JPN-88-044, Proposed Tech Specs Changes Re Second Time Delay for Actuation of Degraded Voltage Protection Sys
| ML20153C381 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 08/24/1988 |
| From: | POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK |
| To: | |
| Shared Package | |
| ML20153C287 | List: |
| References | |
| JPN-88-044, JPN-88-44, NUDOCS 8809010117 | |
| Download: ML20153C381 (12) | |
Text
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ATTACHMENT I TO JPN-88-044 PROPOSED TECHNICAL SPECIFICATION CHANGES REGARDING A SECOND TIME DELAY FOR ACITJATION OF THE
_ DEGRADED VOLTAGE PROTECTION SYSTEM (J PTN48 Oll)
)
l New York Power Authority i
JAMES A. FITZPATRICK NUCLEAR POWER PIANT Docket No. 50-333 DPR 59 l
8009010117 000824 PDR ADOCK 05000333 P
PNV 1
JAFNPP 3.2 BASES (cont *d)
The recirculation pump trip has been added at the cuggestion of ACRS as a mesns of limiting the conse-quexces of the unlikely occurrence of a failure to ceram during an anticipated transient. The response cf the plant to this postulated event falls within the envelope of study events given in General Electric Company Topical Report, NEDO-10349, dated March, 1971.
The Emergency Bus Undervoltage Trip System transfers the 4 kv emergency electrical buses to the Emergency Dicsel Generators in the event an undervoltage c:ndition is detected. The system has two levels of pratection: (1) degraded voltage protection, and (2)
Icca-of-voltage protection. Degraded voltage prctection prevents a sustained low voltage condition from damaging safety-related equipment. The degraded voltage protection has two time delays. A short time delcy coincident with a loss-of-coolant accident (LOCA) and a longer time delay to allow normal plant evolutions without unnecessarily starting the Emergency Diesel Generators. The loss-of-voltage protection prevents a more severe voltage drop from cauaing a long term interruption of power. Time deltys are included in the system to prevent inadvertent transfers due to spurious voltage decreases. Therefore, both the duration and severity cf the voltage drop are sensed by the Emergency Bus Undervoltage Trip System.
Amendment No. 396 60
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JAFEPP TABLE 3.2-2 (cont'd)
INSTRUMENTATION THAT INITIATES OR CONTROLS THE CORE AND CONTAINMENT COOLING SYSTEMS l
i l
Minimum No.
Total l
of ')perable Number of Instru-Instrument ment Channels Pro-Item Channels Per vided by Design for No.
Trio System (1)
Trio Function Trio Level Settino Both Trio Systems Remarks j
37 1 (1 per 4kV bus) 4kV Emergency Bus 108 2 1.5 2 Inst. Channels
- 1. Initiates both 4kV Undervoltage Relay secondary volts Emergency Bus Under-(Degrade 3 Voltage) voltage Timers. (Degraded voltage LOCA and non-LOCA)
- 2. Notes 4 and 6.
38a (1 per 4KV bus) 4kV Emergency Bus 9.0 1 1.0 sec.
2 Inst. f'hannels
- 1. Note S.
l Undervoltage Timer (Degraded Voltage LOCA) 38b (1 per 4kV bus) 4kV Emergency Bus 45 2 5.0 sec.
2 Inst. Channels
- 1. Note 5.
Undervoltage Timer (Degraded Voltage non-LOCA) 39 (1 per 4kV bus) 4kV Emergency Bus 85 4.25 2 Inst. Channels
- 1. Initie..es 4kV Emergency Undervoltage Relay secondary volts Bus Undet altage Loss (Loss of Voltage) of Voltage Timer.
- l
- 2. Notes 4 and 7.
40 (1 per 4kV bus) 4kV Emergency Bus 2.50 r 0.05 sec.
2 Inst. Channels
- 1. Note 5.
Undervoltage Timer (Loss of Voltage) l 41 2
Reactor Low Pressure 285 to 335 psig 4 Inst. Channels Permissive for closing re-circulation pump discharge valve.
Amendment No. 14, 44, %
70c l
'l JAFNPP f
TABLE _l,2-2 (Cont'd) l INSTRUMENTATION THAT INITIATES OR CONTROLS THE CORE AND CONTAINMENT COOLING SYSTEMS NOTES FOR TABLE 3.2-2 1.
Whenever any ECCS subsystem is required by specification 3.5 to be operable, there shall be two operable trip systems. From and after the time it is found that the first column cannot be met for one of the trip systems, that trip system shall be placed in the tripped condition or the reactor shall be placed in the cold condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
l 2.
