ML20024G762
| ML20024G762 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 07/10/1973 |
| From: | NORTHERN STATES POWER CO. |
| To: | |
| Shared Package | |
| ML20024G759 | List: |
| References | |
| NUDOCS 9104290338 | |
| Download: ML20024G762 (7) | |
Text
{{#Wiki_filter:_ EXHIBIT B (Page 1 of 7)
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mia c- TABLE 3.7.1 wo ' b PJ PRIMARY COIRAIIU4EIE ISOLATION
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% Isolation Valve number of Valves Maximum 04 Group Identification Operating Normal ;
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$o Inboard Outboard Time (Sec) Position -
od y O PJ O Main Steam Line Isolation 4 4 3 I TI 5 Open
*$ 1 Closed 1 1 60 1 Main Steam Line Drain 1 1 60 Closed 1 Recirculation Loop Sample Line 2 60 Open 2 Drywell Floor Drain 2 60 Oper.
2 Dryvell Equipment Drain 2 60 Closed a 2 Dryvell Vent 1 60 Closed 2 Dryvell Vent Eypass 2 60 Closed 2 Drywell Purge Inlet 60 Closed i d 1 '# ?N 2 Drywell and Suppression Chamber Air Makeup i g:
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Suppression Chamber Vent 2 r 1;{:. [NEQ g: 2 Suppression Chamber Vent Bypass ,~ 1
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EX11IBIT B (Page 2 of 7) . 3.0 LD11 TING CONDITIONS FOR OPERATI0tt 4.0 SURVEILIANCE REQUIREMENTS
- 4. Pressure Suppression Chamber-Drywell Vacuum 4. Pressure Suppression Chamber-Drywell Vacuum Breakers Breakers
- a. When primary containment is required, all a. Operability and full closure of the drywelg drywell-suppression chamber vacuum breakers suppression chamber vacuum breakers shall W shall be operable and positioned in the be verified by performance of th2 following:
closed position as indicated by the posi-tion indication system, except during (1) Monthly each operable drywell-testing and except as specified in 3.7.A. suppression chamber vacuum breaker 4.b and c, below. shall be exercised through an open-ing-c1csing cycle.
- b. Any drywell-suppression chamber vacuum breaker may be nonfully closed as indi- (2) Once each operating cycle, drywell cated by the position indication system to suppression chamber leakage shall provided that drywell to suppression be demonstrated to be less than that chamber differential pressure decay does equivalent to a one-inch diameter not exceed that shown on Figure 3.7.1. orifice and each vacuum breaker shall be visually inspected. , ,, 0: @
i c. Up to two drywell-suppression chamber j , _ <
;, j gM vacuum breakers may be inoperable pro- b. When the position of any3drywell-suppressi "
vided that: (1) the vacuum breakersis chamber vacutan breakertvalve is indicated f determined to be fully closed as indi- -to be not fully.=1osed'at alhimi stnd l cated by the position indication system ; closure is required @th drh11$ 3 or if drywell to suppression chamber lpression;chamheirfdiffe ~~ t2si differential pressure decay does not 2 .y _ ;decaygshall be exceed that shown on Figure 3.7.1 or y; f p '(thanithat? . (2) the vacuum breaker is secured in y ately; ,, the closed position. 2 :: sequent {
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1 EXIIIBIT B (Page 3 of ') 3.0 LLMITING CONDITIONS FOR OPERATION 4.0 SURVEILLANCE REQUIREMENIS j -____ l S. Oxygen Concentration 5. Oxygen Concentration
- a. Af ter completion of the startup test Whenever inerting is required, the primary i program and demonstration of plant containment oxygen concentration shall be i electrical output, the primary contain- measured and recorded on a weekly basis.
ment atmosphere shall be reduced to less than 5% oxygen with nitrogen gas whenever the reactor coolant pressure is above 110 psig in the power operat-ing condition, except as specified in 3.7.A.S.b.
- b. Within the 24-hour period subsequent to placing the reactor in the run mode fol-lowing shutdown, the containment atmosphere oxygen concentration shall be reduced to less than 5% by weight, and maintained in this condition. Deinerting may commence ,
24 hours prior to leaving the run mode for a reactor shutdown. , g J l 3.7/4.7 147A Rev a
e EXHIBIT B (Pega 4 of 7) Bases Continued: 3.7 A. Primary Containment He purpose of the vacuum relief valves is to equalize the pressure between the drywell and suppres-sion chamber and between the suppression chamber and reactor building during loss of coolant accident so that structural integrity of the containment is maintained. The vacuum relief system between the pressure suppression chamber and reactor building consist of two 1007. vacuum relief breakers (2 parallel sets of- 2 valves in series). Operation of either system will maintain the pressure differential less than 1 psig. W e external design pressure is 2 psig. One valve may be out of service for repairs for a period of seven days. This period is based on the low g probability that system redundancy would be required during this time. If repairs cannot be completed within seven days, the reactor coolant system is brought to a condition where vacuum relief is no longer required.
