ML20212Q734
| ML20212Q734 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 04/17/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20212Q693 | List: |
| References | |
| NUDOCS 8704240028 | |
| Download: ML20212Q734 (15) | |
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. Enclosura 2 4
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION I SUPPORTING AMENDMENT NO. 27 TO FACILITY OPERATING LICENSE NO. DPR-73 l
f GENERAL PUBLIC UTILITIES NUCLEAR CORPORATION i
THREE MILE ISLAND NUCLEAR STATION UNIT NO. 2 DOCKET NO. 50-320
1.0 INTRODUCTION
I l On June 18, 1985 GPUN submitted Technical Specification Change Request No. 49. This proposed change requested deletion of all operability i requirements for the Three Mile Island Unit 2 (TMI-2) control room emergency air cleanup system and deletion of quantitative airflow require-ments specified for the auxiliary building and fuel handling building j ventilation systems. The submittal and references included supporting
! information to demonstrate that these changes would result in no adverse effect on plant safety. The control room emergency air cleanup system is t
the only system still dependent on the onsite class IE AC distribution system (i.e., diesel generators) during a loss of offsite power. The
- licensee's goal was to demonstrate that none of the remaining loads on 1
j' the diesel generators were required to protect the health and safety of j the public, and that therefore, the Technical Specification requirement I
to maintain the diesel generators in emergency standby is no longer necessary.
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On July 31, 1985 GPUN submitted Technical Specification Change Request No. 51. The proposed change requested deletion of availability and operability requirements for the class IE diesel generators and the remaining systems which depended on the diesel generators during a postulated loss of offsite power. The proposed change also requested deletion of requirements for the fire protection system and emergency buses associated with the diesel generators.
. The NRC staff requested additional information and clarification of these proposed changes in a letter dated October 2,1985.' GPUN provided additional information and modified their requests in letters dated November 20, 1985, February 26, 1986 and May 20, 1986. The current request retains all the operability requirements for the components of the control room emergency air cleanup system but deletes the requirements for a standby onsite AC power supply (diesel generators) for the system.
2.0 DISCUSSION AND EVALUATION TMI-2 is in a long-tem cold shutdown for post-accident cleanup, including removal of the damaged fuel. Short-lived fission products which make up the preponderance of the postulated accident source term in operating reactors have decayed to negligible levels. The decay heat l
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produced by fission products following reactor shutdown is less than 10 kilowatts and forced cooling (i.e. circulation of coolant by reactor coolant pumps) of the core has been unnecessary since 1981.
Section 3.7.7.1 The current technical specification requires that the control room ventilation and eniersency air cleanup system remains operable by specifying operability requirements of the various major components of the system. Currently, the control room ventilation and emergency air t
cleanup system is powerod by one of two redundant offsite AC power distribution systems. An onsite vital (standby) power distribution system consisting of diesel generators and their associated distribution system provides a backup to the redundant offsite systems . In the event of loss of offsite power, the onsite vital power distribution system maintains the operability of the control room ventilation and emergency air cleanup system.
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The licensee has proposed to eliminate the availability of the standby onsite AC power system, currently a Technical Specification requirement, as a backup to offsite power. In the event of a loss of offsite power (LOOP) the control room ventilation and emergency air cleanup system would be inoperable for the period of time required to restore offsite
- power to the station. The staff has evaluated the need for maintaining the control room ventilation and emergency air cleanup system operational and the control room habitable at all tines.
Currently at TMI-2, continuous control room staffing is required to periodically monitor plant conditions. Additionally, TMI-2 control room staffing is required for core alterations (e.g., defueling) and certain water prccessing activities which involve the reactor coolant system.
The staff has evaluated the licensee's request to eliminate diesel generator requirements by evaluating possible TMI-2 initiated accidents and resulting consequences. The types of accidents possible at TMI-2 during the current cleanup phase (long-term cold shutdown) differ markedly from those possible in an operating reactor. The staff and the licensee j have evaluated a broad spectrum of potential accident scenarios at TMI-2 which could, in the absence of an operable control room emergency air cleanup system, affect control room habitability. These included liquid spills, fires, canister drops, and loss of coolant accidents. None of these accidents would be caused by a loss of offsite power and thus are extremely unlikely to
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occur simultaneously with the unavailability of the control room emergency air cleanup system. An accident secuence res_ulting in both the unavailability of the control room emergency air cleanup system and a challenge to control room habitability would require simultaneous and independent accidents, an extremely low probability event. The source tems from postulated accident scenarios at TMI-2 are much smaller than those generated by cperating reactor because there is little or no source of energy for dispersal of core material and the material that could comprise this source term would not include short-lived fission products.