"Deleted" 3.
Refer to Technical Specification 3.5. A for limiting conditions for operation, failure of one (1) instrument channel disables one (1) pump.
4.
Tripping of 2 out of 2 sensors is required for an undervoltage trip. With one operable sensor, operation may continue with the inoperable sensor in the tripped condition.
5.
The 4kV Emergency Bus Undervoltage Timers (degraded voltage LOCA, degraded voltage non-LOCA, and loss-of-voltage) initiate the following: starts the Emergency Diesel-Generators; trips the normal / reserve tie breakers and trips all 4kV motor breakers (in conjunction with 75 percent l
Emergency Diesel-Generator voltages); initiates diesel-generator breaker close permissive (in conjunctiori with 90 percent Emergency Diesel-Generator voltages) and; initiates sequential starting of vital loads in conjunction with low-low-low reactor water level or high drywell pressure.
6.
A secondary voltage of 108 volts corresponds to approximately 90.8% of 4160 volts on the bus.
7.
A secondary voltage of 85 vcits corresponds to approximately 71.5% of 4160 volts on the bus.
Amendment No. es, 6T, K 71 i
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JAFNPP TABLE 4.2-2 MINIMUM TEST AND CALIBRATION FREQUENCY FOR CORE AND CONTAINMENT COOLING SYSTENS Instrument Chn===l Instrument Functional Test Calibration Frequencie Instrument Checkf4) 1)
Reactor Water Level (1)(5)
(15)
Once/ day 2a) Drywell Pressure (non-ATIS)
(1)
Once/3 mo:.ths -
None 2b) Drywell Pressure (ATTS)
(1)(5)
(15)
Once/ day
- 30) Reactor Pressure (non-ATTS)
(1)
Once/3 months None 3b) Reactor Pressure (ATTS)
(1)(5)
(15)
Once/ day 4)
Auto Sequencing Timers None Once/ operating cycle Nt,ne 5)
(1)
Once/3 months None 6)
Trip System Bus Power Monitors (1)
None Nese 8)
Core Spray Sparger d/p (1)
Once/3 months Once/ day 9)
Steam Line High Flow (HPCI & RCIC)
(1)(5)
(15)
Once/ day 10)
Steam Line/ Area High Temp. (HPCI & RCIC)
(1)(5)
(15)
Once/ day 12)
HPCI & RCIC Steam Line Low Pressure (1)(5)
(15)
Once/ day 13)
HPCI & RCIC Suction Source Levels (1)
Once/3 months None-11) 4kV Emergency Bus Under-Voltage Once/ operating cycle Once/ operating cycle None (Loss-of-Voltage, Degraded Voltage LOCA and non-LOCA) Relays and Timers.
15)
HPCI & RCIC Exhaust Diaphragm (1)
Once/3 months None Pressure High 17)
LPCI/ Cross Connect Valve Position Once/ operating cycle None None NOTE:
See listing of notes following Table 4.2-6 for the notes referred to herein.
Amendment No. M, $T, M, 99, p 79
= - -
2.
ATTACHMENT II TO JPN-88444 SAFE 1T EVALUATION FOR PROPOSED TECHNICAL SPECIFICATION CHANGES REGARDING A SECOND TIME DELAY FOR ACTUATION OF THE DEGRADED VOLTAGE PROTECTION SYSTEM (J1 % 88 011) i
- Y I
k New York Pour Authority JAMES A. FITZPATRICK NUCLEAR POWER PIANT Docket No. 50 333 DPR 59 I
' 1 to JPN-88-Gl4 SAFE'IY EVALUATION Page 1 of 6 1.
DESCRIPI' ION OF Tile PROPOSED CilANGES The proposed changes to the James A. FitzPatrick Technical Specifications revise Technical Specification Bases 3.2, and Tables 3.2-2 and 4.2-2 on pages 60,70c,71, and 79.
Page 60 Bases 3.2 Insert two new sentences in the last paragraph to read:
'The Degraded Voltage Protection has two time delays. A short time delay coincident with a loss-of coolant t.ccident (LOCA) and a longer time delay to allow normal plant evolutions without unnecessarily starting the Errergency Diesel Generators."
Page 70c Table 3.2-2 (cont (d)
Change Remark 1. of Table entry 37 to read:
Initiates both 4kV Emergency Bus Undenoltage Timers. (Degraded Voltage LOCA and non LOCA)
Rename Table entry 38 to 38a and add a new Table entry 38b below Item 38a. The new entry is identical to the existing Item 38 with the exception of the following two items:
Trip function Trip Level Setting 4kV Emergency Bus Undervoltage 45 + 5.0 sec.
