NOC-AE-02001255, Technical Specifications Bases Change

Technical Specifications Bases Change

ML020450261
Person / Time
Site:	South Texas
Issue date:	01/28/2002
From:	Head S South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-02001255, STI:31400251
Download: ML020450261 (6)

Text

MLM=1iB Nuclear Operating Company SIm m"-

South Texas Pro/ect Electrnc GenCrating Station PO. Box 289 Wadsworth. Texas 77483 January 28, 2002 NOC-AE-02001255 File No.: G20.02.02 G21.02.02 10CFR50.59 STI: 31400251 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Technical Specification Bases Change STP Technical Specification Bases pages B 3/4 5-1, B 3/4 5-2 and B 3/4 5-3 are attached for your information and for the update of the NRC copy of the STP Technical Specification Bases. These revisions reflect the changes approved under Amendments 135 and 124 for Unit 1 and Unit 2. The Bases pages that were issued as part of the Amendment approval packages were based upon the pages provided to the NRC as attachments in the associated STP License Amendment Requests (LARs). However, per agreement with the reviewer, the Bases material regarding the auto-open capability has been deleted consistent with TSTF-316. Therefore, the current version of the Bases was revised to reflect the changes approved under these Amendments.

If there are any questions, please contact A.W. Harrison at (361) 972-7298 or me at (361) 972-7136.

Scott M. Head Manager, Licensing mkj

Attachment:

Revised Technical Specification Bases Pages 3/4 5-1, 3/4 5-2 and 3/4 5-3 O:\QUALITY.ANDLICENSING\TSB\AMENDMENT\02\NOC-AE-02001255

cc:

Ellis W. Merschoff Jon C. Wood Regional Administrator, Region IV Matthews & Branscomb U.S. Nuclear Regulatory Commission 112 East Pecan, Suite 1100 611 Ryan Plaza Drive, Suite 400 San Antonio, Texas 78205-3692 Arlington, Texas 76011-8064 Institute of Nuclear Power Mohan C. Thadani Operations - Records Center Project Manager 700 Galleria Parkway U. S. Nuclear Regulatory Commission Atlanta, GA 30339-5957 1 White Flint North, Mail Stop: O-7D1 11555 Rockville Place Richard A. Ratliff Rockville, MD 20852-2738 Bureau of Radiation Control Texas Department of Health Cornelius F. O'Keefe 1100 West 49th Street U. S. Nuclear Regulatory Commission Austin, TX 78756-3189 P. 0. Box 289, Mail Code MN1 16 Wadsworth, TX 77483 R. L. Balcom/D. G. Tees Reliant Energy, Inc.

A. H. Gutterman, Esquire P. 0. Box 1700 Morgan, Lewis & Bockius Houston, TX 77251 1800 M. Street, N.W.

Washington, DC 20036-5869 C. A. Johnson/A. C. Bakken, III AEP - Central Power and Light Company M. T. Hardt/W. C. Gunst P. 0. Box 289, Mail Code: N5022 City Public Service Wadsworth, TX 77483 P. 0. Box 1771 San Antonio, TX 78296 U. S. Nuclear Regulatory Commission Attention: Document Control Desk A. Ramirez/C. M. Canady Washington, D.C. 20555-0001 City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 OAQUALITY ANDLICENSING\TSB'AMENDMENT02\NOC- AE- 02001255

ATTACHMENT REVISED BASES PAGES

3/4. 5 EMERGENCY CORE COOLING SYSTEMS BASES 3/4.5.1 ACCUMULATORS The OPERABILITY of each Reactor Coolant System (RCS) accumulator ensures that a sufficient volume of borated water will be immediately forced into the reactor core through three cold legs in the event the RCS pressure falls below the pressure of the accumulators.

This initial surge of water into the core provides the initial cooling mechanism during large RCS pipe ruptures.

If one accumulator is inoperable for a reason other than boron concentration, the accumulator must be returned to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. In this Condition, the required contents of two accumulators cannot be assumed to reach the core during a LOCA. The 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is a risk-informed Completion Time that minimizes the potential for exposure of the plant to a LOCA under these conditions.

If the boron concentration of one accumulator is not within limits, it must be returned to within the limits within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. In this Condition, ability to maintain subcriticality or minimum boron precipitation time may be reduced. The boron in the accumulators contributes to the assumption that the combined ECCS water in the partially recovered core during the early reflooding phase of a large break LOCA is sufficient to keep that portion of the core subcritical. One accumulator below the minimum boron concentration limit, however, will have no effect on available ECCS water and an insignificant effect on core subcriticality during reflood. Boiling of ECCS water in the core during reflood concentrates boron in the saturated liquid that remains in the core. In addition, current analysis techniques demonstrate that the accumulators do not discharge following a large main steam line break for the majority of plants. Even if they do discharge, their impact is minor and not a design limiting event. Thus, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is allowed to return the boron concentration to within limits.

The surveillance limits on accumulator volume represent a spread about an average value used in the safety analysis and have been demonstrated by sensitivity studies to vary the peak clad temperature by less than 20 0 F. The surveillance limit on accumulator pressure ensures that the assumptions used for accumulator injection in the safety analysis are met.

The boron concentration should be verified to be within required limits for each accumulator every 31 days since the static design of the accumulators limits the ways in which the concentration can be changed. The 31 day Frequency is adequate to identify changes that could occur from mechanisms such as stratification or inleakage. Sampling the affected accumulator within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after a 1% volume increase will identify whether inleakage has caused a reduction in boron concentration to below the required limit. It is not necessary to verify boron concentration if the added water inventory is from the refueling water storage tank (RWST), because the water contained in the RWST is within the accumulator boron concentration requirements SOUTH TEXAS - UNITS 1 & 2 B 3/4 5-1 Unit 1 - Amendment No.

