ML20063M040
| ML20063M040 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/03/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20063M039 | List: |
| References | |
| NUDOCS 9403080359 | |
| Download: ML20063M040 (6) | |
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7 I E UNITED STATES d i NUCLEAR REGULATORY COMMISSION 4..s, 4j WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.72 TO FACILITY OPERATING LICENSE N0. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION DOCKET NO. 50-482
1.0 INTRODUCTION
By application dated February 7,1994, Wolf Creek Nuclear Operating Corporation (the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License No. NPF-42) for the Wolf Creek Generating Station.
The proposed changes would allow an increase in reactor coolant temperature in order to support operation at the rated thermal power of 3565 megawatts thermal (MWt). The proposed amendment changes reactor protection system overtemperature and overpower delta-tamperature setpoints by increasing the nominal reactor coolant temperature from 581.2*F to 586.5'F, changing the axial flux difference penalties, and changing the setpoint uncertainty allowances.
The proposed amendment also increases the maximum indicated reactor coolant system average temperature of Technical Specification 3/4.2.5, DNB Parameters, from 585.0*F to 590.5'F.
2.0 BACKGROUND
The NRC issued Amendment No. 69 to the Wolf Creek Generating Station Facility Operating Lic.ense on November 10, 1993.
The amendment increased the rated thermal power for Wolf Creek from 3411 megawatts thermal (MWt) to 3565 MWt.
The amendment also included changes in reactor coolant temperature specifications to reflect the planned operation of Wolf Creek at the higher power level and reduced operating temperatures. The desire to operate at reduced reactor coolant temperatures is related to minimizing the propensity for some forms of steam generator tube corrosion mechanisms.
Upon attempting to implement the power increase, the licensee discovered that the unit was unable to achieve 3565 MWt at the reduced operating temperatures and associated steam pressures. The proposed amendment would allow operation at increased operating temperatures in order to allow the plant to reach its licensed power level.
The licensee plans to implement modifications during the next refueling outage which will allow operation at the licensed power level and reduced operating temperatures.
9403090359 940303 DR ADOCK 05000482 PDR
- 3.0 EXIGENT CIRCUMST 10fjli The Commission's regulations, 10 CFR 50.91, contain provisions for issuance of amendments with less than a 30 day comment period if either emergency or exigent circumstances are determined to exist.
Emergency situations involve those cases in which failure to act in a timely way results in the derating or shutdown of a nuclear power plant, or in prevention of either resumption of operation or of increase in power output up to the plant's licensed power level.
Under emergency circumstances, the Commission may issue a license amendment involving no significant hazards consideration without prior notice and opportunity for a hearing or for public comment.
In such a situation, the Commission publishes a notice of issuance under 10 CFR 2.106, providing for opportunity for a hearing and for public comment aftar issuance.
The processing of an amendment under exigent circumstances usually applies to i
those cases in which the licensee and Commission must act promptly, but failure to act promptly does not involve a plant shutdown, derating, or delay in startup.
For both emergency and exigent circumstances, the licensee is required to explain the reason for the condition and why it could not be avoided. This requirement is intended to prevent the abuse of the special provisions of 10 CFR 50.91(a)(6).
Under exigent circumstances, the Commission notifies the public in one of two ways: by issuing a Federal Reaister notice providing notice of an opportunity for hearing and allowing at least two weeks from the date of the notice for prior public comment; or by using local media to provide reasonable notice to the public in the area surrounding a licensee's facility and providing special instructions for providing comment.
For this amendment request, the Commission employed the first approach with a Federal Reoister notice published on February 15, 1994 (59 FR 7269) which presented the staff's proposed no significant hazards consideration determination and requested public comment within 15 days after the date of publication of the notice.
The Commission issued Amendment 69 to the Wolf Creek Generating Station Facility Operating License on November 10, 1993. The amendment increased the rated thermal power for Wolf Creek from 3411 MWt to 3565 MWt. The amendment also included changes in reactor coolant temperature specifications in order to reduce the propensity for some forms of steam generator tube corrosion.
The licensee's implementation of the power rerate and temperature reductions were performed during the period from November 17, 1993 to December 21, 1993.
During the implementation, the licensee discovered that the unit was unable to achieve 3565 MWt at the reduced operating temperatures.
The reduced operating temperature specifications had therefore resulted in an effective derating of the unit.
