ML19290A385
| ML19290A385 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/12/1974 |
| From: | US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19290A383 | List: |
| References | |
| NUDOCS 7911060623 | |
| Download: ML19290A385 (4) | |
Text
((% \\ l UNITED STATES ATOMIC ENERGY COMMISSION l
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W ASHINGTON, D.C. 20545
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%n e SAFETY EVALUATION BY THE DIRECTORATE OF LICENSING SUPPORTING AMENDMENT NO. 4 TO LICENSE NO. DPR-50 (Change No. 3 to Appendix A of Technical Specifications)
METROPOLITAN EDISON COMPANY JERSEY CENTRAL POWER AND LIGHT COMPANY PENNSYLVANIA ELECTRIC COMPANY THREE MILE ISLAND NUCLEAR STATION - UNIT 1 DOCKET NO. 50-289 Introduction On July 12, 1974, the Station Superintendent (J. Herbein) notified the Licensing Project Manager (R. Bernero) that the Three Mile Island Nuclear Station - Unit 1 (TMI-1) was operating at power with one steam generator safety valve weeping. The valve vendor advised gagging the valve to prevent damage to it and possibly stop the leak.
Since Section 3.4.1 of the Technical Specifications requires all 18 ateam generator safety valves to be operable while the system is hot, the Sup rintendent requested an urgent change to the Technical Specifications. The urgency is based on the current high power de= ands in the FMJ grid due to continuing hot. weather.
Discussion Technical Specifications have been set in the past just as they are now for TMI-1, to require the full complement of steam generator safety valves to be operable with no qualification for operation with one or more inoperable. The full complement is needed to provide relief capacity with suitable design margin of rated full power steam flow. The plant overpower trip set point is, of course, normally set to a point commensurate with operation at rated full power.
Recent experience has led the Regulatory staff to consider Technical Specifications which could allow plant operation with one or more steam generator %fety 'ralves inoperable provided that there is a commensurate reduction la the overpower trip set point.
Such speci-fications are now being prepared and issued in current cases.
1556 256 E
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o The basis of calculation to determine the appropriate overpower trip reduction is to assume that the maximum number of disabled safety valves on any steam generator is the number of disabled valves on each steam generator. It is further assumed that the capacity of any disabled valve is equal to the relief capacity of the highest capacity valve in the system. Thus, there is no reduction of design margin when operating in the degraded mode and no need to analyze operation with asymmetric relief capacity.
TMI-l is a two steam generator plant with the following set of safety valves on each steam generator:
Valve Setting (psig)
No. of Valves Relief Capacity (Ibs/hr) 1040 1
194,000 1050 2
792,000 1060 2
799,000 1080 2
814,000 1092.5
_j!_
824,000 Total per steam g'enerator 9
6,650,000 Total plant 18 13,300,000 The normal overpower trip set point is 105.5% of rated power (2535 MWth).
A revised set point may then be calculated by the formula:
Set Point = 13,300,000 - 2n(824,000) x 105.5 n
13,300,000 where n = the maximum number of safety valves disabled on any one steam generator.
This leads to the table of set points:
Maximum Number of Safety Maximum Overpower Trip Valves Disabled On Any Set Point Steam Generator
(% of Rated Power) 0 105.5 1
92.4 2
79.4 3
66.3 1556 257
. As a matter of judgment, the allowable number of disabled valves should be limited to no more than three of the nine valves on a steam generator.
Conclusion The staff, therefore, concludes that it is acceptable to amend Section 3.4.1 of the Technical Specifications to permit operation at temperature with safety valves disabled provided that the overpower trip setting is reduced in accordance with the preceding table. The staff further concludes that this amendment does not:
(1) involve a significant hazards consideration or a safety consideration of a type or magnitude not considered by any previous staff safety review of this facility, (2) potentially involve a substantial increase in the probability or consequences of an accident considered in any previous staff safety review, or (3) potentially decrease the margin of safety during normal plant operation, anticipated operational occurrences or postulated accidents considered in any previous staff safety review.
Based on the foregoing analysis, the staff finds that there is reasonable assurance that the health and safety of the public will not be endangered, by approval of this amendment to License No. DPR-50.
l e
Robert M. Bernero, Project Manager Light Water Reactors Branch 2-3 Directorar~ of Licensing h.0.f A. Schwencer, Chief Light Water Reactors Branch 2-3 Directorate of Licensing Date of Issuance:
3R.12i974 1556 258
9 ADDENDUM TO SAFETY EVALUATION BY THE DIRECTORATE OF LICENSING SUPPORTING AMENDMENT NO. 4 TO LICENSE NO.DPR-50 (Change No. 3 to Appendix A of Technical Specifications)
The staff safety evaluation, dated July 12, 1974, discusses the justification of the change to Technical Specification 3.4.1 to permit plant operation with disabled steam safety valves provided that the overpower trip setting is reduced. While incorporating this change into the Technical Specifications, a number of purely editorial changes are appropriate for this page (3-25) of the Technical Specifications. They are:
a.
Specification 3.4.7 - delete since this applied only until the plant achieved 5% power for the first time. The specification is now obsolete.
b.
Specifications 3.4.2 to 3.4.6 - renumber these to 3.4.1 to 3.4.5 to simplify wording and clarify intent that the 48-hour maintenance allowance (old 3.4.6) applies to all equipment except steam safety valves.
_q c.
Specification 3.4.1 - renumber as 3.4.6 and revise to state required reduction in overpower trip set points, etc.
These changes to page 3-25 are purely editorial and do nct affect the conclusions of the staff safety evaluation, dated July 12, 1974.
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Robert M. Bernero, Project Manager Light Water Reactors Branch 2-3 Directorate of Licensing
,d' jf, A. Schwencer, Chief Light Water Reactors Branch 2-3 Directorate of Licensing Date of Issuance: JUL 1 9 E74 1556 259