ML20212F942
| ML20212F942 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 12/31/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20212F908 | List: |
| References | |
| NUDOCS 8701120220 | |
| Download: ML20212F942 (7) | |
Text
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ATTACHMENT II TO JPN-86-64 New York Power Authority James A.
FitzPatrick Nuclear Power Plant Docket No. 50-333 DPR-59 Safety Evaluation for Technical Specification Changes Regarding a Second Level of Undervoltage Protection (PTS-81-019)
I.
DESCRIPTION OF THE PROPOSED CHANGES This amendment application alters pages 54, 60, 70c, 71 and 79.
On page 54, a new specification 3.2.H, "4kV Emergency Bus Undervoltage Trip" has been added to describe the limiting conditions for operation. This specification refers to Table 3.2-2 for the specific limiting conditions for operation.
On page 60, a new paragraph has been added to Bases 3.2 which briefly describes the functions of the 4kV Emergency Bus Undervoltage Trip System.
On page 70c, Table 3.2-2 " Instrumentation that Initiates or Controls the Core and Containment Cooling Systems", two new iter.s have been added.
They are: Item 37 "4kV Emergency Bus Undervoltage Relay (Degraded Voltage)"; and Item 38 "4kV Emergency Bus Undervoltage Timer (Degraded Voltage)." Table 3.2-2 lists: (1) the minimum number of operable instrument channels per trip system, (2) the trip function, (3) trip level settings, (4) total number of instrument channels provided by design for both trip systems, and (5) remarks associated with each table entry.
Also on page 70c, the instrumentation associated with the existing undervoltage protection (loss-of-voltage) has been retitled to distinguish it from the new second level of undervoltage protection (degraded).
In the column titled Trip Function, "(loss-of-voltage)" has been added to clearly identify these instruments (Items 39 and 40).
No change has been'made to the minimum number of operable instruments channels per trip system, trip level setting, or the total number of instrument channels provided, for either the loss-of-voltage relay or loss-of-voltage timer.
In the remarks column associated with Item 39, remark 1 has been clarified to indicate that this instrumentation initiates the loss-of-voltage undervoltage timer.
i 0701120220 861231 DR ADOCK 05000333 PDR
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The remark previously associated with Item 40 has been moved to page 71 (Notes for Table 3.2-2) and has been made into a note L
(Note 5).
This was done because this text applies to both_the i
loss-of-voltage and degraded voltage timers.
Therefore, Note 5 4
appears in the remarks column for_both undervoltage timer trip l
functions (Items 38 and <40).
This note was modified'to l-
_ accurately describe the sequence of events which would occur auring an undervoltage condition.
The Reactor Low Pressure trip function was not assigned an item number in the current amendment of Table 3.2-2.
Item 41 i
has been assigned to this trip-function to correct this typographical error.
[
on page 71 " Notes for Table 3.2-2", four new notes (4 through 7) have been added:
1 Note 4 has been added to clarify how the undervoltage trip system functions.
The note permits continued plant operation with one of two undervoltage trip sensors t
inoperable if the inoperable sensor is placed in the tripped condition.
Note 5 contains the text which previously appeared on page 70c (Table 3.2-2) in the remarks column of Item 40. Minor j
changes are made to.the text to correct and clarify it. A slash "/" was also added between " normal / reserve" to correctly identify the tie breakers mentioned.
3 1
i Notes 6 and 7 specify the relationship between the trip i
level settings and the bus voltages for the degraded and j
loss-of-voltage conditions respectively.
)
On page 79, Table 4.2-2 " Minimum Test and Calibration i
Frequency for Core and Containment Cooling Systems" lists the i
functional test frequency, calibration frequency, and instrument check frequency. The single table entry asscciated with the Emergency Power Undervoltage Trip system (Item 14) has been divided into two items in the proposed revision.
Item 14a is the 4kV emergency power undervoltage loss-of-voltage channel, l
and item 14b is the 4kV Emergency Power Undervoltage degraded i
voltage instrument channel.
l i
on the proposed revision to Table 4.2-2, item 14 has been j
renumbered 14a and the phrase " Loss-of-Voltage" has been added l
in the instrument channel column to distinguish it from the new l
degraded voltage relays and timers.
l Item 14b is a new table entry for the 4kV Emergency Power Undervoltage degraded voltage relays and timers. The same instrument check, functional test and calibration frequencies
+
have been specified for the new degraded voltage relays and timers as for the existing loss-of-voltage instruments.
II.
PURPOSE OF THE PROPOSED CHANGES These changes to the James A.