Additionally, the source term material would primarily consist of particulate materials which can be readily filtered using any of a variety of individual respirators. A sufficient number of respirators are stecked in the control room and thus are readily available to personnel.
The staff has also evaluated possible TMI-1 initiated accidents on TMI-2 control room habitability. TMI-1, which is adjacent to TMI-2. is in a nomal operating cycle for power reactors with periods of power operation periodically interrupted by variable length shutdowns for refueling, maintenance and repairs. A severe accident at TMI-1 while it is at power could generate a source term which could affect the TMI-2 control room
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habitability. It is very improbable that this type of accident would occur and even more unlikely that it would be coincident with a loss of offsite power (LOOP) at TMI-2. If there were no coincident TMI-2 LOOP, l
! the TMI-2 control room emergency air cleanup system would function normally and be unaffected by any TMI-1 accident.
GPUN has committed in its letters of February 26, 1986 and May 20, 1986 to terminate all recovery activities and place systems in a safe stable configuration at TMI-2 during an emergency event at TMI-1. This would include core alterations, RCS water processing, transfer of fuel bearing canisters and casks, and movement of heavy loads in the reactor building.
While an accident at TMI-1 could affect habitability in TMI-2, it would not cause equipment failures or additional accidents to occur at TMI-2.
No active components are required to maintain the current safe shutdorn of THI-2. With recovery activities terminated, periodic monitoring of TMI-2 is all that is required. No effect on plant safety would occur due to temporary inaccessibility of the THI-2 control room. Although not required, short-term access to THI-2 could be provided by use of self l
contained breathing apparatus. The staff has determined that intermittent access is acceptable for periods up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> under these conditions. The staff has previously determined that offsite AC power can be restored at THI within five hours. With the restoration of l
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offsite power, the TMI-2 control room emergency air cleanup system would again become operable and personnel could resume the monitoring of activities frcm the control room.
The staff is requiring that GPUNC incorporate in the TMI-2 emergency plan its commitments regarding termination of recovery activities at TMI-2 ,
during emergency events at TMI-1. The licensee has agreed to implement the changes to the emergency plan.
The staff finds the licensee's proposal acceptable and accordingly approves the licensee's proposal to eliminate the standby emergency onsite AC power supply to the control room ventilation and emergency air cleanup system. An asterisk and associated footnote have been'added to Section 3.7.10 to clarify the fact that standby emergency onsite AC power is no longer required for the control room emergency air cleanup system.
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Sections 3.8.1 and 3.8.2, Tables 3.8.1 and 3.8.2 Section 3.8.1 of the current tecFnical specifications specify AC electrical power supply operability requirements. Two physically independent offsite transmission networks and a onsite Class IE distribution system is required. Additionally the specification requires two separate and independent operable class IE diesel generators.
Secticn 3.8.2 requires that specific AC electrical busses listed in the Recovery Operations Plan be operable and energized. Tables 3.8.1 and 3.8.2 specify testing frequency of the diesel generators under different conditions of offsite power availability. The licensee proposed deletion of operability requirements for the Class IE diesel generators from Technical Specification 3.8.1 and the elimination of the requirements to verify the position of AC busses energized by diesel generator actuation.
Low voltage AC vital busses formerly energized by diesel generators would be energized, in the case of a loss of offsite power, by the inverter and battery system.
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The diesel generators, prior to the TMI-2 accident provided backup emergency AC power for a number of vital systems including the decay heat removal system, high pressure safety injection and later after the accident to the installed mini-decay heat removal system. As the plant progressed to the current state of stable long-term cold shutdown, without a need for forced cooling, the reovirements for these systems were eliminated and their operability requirements in the Technical Specifications deleted. The last remaining load on the diesel generators is the control room ventilation and emergency air cleanup system. With the deletion of the requirement to maintain the operability of this system at all times, including during a loss of offsite power, the need for the diesel generators is eliminated. The staff finds the licensee's propesal acceptable and recormends the elimination of the operability requirements for the diesel generators. Testing requirements (Tables 3.8.1 and 3.8.2) would also be eliminated. The changes to Technical Specification 3.8.2 realign the AC busses in response to the elimination nf the diesel generators.
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Section 3.7.4 and 3/4.7.4 This Technical Specification specifies the operability requirements of i
- l. the nuclear service river water system. The nuclear service river water system currently provides cooling water for a number of non-safety related cooling systems as well as cooling for the diesel generators.
