ML20073L287
| ML20073L287 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 04/13/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073L250 | List: |
| References | |
| NUDOCS 8304200615 | |
| Download: ML20073L287 (3) | |
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/,. r = at :g'g UNITED STATES
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NUCLEAR REGULATORY COMMISSION i;
WASHINGTON, O C. 20555
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C SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 68 TO FACILITY OPERATING LICENSE NO. DPR-66 DUQUESNE LIGHT COMPANY OHIO EDISON COMPANY PENNSYLVANIA POWER COMPANY BEAVER VALLEY POWER STATION, UNIT NO. 1 DOCKET NO. 50-334 I
Introduction By letters dated September 29, 1982, supplemented by letters dated December 8, 1982 and February 9,1983, Duquesne Light Company has requested changes to the Technical Specifications on control ~ ro:i position indication for Beaver Valley Power Station, Unit No.1.
l The subject of the analog rod position indication (RPI) system in Westinghouse PWR's has been under review for the last 1 1/2 years. We have reviewed material submitted by the licensee and have issued Amendment Nos. 51, 52 and 57 (dated June 14. June 25 and September 7,1982, respectively). Subsequent to these, "the licensee submitted additional material for our review. As part of this review, we have met with Westinghouse on this subject several times and are
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currently reviewing its report on the Analog RPI System (Reference 2).
A description of the history of the above-mentioned Amendments may be found in P.eference 1,
Background
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The RPI system was originally installed to provide an accurate means of telling the location of individual control rods during power operation in order to avoid misaligred rods. Nestinghouse core safety analysis shows that a control rod misalignment of +24 steps is acceptable. Since there is a 12-step inherent uncertainty wTth the RPI, this leaves a margin of no more than a +12-step indicated misalignment. Hence the Technical Specifications l'
require-individual control rods to be aligned with their banks within +12 steps. The RPI systen was not originally intended to be used in the shutdown i
modes.
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, Calibration of the RPI system, however, has been a ?roblem both during power operation and in the shutdown modes. Various solutions to the calibration problems for Modes 1 and 2 (power operation) have been worked out and currently there is a +12-step accuracy rhquirement for Modes 1 and 2.
The RPI for each individual rod is calibrated at the beginning of a fuel cycle at operating temperature.
It has been observed that the calibration of the RPIs is highly temperature-sensitive. Thus as the reactor cools down (Modes 3, 4 and 5), the RPI system, which was hot-calibrated, becomes inaccurate and may be off by as much as 60 steps (total rod length is 228 steps). Thus the Technical Specification, which st~ates that the RPIs and group demand counters must agree within +12 steps, cannot be met as the plant cools down. While it is possible to circumvent this problem in Modes 3, 4, and 5 by inserting fully all the rods (the Technical Specifica-tion could be met because it does not apply to the rods that are fully inserted), many operators prefer to operate with the shutdown banks " cocked" in order to have negative reactivity instantaneously available if needed.
The dilemma is that with the rods " cocked", the RPI cannot meet the il2-step accuracy requirenent during these modes.
While it would be extremely useful to have the RPI system indicating rod positions, it is not possible, as discussed above, to use the system accurately in Modes 3, 4, and S.
The Tfcansees indicated that there was problem with the interpretation of the present specification and that it created the need to file a large number of Licensee Event Reports.
Evaluation To prevent inadvertent criticality from Modes 3, 4 and 5, the Technical Specifications require that the reactor be maintained in a sub-critical condition (keff <0.99).
This is accomplished thru increase of boron concen-tration and insertion of control rods. Calculation of the necessary boron concentration takes into account the positions of the control rods.
By letter dated February 9,1983, the licensee proposed Technical Specification changes such that only the group demand counters need to be operable and capable of determining rod position for Modes 3, 4, and 5 In this way the analog RPI systen is used only for Modes.1 and 2, where-it was originally intended to be used.
The group demand counters have proven to be extremely reliable over the 15 years they have been used in Westinghouse reactors; they are the most accurate means of determining rod position, and are in fact used to calibrate the RPIs.
Based on our review we find that the safety consideration of maintaining adequate sub-criticality can be accomplished by requiring that the group demand counters be used for rod position indication. The requirement to maintain a 112-step accuracy with the RpIs is not necessary.
In addition, the requirement that reff <0.99 for Modes 3, 4, and 5 provides the margin to inadvertent criticaTity. We conclude that the licensee's proposed Technical Specification change is acceptable.
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Environmental Consiceration We have determined that the amencment does not authorize a change ir, effluent :ypes or Octal amounts nor an increase in pcwer level and will not result in any significant environmental impact.
Having mace this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR Sl.5(d)(4), that an environmental impact statement or negative declaration and environ-mental impact appraisal need not be prepared in connection with the,
issuance of this amendment.
Conclusion f
We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated does not create the possibility of an accident of a type different from any evaluated previously, and does not involve a significant reduction in a margin of safety, the amendment 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 Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
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i References 1.
Letter, ;. J. Carey of Duquesne Light Company to NRC, dated l
September 29, 1982, 2.
Letter, J. J. Carey of Duquesne Light Company to NRC, dated l
December 8,1982 i:
3.
Letter, J. J. Carey of Duquesne Light Company to NRC, dated i
February 9,,1983.
Da ted:
April 13,1983
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l Principal Contributor :
M. Chatterton l
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