Following the completion of various safety and nuclear design analyses, the licensee submitted revisions to the temperature specifications on February 7, 1994, in order to allow the unit to reach its licensed power level.
The licensee has determined that this is the only feasible method to increase power output until design changes can be implemented during the next refueling
. outage. The staff has determined that the licensee cannot avoid the current condition limiting the power output of Wolf Creek Generating Station and has filed a timely application to allow operation at increased operating temperatures until design modifications can be implemented during the next refueling outage.
Therefore, the special provisions of 10 CFR 50.91(a)(6) are applicable to this proposed amendment.
The amendment may have satisfied the criterion for issuance under emergency circumstances because the licensee was unable to increase power output to the plant's licensed power level.
However, the plant has been able to continue power production at a levcl above the initial licensed power of 3411 MWt.
In an effort to balance the desire to provide an opportunity for prior public comment whenever possible and the economic impact of the derating of the Wolf Creek Generating Station, the staff is issuing this amendment un an exigent basis following a 15-day comment period as permitted by 10 CFR 50.91(a)(6).
4.0 EVALUATION A.nendment No. 69 to the Wolf Creek Generating Station Facility Operating License involved an increase in the unit's maximum licensed power level from 3411 MWt to 3565 MWt.
The changes also reflected a planned hot leg temperature reduction of 5 degrees Fahrenheit (5'F) and a possible 15'F reduction which may be pursued in the future.
In support of the amendment, the licensee provided the results of analyses and evaluations performed to determine the impact of the changes in power level and operating temperature on the nuclear steam supply system (NSSS) and balance of plant (80P). Many of the supporting analyses for the rerate associated with Amendment 69 were performed with an assumed hot leg temperature of 620*F which represented an increase of approximately 1.8'F compared to the operating conditions prior to s
the rerate. As stated in the staff's safety evaluation related to Amendment i
69, the 5'F hot leg temperature reduction which was associated with the rerate was proposed in order to meet safety limit design criteria (Departure from Nutleate Boiling (DNB)). A comparison of the operating conditions associated with the rerate and proposed amendment are provided below:
Prior to Amendment 69 proposed l
Parameter Amendment 69 Uccer Bound Lower Bound Amendment Core Power 3411 MWt 3565 MWt 3565 MWt 3565 MWt l
Thermal Design 374,400 374,400 374,400 374,400 Flow gpm gpm gpm gpm Vessel Outlet 618.2*F 620.0*F*
603.2'F 618.2*F Temperature
]
Vessel Average 588.5'F 588.4*F*
570.7'F 586.5'F Temperature
_ Upper Bound value was used for most analyses.
For selected analyses, including the loss of flow transient and core design, values of 613.2*F and 581.2*F respectively, were used for the assumed vessel outlet and average temperature The licensee's evaluation determined that the only Updated Safety Analysis Report (USAR) Chapter 15 transient which required re-analysis to support the proposed increase in reactor coolant temperature was the complete loss of forced reactor coolant flow DNB evaluation.
The remaining transient analyses had been performed assuming the limitir,g vessel average tenperature of either 588.4*F or 570.7'F. The methodology md assumptions, other than reactor coolant temperatures, used in the analysis of the loss cf clow transient were the same as those submitted in supscrt of Amendments Nos il and 69.
Amendment 61 supported operation of Wolf Creek followir:g sixth refutling outage and represented a transfer of many of the safety e.. nis and nuclear design functions from the fuel vender to Wolf Creek Nuc't.o Nrating Corporation. As listed in Technical Specification 6.9.lM
<e Operating Limits Report, the methodologies utilized by the licenseu,
aen revtewed 1
and approved by the staff. The reanalysis of the compleu 5 -
af forced reactor coolant flow transient at the higher reactor cool 3
- nirature, 586.5'F average temperature, demnstrated that the departw nucleate a,
boiling ratio (DNBR) remained above the safety analysis 1in '
j The licensee examined the nuclear design operational and tre H m + limits necessary for the remainder of Cycle 7 operation at a core p > ar >f 3565 MWt and proposed increase in reactor coolant average. tem erattre to Ski.5'F.
