ML14183A408
| ML14183A408 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 08/24/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML14183A407 | List: |
| References | |
| NUDOCS 9908250186 | |
| Download: ML14183A408 (6) | |
Text
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STATES NUCLEAR R3EGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ULTIMATE HEAT SINK TECHNICAL SPECIFICATION H. B. ROBINSON, UNIT 2 DOCKET NO. 50-261
1.0 INTRODUCTION
By letter dated July 30, 1999, Carolina Power & Light Company (CP&L or the licensee) requested a temporary change to the Technical Specifications (TS) for the H. B. Robinson Steam Electric Plant, Unit 2, in accordance with 10 CFR 50.90. Specifically, the licensee proposed to revise TS 3.7.8, "Ultimate Heat Sink (UHS)" to provide a new Required Action and Completion Time for the UHS in the event that service water (SW) temperature exceeds the design limit of 95 degrees Fahrenheit (oF). The proposed new Action would require restoring the SW temperature to within the design limit with a Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in place of the currently allowed restoration time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
2.0 BACKGROUND
The licensee, in anticipation of the UHS temperature exceeding 950F during the current summer, by a letter dated April 12, 1999 had requested an identical change to TS 3.7.8 as requested in the summer of 1998. This amendment, which was granted on June 4, 1999, via amendment number 183, is valid for the summer months until September 30, 1999, and allows plant operation above 950F for up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The purpose of the change was to reduce the risk associated with plant shutdown transients.
Long-term resolution of this situation has been proposed in previous submittals, which include revising UHS Required Actions and Completion Times in the event that SW temperature exceeds the design limit either through an industry Technical Specification Task Force item (TSTF-330) that would allow extended Allowed Outage Time (AOT) for restoring the UHS temperature to < 950F, or alternately by increasing the UHS Limiting Condition for Operation (LCO) temperature value from 950F to 97oF. Specifically, on May 27, 1999, a TS change request was submitted to increase the maximum allowable UHS temperature from 950F to 970F.
Due to the nature and complexity of this May 27, 1999 submittal, an NRC decision on this proposed amendment was requested by June 30, 2000.
A severe and sustained period of hot weather in the area of H. B. Robinson (HBR), combined with the thermal and hydrological characteristics of the UHS, have resulted in a situation where, on occasion, the existing 8-hour Completion Time may not be of sufficient duration to allow UHS temperature to return below 950F. This extended period of severely hot weather is expected to last through the summer, and could result in unwarranted plant power reductions and shutdowns during a time of record energy demand.
9908250186 990824 PDR ADOCK 05000261 P -
-2 The UHS provides a heat sink for the operating and decay heat produced by various plant components during normal operation, transients, and accidents. The SW System (SWS) and the Component Cooling Water (CCW) System are used to transfer heat from plant components to the UHS. The UHS at Robinson is defined as the Lake Robinson Impoundment, including necessary retaining structures, and the canals or conduits connecting the sources with, but not including, the cooling water intake structures. The UHS temperature is a function of insolation, operation of H. B. Robinson, Units 1 (fossil) and 2 (nuclear), hydrology of the Lake Robinson watershed, and meteorological conditions which affect the efficiency of evaporative cooling, natural convection, and diurnal radiant heat losses. During the summer, the average heat input due to insolation is comparable to the total heat input from both Robinson Units 1 and 2.
Condensing cooling water and SW discharged from the plant are returned to greater Lake Robinson via a 4.2 mile-long discharge canal, which terminates in the lake near its upper end (SWS intake is at the lower end of the lake). During full power operation, the n6rmal transient time of water through the discharge canal is approximately 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Hence, the effect of a plant shutdown in the event that the SWS temperature limit is exceeded will not immediately be effective on the temperature of the SW entering the plant. However, in the summer months during periods of hot weather, a diurnal effect of alternating insolation of the lake water during the day and increased radiant and evaporative heat loss during the night results in a variation of lake water temperature around a 24-hour cycle.
