ML20084S063

Ro:During 730303-26 Maint Outages,Primary Containment Local Leak Rate Tests Revealed Four Feedwater Check Valves, Two MSIVs & One Reactor Head Cooling Check Valve & Personnel Air Lock W/Leak Rates in Excess of Tech Spec Limits

ML20084S063
Person / Time
Site:	Dresden
Issue date:	06/20/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
468-73, NUDOCS 8306160129
Download: ML20084S063 (4)

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' W.: Comnr '~oalth Edison w , ' # '['y One F W s knif Pl.ita. C%ca o, Ihnms v' Addresc Reply to Port Office Box 767 J Chicago. Ilhnois 00G90 50-249 WPW Ltr.#468-73 Dresden Nuclear Power Station R. R. fl Morris, Illinois 60450 June 20, 1973 , _

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SUBJECT:

LICENSE DPR-25, DREFDEN NUCLEAR POWER STATION. UNIT 43,f.U 3 SECTION 6.6. C. I GF THE TECHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

This letter reports a condition relating to the unit, in which local leak rate testin;; of the primary containment revealed seven contain-rent .penetraticasavith leakage in excess of Technical Specifications t'-

limits.

INVESTIGATION AND CORRECTIVE ACTION The unit was shutdown for a naintenance outage from March 3, 1973 to May 26, 1973. During that period, pri::ary containment local leak rate tests were performed in accordance with Technical Specifications Section 4.7.A.2.e. The testa revealed that four feedwater check valves, ~ two main steam isolation valves, one' reactor head cooling check valve and the ' '

personnel air lock had leak rates in excess of Technical Specifications Sec t ion 4. 7. A. f. The Technical Specifications local leak rate limits are

57. Lto (48) or 29.3 standard cubic feet per hour (scfh) for any one pene-tration or isolation valve and 11.5 scfh at 25 psig for any one main steam isolation valve.

A) Feedwater Check Valves Reference (P&ID M-347)

Initial testing of the feedwater check valves revealed the following leak rates:

Valve No. Leak _ Rate (sefh) 220-62A 1941.5 220-5SA 4295.0 220-62B 3136.6 220-58B 144,7 0

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hv Hr. A. Gioruusso June 20, 1973 All four valves were disassembled and repaired by machining the valve seating surfaces. The seat ring and disc were replaced on valve 220-62B because machining did not remove all the irregularities in its seating surfaces. These check valves have two seating areas: one consists of the valve disc and seat ring and the other is a seat ring to valve body seal. The majority of the leakage through the valves was determined to be via the seat ring to valve body seal. Because of similar problems with the Unit 2 feedwater check valves, a modification was performed on these valves whereby the stainless steel body to seat seal ring was replaced with a

" Silastic" silicone rubber "0" ring. The stainless steel seal ring requires a large differential pressure across the check valve in order to provide a tight seal. Changing to the silicone rubber "0" ring produced a much better seal even at the low icak test pressure of 48 psig. Following the extensive repairs outlined above, the valves were reinstalled and retested satisfact-orily. The leak rates exhibited af ter repair of the valves were as follows:

Valve No. Leak Rate ( s e f h)_

220-62A 0.0 220-58A 20.0 220-623 11.0

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As previously mentioned, these valves are designed to seal under a high differential pressure condition. Under operating conditions, the valves would experience this high dif ferential in conjunction with a water seal on the valve seating surfaces thereby reducing Icakage through the valves.

B) Main Steam Isolation Valves (Reference P&ID M-345

. .The initial leak test of MSIV 203-2C revealed a leakage through -

the valve of 49.0 scfh. The valve was disassembled and its seating surfaces refinished under the supervision of the valve manufacturer's technical representative. Af ter repair of the valve, a subsequent leak test showed the combined leakage through FGIV 203-2C and ISIV 203-1C to be only 1.6 scfh.

Valve 203-1C is located in the same steam line as 203-2C and is between the reactor vessel and MSIV 203-2C. Therefore, ICIV 203-1C would be the limiting leak rate in an accident situation and Icakage through this valve was well within Technical Specifications limits.

Ibin Steam Isolation Valve 203-2B exhibited an initial leak rate of 29.224 scfh. This valve was repaired in the same manner as MSIV 203-2C and retested. The retest showed the combined Icakage through MSIV 203-2B and MSIV 203-1B to be 4.847 scfh. Leakage through MSIV 203-1B would be the limiting Icak rate for the "B" steam line in an accident situation.

C) Reactor Head Cooline check Valve 205-2-7 (Reference PLID M-357)

The initial leak test of reactor head cooling check valve 205-2-7 showed a leak rate of 254.8 sefh. The valve was disassembled and repaired by lapping the disc. The valve was then reassembled and retested. The leak rate for valve 205-2-7 af ter repair was only 0.3 scfh.

Hr. A. Ciambusso O O June 20, 1973 As with all check valves, the reactor head cooling check valve is designed to seal under a high differential pressure condition. Also,  !

motor operated valve 205-2-4 which is immediately downstream of the check valve exhibited no measurable leakage.

D) _ Personnel Air Lock The initial leakage from the personnel air lock of 52.7 scfh was determined to be via the handwheel shaft seals. After tightening the seal packing glands, the lock was retected and showed no measurable leakage.

The packing in the air lock handwheel shaft seals will be replaced during the next unit shutdown. In addition, a surveillance routine will be established to renew clie packing in these seals each operating cycle so as to prevent a recurrence of this problem.

Sincerely, Mth k'UN W. P. Worden

$uperintendent

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UNIT 3 PRIMARY CO?TTAI!.?!ENT PENETRATIONS EXHIBITING EXCESSIVE LEAKAGE I'

INITIAL LEAKAGE AFTER PENETRATION LEAKAGE (sefh) REPAIR REPAIR (scfm)

-Parsonnel Air Lock 52.771 Tightened Stem Seals 0.0

-Hain Steam Valve 203-2C 49.001 Lapped Seat 1.615 Rasetor Head Cooling Valve 205-2-7 254.810 Lapped Disc 0.256 .

Feedwater Valve 220-62A 1941.550 Machined Seat & Disc 0.0 Feedwater Valve 220-62B 3136.600 Replaced Sea't & Disc 10.999

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N.- .a 220-58A 4295.700 ' Hachined Seat & Disc 20.0 Feedwater Valve 220-58B 144.700 Machined-Seat & Disc 6.057 Hain Steam Valve -

203-2B 29.224 Lapped Seat 4.847

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1) Leak rate limit for any one penetration or isolation valve is 57. Leo (48) or 29.3 scfh.

2) Leak rate limit for HSIV's is 11.5 scfh @ 25 psig for one valve.

3) All four feedwater check valves were modified by replacing stainless steel seat to body seal ring with " silastic" silicone rubber "0" ring.

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