ML20059H691
| ML20059H691 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, McGuire  |
| Issue date: | 11/04/1993 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML20059H684 | List: |
| References | |
| NUDOCS 9311100172 | |
| Download: ML20059H691 (9) | |
Text
{{#Wiki_filter:y . , 4 i-4 ATTACHMENT 1 DUKE POWER COMPANY MCGUIRE NUCLEAR STATION PROPOSED TECHNICAL SPECIFICATION REVISIONS 9311100172 931104 E
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t PLANT. SYSTEMS , 3/4.7.6 CONTROL AREA VENTILATION SYSTEM
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LIMITING CONDITION FOR OPERATION s 3.7.6 Two independent Control Area Ventilation Systems shall be OPERABLE. APPLICABILITY: ALL MODES t ACTION: (Units 1 and 2) H0 DES 1, 2, 3 and 4: '
- a. With one Control Area Ventilation System inoperable for reasons other than the heaters specified in 4.7.6.b and 4.7.6.e.4, restore the in-operable system to OPERABLE status within 7+' days or be in at least HOT STANDBY within the next 6 hours and in COLD SHUTDOWN within the -H following 30 hours. ,
- b. With the heaters tested in 4.7.6.b and 4.7.6.e.4 inoperable, restore the inoperable heaters to OPERABLE status within 7 days, or file a l' Special Report in accordance with Specification 6.9.2 within 30 days, specifying the reason for inoperability and the planned actions to return the heaters to OPERABLE status.
) MODES 5 and F:
- a. With one Control Area Ventilation System inoperable for reasons other than the heaters specified in 4.7.6.b and'4.7.6.e.4, restore the inoperable system to OPERABLE status within.7 days or initiate and i
maintain operation of the remaining OPERABLE Control Area Ventilation System in the recirculation mode; and
- b. With both Control Area Ventilation Systems inoperable for reasons other +
than the heaters specified in 4.7.6.b and 4.7.6.e.4, or with the ; OPERABLE Control Area Ventilation System, required to be in the recirculation mode by ACTION a., not capable of being. powered by an 't OPERABLE emergency power source, suspend all operations involving i CORE ALTERATIONS or positive reactivity changes. '
- c. The provisions of Specification 3.0.4 are not applicable.
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- d. With the heaters tested in 4.7.6.b and 4.7.6.e.4 inoperable,. restore the inoperable heaters to OPERABLE status within 7 days, or file a i Special Report in accordance with Specification 6.9.2 within 30 days, specifying the reason for inoperability and the planned acations to !
return the heaters to OPERABLE status. ' V(Lm % %edJy& D A M T M c/ L c/ wAw~ a , ss n y At$o. ns -
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4 ^ ] *teyLc. ya<t. c&Q McGUIRE - UNITS 1 and 2 3/4 7-13 Amendment No.122(Unit 1) Amendment No.104(Unit 2)
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ATTACHMENT 2. DUKE POWER COMPANY l MCGUIRE NUCLEAR STATION -') i i TECHNICAL JUSTIFICATION -! i, o ,I 4 I f I 5 i
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l { I Justification and Safety Analysis '
Introduction:
The proposed change to the Technical Specifications is to allow ; extended outage time for each train of the control area ventilation- ; system (VC) to allow system maintenance to improve system ! reliability. The one time extension to fourteen days (for each train, one at a time) will allow completion of the maintenance activities while one or both units are on-line; otherwise, it would be necessary to shutdown both units to complete-the maintenance , activities or to divide the maintenance activities into less that- , seven day segments, which would increase the unavailability of the . VC System. , The maintenance activities, described in detail below, will allow . major maintenance on the chiller package for each train. While the , chiller is inoperable, it will not be possible to provide cooling for the affected VC train. As the affected train would be unable i to meet the Surveillance Requirements for operability for control room cooling, the affected VC train must be considered to be , inoperable. l Justification for Allowed Outage Time Extension: , The present allowed outage time of seven days is insufficient to : complete the maintenance activities as planned. Duke is proposing a one-time allowed outage time extension to fourteen days to' ; f acilitate the maintenance activities. Duke believes that fourteen ' days will be sufficient to complete the maintenance activities and i will take steps to reduce that time as much as possible. Some of the methods to reduce the downtime include continued planning, ! training on " mock-ups", prefabrication, and organizat ton of parts ; and components. , Description of Maintenance Activities: l With the VC system in service for more than 12 years, major maintenance is needed on the chiller package in order to assure the long term reliability of the system. During the planned maintenance on each train, the following major tasks will he j accomplished:
- 1) Replacement of the windage baffle i
- 2) Motor bearing replacement j
- 3) Transmission rebuilding. !
