ML20078H396
| ML20078H396 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/31/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20078H387 | List: |
| References | |
| NUDOCS 9502060189 | |
| Download: ML20078H396 (5) | |
Text
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j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2068H001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.193 TO FACILITY OPERATING LICENSE NO. OPR-5Q METROPOLITAN EDISON COMPANY JERSEY CENTRAL POWER & LIGHT COMPANY PENNSYLVANIA ELECTRIC COMPANY GPU NUCLEAR CORPORATION THREE MILE ISLAND NUCLEAR STATION. UNIT NO. I DOCKET NO. 50-289 l
1.0 INTRODUCTION
By letter dated May 17, 1993, GPU Nuclear Corporation (GPUN, the licensee) submitted Technical Specifications Change Request (TSCR) No. 221 for the Three Mile Island Nuclear Station, Unit No.1 (TMI-1). This proposed TSCR would revise Table 3.5.1, Section C, Footnote (e), " Engineered Safety Features," in the TMI-I Technical Specifications (TSs).
By letter of December 23, 1994, GPUN submitted supplemental information that further revised Footnote (e) as a result of discussions with the staff. This revised Footnote (e) is to apply to both the loss of offsite power (LOOP) and degraded grid voltage electrical circuitry for each of the two 4160-V ac emergency safety (IE) buses and removes potentially unambiguous language from the footnote.
The revised Footnote (e) clarifies actions to be taken if an undervoltage relay, its associated auxiliary relay, or its timer is inoperable.
In addition, it gives action requirements for the low-voltage relays that are consistent with the action requirements for other similar safety components.
Further, it deletes the requirement to place an inoperable relay in a tripped state within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> since tripping a failed degraded grid volta 5e relay for the TMI-l electrical circuitry design prevents the associated block loading timer from functioning.
The December 13, 1994, letter provided additional information that did not ch nge the initial proposed no significant hazards consideration 9
astermin; tion.
Description of the TMI-1 LOOP and Dearaded Grid Voltaae Electrical Circuitry Desians The staff obtained descriptive information for the circuitry design from TMI Unit 1 personnel during an August 25, 1994, site visit to TMI. This information is given here to enhance understanding of the staff's evaluation and the need for the TSCR.
9502060189 950131 PDR ADOCK 05000289 P
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i The LOOP electrical circuitry for each of the two 4160-V ac Emergency Safety (ES) buses comprises three separate channels.
Each of the three channels for l
a 4160 volt alternating current (vac) ES bus monitors the voltage of one of the.three bus phases and contains a potential transformer, a solid-state undervoltage relay, and an auxiliary relay. The potential transformer output circuit for each channel is connected to a solid-state undervoltage relay.
l This relay sends an actuation signal to an auxiliary relay.
Each of the three channels is set to actuate if the monitored voltage for the attendant 4160 vac-
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bus phase falls below 2400 vac. Auxiliary relay contacts from the three channels and a timer are arranged so that if any two of the three channels are actuated for 1.5 seconds or more, a LOOP actuation occurs. This actuation results in isolating the associated 4160 vac ES bus and starting the attendant l
In a similar manner, the degraded grid voltage electrical circuitry for each 4160 vac ES bus comprises three add'tional separate channels.
Each of these channels comprises a potentia; tansformer that is shared with one of the channels for a LOOP, a colid-state relay, and an auxiliary relay. These channel-attendant circuit elenents are arranged so that the potential transformer connects to a solid-state relay and this relay sends an actuation signal to an auxiliary relay.
Each degraded grid voltage channel for r 4160 vac ES bus monitors the voltage of one of the three bus-attendant phases and is set to actuate if this voltage decreases to below 3760 vac. Auxiliary relay contacts and a timer are arranged so that if any two of the three channels are actuated for 10 seconds or more, the bus is i
isolated. This isolation results in removing the offsite power source and connected loads from the associated 4160 vac ES bus and starting the emergency diesel generator (EDG) for that bus.
In addition, an auxiliary relay contact from one degraded grid voltage circuit channel is arranged in one engineered safety actuation system (ESAS) circuit channel so that if the degraded grid voltage channel actuates, the ESAS i
circuit channel is prevented from actuating. Two additional auxiliary relay contacts from the other two degraded grid voltage circuit channels are arranged similarly in the other two ESAS circuit channels. Thus, with this circuit design, if a degraded grid voltage channel actuates (trip state), then the control logic nece.ssary to actuate the ESAS is reduced from any 2 of the 3 i
channels tripping to 2 of the 2 remaining channels tripping.
- However, additional channel circuitry is provided so that, if the attendant 4160 vac bus EDG output circuit breaker closes and any degraded grid voltage channel is in a trip state, then the control logic necessary to actuate the ESAS automatically returns to any 2 of the 3 channels tripping.
j Technical Specifications Chanae Reauest i
As indicated above, the TSCR revises Footnote (e) of Section C in Table 3.5-1
- of the TMI-1 TSs to replace the current Footnote (e).
