ML20054C683
| ML20054C683 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/01/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20054C658 | List: |
| References | |
| NUDOCS 8204210499 | |
| Download: ML20054C683 (5) | |
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SAFETY EVALUATION BY THE OFFICE OF WUCLEAR REACTOR REGULATION GPU NUCLEAR CORPORATI0t{
METROPOLITAN EDISON COMPANY
~1 PENNSYLVANIA ELECTRIC COMPANY
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JERSEY CENTRAL POWER AND LIGHT COMPANY DOCKET NO. 50-320 THREE MILE ISLAND NUCLEAR STATION, UNIT NO. 2 INTRODUCTION By. letter dated December 11, 1981, Metropolitan Edison Company > proposed changes to Sections 3.7.1, 3.7.2 and 3.8.2.1 of the Recovery Mode Technical Snecifications for Three Mile Island Unit 2 '(TMI-2) by requesting that the requirements for the operability of the Long Term B (LTB) steam generator cooling system and its associated electrical busses 2-31 and 2-41 be deleted.
The requirements of the Recovery Mode Technical Specifications were imposed on the Licensee by Order of the Director, Nuclear Reactor Regulation, dated February 11, 1980 (45 Fed.
Reg. 11282). Although this mode of reactor coolant system (RCS) heat removal has been maintained as one of the backup cooling modes available, the presently used " loss to ambient" mode has been successful in removing decay heat since i
it'was fully implemented in January 1981.
This change would also remove the operability requirements for LTB associated secondary cooling water and electrical busses from the proposed technical specifications. The Mini-Decay Heat Removal System (MDHRS) and Decay Heat Removal System (DHRS) would tnen bdcome the backup core cooling modes.
MDHRS and DHRS are required to be operacle per proposed Technical Specification subsections 3.7.3.3 and 3.7.3.2 respecti tely.
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SUMMARY
The licensee has requested NRC staff approval to delete the operability require-8204210499 820419 PDR ADOCK 05000320 0
2 ments of Long Tem "B" steam generator cooling system as a backup mode for As discussed in this removing decay heat from the reactor coolant system.
safety evaluation, the " loss to ambient" cooling made will continue to be the primary mode for core cooling with the Mini-Decay Heat Removal System and the The " loss to ambient" cooling mode Decay Heat Removal System as alternatives.
has proven itself as an effective way to remove decay heat and its failure is The other Decay Heat Removal Systems unlikely because it is a passive system.
are available as approved alternatives.
The staff, therefore, has found that the deletion of Long Term "B", its associated secondary cooling water and electrical supply from the proposed technical. specifications are acceptable.
- EVALUATION By Order of the Director, Office of Nuclear Reactor Regulation, dated a new set of fomal license requirements was imposed to February 11, 1980, This order incor-reflect the post accident condition of the TMI-2 facility.
porated operability requirements for the Long Term "B" (LTB) steam generator This is a water solid, closed loop, cooling system which is cooling system.
By in turn cooled by the Secondary Services Closed Cooling Water System.
Amendment of Order dated November 14, 1980, the Mini-Decay Heat Removal System (MDHRS) was also incorporated into the proposed technical specifications as an MDHRS is also a closed loop water solid system sized alternate cooling mode.
such that one pump and one heat exchanger (two of each are installed) could The MDHRS would be cooled by remove up to approximately 1 MW of decay heat.
the Nuclear Services Closed Cycle Cooling System.
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Currently the reactor coolant system (RCS) is generating less than 50 KW of This heat is being removed via the " loss to ambient" cooling mode.
decay heat.
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3-Since the approval of this method by the NRC staff in January 1981, it has sh'own to be an effective and reliable means for core cooling.
In the staff's opinion, since this is a passive mode of heat removal, the chances that an event occurring that would prevent loss of decay heat to be released to ambient is unlikely.
In addition, LTB was originally designed for a decay heat rate corresponding to that existing shortly after the accident with a design heat exchange rate of 12.11.E3 KW (41.35 E6 BTU /hr),
Presently, the decay heat is less than 50 KW (17.07 E4 BTU /hr). Consequently, the LTB system is oversized for its potential current usage.
The'only transient that would result in a temperature and pressure increase such that " loss to ambient" would no longer be effective would be a recriticality accident.
This event was discussed i-n tha Final Programmatic Impact Statement (PEIS) for TMI-2 issued in March 1981.
Paragraph 4.1 of the PEIS states that "the most probable (although very unlikely) cause of recriticality was found l
to be boron dilution, which would be a slow enough process that any approach to criticality can be detected and remedied." This statement is still valid.
The staff, therefore, has concluded that this accident does not need to be con-sidered a factor in maintaining the core in its present thermodynamic condition.
All other causes of recriticality are, in the staff's opinion, also very unlikely and need not be considered.
Since the present mode of decay heat removal is effective and dependable, and the MDHRS and Decay Heat Removal System are required per proposed technical specifications to be operable thereby providing adequate backup modes, this proposed chance to delete the operability reouirements for the LTB system l
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. i ificant increase in the is, therefore, acce-table and will not result in a s gn probability or consequences of accidents previously considered nor a significan reduction in a margin of safety and does not therefore involve a significant hazards consideration.
ENVIRONMENTAL COASIDERATIONS We have determined that the change does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we-have further concluded that the change involves an action which is insignificant from the. standpoint of environmental impact and, pursuant to 10 CFR 51.5 (d)(4) that an environmental impact statement or negative declaration and environmenta impact appraisal need not be prepared in connection with the issuances of this change.
CONCLUSION Based upon our review of the effectiveness history of the " loss to ambient" l
cooling mode, and the availability of approved backup decay heat modes required operable per the proposed technical specifications, the staff finds that the deletion of the Long Term B cooling mode, its associated second-ary closed cooling water and its electrical busses from the proposed technical The associated bases for the proposed technical specifications is acceptable.
specifications have also been modified as reosested by the licensee.
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5 We have also concluded, based on the considerations discussed above, that:
(1) because the cnange does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, it does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Comission's regulations and the implementation of this change will not be inimical to the common defense and security or to the health and safety of the public.
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