ML20127J331
| ML20127J331 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 01/19/1993 |
| From: | WISCONSIN ELECTRIC POWER CO. |
| To: | |
| Shared Package | |
| ML20127J327 | List: |
| References | |
| NUDOCS 9301250106 | |
| Download: ML20127J331 (8) | |
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TABLE 15.3.5-3 EMERGENCY COOLING 1
2 3
4 5
OPERATOR ACTION NO. OF MIN.
MINIMUM PERMISSABLE IF CONDITIONS OF NO. OF CHANNELS OPERABLE DEGREE OF BYPASS COLUMN 3 OR 4 NO, FUNCTIONAL UNIT CHANNELS TO TRIP CHANNELS REDUNDANCY CONDITIONS CANNOT BE MET 3.
AUXILIARY FEEDWATER (Continued) c.
Undervoltage on 4KV Buses 2/ bus I/ bus I/ bus Hot Shutdown ***
Starts Turbine Driven Pump S.I. INITIATING FUNCTIONS AND REQUIREMENT AS IN 1 AB0VE d.
Safety Injection Signal Starts Motor Driven Pumps 4.
SAFETY RELATED ELECTRICAL BUSES Degraded Voltage (4.16KV) 3/ bus 2/ bus 2/ bus 1/ bus a.
(A05,A05) b.
Loss of Voltage (4.16KV) 2/ bus 1/ bus 1/ bus 1
(A05, A06)
Hot Shutdown ***
c.
Loss of Voltage (480V) 3/ bus 2/ bus 2/Dus 1
'(603,804)
- - Must activate 2 switches simultaneously.
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- - If minimum conditions are not met within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after reaching hot shutdown, the unit shall be in cold shutdown
- within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of the event causing the unit shutdown arc available-arni-the-asseeistedwliesel-43erseestet+aperat4w3
- * * * - f4s rxl c pe ra t i n y a. ided-belf+-diesel gc n c ra te d
! f :i n i = c ced i t i on s a r e not-eet-stMr. 7 days,. the crd prov;dirg pc a to the-aMeeted-safegitards bn.
aMeete4%n i t 'hal1.. bc plwed - i n hat. sbutdtwee-The applicable Limiting Declare the associated emergency diesel generatsfinoperable for the affected tjus.
Condition for' Operation (LCO) shall be er.tered. Separate LCOs nay be entered for the Degraded' Voltage;and
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toss.of Voltage functions. ~
Unit 1 - Amendment No.
' ' Unit 2 - A:nendment No.
Page 2 af 2
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HAPETY EVALUATIOll DEGRADED VOLTAGE RELAY SETPOINT Based on rcview of ABB Impell Corporation Calculation 0870-150-007, the setpoints of the degraded voltage relays on the 4160 volt safeguards buses, A05 and A06, for each point Beach Nuclear plant Unit, were found to be non-conservative.
Under certain conditions, his could result in several safety-related loads having voltage levels lower than the minimum value required.
On January 7, 1993, a Temporary Waiver of Compliance was granted by the NRC and certain compensatory actions taken.
The purpose of the setpoint change proposed in Technical Specification Table 15.3.5-1, Item 9, is to assure adequate voltage levels will be present at all safety-related j
loads and to prevent the spurious stripping of offsite power from these buses and subsequent challenges to safety-systems.
Operation of safeguards equipment for extended periods of time in a-degraded voltage condition could result in the failure of the equip-mont to perform its safety function and mitigate the consequences'of an accident.
The new, higher setpoint for_the degraded voltage relays will allow the removal of offsite power and allow the transfer of the affected safeguards buses to the emergency diesel generators-at an appropriate voltage level to protect equipment.
The new set--
point is at the minimum required voltage necessary to protect-equip-1 ment.
Higher settings are not considered possible.
Higher settings could potentially increase the risk of spurious relay actuation, increased challenges to safety-related equipment and, therefore, could affect safeguards equipment reliability.
