ML20248A903
| ML20248A903 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 05/31/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20248A900 | List: |
| References | |
| IEIN-89-026, IEIN-89-26, NUDOCS 8906080223 | |
| Download: ML20248A903 (5) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 34 TO FACILITY OPERATING LICENSE N0, NPF-43 DETROIT EDISON COMPANY WOLVERINE POWER SUPPLY COOPERATIVE, INCORPORATED FERMI-2 DOCKET NO. 50-341
1.0 INTRODUCTION
N By letter dathd April 21, 1989, the. Detroit Edison Company (DECO or the licensee) requested amendment to the Technical Specifications (TSs) appended to Facility,0perating License No. NPF-43 for Fermi-2. The proposed amendment
'would revise the TSs to reflect a design modification to the Reactor-Building's railroad bay air lock doors. The modifications to the doors are a I
result of the licensee discovering via NRC Information Notice No. 89-26,
" Instrument Air Supply to Safety-Related Equipment," the air tupply to the inflatable seals on the doors was not safety related. This design change is a result of industry concerns with the reliability of secondary containment sysi ems to perform their containment function. The Reactor Building, in t
conjunction with the functions performed by the Reactor Building Heating and Ventilation System and the Standby Gas 1reatment System, constitutes fermi-2's secondary containment. Fermi-2's secondary containment boundary provides an essentially leak-tight barrier against uncontrolled flow of air into or out of the Reactor Building. This prevents the dissipation of contaminated air directly to the environment and limits the release of radioactivity.
Ir. order to allow access into and out of the Reactor Building and maintain the secondary containment negative pressure differential, personnel and equipment air locks, and a railroad bay air lock are provided.
Because of the railroad bay air lock door seals' air supply inadequacies, Detroit Edison has performed secondary containment integrity tests to determine if Technical Specification required negative pressures could be maintained without the seals inflated. These tests determined that secondary containment pressure could not be maintained within Technical Specification limits without at least a single air lock door seal inflated. A short-term modification has been implemented which installed a foam seal between the railroad bay outer door and the door's weather stripping. Subsequent testing has confirmed that this modification allows secondary containment to be main-tained within Technical Specification limits with the seals deflated. However, this modification is not desirable as a permanent design.
8906080223 890531 PDR ADOCK 05000341 p
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2 2.0 EVALUATION A design modification is being prepared that will provide the railroad bay door seals with air from a qualified safety related source.
The inner door seal will be supplied from Division I of the Non-Interruptible Air Supply (NIAS) System and the obter door seal will be supplied from Division II of the NIAS System.
The NIAS System consists of two 100 percent capacity air compressors and distribution systems (Division I and Division II). The NIAS System is safety related and seismically supported (Category I). The NIAS System's air compressors are automatically loaded on to the emergency diesel generators (EDGs) upon the loss of offsite power to the air compressor (s) electrical bus (es).
A design modification analysis has determined that sufficient capacity exists in the NIAS System to supply-the railroad bay door seals concurrent with the system's existing loads.
Air supply lines from the associated NIAS Division to each. railroad bay air lock door seal will be seismically qualified and will be provided with a restrictive orifice and individual
- receiver tank. A restrictive orifice will limit NIAS leakage such that a rupture of a door seal will not degrade the function of other equipment which depend on the NIAS System. The individual receiver tanks on each door's air supply kinb will provide a reserve volume sbch that the existing NIAS System's Divisional receiver tanks design basis is not invalidated. The existing and new receiver tanks are designed to provide a 10 minute reserve capacity independent of the NIAS Air Compressor (s) input even,though the NIAS Compressors are supplied by emergency power within approximately 48 seconds after loosing offsite power. The individual receiver tank"on each door seal's air supply line will also assist in normal inflation of the seal.
t Control room alarms for low railroad bay air lock door seal pressure will be installed for each door.
This will allow continuous monitoring by control room personnel of the railroad bay air lock door's secondary containment integrity. The door seals' pressure provides an excellect. indication of the railroad bay air lock's secondary containment integrity because the seals are the only components on the doors which rely on " active" equipment for their safety function operability.
The existing automatic seal inflation circuitry will be removed because it is not safety related and its failure could lead to 6
an unintentional seal deflation. The design modification has provisions for manually inflating and deflating each door seal individually.
D' Implementation of the proposed modification necessitates additional cont'ois to ensure that both railroad bay air lock doors remain closed and sealed because of the vulnerability of the system to a single active failure if only one door is normally required to be closed and sealed.
The existing secondary containment Technical Specification 4.6.5.1.b.1 only requires one railroad bay access door to be closed.
In order to address the proposed modification, the licensee has proposed the subject TS changes.
1.
The existing definition of secondary containment integrity,1.36, does not specifically address the railroad bay air lock. The proposed changes add a clarification to item "d" to prevent a misinterpretation that this item applies to the railroad bay doors. As specified in proposed item "g" both railroad bay access doors are required to be operable and closed because of the vulnerability of the system to a single active failure if only one door is normally required closed.