Timer (Degraded Voltage non LOCA)
Insert 'LOCA' in the Trip Function for entry 38a Pace 71 Notes for Table 3.2 2, Note 5 Insert 'LOCA, degraded voltage non LOCA* into the first line after the phrase ' degraded voltage.'
After the colon in the second line, replace ' initiates the start ol' with ' starts.'
Page 79_ Table 4.2 2 Consolidate items 14a and 14b into a single item (No.14) and add the extended degraded voltage relays and timers. The new entry is identical to the existing item No.14a with the following exception:
Instrument Channel 4kV Emergency Bus Under Voltage (Loss of Voltage sad Degraded Voltage LOCA and non LOCA) Relays and Timers.
, 1 to JPN-88-044 SAFE'IY EVALUATION Page 2 of 6 11.
PURPOSE OF Tile PROPOSED CilANGES The NRC approved and issued Amendment 106 in Reference 3 which incorporated a Second level of Undervoltage Protection System in the FitzPatrick Technical Specifications. - Since then, two actuations of this protection system have occurred during normal plant start ups. These actuations occurred when plant electrical loads are transferred from the reserve station transformers (off site power source) to the normal station transformer (main generator source).
The emergency bus degraded voltage protection system is designed to assure an adequate supply of AC power for all Engineered Safety Feature (ESF) loads. The protection system fast-starts the emergency diesel generator pair associated with a 4 kV emergency bus when the bus voltage drops below 90% of nominal voltage for 9 seconds (Technical Specification Table 3.2 2, Items 37 and 38). The 9 second time delay was selected so that short term voltage drops due to expected operating evolutions (such as starting of a large motor) would not actuate the protection system.
The voltage transient associated with the routine transfer of electrical loads from the reserve station transformers (off site power source) to the normal station transformer (main generator source) during startup can be of sufficient magnitude and duration to actuate the degraded voltage protection system. This is most likely when the off site grid voltage is near the low end of its normal range. With reduced off site voltage, the transfer transient starts with the electrical buses initially at a lower voltage. Licensee Event Reports (LER),
submitted to the NRC after the two EDG starts, describe these occurrences (References 4 and 5).
Although the degraded voltage protection system was designed to withstand short term voltage drops due to expected operating evolutions, the design of the system did not consider the significant voltage transient associated with bus transfers. The bus transfer voltage transients have now been analyzed and modifications to the plant with corresponding changes to plant operating procedurec and Technical Speciliations are proposed.
Under normal operating conditions (non LOCA), a 45 second time delay would prevent an EDG actuation during expected voltage transients. Under LOCA conditions, the LOCA signal willindependantly start the EDGs. If a degraded voltage condition subsequently exists on an emergency 4kV bus, the degraded vohage protection system will shed the 4kV loads, transfer the emergency bus to the EDGs and then sequence the emergency loads back onto the bus. This allows the EDGs to supply.the emergency loads as previously evnluated.
The proposed changes will protect safety related electrical equipment from degraded voltage conditions under both LOCA and non LOCA conditions without impacting normal plant operations.
Ill.
IMPACT OF Tile PROPOSED CilANGES In LER 87 009 (Reference 4, Corrective Action 3) the Authority committed to reevaluate the undervoltage and time delay setpoints for the Emergency Bus Degraded Voltage Protection System. NRC Branch Technical Position (BTP) PSB 1
- Adequacy of Station Electrical Distribution System Voltages * (Reference 6) provides guidance for selecting the degraded voltage time delay setpoints. The BTP recommends two
[
separate time delays: one for normal operation and the second coincident with a safety injection actuation j
(LOCA) signal. The FitrPatrick degraded voltage protection system will be modified to incorporate the two time delays as recommended in the BTP. In light of the BTP, the results of the FitzPatrick specific reevaluation are as follows:
1.
BTP ltem B.1.b.1 l
- The first time delay should be of a duration that established the existence of a i
sustained degraded voltage condition (l.c., something longer than a motor starting transient).. The subsequent occurrence of a safety injection actuation signal 1
j
- = _ -
1
- 1 ts JPN-88444 SAFE'IY EVALUATION Page 3 of 6 l
l (SIAS) should immediately separate the Class 1E distribution system from the offsite power system."
NYPA Design:
The present degraded voltage protection design with a 9 second time delay (with a coincident LOCA) will be retained. This time delay was previously evaluated and approved by the NRC in Reference 3. The LOCA signals (Iow reactor water level or high drywell pressure) that will be used in the undervoltage protection logic are the same signals which start the EDG's.
