ML20210J171

Application for Amends to Licenses NPF-72 & NPF-77,proposing Temporary Changes to TS Re Upper Temperature Limit for Ultimate Heat Sink

ML20210J171
Person / Time
Site:	Braidwood
Issue date:	07/30/1999
From:	Tulon T COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20210J173	List: ML20210J171 ML20210J175
References
NUDOCS 9908040218
Download: ML20210J171 (8)

Text

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firaces ilk, 11.64407 % I9 Tel Hi%45&2801 July 30,1999 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D C 20555 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 s

Subject:

Request for an Exigent Temporary Technical Specification Change Related To Upper Temperature Limit for the Ultimate Heat Sink in accordance with 10 CFR 50.90, Commonwealth Edison (Comed) Company proposes temporary changes to Appendix A of the Opaating Licenses Nos. NPF-72 and NPF-77, the Technical Specifications (TS), for Braidwood Station, Units 1 and 2.

Comed is requesting this amendment request be reviewed on an exigent basis. The justification for this request, in accordance with 10 CFR 50.91.a(6), is provided in Section D of Attachment A.

The proposed temporary change will modify the upper temperature limit of the Ultimate Heat Sink from 98 F to 100 F and will be in place until September 30,1999. This date typically marks the end of the peak electrical demands.

Attachment A contains a detailed description of the proposed changes and the technical basis for this change. Attachment B provides the proposed markup to the Units' TS. Attachment C provides information supporting a finding of no significant hazards consideration in accordance with 10 CFR 50.92(c). Attachment D provides information supporting an Environmental Assessment.

The Plant Operations Review Committee and the Nuclear Safety Review Board, in accordance with the Comed Quality Assurance Topical Report, have reviewed the

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proposed changes.

Comed is notifying the State of Illinois of this license amendment request by transmitting a copy of this letter and its attachments to the designated State Official.

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040007 9900040218 990730 PDR ADOCK 05000456 P

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A Unicum Compan)

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July 30,1999

' U. S. Nuclear Regulatory Commission -

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. Comed requests the proposed temporary changes be approved on an exigent basis, and be effective immediately upon approval. Comed intends to implement the I

proposed temporary change immediately upon approval.

Should you have any questions related to this request, please contact Mr. T. W.

J Simpkin, Braidwood Station Regulatory Assurance Manager at (815) 458-2801 extension 2980.

Respectfully,

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1M T. J. Tulon

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Site Vice President-ood Station

-Attachments:

Affidavit Attachment A: Description and Summary Safety Analysis for Proposed Changes Attachment B: Marked-Up TS Pages for Proposed Changes Attach'wnt C: Information Supporting a Finding of No Significant Hazards Consideration.

Attachment D: Information Supporting an Environmental Assessment i

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Regional Administrator - NRC Region 111 NRC Senior Resident inspector-Braidwood Station Office of Nuclear Facility Lafety - IDNS f

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STATE OF ILLINOIS

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IN THE MATTER OF:

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COMMONWEALTH EDISON (COMED) COMPANY

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Docket Numbers BRAIDWOOD STATION - UNITS 1 and 2

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STN 50-456 and STN 50-457

SUBJECT:

Request for an Exigent Temporary Technical Specification Change Related to Upper Temperature Limit for tne Ultimate Heat Sink AFFIDAVIT I affirm that the content of this transmittal is true and correct to the best of my knowledge, information and belief.

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T. J. Tulon

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Site Vice President wood Station Subscribed and swom to before me, a Notary Public in and

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' NOTARY PUBUC, STATE OF ILLINOIS for the State above named, this day of MycOMMISSION EXPlRES 612002

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Notary pubsic 4

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ATTACHMENT A Proposed Chango to Op: rating Licenses and Technical Specifications for Braidwood Station, Units 1 and 2 1 of 5 DESCRIPTION AND

SUMMARY

SAFETY ANALYSIS FOR PROPOSED CHANGES A.

SUMMARY

OF PROPOSED CHANGES The proposed temporary Technical Specification (TS) change revises the upper temperature limit of the Braidwood Station Ultimate Heat Sink (UHS) from a current value of less than or equal to 98 F to a value of less than or equal to 100 F. This change is proposed to be in effect until September 30,1999.

Prolonged hot weather in the area has resulted in sustained elevated UHS temperatures. Analyses have been conducted to demonstrate that Braidwood Station, Units 1 and 2, can safely operate with a higher UHS temperature, and that the UHS can continue to perform its intended function without any undue risk to the health and safety of the public. Comed is requesting this amendment request be reviewed on an exigent basis. The justification for this request, in accordance with 10 CFR 50.91.a(6) is provided in Section D of this attachment.

