ML20091B353
| ML20091B353 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/20/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20091B351 | List: |
| References | |
| NUDOCS 9106030123 | |
| Download: ML20091B353 (3) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 162 TO FACILITY OPERATING LICENSE N0. DPR-50 METROPOLITAN EDISON-COMPANY JERSEY CENTRAL POWER & LIGHT COMPANY PENN5YLVANIA ELECTRIC COMPANY GPU NUCLEAR CORPORATION THREE MILE ISLAND NUCLEAR STATION, UNIT N0. 1
-DOCKET N0. 50-289 1.0 INTRODUCTICN By letter dated March 25, 1991, GpU Nuclear Corporation (the licensee) requested an amendment to the Technical Specifications (TS) for Three Mile Island Unit 1, (TMI-1). The proposed change would add an allowable outage time (i0T) for the Turbine Bypass Valves -(TBVs) to clarify time requiremen+.s when fawer than four of the six TBVs_are operational.
2.0 BACKGROUND
The THI-1 design incorporates six TBVs that bypass the main turbine and direct steam from the main steam system into the main condenser.
The primary purpose of the valves is to orovide pressu're control following a load rejection or primary-to-secondary load mismatch by passing approximately M.5% of full steam flow.
Other means of providing pressure control in the inain. team syster under these conditions are the atmospheric dump valves (ADVs) and :he Main Steam Safety Valves (MSSVs). The current TS, in-Section 3.4.1, hue' certain requirements for maintaining decay heat removal capability.
One of those requirements is that four'of the six TBVs must be operable.
The TS give no time limit to return TBVs to operable status in the event that less than four are operable.
Because this condition has occurred for a limited time in the past, and because_the lack of a specified A0T has-caused some confusion in-the past, the licensee has taken the initiative to upgrade the TS in this area.
The proposed change also includes some minor format improvements for clarification.
Only page 3-25 is affected by thue proposed changes.
3.0 -EVALUATION
-The licensee has proposed adding an A0T of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for having fewer than four TBVs operatiTinal when reactor coolant system temperature is greater than 250 degrees Fahrenheit.
The following additional sentence is proposed: "With more than two turbine bypass valves inoperable, restore operability of at least four turbine bypass valves within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />." The licensee did not propose an. action statement, however, for definitive action if four valves could not be made operational within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The licensee's safety evaluation justifying the 9106030123 910520
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change states that the only safety function provided by these valves is reduction of radioactive doses during certain accident scenarios.
Specifically, following a steam generator tube rupture accident, the THI-1 Updated final Safety Analysis Report (UFSAR) takes credit for bleeding steam into the main condenser via the TBVs to take advantage of the scrubbing action of the main I
condenser in removing radioactive particulates and iodines, thereby significantly reducing the qeantities of these isotopes releasad to the environment.
The other two methods of pressute relief, the ADVs and the MSSVs, are less desirable because they discharge directly to the atmosphere with no scrubbing action.
The licensee states that with no 13Vs operable following a steart generator tube rupture, radioactive releases to the atmosphere would still be well within the limits of 10 CfR part 100. The Standard TS for Babcock &
Wilcox (B&W) designed plants have no operability requirements for TBV's because other B&W plants do not necessarily assume the dose reduction realized by dumping steam to the main condenser via the TBVs following a steam generator tube rupture.
The licensee did give consideration to revising the UFSAR and removing the TBV operability requirements from the TS altogether. The licensee also stated that, because the TBVs are the preferred method of depressurizing the above) generators during a plant cooldown (f)r the same reasons as discussed steam
, it would be incorrect to require a plant shutdown and cooldown for most cases of TBV inoperability.
Therefore, although an A0T would now be spelled out in the TS for the TBVs a decision regarding what action would be taken with the plant if the A0T could not be met would be made on a case-by-case 19 sis.
Shutting down the plant only because fewer than four TBVs are operable could actually result in a higher radiation dose to the public because ADVs may have to be used to vent slightly radioactive steam directly to the atmosphere.
The licensee therefore states that plant shutdown and cooldown in this instance may not be in the best interest of public health and safety.
The staff has reviewed the licensee's justification for this TS change and has no reason to disagree with the conclusions.
Since there is a safety benefit that can be realized by having TBVs operable in the event of a steam generator tube rupture, the licensee should make a good faith effort to maintain as many TBVs operable as possible at all times.
Consistent with other provisions in the TMI-1 TS, the staff agrees that the appropriate action in the event of less than four TBVs operable is not to necessarily shut down the plant, unless there is a clear net safety benefit in doing so.
Page 4-Sa was included with this amendment solely to correct an administrative error in Amendment No.161, issued on April 22, 1991. The error was that the changes approved in Amendment No.156 were inadvertently omitted in Amendment No. 161.
3.0 STATE C0NSULTAT10N in accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in
j 3-10 CFR Part 20.
The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released of f site, and that there is no significant increne in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the i
amendment involves no significant hazards consideration, and there has been no public consnent on such finding (56 FR 15642).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR $1.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of j
the amendment.
5.0 CONCLUSION
The Commission 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 Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
R. Hernan Date:
May 20, 1991 i
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