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The existing Limiting Condition for Operation (LCO) in conjunction with the proposed secondary containment integrity definition has no provisions for normal ingress and egress through the railroad bay air lock or for routine testing of doors alarm / indication instrumentation if both doors are required closed. Thus, the proposed footnote will temporarily suspend the proposed "two door closed and OPERABLE" requirement for ingress and egress through the railroad bay air lock and for routine testing of the doors alarm / indication instrumentation. The temporary suspension of the LCO will only be allowed for four hours provided one of the two doors is open and the other air lock door is OPERABLE and clo!,ed. The existing Technical Specification allows four hours to recover from a complete loss of secondary containment integrity before a reactor shutdown is recuired. The proposed footnote's 12-hour time period is needed to allow sufficient tire for transfer of new fuel. The railrond bay air lock is needed to temporarily store the empty new fuel shipping N
cratestin order to off-load a complete shipment of new fuel. Closing and opening the inner air lock after. placement of each new fuel shipping crate in the air lock is unnecessary, because of the short period of time one of the two doors will be open and the infrequent number of shipments (approximately 8 per 18 months). Additionally, both of the footnote's time limits'are justified based on the low probability of a single failure on the closed door the low frequency of a door being open and the low probability of an a,ccident requiring secondary containment integrity.
3.
The existing LCO, in conjunction with the proposed two door closed and
,0PERABLE requirement, has no h-alistic provisions for a single inoperable railroad bay air lock door. The existing action "a" is based on the complete loss of one or more secondary containment penetrations and/or barriers, or the loss of secondary containment pressure. The proposed ACTION "b" provides requirements for the situation where only one railroad bay air lock door is inoperab?e; in this case, the railroad bay secondary containment penetration is still isolated by the other railroad bay door. The existing actions are based upon situations where secondary containment integrity is completely compromised. The seven day out of service time limit on proposed ACTION "b.1" is consistent with Technical Specification 3.6.5.3, Standby Gas Treatment System (SGTS). The SGTS configuration and function, and the proposed modification configuration are similar in that both systems suppert secondary containment integrity, both systems have 100t redundant capabilities and both systems are safety related. Proposed action "b.2) is consistent with existing action "b".
4.
The existing 31-day Surveillance requirement 4.6.5.1.b.1 only requires verification of one railroad bay air lock door. The proposed change to this surveillance requirement will require that at least once per 31 days both railroad bay air lock doors are verified closed and sealed.
The proposed changes enhance the overall safety of the system based on the following:
Two railroad bay air lock doors will be required closed during normal o
operation as opposed to one railroad bay door which is currently required e
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This will effectively increase the capability and reliability of secondary containment integrity compared to the existing configuration.
The design modification will supply the safety-related railroad bay air o
lock door seals with safety related air from the existing fully qualified and redundant NIAS System. The design modification analysis has evaluated the NIAS System and determined that it is capable of handling the increased railroad bay door seal (s) loads. Additionally, the design modification will include provision (s) (restrictive orifices and receiver tanks) such that a rupture of railroad bay air lock seals will not affect the function of other equipment which depend on the NIAS System.
Control room alarms for low railroad bay air lock door seal pressure will o
be installed for each door. This will allow continuous monitoring by control room personnel of the railroad bay air lock door's secondary containment integrity. The door seal's pressure provides an excellent indicatio'n of the railroad bay air lock's secondary containment integrity because the seals are the only components on the doors which rely on
" active." equipment for their safety function operability.
The propose'd actions are consistent with accepted industry standards for o
related equipment of similar redundancy and safety classification which are also required to support secondary containment integrity, Theproposedfootnote,whichwillallowopeningofo$eofthetwoairlock o
g bay doors, is only applicable if 'the other air lock door is operable and closed.
Both of the time limits in the footr.ote are based on engineering judgement considering the low probability of a single failure on the closed door, the low frequency of a door being open and the low probability of an accident requiring secondary containment integrity.
Additionally, if within the 4 or 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> time period, allowed for one railroad bay air lock door to be open, the closed door becomes inoperable because of a loss of seal pressure (the only active component dependent on an active system) control room personnel would immediately receive the low seal pressure alarm.
Based on the above evaluation the staff finds the proposed changes to the TSs to be acceptable.
3.0 ENVIRONMENTAL CONSIDERATE 0N_
This amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements. We have determined that this amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents which may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issueo a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the
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5 eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
l Pursuantto10CFR51.22(b),noenvironmentalimpactstatementorenvironmental assessment need be prepared in connection with the issuance of this amendment.
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4.0 CONCLUSION
Wehaveconcluded,basedontheconsiderationsdiscussedabove,that(1) the^* is reasonable assuranca that the health and safety of the public will l
not.,e endangered by operation in the proposed manner, and (2) such activities i
will be conducted in compliance with the Comission's regulations, and the issuance of this amendment will not be inimical to the comon defense and security or to the health and safety of the public.
i Principal Contributor: John Stang s
Date: May 31, 1989 l
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