B. DESCRIPTION OF THE CURRENT REQUIREMENTS TS Section 3.7.9, " Ultimate Heat Sink (UHS)," requires the UHS to be operable in Modes 1,2,3 and 4. Per Surveillance Requirement (SR) 3.7.9.2, the UHS is considered operable if the average water temperature does not exceed 98 F. This SR verifies tht!

the Essential Service Water (SX) System is available to cool the Component Cooling Water (CC) System to at least its maximum design temperature with the maximum accident or normal design heat loads for 30 days following a Design Basis Accident.

C. BASIS FOR THE CURRENT REQUIREMENTS The two principle functions of the UHS are to dissipate heat following a reactor shutdown and to dissipate the residual heat generated by accident conditions. The maximum heat load on the UHS consists of one unit undergoing post-Loss of Coolant Accident (LOCA) cooldown concurrent with loss of offsite power, and the unaffected unit undergoing a safe non-accident shutdown. Both units are assumed to be at full power operation prior to the shutdown. This condition represents the UHS maximum heat load. To perform the principle functions, the UHS must contain sufficient volume of water at or below the

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maximum temperature that would allow the Essential Service Water (SX) System to

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operate for at least 30 days following the design basis LOCA without the loss of Net 4

Positive Suction Head (NPSH), and without exceeding the maximum design temperature of the equipment served by the SX system.

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'3 ATTACHMENT A Proposed Ch:nge to Operating Licenses and Technical Specifications for Braidwood Station, Units 1 and 2 2 of 5 D. NEED FOR REVISION OF THE REQUIREMENT Comed is requesting this proposed temporary change be reviewed on an exigent basis in accordance with the requirements of 10 CFR 50.91a(6). This requires that the change be determined not to involve a significant hazards consideration, and the licensee shall explain the exigency and why the condition could not be avoided. Attachment C of this amendment request is provided to support a finding of no significant hazards consideration. The reason for the exigency is that prolonged hot weather in the area has resulted in sustained elevated UHS temperatures. High temperatures during the daytime, in conjunction with very little cooling at night and very little precipitation, have resulted in elevated water temperatures in Braidwood Station's UHS. We foresee the possibility that the UHS temperature may approach or temporarily exceed the 98*F limit j

during periods of sustained hot weather conditions over the remaining summer months.

In addition, there are no controllable measures that can be taken to immediately reduce j

the temperature of the UHS, in that reduction of the heat input by derating the units

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would have a negligible short-term effect on the temperature of the UHS.

These meteorological conditions have caused an elevated UHS temperature beyond the control of the plant and the opportunity to make a timely application did not exist.

During fuH power operation, the nominal transit time of water through the Braidwood Cooling Lake is approximately 3 days. A plant shutdown or power reduction in the event i

that the UHS limit is exceeded will not have an immediate effect on the UHS temperature. However, the normal ambient heat losses from the UHS during non-daylight hours will allow the UHS temperature to fall below the current Technical Specification limit.

E. DESCRIPTION OF THE PROPOSED CHANGES Surveillance Requirement (SR) 3.7.9.2 of TS Section 3.7.9, " Ultimate Heat Sink (UHS)"

will be revised to read " Verify average water temperature of UHS s 98 F after September 30,1999 (s 100 F through September 30,1999)." The frequency will remain at once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

F.

SUMMARY

SAFETY ANALYSIS OF THE PROPOSED CHANGES The UHS is the sink for heat removed from the reactor core following all accidents and anticipated operational occurrences in which the unit is cooled down and placed on Residual Heat Removal (RHR) operation. The operating limits are based on conservative heat transfer analyses for the worst case LOCA. The UHS is designed in accordance with Regulatory Guide 1.27, which requires a 30-day supply of cooling water in the UHS while not exceeding the design basis temperatures of safety equipment.

The following is based on an evaluation of Updated Final Safety Analysis Report (UFSAR) Chapter 6,

• Engineered Safety Features," for containment response analyses and UFSAR Chapter 15, " Accident Analysis," for LOCA and non-LOCA analyses.

1-ATTACHMENT A Proposed Change to Operating Licens:s and Technical Specifications for

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Braidwood Station, Units 1 and 2 j

3 of 5 For non-LOCA analyses, the UHS temperature is not used as an input. These analyses do not depend upon heat removal via UHS for mitigation of the consequences of the event. Therefore, the proposed temperature has no impact on non-LOCA analyses.

For LOCA analyses, the UHS temperature affects the assumption for the Residual Heat Removal (RHR) heat exchanger. An SX temperature of 100 F is already assumed for cooling the RHR heat exchanger. Therefore, the proposed temperature has no impact on LOCA analyses and does not result in a change to the calculated peak cladding temperature.

For containment response analyses, the UHS temperature affects the assumptions for the RHR heat exchanger and the Reactor Containment Fan Cooler (RCFC). A Component Cooling (CC) water temperature of 120 F is assumed for the RHR heat exchanger. This CC water temperature is based on an SX temperature of 100 F. An SX temperature of 100 F is already assumed for the inlet temperature to the RCFC.