2.
BTP ltem B.1.b.2
- The second time delay should be of a limited duration such that the permanently connected Class 1E loads will not be damaged Bases and justification must be provided in support of the actual delay chosen.'
NYPA Design:
The time delay setpoint evaluation has been completed for time delays of up to 60 seconds. The evaluation considered:
a.
600V hlCC Control Circuits All 600V hlCC control circuits can with tand a low voltage which is insufficient to energize the starter coil for 2 minutes without blowing the control power fuses or otherwise damaging or disabling the circuit. (References 1 and 11) 600V Class 1E starter dropout and pickup voltages are 70% and 85% of the rated voltage respectively. (References 7 and 11) b.
575V and 4000V hiotors All safety.related and non safety related motors can be operated continuously within + 10 percent of nameplate vohage. (References 8 and 11)
The 4000V Residual licat Removal pump motors will start and accelerate at 75% rated voltage. The Core Spray pump motor will start and accelerate at 70% rated voltage.
Other 4000V and 600V load center motors will start and accelerate at 70 to 80 percen; rated voltage. (References 1 and 12)
Class B insulation is specified for motors used at FitzPatrick. (References 9,10, and 11) c.
Class 1E 4160V and Class 1E 600V Switehgear The breaker control circuits for the 4160V and 600V load center bus loads are supplied by the station batteries and thus are indepeadcat of the grid voltage. (References 1 and 11) d.
120V AC Emergency Power System A major portion of the instrumenution is powered by the station batteries or the Uninterruptable Power Supply hiotor.hiotor Generator set (which is driven by a battery powered DC motor should the AC voltage fall below the capability of its AC motor) and thus these instruments are not affected by the grid voltage. (Reference 41 and 11)
)
1
Attachm:nt 11 to JPN-88-044
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SAFETY EVALUATION Page 4 of 6 Control desices and circuits fed from the 120V AC emergency buses will function at 85 percent voltage. (References 1 and 11)
Reference 13 contains the results of the analyses conducted to determine the voltage transient associated with load transfers from the reserve station transformer to the normal station transformer. The minimum voltage calculated during the transient was 3732V on the 4160V emergency bus (89.7% of rated voltage) based on an initial offsite grid voltage of 117.45kV.
Based upon the two minute (70% to 85% mitage) capability of MCC control circuits,60 second (75%
voltage) capability of motors, and 85% voltage capability of 120V AC emergency bus circuits, a 60 second time delay for the second level undervoltage relay during a non LOCA condition is acceptable. The voltage on the emergency buses during this condition will not be below 89.7% rated and therefore the permanently connected Class 1E loads will not be adversely affected.
A Technical Specification value of 4515 seconds is selected for the extended degraded voltage timer. This delay is less than the analyzed limit of 60 seconds while long enough to provide sufficient time for an operator to adjust the load tap changer on the normal station transformer to bring the emergency bus voltage within the normal range.
Plant procedures will be changed to reflect the voltage transient analyses. When the offsite grid is below 117.45kV, load transfer from the resene station transformers to the normal station transformer will be prohibited. The grid voltage normally varies between 117kV and 122kV (Reference 1).
IV.
EVALUATION OF SIGNIFICANT IIA 7,ARDS CONSIDERATION Operation of the FitzPatrick Plant in accordance with the proposed Amendment would not invohr a significant hazards consideration as stated in 10 CFR 50.92 since it would not:
1.
invohr a significant increase in the probability or consequences of an accident previous.y evaluated. The degraded voltage protection system is designed to mitigate a potential accident initiator. After any reactor or turbine trip, all house loads (including safety related equipment) are powered from the off site electrical power grid. If the grid is unavailable or degraded, the on-site emergency diesel generators must function to power the emergency buses.
The existing degraded voltage protection system, installed in 1987, requires modification because its actuation time delay is too short to withstand routine operating evolutions. During the current operating cycle, actuations of the existing system have caused two unnecessary cold fast starts of the emergency diesel generators. Without the fast intervention of the plant operators, this would have led to unplanned losses of the reserve power source to the emergency buses and could have led to reactor scrams. The proposed change, incorporating a dual time delay feature as recommended by the NRC in Branch Technical Position PSB 1, will restore the undervoltage protection system to its intended function as previously analy7ed by the NRC and reduce the probability of the transient initiating sequence discussed above.
2.
create the possibility of a new or different kind of accident from any accident previously evaluated. The failure of the modified degraded voltage system to operate would essentially place the plant in the same configuration that existed before the system was installed.