Both the current and revised footnotes are given below.
f
e 1
- Current Footnote (e):
If a relay fails in the untripped state, it shall be placed in a tripped state within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to obtain a degree of redundants of 1.
The relay may be removed from the tripped state for up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for functional testing pursuant to Table 4.1-1.
Revised Footnote (e):
The operability requirement for the undervoltage relay, its associated auxiliary relay, and the timer 1.
If one 4.16 kv ES Bus does not meet the minimum conditions, restore the function to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in hot shutdown within an additional 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
2.
If both 4.16 kv ES Buses do not meet the minimum conditions. then restore at least one 4.16 kv ES Bus to meet the minimum conditions within I hour or be in hot shutdown within an additional 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
2.0 EVALUATION The current footnote explicitly addresses only relays.
The revised footnote explicitly addresses associated auxiliary relays and timers in addition to undervoltage relays. Thus, this action alone is not viewed as changing an existing TSs requirement or adding a new TSs requirement but rather as clarifying actions to be taken should any LOOP or degraded grid voltage channel circuit elements become inoperable.
Current TSs require implementation of Specification 3.0.1 (c.mence reactor shutdown within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) if two relays in either the LOOP circuitry or the degraded grid voltage circuitry are inoperable. Such LOOP or degraded grid voltage channel inoperability results in applying an action requirement that is consistent with that for the ESAS analog instrumentation channels.
Treating tne LOOP or degraded grid voltage channels in this manner is inappropriate because of design differences between an ESAS-type instrumentation system design and that for the two 4160 vac emergency safety buses.
In the case of the ESAS analog instrumentation channels, each channel can contain circuit elements that are common to both trains and, as such, an inoperable channel impacts both trains simultaneously.
For the two 4160 vac ES buses, separate sets of LOOP and degraded grid voltage undervoltage relays along with attendant circuitry are provided for each train (one safety bus) and, as such, inoperability of a relay or attendant circuitry or both only impacts that train. Thus, regarding this area, the current TSs and Footnote (e) are overly restrictive and are not consistent with the intent of l
requirements contained in the Revised Standard Technical Specifications (RSTSs) for Babcock & Wilcox plants (NUREG-1430).
The revised Footnote (e) explicitly addresses this area by providing action statements that apply if minimum conditions for either one of the two or both trains of LOOP or
.. degraded grid voltage circuitry are not met. Minimum conditions for a train of circuitry (either LOOP or degraded grid voltage) means that, as a minimum, two of the three channels are operable with a minimum degree of redundancy of one. The 72-hour allowed outage time (A0T) for a train of circuitry to be degraded below minimum conditions is consistent with the 72-hour A0T provided in the RSTSs for an inoperable EDG. The revised Fot.taote (e) also requires that if both trains do not meet the minimum conditions, then within I hour at least one train is to be restored to meet minimum conditions 1r the reactor is to be in hot shutdown within an additional 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. This situation requires immediate action since it indicates that the functional. operation of both trains of circuitry is-degraded below minimum conditions. The resulting immediate action is also consistent with that provided in the RSTSs.
Finally, the revised Footnote (e) removes the current requirement to place an ir. operable undervoltage relay ~in its trip state within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Although the requirement to place an inoperable undervoltage relay or attendant circuit channel or both in its trip state is consistent with a requirement contained in the RSTSs, for the TMI-1 degraded grid voltage circuitry design, this L
action is not consistent with the intent of the requirement. The intent of the related requirement contained in the RSTSs is to maintain the same degree of redundancy with an inoperable undervoltage relay or attendant circuit i
channel or both as is the case with all circuit channels operable. As such, in a three-channel undervoltage circuitry design requiring coincident actuation of two of the three channels, with all channels operable the degree j
of redundancy is one and if one of the circuit channels is inoperable and placed in the trip state, the resulting logic requires actuation of one of the i
remaining two operable channels, thus maintaining a degree of redundancy of one. However, as described above, for the three-channel TMI-1 degraded grid j
voltage circuit design, placing an inoperable channel in the trip state i
reduces the degree of redundancy. Thus, with all three degraded voltage circuit channels operable, the degree of redundancy is one, and with one of the three channels inoperable and placed in the trip state, the degree of redundancy is reduced to zero.
Therefore, in this design, the current requirement to place an inoperable degraded voltage channel in its trip state i
is not consistent with the intent of the requirement contained in the RSTSs.
j SUPf1ARY.
i On the basis of the findings provided in the above evaluation, the staff l
concludes that the revised Footnote (e) provides TSs action requirements for undervoltage circuitry channel elements that are consistent with other similar safety components, is consistent with the intent of requirements contained in j
the RSTSs, and is acceptable.
j
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State i
official was notified of the proposed issuance of the amendment.
The State i
official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes requiren,ents with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendment involves no significant increase in the amounts or types of effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Comission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public coment on such finding (58 FR 59750). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The Comission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed _ manner, (2) such activities will be conducted in compliance with the Comission's regulations, and (3) the issuance of the amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
F. Ashe j
Date:
January 31, 1995 i
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