from the primary coolant system.

On February 27,17/2, all welds in the vibration-affected por-tions of the charging system piping were dye-penetrant tested to detect any indications of surface cracking. No indications were detected. In addition, an interim surveillance program has been established that moni-tors for changes in the nature of piping system vibrations, the condition of piping hangers and the presence of leakage.

Plans were made sometime ago to modify the charging pump dis-charge piping configuration to minimize piping vibration. The materials necessary for- this modification have been procured but some have not yet been delivered. It is anticipated that these materials will be delivered during April and the modifications will be undertaken shortly thereafter.

The reduction of the vibrations should eliminate the difficulties that have been experienced in the charging pump discharge piping.

A safety analysis was performed assuming a break were to occur in all discrete locations of vibration-affected areas of charging system piping. Based on this safety analysis, it was concluded that the Technical Specifications (Article 3 2.3.c) contain appropriate rules to insure that at least one path is available to provide makeup water to the primary coolant system following the discovery of a break anywhere in the vibration-affected areas of charging system piping. These rules also limit the time in which the plant can be operated with only a single path of makeup water to the primary coolant system.

Yours very truly, Ralph B. Sewell (Signed)

RBS/ map Ralph B. Sewell Nuclear Licensing Administrator CC: Boyce H. Grier, USAEC

_ _ __ _____