The core power distribution limits were determined as de cribtd a the NRC approved topical report NSAG-607, Rev 0, " Reload Safety Evat rion Methodology for the Wolf Creek Generatirg Station." The maneuvering ana'33es determined that more restrictive axial flux di"erenca limits were required to support operation at the increased reactor coolant temperatures. The more restrictive axial flux d n, ence pennty associated with the overtemperature delta-temperatur pen ction function is part of the proposed amendment.
The licensee t %at d other nuclear design parameters for operation for the remainder c, ole 7 at increased reactor coolant temperatures and determined all were bouued by the values assumed in the safety analyses.
Amendment 69 supporting analyses related to piping and component integrity were reviewed and determined to remain bounding of the proposed operating temperatures. As stated above, these analyses were performed at the vre limiting hot leg temperature of 620*F or 603.2'F.
This bounds the proposed operating condition for hot leg temperatures of 618.2*F and average coolant temperature of 586.5'F.
i The licensee also reperformed the uncertainty analyses which determined the total allowance (TA), sensor error (S), and "Z" terms in Table 2.2.1, Reactor Protection System Instrumentation Trip Setpoints.
Discussions with the l
licensee determined that the changes were a result of minor changes to the calcu!ations and that the overall uncertainty methodology remained similar to that used since the initial licenstr*g of the facility.
~
. The staff has reviewed the licensee's proposed Technical Specification changes and supporting evaluations and finds the changes acceptable.
5.0 flNAL NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards considerations if operation of the facility in accordance with the amendment would not:
(1) involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of' accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
Operation of the facility in accordance with the proposed amendment will not involve a significant increase in the probability or consequences of an accident previously evaluated. The probability of occurrence and the cansequences of an accident evaluated previously in the Updated Safety Analysis Report (USAR) are not increased due to the proposed technical specification change.
Plant operation at 3565 MWt with the revised temperatures does not affect any of the mechanisms postulated in the USAR to cause loss-of-coolant accident (LOCA) or non-LOCA design basis events.
Analyses, evaluations, and minimum departure from nucleate boiling ratio (CNBR) calculations confirm that the USAR conclusions remain valid for the proposed changes.
On these bases it is concluded that the probability and consequences of the accidents previously evaluated in the USAR are not increased.
Operation of the facility in accordance with the proposed amendment will not create the possibility of a new or different kind of accident from any accident previously evaluated.
The proposed technical specification changes do not increase the probability of occurrence of a malfunction of equipment important to safety or increase the consequences of a malfunction of equipment evaluated in the USAR.
The technical specification changes do not create the possibility of a new or different kind of accident from any accident previously evaluated because the change in operating T will not pose a new no operating configuration that would create a new failure,scenarie.
The proposed changes do not change the plant configuration in a way that introduces a new potential hazard to the plant and do not involve a significant reduction in the margin of safety. No new failure modes will be created by the proposed changes for any plant equipment.
Operation with a O' - 5'F T, reduction is bounded by the analyses performed previously for o
the power rerate and approved by the NRC in Amendment No. 69 to the Wolf Creek Generating Station (WCGS) Technical Specifications on November 10, 1993, and does not create a new or unanalyzed condition.
For these reasons, the possibility of a new accident which is different from any already evaluated in the USAR is not created.
Operation of the facility in accordance with the amendment will not involve a significant reduction in a margin of safety.
The analyses and evaluations discussed in the safety evaluation demonstrate that all applicable safety analysis acceptance criteria continue to be met for the proposed operating
- 1 conditions. The change in operating T does not involve a significant 3
reduction in a margin of safety because,,the operating temperature is one of the inherent assumptions that determines the safe operating range defined by the accident analyses, which are in turn protected by the technical specifications.
The acceptance criteria for the accident analyses are conservative with respect to the operating conditions defined by the technical specifications.
The analyses performed for the power rerate and this proposed' change confirm that the &ccident analyses criteria are met at the revised configuration.
Therefore, it is concluded that the proposed change does not involve a reduction in a margin of safety' described in the bases to any technical specification.
Based upon the above considerations, the staff concludes that the amendment meets the three criteria of 10 CFR 50.92.
Therefore, the staff has made a final determination that the proposed amendment does not involve a significant.
hazards consideration.
6.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Kansas State official was notified of the proposed issuance of the amendment.
The State official had no comments.
7.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use d -
facility component located within the restricted area as defined in 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 offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (59 FR 7269). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
8.0 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: William Reckley Date: March 3,1994
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