Unit 2 - Amendment No.

CR 02-1489

EMERGENCY CORE COOLING SYSTEMS BASES 3/4.5.1 ACCUMULATORS (Continued)

Verification every 31 days that power is removed from each accumulator isolation valve operator when the pressurizer pressure is >1000 psig ensures that an active failure could not result in the undetected closure of an accumulator motor operated isolation valve.

If this were to occur, only one accumulator would be available for injection given a single failure coincident with a LOCA. Since power is removed under administrative control, the 31 day Frequency will provide adequate assurance that power is removed.

This SR allows power to be supplied to the motor operated isolation valves when pressurizer pressure is < 1000 psig, thus allowing operational flexibility by avoiding unnecessary delays to manipulate the breakers during plant startups or shutdowns.

3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS The OPERABILITY of three independent ECCS subsystems ensures that sufficient emergency core cooling capability will be available in the event of a LOCA assuming the loss of one subsystem through any single failure consideration. Each subsystem operating in conjunction with the accumulators is capable of supplying sufficient core cooling to limit the peak cladding temperatures within acceptable limits for all postulated break sizes ranging from the double ended break of the largest RCS cold leg pipe downward. One ECCS is assumed to discharge completely through the postulated break in the RCS loop.

Thus, three trains are required to satisfy the single failure criterion. Note that the centrifugal charging pumps are not part of ECCS and that the RHR pumps are not used in the injection phase of the ECCS. Each ECCS subsystem and the RHR pumps and heat exchanges provide long-term core cooling capability in the recirculation mode during the accident recovery period.

When the RCS temperature is below 3500 F, the ECCS requirements are balanced between the limitations imposed by the low temperature overpressure protection and the requirements necessary to mitigate the consequences of a LOCA below 3500 F. At these temperatures, single failure considerations are not required because of the stable reactivity condition of the reactor and the limited core cooling requirements. Only a single Low Head Safety Injection pump is required to mitigate the effects of a large-break LOCA in this mode.

However, two are provided to accommodate the possibility that the break occurs in a loop containing one of the Low Head pumps. Low Head Safety Injection pumps are not required inoperable below 350'F because their shutoff head is too low to impact the low temperature overpressure protection limits.

Below 2000 F (MODE 5) no ECCS pumps are required, so the High Head Safety Injection pumps are locked out to prevent cold overpressure.

SOUTH TEXAS - UNITS 1 & 2 B 3/4 5-2 Unit 1 - Amendment No.

Unit 2 - Amendment No.

CR 02-1489

EMERGENCY CORE COOLING SYSTEMS BASES 3/4.5.2 and 3/4.5.3 ECCS SUBSYSTEMS (Continued)

The Surveillance Requirements provided to ensure OPERABILITY of each component ensure that, at a minimum, the assumptions used in the safety analyses are met and that subsystem OPERABILITY is maintained. Surveillance Requirements for flow testing provide assurance that proper ECCS flows will be maintained in the event of a LOCA.

3/4.5.4 (This specification number is not used) 3/4.5.5 REFUELING WATER STORAGE TANK The OPERABILITY of the refueling water storage tank (RWST) as part of the ECCS ensures that a sufficient supply of borated water is available for injection by the ECCS in the event of a LOCA or a steamline break. The limits on RWST minimum volume and boron concentration ensure that: (1) sufficient water is available within containment to permit recirculation cooling flow to the core, (2) the reactor will remain subcritical in the cold condition (68 0 F to 2121F) following a small break LOCA assuming complete mixing of the RWST, RCS, Spray Additive Tank, Containment Spray System and ECCS water volumes with all control rods inserted except the most reactive control rod assembly (ARI-1), (3) the reactor will remain subcritical in cold condition following a large break LOCA (break flow area > 3.0 ft 2) assuming complete mixing of the RWST, RCS, Spray Additive Tank, Containment Spray System and ECCS water volumes and other sources of water that may eventually reside in the sump post-LOCA with all control rods assumed to be out (ARO), and (4) long term subcriticality following a steamline break assuming ARI-1 and preclude fuel failure.

The maximum allowable value for the RWST boron concentration forms the basis for determining the time (post-LOCA) at which operator action is required to switch over the ECCS to hot leg recirculation in order to avoid precipitation of the soluble boron.

The contained water volume limit includes an allowance for water not usable because of tank discharge line location or other physical characteristics.

The limits on contained water volume and boron concentration of the RWST also ensure a pH value of between 7.5 and 10.0 for the solution recirculated within containment after a LOCA. This pH band minimizes the evolution of iodine and minimizes the effect of chloride and caustic stress corrosion on mechanical systems and components.

3/4.5.6 RESIDUAL HEAT REMOVAL (RHR) SYSTEM The OPERABILITY of the RHR system ensures adequate heat removal capabilities for Long-Term Core Cooling in the event of a small-break loss-of -coolant accident (LOCA), an isolatable LOCA, or a secondary break in MODES 1, 2, and 3. The limits on the OPERABILITY of the RHR system ensure that at least one RHR loop is available for cooling including single active failure criteria.

SOUTH TEXAS - UNITS 1 & 2 B 3/4 5-3 Unit 1 - Amendment No.

Unit 2 - Amendment No.

CR 02-1489