Currently the only safety related load on the nuclear service river water system are the diesel generators. The licensee proposes to delete the operability requirements for the nuclear service river water system since the requirement to maintain the operability of the diesel generators is eliminated. The staff finds the licensee's proposal acceptable, recognizing that there is no safety related requirement to maintain the operability of the nuclear service river water system if the diesel generator heat load is eliminated.
Section 3.7.10 This Technical Specification requires an operable deluge and/or sprinkler system in a number of locations throughout the plant. These areas are listed in the subsection of 3.7.10.2. The licensee proposed to delete the requirement for an operable fire suppression system in the diesel generator rooms. Since the diesel generator operability i
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requirements are being deleted, the staff agrees that a fire protection system in the diesel generator room should no longer be required. The existing requirement for a fire detection system in this area will, however, be retained to provide assurance that a fire, initiated in the diesel generator room, will not pose a threat to other areas in the plant.
Section 3.9.12.1 and 3.9.12.2 The current Technical Specifications requires that at least two of the four fuel handling building / auxiliary building air cleanup system fans be operable. Section 3.9.12.1 pertains to the fuel handling building air cleanup exhaust system and Section 3.9.12.2 pertains to the auxiliary building air cleanup exhaust system. The Action statement of these two sections require the licensee to return the airflow to within acceptable quantitative limits of the Recovery Operations Plan within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the system becoming inoperable or suspend all operations involving movement of
- liquid and gaseous radioactive wastes in the fuel handling building /
auxiliary building. Sections 4.9.12.1 and 4.9.12.2 of the Recovery Operations Plan delineates operability by specifying exhaust flow rate, maximum filter pressure drop, and minimum negative building pressure.
These sections were erroneously referred to as part of the Appendix A Technical Specifications in the proposed no significant hazards con- i sideration determination published in the February 11, 1987 issue of the Federal Register (52 FR 4408). The exhaust flow rate values listed in these sections can only be achieved by operation of at least two exhaust fans.
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The licensee proposed to delete the requirement in Technical Specifications 3.9.12.1 and 3.9.12.2 for the operation of a minimum of two exhaust fans. The determination of operability of these systems would not be tied to the operation of a specific number of fans or exhaust flow rate but rather the filter pressure drop and the building pressure. Changes in the Recovery Operations Plan to reflect this have been proposed.
The staff finds that the proposed change in emphasis from specifying exhaust flow rate to building negative pressure more accurately reflects the purpose of this specification which is to assure,1) airflow into the auxiliary and fuel handling buildings, and 2) that exfiltration will not cccur. It provides the licensee with greater operational flexibility without increasing the risk of inadvertent release of radioactivity. The staff finds the licer.see's proposal acceptable. However, to assure early detection of any system degradation, the staff has added a requirement to perform a daily check of pressure indication on the pressure alarm. The licensee has agreed to the requirement.-
The. licensee's original request proposed changing the interval of time
- from 4 to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> between the loss of the air cleanup exhaust systems and
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the termination of operations involving the movement of liquid and gaseous radioactive wastes in the fuel handling building. Subsequent discussions with the ifcensee established that there was insufficient technical justification for the change and the licensee withdrew the request.
3.0 CONTACT WITH STATE OFFICIAL s.
The NRC staff has advised, by letter dated February 20, 1987, the Director, Bureau of Radiation Protection, Department of Environmental Resources, Commonwealth of Pennsylvania, of the proposed determination of no significant hazards consideration. No comments were received.
4.0 ENVIRONMENTAL CONSIDERATION
We have determined that the amendment does not authorize a change in effluent types or total amounts and will not result in a significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration (52 FR 4408), and no public comments or requests for a hearing were received. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuantto10CFR51.22(b),no ;
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environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
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5.0 CONCLUSION
. Based upon our evaluation of the proposed changes to the THI-2 Technical Specifications as modified by agreement with the licensee, and subject to the implementation of the required changes to the THI-2 emergency plan, the staff finds that the licensee's request is acceptable.
We have further 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, and (2) such activities will ,be conducted in compliance with the Commission's regulations and the implementation of this change will not be inimical to th'e common defense and security or to the health l I
and safety of the public. 1 I
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Distribution Copies:
Docket File 50-320 NRC PDR Local PDR TMI-2 HQ file FMiraglia Wasnik WTravers PPall OGC/LChandler-Stewis .
- LHarmon EJordan BGrimes JPartlow TBarnhart (4)
WJones F08 for appropriate Division ACRS (10)
OPA LFMB (w/cy of TAC w/Amd No & date issued) t 1
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