Other refurbishment activities will also be completed as deemed necessary. (1) J
Sa.fety' Analysis: j Duke has assessed the safety significance of this planned ] modification and has determined the safety significance of the , change to be minimal as the probability of an accident requiring l use of the inoperable VC train during the additional seven days is ! negligibly small. The VC System provides filtration and cooling ) for the Control Room. Other than normal cooling, the system is ; needed only in the event of a toxic gas spill or a core melt. A l core melt is precluded by the operability of the emergency core . cooling system. The ECCS will remain operable as required by the ' Technical Specifications.. For a substantial radioactive release to occur requiring use of the filter train of the VC, multiple , failures would have to occur: the various ECCS subsystems and ultimately containment in concert with a LOCA. Such an event is ; not considered credible, especially in light of leak before break and Technical Specification limits on reactor coolant system leakage. The probability of either of these events occurring - during the 14 day period is very low. As discussed in FSAR Section 6.4.3, gaseous chlorine is the only toxic gas normally onsite that might be drawn into the VC intake. Normally, two 150 pound chlorine cylinders are stored as to be of potential concern (one connected, one spare). Chlorine detectors (OVCMT 5010, 5020, 5030, 5040, shown on FSAR Figure 6-191 are installed just downstream of the radiation monitors. For chlorine , to be drawn into the intake, a storage cylinder would have to rupture, then the gas would need to travel about 450 feet around the turbine building to the elevated intake. As discussed in FSAR , Section 6.4.3, this is a highly improbable event (chlorine gas is ' heavier than air and will, therefore, stay on the ground. Any wind would tend to disperse and dilute the chlorine. To further reduce the risk from the allowed outage time extension, - transport of toxic gas containers on site will be prohibited during the time that only one VC train is operable. Upon receipt of a radiation signal or a high chlorine signal, the i affected intake can be isolated by the Control Room Operator. The , system would then operate from the uncontaminated air intake. As
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normal operation is from both intakes, no further realignments are- ; required to assure safety function following the isolation of a single intake. Cross connecting duct work assures that air from either intake may be drawn through either filter train. As the intakes are physically independent (opposite sides of the auxiliary building), the ability of the system to deal with a toxic gas or radioactive release is unimpaired by the proposed change. In the unlikely event that an alternate source of air is required, air masks (fed from a standby source of breathing air) and SCBA (Self -{ Contained Breathing apparatus) equipment are available in the l Control Room. ; (2) l
Maintenance on each chiller unit will render the cooling capability for that train inoperable. Loss of the opposite train chiller. ' would result in a loss of Control Room cooling. Performance of the planned maintenance activities during the colder months of the year (February - March, 1994) _ will allow for greater Control Room cooling with the outside air intakes. With the exception of Control Room temperature, all Technical E Specification surveillances are on a' thirty-one day basis, thus it will not be necessary to perform any surveillances on the required 'i train while the opposite train is out of service. The second train , to be taken out of service will have further assurance that the , opposite train will be operable as it (the operable train) will ! have recently been overhauled and subjected to post maintenance ' system testing. Therefore, the impact of this one-time AOT extension on public-health risk is insignificant. The extended allowed outage time would increase the probability of ! a required shutdown due to both trains of VC being inoperable.- McGuire is taking measures to assure that while one train is inoperable for the maintenance, the operable train remains operational. As the Control Area Ventilation System is a shared system, the support systems may be from either-unit; that is, if i the operable system is aligned to the Unit I diesel generator and nuclear service water system, it may be realigned to the Unit 2 > support systems if any trouble is encounterad. l In order to assure the operability of the operable-train, normal , performance testing and preventative maintenance will be performed , on the system in order to identify and resolve any problems prior-to starting maintenance activities (on the opposite train), and the : performance of preventative maintenance on the system will-ensure l maximum reliability for the system. As previously discussed, no ! Technical Specification surveillance will come due during the extended AOT, and the second train to be taken out of service will , have further assurance of the required opposite . train being: operable as the required train will be fully tested in accordance with post maintenance testing and the previously. discussed j measures. The operators will be fully aware of the situation. The impact of . losing the operable train would be the shutdown of both units within seven hours of the initial event (one~ hour to return the , train or' shutdown within the following'six hours). The impact of a station shutdown on McGuire (thermal cycling of equipment) and on. the Duke system is a situation that Duke' seeks to avoid, thus J McGuire will be examining other measures that may'be taken -. to i prevent degradation of the operable train during maintenance on the ! redundant train. However, should the operable train become degraded and declared inoperable, a shutdown of both units will be
-initiated in accordance with Technical Specification 3.0.3.
