ML20084D821
| ML20084D821 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 11/27/1970 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| 04567, 4567, NUDOCS 8304120443 | |
| Download: ML20084D821 (2) | |
Text
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Conunonwealth Edison Company 72 WEST ADAMS STREET
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- C H I C A G O, ILLINOIS 60690 Dresden Nuclear Power Station.!'
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1:urris, Dir ec t or Division of React.or Licensing U. S.
Atomic Energy Cocaissieu n'a s hing t on, D.C.
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SU!UECT:
LICE'iSE DPR-19 DRESDEN NUCLEAR POUER STATION UNIT 2, SECTION 6.6.C.1 0F TiiE TECH:;ICAL SPECIFICATIONS l
l Tne follo.fing informacioa is submitted relative to fast closure tiac of the 203-1C inboard main steam isolation valve on October 27, 1970.
Problem & Initial Action The unit was operating at about 370 Ele and quarterly carveillance testing of the Main Steam Isolation Valves (MSiv's) was in progress.
Jaile surveillance testing the MSIV's, at 8:00 p.u. ca_0ctober 27, 1970, it was found that valve 203-lc had a closure time of 2.0 sec., which A
is less than the normal range for closure time (3.0 to 5.0 sec.).
On Jiovember 5, 1970, main steau line "C" was isolated.
Valve 203-1C was v
closed at 10: 26 a.m. and valve 203-2C was closed at 11:45 a.m.
Investigation and Corrective Action Investigation of valve 203-1C, following plant shutdown on Novem-ber 14, indicated t hat a loose oil fitting had allowed the escape of oil and thus caused the short closure time of the valve.
Tne oil was replaced and the fitting tightened. The valve was reset to close within the normal range of 3 to 5 seconds.
Discussion Technical Specification for timing of MSIV's, section 3.7.D.1 and Table 3.7.1 indicates the required maximum operating time of 5 seconds, but also indledtes a range of operating time of 3 to 5 seconds.
The purpose of catablishing maximum closure times of automatic primary coatainment isolation valves as stated in the Bases (Section 3.7.A) is to minimize the NOM
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Dr. Peter A.11 orris Page 2 November 2/, 19/0 potential leaka;;c paths from the containment in the event of a loss of coolant a c c id e m.
It was therefore concluded that the "lL1.;icum Operat ing Time" as specified in Table 3.7.1 is ' exactly what is inteade1 to ineet the prima ry containnent isolation function.
Cencral ElecLric Co..ipany was consuited respecting the 2 second operating time as related to the range of 3 to 5 seconds stated in Table 3. 7.1.
General Electric Company respondeI that this range is the normal range to which the closure tice should be adjusted and that the 2 second time for cae valve even with a 3 second I
average for the others was conservative for the analyzed ptessure traasient for the vorst case containment isolatica.
General Electric Company also j
stated that the fast closure was of no concern respecting the integrity of the valve.
It was therefore concluded that 11S1V operability as reynired in sectica 3.7.D.2 did exist even for the 2-second valve and thac valve closure was not required.
Ifosever, because of indicated coacern 1.y the AEC the matter was reviewed by the SRB and referred to the NRB on :: oven-ber 2,
!970 The NRB reported that its finding on November 5, 1970, was that the Station's consideration was in error.
Therefore the 203-1C valve was immediately closed on November 3.
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