Therefore, the proposed temperature has already been determined to be acceptable by these analyses. The peak containment temperature and pressure and long term containment temperature profile used in Environmental Qualification remain unchanged.

Specific analyses presently support a maximum SX temperature of 100 F. These analyses evaluated the operation of and the components needed to support operation of the CC Water closed loop system, the Auxiliary Feedwater pumps, the Emergency Core Cooling System pumps, the Containment Spray pumps, the SX pumps (including SX pump NPSH), the Control Room chillers, the Emergency Diesel Generator, and the RCFCs. The support equipment includes oil coolers, room cubicle coolers, jacket water cooling systems.

An analysis of the Ultimate Heat Sink was performed and verified that the UHS is capable of providing sufficient cooling for normal shutdown of one unit and accident conditions in the other unit. The meteorological conditions chosen for the Braidwood l

Station UHS analysis utilized a synthetic 36-day period consisting of the most severe 5 days, most severe 1 day, and the most severe 30 days based on Braidwood's licensing basis meteorological data.

Heat sink temperatures for these weather periods were evaluated. In the model, the heat sink is represented by a number of small segments upon which mass and heat balance calculations are performed. The model predicts the transient response of the heat sink to all of the transient phenomena of plant heat rejection, wind speed, dry bulb, and dew-point air temperature and solar radiation.

Two cases were evaluated with different number of SX Pumps in operation as follows:

Case 1: 3 SX pumps in operation, The initial UHS temperature is 100 F and subsequent temperatures remain below 100oF.

• s i-ATTACHMENT A Proposed Change to Op rating Lic:ns:s and Technical Specifications for Braidwood Station, Units 1 and 2 4 of 5 Case 2: 4 SX pumps in operation, an UHS initial temperature of 99.18 results in j

temperatures which generally remain below the initial temperature; but which j

increases to a short duration peak of 100 F and then decreases.

From the above Case 2, extrapolating data assuming an initial temperature of 100 F, would result in a maximum temperature just above 100.8 F for a period of approximately 1-hour. Although above 100 F, the components will continue to perform their safety function for the following reasons:

A. The UHS temperature peak is of short duration at approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 1

into the accident scenario, which is past the time period where the maximum

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residual heat load from containment will be required.

i B. The assumption in the Design Basis Analysis of a constant SX temperature of 100 F is conservative with respect to the calculated SX temperature profile over the duration of the event.

C. The magnitude and duration of the peak is not sufficient to cause adverse effects on the equipment and components.

i Four SX Pumps can be operated to provide cooling during the accident scenario for one unit undergoing a LOCA/ LOOP event (this accident requires only one SX pump) and the other unit undergoing a normal shutdown. With an inlet temperature of 100 F at the beginning of the accident, the average Ultimate Heat Sink temperature when averaged over any 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period will remain at or below 100 F.

The risk impact associated with operation with the UHS temperature at 100 F was evaluated qualitatively. Because the proposed temperature has already been determined to be acceptable by the LOCA and containment pressure response analyses, there is no increase in risk associated with post-accident heat removal. In addition, specific component analyses exist, which demonstrate component operation at the proposed temperature. Increasing the UHS temperature could potentially influence the loss of condenser vacuum initiating event frequency through an increase in the Circulating Water temperature. It was determined that operating at 100 F, condenser vacuum is reduced only slightly, and there is still sufficient margin to condenser operating limits. Therefore, the change of loss of condenser vacuum initiating event frequency is judged to be negligible. No other adverse influences on risk were identified through examination of the Probabilistic Risk Analysis (PRA) model for the plant. This supports the conclusion that the risk impact of increasing the UHS temperature to 100 F is negligible. Furthermore, there is some risk associated with plant shutdown which would be required if the current UHS temperature limit is exceeded. This risk is judged to be greater than the negligible risk impact produced by operating with a UHS temperature of 100 F.

G. IMPACT ON PREVIOUS SUBMITTALS All submittals currently under review by the NRC were evaluated to determine the impact of this submittal. No submittals currently under review are impacted by the information i

presented in the license amendment request.

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- ATTACHMENT A Proposed Change to Operr. ting Lic:ns:s and Technical Specifications for Braidwood Station, Units 1 and 2 5 of 5 H. SCHEDULE REQUIREMENTS Comed is requesting this proposed temporary change be reviewed on an exigent basis in accordance with the requirements of 10 CFR 50.91(a) (2). Prolonged hot weather in the area has resulted in sustained elevated UHS temperatures. The average

- temperature of the UHS has peaked above 96 F over the last several days. Continued hot weather conditions may result in the temperature exceeding 98 F before the time it would take the NRC to publish a Federal Register Notice allowing 30 days for prior public comment per 10 CFR 50.91.a requirements. We request this change be made effective immediately upon issuance and we intend to implement this proposed temporary change upon issuance until its expiration on September 30,1999.

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REFERENCES

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