'Ihe capacity of the. ten (10)drywell vacuum relief valves is sized to limit the pressure differential between the suppression chamber and drywell during post-accident drywell cooling operations to less than the design limit of 2 psig. The relief valves are sized on the basis of the Bodega Bay pressure suppression system tests. Since they are in series with the reactor building to suppression charrber vacuum relief valves pressure drop across these valves must be included in the evaluation of drywell negative pressures, even though there does not appear to be a mechanism for causing negative pres-sures in excess of the 2 psig design pressure. With eight of the ten valves in service, the differ-ential pressure across the valves for maximum flow 'onditions would increase approximately 127. above the ten valve differential pressure. With this additional pressure drop the total differential pressure would still be less than the 2 psig design external pressure of the drywell. Containment integrity would therefore not be impaired. _
$ . j l N3 M; In addition to the above considerations, postulated leakage through the vacuum breaker; to} the; suppress i sion chamber air space could result in a partial bypass of pressure suppression in the:eventiof ajIACA'i@
or a small or intermediate steam leak. This effect could potentially resulttin exceedins'tcodtaitesett D design pressure. . As a result of. the leakage potential, the contairment;responselba5j ~ ' for a number of postulated conditions. It was found that,the maximum *
.L postulated break size was equivalent to a six-inch diametir orifice.1/allowsble 2 1his hypass M typetsf
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.1/Report on Torus to Drywell Vacuum Breaker Tests and Modifications for Monticello Nuc1'est GenerstLhm t dated March 12, 1973, submitted to Mr. D J Skovholt, AEC-DL, from Mr. L 0 Mayer, .WSP , y ,
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EXHIB1T B (Page 5 of 7 ) 3/4 inch opening of any one valve or 1/8 inch opening for all ten valves, measured at the bottom of - the disc. The position indication system is designed to detect closure within 1/8 inch at the bottom of the disc. . At each refueling outage and following any significant maintenance on the vacuum breaker valves, posi-tive seating of the vacuum breakers will be verified by leak test. The leak test is conservatively designed to demonstrate that leakage is less than that equivalent to leakage through a one-inch orifice which is about 37. of the maximum allowable. This test is planned to establish a baseline for valve performance at the start of each operating cycle and to ensure that vacuum breakers are maintained as nearly as possible to their design condition. This test is not planned to sem as a limiting condi-tion for operation. During reactor operation, an exercise test of the vacuum breakers will be conducted monthly. This test will verify that disc travel is unobstructed and will provide verification that the valves are closing fully, through the position indication system. If cne or more of the vacuum breakers does not seat fully as detemined from the indicating system, a leak test will be conducted to verify that leakage is within the maximum allowable. Since the extreme lower limit of switch detection capability is approximately 1/16", the planned test is designed to strike a balance between the detection switch capability to verify closure and the maximum allowable leak rate. A special test was performed to establish the basis for this limiting condition. During the first refueling outage all ten vacuum breakers were shimmed 1/16" open at the bottom of the d sc. The bypass area associated with the shimming corresponded to 507. of the maximum allowable.1- The results of this test are shown in Fig-ure 3.7.1. When a drywell-suppression chamber vacuum breaker valve is exercised through an opening-closing cycle, the position indicating lights at the remote test panels are designed to function as follows: < n
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Full closed 2 Green - On 2 Red - Offz. gy y y
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2 Red g$h I %. -H X ap 4_ g :t{e.e Ihe remote test panel consists of a push button to actuate the air cylinde' r f for testingi two:redV $t 4 y - % ; 11 F: 4
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EXHIBIT B (Page 6 of 7) i i i and two green lights for each of the ten valves. There are four indpendent limit s.ritches on each - l valve. The two switches contro111tig the green lights are adjusted to provide an indication of disc opening of less than 1/8" at the bottoci of the disc. The two switches controlling the red lights ~ j are adjusted to provide itudication of the disc very near the full open position. ; Operability of a vacuum breaker valve and the four associated indicating light circuits shall be established by cycling the va*% The sequence of the indicating lights will be observN to be that previously described. If both green light circuits are inoperable, the valve shall be con- l sidered inoperable and a pressure test is required irciediately and upon indication of subsequent i operation. If both red light circuits are inoperable, the valve rhall be considered inoperable, however, no pressure test is required if positive closure indication is present. I %e 57. cxygen concentration minimizes the possibility of hydrogen combustion following a loss of coolant accident. Significant quantities of hydrogen could be generated if the core cooling sys- j tems failed to sufficiently cool the core. %e occurrence of primary system leakage following a ! major refueling outage or other scheduled shutdown is more probable than the occurrence cf the l loss of coolant accident upon 1.hich the specified oxygen concentration limit is based. Permitting access to the drywell for Icak inspections during a startup is judged prudeast in terms of the added l plant safety offered without significantly reducing the margin of safety. hs, to preclude the f possibility of starting the reactor and operating for extended periods of time with significant leaks in the primary (Continued on page 159) ! [ ] i
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