FitzPatrick Technical Specifications are required to support the installation and operation of plant modifications associated with a second level of undervoltage protection on the plant's two 4kV emergency electrical buses.
The purpose of this new trip system is to assure that equipment and circuits are not damaged or rendered incapable of performing their intended function due to a degraded voltage condition on either of the plant's emergency electrical buses.
The function of the new degraded voltage protection is very similar to the existing loss-of-voltage protection.
The Emergency Bus Undervoltage Trip System transfers the 4kV emergency electrical buses to the Emergency Diesel Generators in the event an undervoltage condition is detected on both the normal and reserve AC power sources.
The system has two levels of protection: (1) degraded voltage protection, and (2) loss-of-voltage protection.
Degraded voltage protection prevents a sustained low voltage condition from damaging equipment.
The loss-of-voltage protection prevents a more severe voltage drop from damagir.g equipment.
Time delays are included to prevent inadvertent transfers due to spurious voltage transients.
Both the duration and severity of the voltage drop are sensed by the system.
A detailed description of the proposed modification is included in Reference 1.
The Technical Specification changes proposed by this amendment application are similiar to those described in References 1 and 4.
The trip voltage specification remains identical to the 1977 PASNY submittal (Reference 1).
A different timer setpoint and tolerance bands are now proposed.
The evaluation of the new setpoints is discussed in Section III to this safety evaluation.
III. IMPACT OF THE PROPOSED CHANGES The impact of the proposed changes would be an increase in the level of safety of FitzParick plant.
Consistent with the
" Defence in Depth" concept for nuclear plant safety, the proposed changes add an additional layer of protection to the emergency electrical distribution system.
The modification is designed to mitigate the consequences of a sustained degraded voltage condition on an emergency bus.
The degraded voltage setpoint is above that which could damage electrical equipment and above the setpoint for the existing loss of voltage protection systems.
This degraded voltage condition was not considered in the original design of FitzPatrick, nor was it analyzed in the FSAR or SER.
t
The new trip voltage tolerance band was selected to reflect the accuracies of the installed instrumentation and provides a tighter, more conservative, bandwidth than the acceptable tolerances provided in Reference 1.
The tima delay timer setpoint and tolerances are changed from the previously approved value of 10 i 0.2 seconds to 9.0 1.0 seconds.
This change was evaluated against the NRC safety evaluation for the degraded grid voltage modification (Reference 2).
The Technical Evaluation Re. port included as an attachment to this safety evaluation provided acceptance criteria for the timer setpoints in Section 3.3, items 3.a, b, and c.
The new setpoint and tolerance band compare to these criteria as follows:
NRC Criterion "3.3 Discussion (3) The time delay selected shall be based on the following conditions:
(a)
The allowable time delay, including margin, shall not exceed the maximum time delay that is assumed in the FSAR accident analysis."
NYPA Desian The proposed time delay of 9.0 i 1.0 seconds results in a maximum time delay of 10.0 seconds.
This is below the maximum value of 10.2 seconds proposed in Reference 1 and approved by the NRC in Reference 2.
This design will sequence the emergency loads during a loss of coolant accident with a coincident degraded voltage condition in the same amount of time as during the loss-of-voltage condition.
This delay time was included in the conceptual design proposed in Reference 1 and approved by the NRC in Reference 2.
The total time for the emergency loads to start will be less than 27 seconds.
This is within the 33 second maximum restart time assumed in the FSAR for an interruption of both of the reserve AC power sources during a major accident.
NRC Criterion
"(b) The time delay shall minimize the effect of short duration disturbances from reducing the unavailability of the offsite power source (s)."
l l
1 NYPA Desian The proposed time delay of 9.0 i 1.0 sec. results in a minimum time delay of 8.0 sec.
This time delay is long enough to override any short inconsequential grid disturbances.
The starting time for the RHR and Core Spray pumps are approximately 2 sec.
The maximum starting time for the nonemergency 4 kV motors is 7 sec. (Reference 1).
Any voltage dips caused from the starting of large motors will not trip the offsite sources.
NRC Criterion
"(c) The allowable time duration of a degraded voltage condition at all distribution system levels shall not result in failure of any safety systems or components."
NYPA Desian The time delay will not cause any failures of any safety related equipment.
During a loss of coolant accident with a coincident degraded voltage condition, safety related equipment will be powered from the degraded bus for approximately 10 seconds.
If the degraded voltage condition were to occur during normal operation, safety related equipment could be exposed to degraded voltage for approximately 20 seconds.
These short term exposures to degraded voltage would not damage equipment.
In addition, most of the safety related equipment is either rated for voltages lower than the degraded voltage setpoint, or is not connected to the emergency bus.