The proposed setpoint is conservative and provides an appropriate level of equipment protection consistent with ensuring equipment reliability for the following reasons:
- 1) The calculation which determined the new setpoint is based on worst case conditions of bus-loading and system configuration and contains many conservative assumptions.
- 2) Three relays are installed on each 4160 volt safeguards bus to protect equipment from operating for an extended-period of time.
Any two of the relays-sensing a degraded voltage condition will result in the required action.
- 3) Undervoltage protection-will protect equipment from a loss of power or severely degraded voltage condition.
- 4) The-4160 volt safeguards-buses-protected by these-relays--
provide power to safety-related loads.
Failure of the.
relays-on one bus to actuate at the exact setpoint'would subject only;one safeguards train to voltages slightly-less than-the minimum. required, r
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- 5) The proposed relay setting is necessary based on the worst case which, as dctermined in the calculations, occurs on the Unit 1, Train A (A05) safeguards bus.
This setting is conservative with respect to protecting equipment on all other safeguards buses.
- 6) According to the relay manufacturer, the relay tolerance is expected to be 10.4% at a control power voltage of 110 to 140 volts DC.
Control power is supplied from the station batteries at 125 volts DC and is not expected to vary outside this range.
- 7) According to the personnel that perform the relay calibrations, there has been no observed drift in the relay setpoints since installation.
The new degraded voltage relay setpoint provides assurance that equipment supplied by the safeguards buses will be protected from
. The new setpoint is also set extended operation at reduced voltages.
at a low enough voltage to prevent apurious actuations and challenges to safeguards equipment.
Therefore, thic relay setpoint is deter-mined to be acceptable.
The Technical Specification required action when the minimum operability requirements for degr ded voltage and loss of voltage protection are not met are being revised to require entry into the Liniting Condition for operation (LCO) for the emergency diesel generator (EDG) associated with the affected bus for that unit.
This proposed change does not change the time that degraded voltage protection or loss of voltage protection for the safeguards buses and related equipment may be inoperable.
This change will allow continued operation with the safeguards buses supplied from the preferred source of power, offsite, with the EDGs maintained as designed, as the alternate, emergency source of power to the safe-guards buses.
Therefore, this change will ensure that redundant sources of power are maintained to the buses, thereby maintaining assurance that the emergency source of power to the safeguards buses will be available when needed.
The LCO is entered with respect to the affected unit only.
This is necessary because the EDGs are shared between both pBNp units.
Inoperable channels of degraded voltage or loss of voltage protection in one unit will not prevent an EDG from performing its required function with respect to the other unit.
The LCO for the EDG is entered since actuation of the relays results in the starting of the associated EDG.
If the relays are inoperable, a reliable source of power, the EDGs, will not automatically start and re-energized the affected bus.
The LCOs for inoperable degraded voltage and inoperable loss of voltage channels may be entered separately.
It is unlikely that both protective functions would be inoperable concurrently.
Channel check, calibration, and test frequencies specified in Table 15.4.1-1,
" Minimum Frequencies For Checks, Calibrations and Test of Instrument 1
- I'-
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Channela " ensure that an inoperable channel,is promptly detected and returnec' to service, This LCO, the required actions, and the suppor-ti:ng su tveillances are consistent with the Westinghouse Standard Technir.al Specifications.
The proposed amendments will ensure the continued safe and reliable eper.stion of the Point Beach Nuclear Plant.
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- -. - - - - - - - ~ _ - - - _ _ - _ _ _ _
e UO SEiNIFICANT_lih3ARDS DETEJL!iU!AT_LO_li DEGRADED VOLTAGE _R_ELAY SETPOIUJ' We have evaluated the continued operation of the Poirt Beach Nuclear Plant with the proposed degraded voltage relay setpoint and with the proposed LCO required actions when the loss of voltage or degraded voltage protection function is inoperable, against the standards of 10 CFR 50.92, " Issuance of Amendment."
We have determined that the continued operation of PBNP in accordance with the proposed amend-ments does not result in a significant hazards consideration.
