ML032820441

Technical Specification (TS) Change 03-02, Revision of Boron Requirements for Cold Leg Accumulators and Refueling Water Storage Tank (RWST) - Update of Proposed TS Bases Revision

ML032820441
Person / Time
Site:	Watts Bar
Issue date:	10/03/2003
From:	Pace P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC 9480, WBN-TS-03-02
Download: ML032820441 (5)

Text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 OCT Q3 2003 WBN-TS-03-02 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 In the Matter of the ) Docket No. 50-390 Tennessee Valley Authority )

WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 - TECHNICAL SPECIFICATION (TS) CHANGE 03-02, "REVISION OF BORON REQUIREMENTS FOR COLD LEG ACCUMULATORS AND REFUELING WATER STORAGE TANK (RWST)" - UPDATE OF PROPOSED TS BASES REVISION (TAC NO. 9480)

TVA's letter dated May 30, 2003, contained a proposed revision to the "Applicable Safety Analyses" section of TS Bases 3.5.4, "RWST." The proposed revision indicated that the number of Tritium Producing Burnable Absorber Rods (TPBARs) installed in the core may vary from 0 to a maximum of 2304. Based on an October 3, 2003, discussion with NRC's M. H. Chernoff, the purpose of this letter is to revise the text of TS Bases 3.5.4 to that shown in the enclosed annotated page. The enclosed update to the Bases revises the maximum limit of TPBARs that may be installed to 240.

The proposed change does not alter TVA's previous analysis of the proposed boron concentration limits and accordingly does not affect TVA's previous no significant hazards consideration conclusion.

Printed on recycledpaper

U.S. Nuclear Regulatory Commission Page 2 OCT 0 3 2003 There are no regulatory comnitments in this submittal. If you have any questions about this request, please contact me at (423) 365-1824.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on this 3rd day of October, 2003.

Sincerely, P. e Manager, Site Licensing and Industry Affairs Enclosure Technical Specification Bases 3.5.4, "Refueling Water Storage Tank" - Update to Reflect 240 Tritium Producing Burnable Absorber Rods cc: Seepage 3

U.S. Nuclear Regulatory Commission Page 3 OCT 0 3 2003 PLP:JLB Enclosure cc (Enclosure):

NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Ms. M. H. Chernoff, Project Manager U.S. Nuclear Regulatory Commission MS 08G9 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. Lawrence E. Nanny, Director Division of Radiological Health 3 rd Floor L & C Annex 401 Church Street Nashville, Tennessee 37243

Enclosure Technical Specification Bases 3.5.4, "Refueling Water Storage Tank" Update to Reflect 240 Tritium Producing Burnable Absorber Rods

RWST B 3.5.4 BASES APPLICABLE required volume is a small fraction of the available volume.

SAFETY ANALYSES The deliverable volume limit is set by the LOCA and (continued) containment analyses. For the RWST, the deliverable volume is different from the total volume contained since, due to the design of the tank, more water can be contained than can be delivered. The minimum boron concentration is an explicit assumption in the main steam line break (MSLB) analysis to ensure the required shutdown capability. The maximum boron concentration is an explicit assumption in the inadvertent ECCS actuation analysis, although it is typically a nonlimiting event and the results are very insensitive to boron concentrations. The maximum temperature ensures that the amount of cooling provided from the RWST during the heatup phase of a feedline break is consistent with safety analysis assumptions; the minimum is an assumption in both the MSLB and inadvertent ECCS actuation analyses, although the inadvertent ECCS actuation event is typically nonlimiting.

The MSLB analysis has considered a delay associated with the interlock between the VCT and RWST isolation valves, and the results show that the departure from nucleate boiling design basis is met. The delay has been established as 27 seconds, with offsite power available, or 37 seconds without offsite power.

Technical Specification Surveillance Requirements 3.5.1.4,

'Accumulators,' and 3.5.4.3, "RWST,O allow a range of match boron concentrations depending upon to the number of tritium producing burnable absorbers rods (TPBARs) installed in the reactor core. Watts Bar Is authorized to place a maximum of 240 TPBARs into the reactor In an operating cycle. The Rnuabr ef TPE'Ro u__: .. t_ be leadeid may -vryfreme Mintimfum of 0 to a miximurm zf 2304 TBARRS. Generally, TPBARs act as burnable absorber rods normally found in similar reactor core designs. However, unlike burnable absorber rods which lose their poison effects over the life of the cycle, some residual effect remains in the TPBARs at the end of the cycle. When larger amounts of excess neutron poisons (as in the case with larger loads of TPBARs) are added to a core, there is competition for neutrons from all the poison and the negative worth of each poison (including the reactor coolant system (RCS) boron) decreases. The positive reactivity insertion due to the negative moderator coefficient that occurs during the cooldown from hot full power to cold conditions following a loss of coolant accident (LOCA) must be overcome by RCS boron. Because the RCS boron is worth less, it takes a higher concentration to maintain subcriticality.

For a large break LOCA Analysis, the minimum water volume limit of 370,000 gallons and the minimum boron concentration limit is used to compute the post LOCA sump boron concentration necessary to assure subcriticality. This (continued)

Watts Bar-Unit 1 B 3.5-26 Revision 13 Amendment 7, _