IV.
EVALUATION OF SIGNIFICANT HAZARDS CONSIDERATION Operation of the FitzPatrick Plant in accordance with the porposed Amendment would not involve a significant hazards consideration as stated in 10 CFR 50.92 since it would not:
1.
involve a significant increase in the probability or consequences of an accident previously evaluated.
The addition of this new emergency bus degraded voltage protection equipment will improve the electrical system's ability to withstand a degraded voltage condition without damage to plant equipment.
This new trip system will assure that safety related equipment and circuits are not damaged, or rendered incapable of performing their intended function, due to a degraded voltage condition on either of the plant's emergency electrical buses.
The function of the new degraded voltage protection is very similar to, and supplements the the existing loss-of-voltage protection.
2.
-create the possibility of a new or different kind of accident from any accident previously evaluated.
This modification was designed to mitigate the consequences of a previously unanalyzed event.
The' conceptual. design of this second level of undervoltage' modification has been approved by the NRC in issuance of their Safety Evaluation Report and the associated Technical Evaluation Report (Reference 2).
A change to the time delay setpoint provides quicker initiation of the protective action, and remains within the acceptance criteria for the previous NRC Safety Evaluation.
The modification was designed to nuclear safety related standards which includes the single failure proof criterion.-
Should this modification not perform as designed, the two possible major failure modes are; (a) failure to actuate upon l
a degraded voltage condition, and (b) inadvertent actuation I
during normal voltage conditions.
Failure mode (a) would result in a plant configuration identical to that described in the existing FSAR Es if the modification was not installed.
Failure mode (b) would result in a loss-of-voltage condition for the affected emergency bus.
This condition would require the operation of the existing loss-of-voltage circuits to transfer the affected emergency bus to its Emergency Diesel Generator System as analysed in the FSAR.
No new failure modes Outside the bounds of the FSAR analyses are created by the installation and operation of this modification.
3.
involve a significant reduction in a margin of safety.
The modification will mitigate the consequences of a previously unanalyzed condition.
The failure to actuate or inadvertant
-actuation will not result in a plant configuration outside the boundary of the FSAR.
The effect of this modification will be an overall improvement to plant safety.
In the April 6, 1983 FEDERAL REGISTER (48FR14870), the NRC published examples of license amendments that are not likely to involve a significant hazards considerations.
Example number (ii) of that list is applicable to this change and states:
"A change that constitues an additional limitation, restriction, or control not presently included in the technical specifications: for example, a more stringent surveillance requirement."
V.
IMPLEMENTATION OF THE PROPOSED CHANGE Implementation of these changes, as proposed, will not impact the ALARA or Fire Protection Programs at FitzPatrick, nor will the changes impact the environment.
b VI. -EDNCLUSION The change, as proposed does not constitute an unreviewed safety question as defined in 10 CFR 50.59, that is it:
- a. will not change the probability nor the consequences of an accident or malfunction of equipment 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 than any evaluated previously in the Safety Analysis Report;
- c. will not reduce the margin of safety as defined in the basis for any technical specification;
- d. does not constitute an unreviewed safety question; and e.
involves no significant hazards consideration, as defined in 10 CFR 50.92.
VII. NOTES and REFERENCES 1.
PASNY letter, G. T. Berry to R. W. Reid, dated October 17, 1977 (JNRC-77-2) regarding proposed undervoltage modification and draft technical specification changes.
- 2. NRC letter, D.
B. Vassallo to J.
P.
Bayne, dated September 14, 1984 transmitted Technical Evaluation Report and associated Safety Evaluation.
3.
NYPA letter, J.
P.
Bayne to D.
B. Vassallo, dated October 23, 1984 (JPN-84-71) rescheduled second level of undervoltage protection modification.
- 4. NRC letter, R. W. Reid to G.
T.
Berry, dated June 3, 1977 regarding onsite emergency power systems. Includes model techncial specifications for second level of undervoltage protection equipment.
- 5. NRC letter, R. W. Reid to G.
T.
Berry, dated August 12, 1976 regarding Millstone Unit 2 event. Includes request for information.
6.
PASNY letter, G. T.
Berry to R. W.
Reid, dated October 18, 1976 submits report entitled " Evaluation of Operability of Safety Related Equipment During a Degraded Voltage Condition."
- 7. NRC letter, W.
Gammill to All Power Reactor Licensees, dated August 8, 1979 regarding adequacy of station electric distribution system voltages.
- 8. James A. FitzPatrick Nuclear Power Plant Final Safety Analysis Report (FSAR), Section 8.0,
" Electrical Power Systems."