As TS 3.7.8 exists today and valid until September 30, 1999, condition A allows an 8-hour AOT for restoring the UHS temperature to 95oF. The proposed change revises the AOT for condition A to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> instead of the currently allowed 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
3.0 EVALUATION The NRC staff evaluated the safety rationale for the requested TS change and verified that the request to revise the 8-hour Completion Time of TS 3.7.8 to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> involves minimal increase in risk to the safe operation of HBR. The SW temperature is an input to the containment analysis contained in Final Safety Analysis Report (FSAR) Section 6.2. The SW temperature is also a design assumption for the spent fuel pool cooling system (SFPCS), auxiliary feedwater (AFW) system, CCW system and its loads, the emergency diesel generators (EDGs),
containment air recirculation cooling (CARC) system, room coolers for certain safety-related areas, and other non-safety-related systems. Where components rely upon SW temperature to maintain the components within operating temperature limits, the licensee's evaluation determined that the components could withstand SW temperatures up to 990F.
Since the summer of 1998, the licensee has further evaluated the capability of components cooled by the SW to perform their intended function. Some components, such as the EDGs, Containment Air Recirculation System Fan Coolers, Steam Driven Auxiliary Feedwater Pump, and CCW System (including Spent Fuel Pool Cooling), were specifically reevaluated because of the complex effect of operation at a higher SW temperature. In addition, the ability to achieve cold shutdown following a fire and a station blackout were evaluated at a higher SW temperature. These calculations and evaluations show that these components are fully capable of performing their intended safety function up to a SW temperature of 990F. These submittals are currently under NRC review, and due to their nature and complexity, an NRC decision on this proposed amendment is not anticipated until June 30, 2000.
-3 In order to avoid transients associated with plant derating that could result due to the unusually hot and dry weather that HBR has been experiencing this summer, the staff concludes that the 72-hour Completion Time requested in the TS change submittals should be allowed. The 72-hour Completion Time of Action A.1 for being slightly above the design basis temperature is acceptable on a temporary basis because 1) the SW-cooled equipment has been analyzed and found to remain within the manufacturer's limits in the event of an accident, 2) the probability of a design-basis accident occurring during the 72-hour period is small, and 3) the compensatory measures that were established and implemented previously for the 8-hour AOT will remain in place to assure continued functionality of the UHS and to minimize plant transients.
Based on these considerations, the staff had earlier concluded that Criterion 1 of Section B and the applicable criteria in Section C.4 to NRC Manual Chapter 9900, "Technical Guidance, Operations - Notice of Enforcement Discretion (NOED);" were met and granted a NOED.
Criterion 1 of Section B states that for an operating plant, the NOED is intended to avoid an undesirable transient as a result of forcing compliance with the license condition, and thus minimize the potential safety consequences and operational risks. This exigent amendment supersedes and terminates the previously granted NOED. It revises TS 3.7.8 allowing the licensee to revise the action time required to restore the UHS temperature to <;95 0F from 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and granted as a one-time amendment to last until September 30, 1999.
3.0 STATEMENT OF EXIGENT CIRCUMSTANCES In its submittal, the licensee requested that the NRC review and approve the proposed change as an exigent amendment. The Commission's regulation as stated in 10 CFR 50.91 provides special exceptions for the issuance of amendments when the usual 30-day public notice cannot be met. The TS change is issued as a follow-up amendment to NOED 99-06-006, which was granted on August 3, 1999. The public notification used was a shortened individual Federal Reqister notice (64 FR 43406) with a comment period of 2 weeks and maintaining the normal 30-day period to request a hearing. A severe and sustained period of high temperature has caused record energy demand in South Carolina, and as a result, system reliability alert levels 1 and 2 have been invoked on occasions during the period of July 21 through July 30, 1999.