Operations procedures are in place to provide alternative Control (3) l 1 l i l
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l i l Room c6oling in the event that the operable VC train is lost. .l Maintenance activities will be completed one train at a time, thus l one VC train will be fully available at all times. If neither VC .; train is fully operable, the station will be in Technical l Specification 3.0.3, which would require that one train be returned - l to operability within one hour or the units be in Hot Standby I within the following six hours, Hot Shutdown within the next six : hours, and Cold Shutdown within the next twenty-four hours. . Additionally, while a train is inoperable for chiller maintenance, the filter package of that train is available, if needed. This .! would not be done to meet requirements in the Technical l Specifications for system operability, but would merely be ; available to provide additional pressurization capability for the Control Room in the event of an accident. ( Also, as previously aiscussed, the failure sequence of ECCS and containment to where the VC System would be required is not a ; credible event. The systems that would be required to fail are ; covered by Technical Specifications and are thus maintained and tested as such to preclude a core melt accident. Again, in j addition to the core melt, the operable filter train would have to fail to affect safety. Such a total failure during the additional i one week AOT is not considered a credible event. As one train is all that is necessary to provide ventilation, and ; one train will be operable at all times, no loss of safety function' is involved. j
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p n .' ( e '- r-0 4 O , , ATTACHMENT 3 -f DUKE POWER COMPANY' MCGUIRE NUCLEAR STATION . NO SIGNIFICANT HAZARDS CONSIDERATIONS ANALYSIS f i Y h 9
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i 1 4 Analysis of Significant Hazard Considerations: Pursuant to 10 CFR 50.91, this analysis provides the information and conclusion that the proposed amendment does not involve any. Significant Hazard Considerations as defined by 10 CFR 50.92. The proposed change would not involve a significant increase in the probability or consequences of an accident previously evaluated. The proposed change will affect only the VC system which is designed to maintain the habitability of the Control Room area as described in the FSAR, Section 6.4 and will not affect the probability of an accident. One train is fully adequate for all conditions, either train can draw outside air from either-independent intake, and one train will be operable at all times, or the station will reduce power or shutdown in accordance with Technical Specification 3.0.3. As the trains are totally redundant, including the ability of each train to draw outside' air-
. form either independent. intake .(should one intake become contaminated), or place the system in recirculation, Control Room doses due to inleakage as presented in Chapter 15 of the McGuire FSAR (Table 15-12) and the NRC Safety Evaluation Report - for Facility Operating License amendments numbers 122.(NPF-9, Unit 1) and 104 (NPF-17, Unit 2) dated July 15, 1991 are unaffected.- The additional allowed outage time thus will not af fect the probability.
or consequences of an accident. The proposed change will not create the possibility of a new or different kind of accident from any accident previously evaluated. The proposed allowed outage time extension is to allow system maintenance to enhance system reliability. Neither the extension-or the planned maintenance activities are of a nature which could lead to any new accident scenarios. The proposed changes would not involve a significant reduction in a margin of safety. With one train of VC operable, all margins are sati.sfied; Control Room doses are unaf fected. - ' Presently,= one train may be inoperable for up to seven days before a station shutdown would be required. The addition of seven days allowed outage time on a one time basis for each train will not have an impact on any safety margins.
~ Based upon the preceding analyses, Duke Power concludes'that the proposed amendment' does not involve a significant hazard consideration as defined by 10 CFR 50,92.
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