Operation of a facility in acccrdance with the provisions of a
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proposed anendment does not result in a significant hazards deter-n mination if it does not 1) involve a significant increase in the I
probability or consequences of any accident previously evaluated,
- 2) create the possibility of a new or different kind of accident previously evaluated, or 3) result in a significant reduction in a margin of safety.
Our evaluation against each of these criterion follows.
Criterion _l Operation of PDNP in accordance with the pruvisions of the proposed amendments does not result in a significant increase in the probability or consequences of any accident previously evaluated.
The revised setpoint for the degraded voltage protection on 4160V Safeguards Buses A05 and A06 removes the non-conservatism in the existing relay setpoint.
The setpoint remains below the voltage levels at which spurious activation which could affect safeguards equipment reliability is expected to occur.
The proposed setpoint is more restrictive than the existing setpoint and provides assur-ance that equipment will not be adversely affected by operation for extended periods of time at reduced voltage levels.
There-fore, added assurance is provided that safeguards systems and equipment will function as designed.
The probability or conse-quences of an any accident previously evaluated will not be increased by this setpoint change.
The required actions for continued operation with less than the required channels for degraded voltage or loss of voltage pro-tection of safeguards equipment have been revised to require the entry into the LCO for the associated emergency diesel generator (EDG) which will allow continued operation for up to seven days while corrective acticn is taken prior to placing the affected unit in hot shutdown.
The present specification also allows 7 days to take corrective action prior to placing the affected unit in hot shutdown.
The requirement to place the affected safeguards buses en the EDG has been eliminated.
The preferred
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source of power to the safeguards buses is from offsite, with the EDGs serving as the safety-related backup source of power.
The EDGs are intended to-be a standby source of power.
-It is unlikely that the degraded voltage protection and the loss of voltage protection would be inoperable at the-same time.
inerefore protection will still be provided, independent of the inoperable channel, for severely degraded or loss of voltage conditions.
Operation of the EDGs for an oxtended period of time when not needed to perform its safety function as analyzed in the PBNP Final Safety Analysis Report, subjects the EDG to increased wear associated with-operation which may affect reliability and,.
therefore, in undesirable.
Degraded voltage and loss of voltage conditions can readily be detected by existing instrumer.tation as well as routine checks, calibrations and tests, and can be compen-sated for by operator action.
Therefore, the elimination of the requirement to place the affected buses on an EDG whi2e main-taining the requirement to take corrective action within 7 days does not result in a significant increase in the probability or consequences of any accident previously evaluated.
The remaining proposed changes, which add the safeguards bus designations to the related items in the Technical Specification Tables is an administrative change.
It does not affect any operational requirement or function related to PBNP.
Therefore, these changes cannot result in an increase in the probability or consequences of any accident previously evaluated.
Criterion 2 Operation of PBNP in accordance with the provisions of the proposod amendments will not create the possibility of a new or different type of accident than any accident previously evaluated.
The design of PBNP is not being altered as a-result of the proposed amendments.
The existing design and function of the degraded voltage protection and loss of voltage protection for-safeguards equipment is being maintained.
Therefora, a new or different type of accident than any accident previously evaluated cannot result.
Criterion 3 Operation of PBNP in accordance with the provisions of the proposed amendments will not result-in a significant reduction in a margin of safety.
The setpoint for the degraded voltage protection is being revised to eliminate the existing non-conservatism in the existing set-point.
The new setpoint is maintained at a level where the reli-ability of safeguards equipment is not expected to be affected by spurious actuations.
Corrcetive action for inoperable degraded voltage and loss of voltage protection channel will still be required to be taken within 7 days or the affected unit placed in hot shutdown.
By not placing the affected-buses on the associated-
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EDG, the EDGs are maintained as the standby source which is their intended and design function.
The EDGs will also not be subjected to the potential for decreased reliability that could be caused by component wear or other failure mechanisms that may be the result of extended operation.
Therefore, a margin of safety is not significantly reduced.
The remaining proposed changes, which add the safeguards bus designations to the related items in the Technical Specification Tables is an administrative change.
It does not affect any opera-ticral requirement or function related to PBNP.
Therefore, a margin of safety is not reduced.
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