FitrPatrick was presiously analyzed in that configuration and therefore, it would not initiate or contribute to a new or different type of accident.
Inadvertent actuation of the extended degraded voltage system would be identical to two actuations of the degraded voltage protection system experienced during the current operating cycle. The result is similar to, but less severe than the loss of off. site power transient presiously I
Attachment il t2 JPN-88444 SAFE'IY EVALUATION Page 5 of 6 i
analyzed. It would be less severe since the non-safety related buses would still be energired from the off-site power sourecs and would be available to mitigate the transient.
Operation of the degraded voltage protection system in conjunction with the existing undervoltage protection systems will protect safety related electrical equipment from degraded vokage conditions under both LOCA and non LOCA conditions without impacting normal plant operations. The selection of the degraded voltage setpoints and time delays is based upon a FitzPatrick specific analysis performed in accordance with NRC recommendations.
3.
invohr a significant reduction in a margin of safety. In addition to assuring that the undervoltage protection systems satisfy their design function, the proposed changes reduce the number of challenges to safety related equipment (cmergency diesel generators) and reduce the probability of a transient initiator (as discussed in IV.1 above). The proposed changes involve an increase in the margin of safety for the FitzPatrick plant.
V.
IhlPLEh!ENTATION OF Tile PROPOSED CIIANGE Implementation of the proposed changes will not impact the A1 ARA or Fire Protection Programs at FitzPatrick, nor will the changes impact the environment.
VI.
CONCLUSION The change, as proposed, does not constitute an unresiewed safety question as defined in 10 CFR 50.59. That i
is, it:
will not change the probability nor the consequences of an accident or malfunction of equipment a.
important to safety as previously evaluated in the Safety Analysis Report; b.
will not increase the possibility of an accident or malfunction of a different type from any presiously evaluated in the Safety Analysis Report; will not reduce the margin of safety as defined in the basis for any technical specification; c.
d.
does not constitute an unresiewed safety question; and c.
invohes no significant hazards consideration, as defined in 10 CFR 50.92.
Vll.
REFERENCES 1.
James A. FitzPatrick Nuclear Power Plant Updated Final Safety Analysis Report, Sections 8.6.6.b,8A.6.g and 8.9.5.
2.
James A. Fit 7 Patrick Nuclear Power Plant Safety Evaluation Report (SER), dated November 20,1972, and Supplements.
3.
NRC letter, II.1. Abelson to J. C. Brons (NYPA), @ed March 20,1987, issuing Amendment 106 to the FitzPatrick Technical Specifications.
4.
NYPA letter, R. J. Converse to the NRC (JAFP 87-05A4), da"d July 10,1987, submitting LER 87 0094)0 entitled: ' Actuation of 4 kV Emergency ' as D
'd Voltage Protection During Load Transfer?
i
- 112 JPN-88-044 s
SAFETY EVALUATION Pap 6 of 6 5.
NYPA letter, R. J. Comerse to the NRC (JAFP-87-0801), dated October 9,1987, submitting LER 87-014-00 entitled: ' Actuation of 4 kV Emergency Bus Degraded Voltage Protection During Load Transfer.'
6.
' Adequacy of Station Electrical Distribution System Voltages," U. S. Nuclear Regulatory Commission, Branch Technical Position PSB 1, Revision 0, July 1981.
7.
NRC letter, T. A. Ippolito to G. T. Berry (NYPA), Enclosure 2, ' Adequacy of Station Electric Distribution System Voltages James A. FitzPatrick Nuclear Power Plant,' EG&G Idaho, Inc.,
Table 1, dated April 15,1981.
8.
FitzPatrick Nuclear Safety Evaluation [[::JAF-SE-85118|JAF-SE-85118]], page 6, item ig, dated September 11, 1985.
9.
General Electric Co Specification 21A9222, Rev.1 for Induction Motors.
10.
Stone and Webster Engineering Corp. Specification for Induction Motors, dated October 22, 1969.
11.
Stone and Webster Engineering Corp. letter, D. J. Patel to L Guaquil (NYPA) providing a report entitled,' Time Delay Extension Study Second level Undervoltage Protection Scheme -
James A. FitzPatrick Nuclear Power Plant," PAS 273:M, dated November 30,1987.
12.
PASNY letter, G. T. Berry to R. W. Reid (NRC), dated December 31,1976.
13.
Stone and Webster Engineering Corp. letter, D. J. Cirrone to L Guaquil (NYPA), prosiding the results of the bus transfer voltage transient analpes, PAS.27601, dated August 22,1988.
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