ML20065M144
| ML20065M144 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/16/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20065M131 | List: |
| References | |
| NUDOCS 8210210121 | |
| Download: ML20065M144 (4) | |
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' aniglo UNITED STATES g
NUCLEAR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 72 TO FACILITY OPERATING LICENSE NO. DPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271 Author: Y. Hsii 1.0 Introduction By letter dated August 19,1982 (Reference 1) Vermont Yankee Nuclear Power Corporation (VYNPC or licensee) has proposed changes to the Technical Specifications of the Vermont Yankee Nuclear Power Station (VY), as supported by Reference 2.
The proposed changes modify the Limiting Conditions of Operation pertaining to the reactor core during the present fuel cycle (Cycle 9).
These changes are:
1.
New values for operating limits related to Minimum Critical, Power Ratio (MCPR) or operating Limit MCPR(0LMCPR).
2.
Removal of certain operational constraints on core exposure and the equation for determining the rod block monitoring (RBM) setpoints.
These operational constraints had been imposed by License Amendment No. 70 to limit plant operation in accordance with the previous OLMCPRs that were found acceptable by the staff.
2.0 Evaluation 2.1 New OLMCPRs 5
The new values for OLMCPRs were calculated by the licensee using'the RETRAN--
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TCPYA01 transient hot channel CPR methodology. The RETRAN-TCPYA01 transient hot channel Critical Power Ratio methodology has been reviewed and, approved by the staff (Reference 3) as an acceptable method for.CPR calculation provided that conservative values are used for input parameters..-to account for their uncertainties.
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In the course of our review of the application of the approved methodology to establish fuel cycle specific Limiting Conditions of Operation, questions arose as to the conservatism of the constant value of fuel pellet - cladding gap conductance used by the licensee. Further discussions with the licensee and additional information.provided by the licensee (Reference 2) satisfied the sta,r as to the conservatism of the value of gap conductance (1000 BTU /
hr. ft 2OF) used by the licensee. The.following considerations led us to conclude that the value used was conservative:
l 8210210121 820916 DR ADOCK 05000271
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The.value of conductance used is. higher than either the power-weighted or volume-weighted hot channel average gap conductance.
2.
Even though the departure from nucleate boiling (DNb) occurs locally at the location or downstream of the peak power node, the integrated thermal hydraulic effect strongly influences DNB in a BWR core. The use of the GEXL critical quality-boiling length correlation accounts for the integrated upstream thermal-hydraulic conditions. Therefore, the.use.of an average value of gap conductance, even though non-con-servative for the peak power nodes, leads to a conservative accounting of the integrated upstream effects, since most of the upstream gap conductances are lower than the average.
3.
The licensee has performed a sens'itivity study (Reference 2) using i
axially-varying nodal gap conductance for the limiting transient (generator load rejection without bypass), the result shows a slightly lowerACPRthangoestheanalysiswithaconstantgap.conductanceof 1000 BTU /hr-ft - F.
We therefore, conclude that the value of gap conductance used by the licensee is acceptable.
The MCPR cperati-ts in the proposed Technical Specifications, Table 3.11-2, were obt
. ram the maximumACPRs, corresponding to various fuel types for all anticipated transients. We have reviewed the proposed OLMCPRs. Because acceptable methodology, conservative input assumptions',
and appropriate transients have been used in calculating the OLMCPRs we have found them acceptable for use during Cycle 9 operation.
2.2 Removal of Operational Constraints l
The operational constraints pertaining to core exposure and the equation l
used for determining.the RBM setpoints had been imposed to limit plant operation to the previous OLMCPRs that had been found acceptable to the staff.
The new OLMCPRs were calculated without using the plant operational con-straints with respect to core exposure or the RBM setpoint equation limitation. Because the OLMCPRs, so calculated, were found to be acceptable (as discus' sed above) the' operational constraints can be removed from the' j
Technical Specifications.7 2.3 Summary Based on our review of the licensee's submittals, we concl'ude that the pro-posed Technical Specifications for Cycle 9 operation are acceptable.
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I 3.0 Environmental Considerations We have [etermined that the amendment does not authorize it change
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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 amendment intolves an action which is insignificant from the standpoint'of 1
environmental ' impact and, pursuant to 10 CFR 551.5(d)(4), that an envirormental impact statement,,or negative declaration and environ-mentalt1mpact appraisal need nottbe-prepared in connection with the issuance of this amendment.
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. 4.0 Conclusion 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 l
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.
Dated: September,16,1982 4
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References:
1.
Letter, L. H. Heider (VYNPC) to USNRC, FVY 82-93, " Supplement 2 to Reload 8 Licensing Submittal", August 19, 1982 Letter, J. Sinclair (VYNPC) to D. Vassallo (USNRC), FVY 82-02, 2.
September 10, 1982.
Letter. D. Vassallo (USNRC) to J. Sinclair (VYNPC), dated 3.
September 15, 1982 0
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