Reliability alert level 2 is implemented when projected load and reserve requirements utilize the available capacity and administrative controls have been implemented during the same period to restrict maintenance and operational activities that have a risk of adversely affecting plant reliability. Lake Robinson has experienced unusually warm and dry weather conditions during the month of July 1999, and in fact, had to exceed the permitted 8-hour AOT under the currently allowed action times on two occasions, one on July 31, 1999, which prompted the request for the NOED, and again on August 1, 1999. Thus, there appears to be insufficient cooling before the onset of insolation on the next day with the diurnal cycle extending beyond the anticipated 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> unless there is intervention via other natural means such as a thunderstorm and more inflow from the Black Creek impoundment. This situation could not have been foreseen sufficiently in advance to avoid the need for exigent action on the proposed change. As the SW temperatures approach or exceed the design limit of 95'F, as seen on these two occasions, the potential exists for repetitive entry into a shutdown transient as diurnal Lake Robinson temperature variations occur. The exigent circumstance arises from the need to avoid transients associated with plant derating or shutdown until the long-term resolution of this condition is implemented. In view of the unusually hot and dry weather conditions that Robinson
-4 Lake is facing, and the fact that the TS amendment is being approved as a one-time amendment effective until September 30, 1999, the NRC staff finds that (1) exigent circumstances exist, as provided for in 10 CFR 50.91(a)(6), in that the licensee and the Commission must act quickly and that time does not permit the Commission to publish a Federal Register notice allowing 30 days for prior public comment, and (2) the licensee has not failed to use its best efforts to make a timely application and avoid creating the exigent circumstance. The NRC has also determined that the amendment request involves no significant hazards consideration, and that appropriate conditions existed which resulted in the need for the exigent request.
4.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The Commission has provided standards for determining whether a significant hazards consideration exists (10 CFR 50.92(c)). A proposed amendment to an operating license for a facility involves no significant hazards consideration if operation of the facility in accordance with the proposed 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.
The licensee has analyzed the proposed amendment to determine if a significant hazards consideration exists, as follows:
(1)
Does the change involve a significant increase in the probability or consequences of an accident previously evaluated?
The proposed change does not involve any physical alteration of plant systems, structures or components. The proposed change provides a revised allowed time for the plant condition where UHS temperature exceeds the design limit of 950F. SW system temperature is not assumed to be an initiating condition of any accident analysis evaluated in the safety analysis report (SAR). Therefore, the revised limitation for SW temperature to be in excess of the design limit does not involve an increase in the probability of an accident previously evaluated in the safety analysis report. The SW system supports operability of safety-related systems used to mitigate the consequences of an accident. Plant equipment has been analyzed and determined able to perform its safety-related function through the allowed maximum SW temperature of 990F.
Performance of the containment has not been the subject of a specific re-analysis at the proposed temperatures with current licensing basis methodologies. However, based on engineering judgement, the [effect] on containment performance from the elevated SW temperature for the proposed period of time would not be significant. The magnitude of any increase in SW temperature in excess of the design limit is expected to be small based on historical data and experience for the UHS. Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated in the SAR.
(2)
Does the change create the possibility of a new or different kind of accident from any accident previously evaluated?
-5 The proposed change does not involve any physical alteration of plant systems, structures or components. The temperature of the SW when near or slightly above the design temperature does not introduce new failure mec.hanisms for systems, structures or components not already considered in the SAR. Therefore, the possibility of a new or different kind of accident from any accident previously evaluated is not created.
(3)
Does this change involve a significant reduction in a margin of safety?
The proposed change will allow a small increase in SW temperature above the design basis limit for a limited period of time. This will delay the requirement to shutdown the plant for an additional 64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br /> beyond the currently 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> Completion Time. Design margins are affected which are associated with systems, structures and components which are cooled by the SW system, and system temperature is an input assumption for mitigating the effects of a DBA [design-basis accident]. However, allowing this additional time for SW temperature to exceed the design limit is expected to have a negligible
[effect] on containment performance, and no adverse impact on other analyzed plant equipment. Therefore, there is no significant reduction in margin of safety associated with this proposed change.
The staff has reviewed the licensee's analysis and agrees with it. The staff thus makes a final determination that this amendment does not involve a significant hazards consideration.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the State of South Carolina official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change in the installation or use of a 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 (64 FR 43406). 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 this amendment.
6.0 CONCLUSION
As a result of its evaluation as described above, the staff concludes that the proposed change to TS 3.7.8 provides a significant amount of additional flexibility without any significant reduction in plant safety. The proposed change is, therefore, acceptable.
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
-6 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: Ram Subbaratnam Date:
August 24, 1999