ML17229A746

Application for Amend to License NPF-16,removing Requirement for SITs to Be Operable in Mode 4,which Will Minimize Potential for Inadvertent SIT Discharge During RCS Cooldown/ Depressurization Evolutions

ML17229A746
Person / Time
Site:	Saint Lucie
Issue date:	05/27/1998
From:	Stall J FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17229A747	List: ML17229A746 ML17229A748
References
RTR-NUREG-1432 L-98-115, NUDOCS 9806030218
Download: ML17229A746 (16)

Text

CATEGORY 1 REGULAT INFORMATION DISTRIBUTIO dYSTEM (RIDS)

ACCESSION NBR:9806030218 DOC.DATE: 98/05/27 NOTARIZED: YES DOCKET FACIL:50-389 St. Lucie Plant, Unit 2, Florida Power 6 Light Co. 05000389 AUTP.NAME

• AUTHOR AFFILIATION STAZiL,J.A. Florida Power S Light Co.

RECIP.NAMk RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Application for amend to license NPF-16, removing requirement for SITs to be operable in mode 4,which will minimize potential for inadvertent SIT discharge during RCS cooldown/

depressurization evolutions. A DISTRIBUTION CODE: A001D COPIES RECEIVED:LTR ENCL S1'ZE: I I +2 TITLE: OR Submittal: General Distribution E

NOTES:

RECIPIENT 'D COPIES RECIPIENT COPIES CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-3 LA 1 1 PD2-3 PD 1 1 GLEAVES,W 1 1 R INTERNAL: ACRS 1 1 01 1 1 NRR/DE/ECGB/A 1 1 NRR/DE/EMCB 1 1 NRR/DRCH/HICB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 NUDOCS-ABSTRACT 1 1 OGC/HDS3 1 0 EXTERNAL: NOAC NRC PDR 1 1 D

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N NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD) ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED: LTTR 14 ENCL 13

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Florida Power 5 Light Company, 0

6351 S. Ocean Drive, Jensen Beach, FL 34S57 L-98-115 May 27, 1998 10 CFR 50.90 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Re: St. Lucie Unit 2 Docket No. 50-389 Proposed License Amendment Safet In ection Tanks-MODE 4 Pursuant to 10 CFR 50.90, Florida Power & Light Company (FPL) requests to amend Facility Operating License NPF-16 for St. Lucie Unit 2 by incorporating the attached Technical Specifications (TS) revisions. The amendment will revise TS 3.5.1, Emergency Core Cooling Systems (ECCS) - Safety Injection Tanks, to remove the requirement for safety injection tanks to be operable in MODE 4. Removal of this requirement is consistent with both the Standard Technical Specifications for Combustion Engineering Plants (NUREG-1432) and the TS for St. Lucie Unit 1, and will minimize the potential for inadvertent safety injection tank discharge during reactor coolant system cooldown/depressurization evolutions. It is requested that the proposed amendment, if approved, be issued by September 30, 1998, prior to the next scheduled refueling outage. is an evaluation of the proposed TS changes. Attachment 2 is the "Determination of No Significant Hazards Consideration." Attachment 3 contains a copy of the affected TS page marked-up to show the proposed changes.

The proposed amendment has been reviewed by the St. Lucie Facility Review Group and the Florida Power & Light Company Nuclear Review Board. In accordance with 10 CFR 50.91 (b)(1), a copy of the proposed amendment is being forwarded to the State Designee for the State of Florida.

I Please contact us if there are any questions about this submittal.

Very truly yours, J. A. Stall QD Vice President t- .'.C~v3 St. Lucie Plant

'P8060302i8 980527 PDR ADQCK 05000389 P PDR an FPL Group company

0 I St. Lucie Unit 2 L-98-115 Docket No. 50-389 Page 2

, Proposed License Amendment Safet In'ection Tanks-MODE 4 JAS/RLD Attachments cc: Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, St. Lucie Plant Mr. W.A. Passetti, Florida Department of Health and Rehabilitative Services

St. Lucie Unit 2 L-98-115

'ocket No. 50-389 Page 3 Proposed License Amendment Safet In ection Tanks-MODE 4 STATE OF FLORIDA )

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COUNTY OF ST. LUCIE )

J. A. Stall being first duly sworn, deposes and says:

That he is Vice President, St. Lucie Plant, for the Nuclear Division of Florida Power 8 Light Company, the Licensee herein; That he has executed the foregoing document; that the statements made in this document are true and correct to the best of his knowledge, information and belief, and that he is authorized to execute the document on behalf of said Licensee.

J. A. Stall STATE OF FLORIDA COUNTY OF 5~

Sworn to and subscribed before me this 3 1 day of by J. A. Stall, who is personally known to me.

i nature of N ta Public-State of Florida

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Leslie J. lNh~l 0

I CC646 May 12, 200~

80NDEO neu TROY F~

Name of Notary Public (Print, Type, or Stamp)

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St. Lucie Unit 2

'ocket No. 50-389 Proposed License Amendment Safet In ection Tanks-MODE 4 ATTACHMENT1 to L-98-115 EVALUATIONOF PROPOSED TS CHANGES

St. Lucie Unit 2 L-98-115

'ocket No. 50-389 Attachment 1 Proposed License Amendment Page 1 of 4 Safet In ection Tanks-MODE 4 EVALUATIONOF PROPOSED TS CHANGES 1.0 Introduction The proposed amendment to Facility Operating License NPF-16 for St. Lucie Unit 2 (PSL2) will revise the Technical Specifications (TS) to delete the requirement for safety injection tanks (SIT) to be OPERABLE in Mode 4. Removing the MODE 4 operability requirement for safety injection tanks is based on an engineering evaluation performed by FPL which concluded that, in the event of a large break loss of coolant accident when in this operational mode, the flow rate from one high pressure safety injection pump is sufficient to assure an adequate reactor coolant inventory and core heat removal capacity to meet 10 CFR 50.46 requirements.

It is concluded in Attachment 2 that the proposed TS changes do not involve a significant hazards consideration.

2.0 Pro osedChan es: Descri tionand Bases/Justification Attachment 3 contains a copy of the affected TS page marked-up to show the proposed change.

2.1 Descri tion of Chan es TS 3.5.1: This specification provides the Limiting Conditions for Operation for the Emergency Core Cooling System (ECCS)-Safety Injection Tanks, and will be revised as follows:

APPLICABILITY:Change MODES "1,2,3* and 4*." to read, "1,2, and 3".", and Footnote *: Delete the last sentence which currently states, "In MODE 4 with pressurizer pressure less than 276 psia, the safety injection tanks may be isolated."

2.2 Basis/JustificationforPro osed Chan es The operability of each safety injection tank ensures that a sufficient volume of borated water will be immediately forced into the reactor core through each of the cold legs in the event the Reactor Coolant System (RCS) pressure falls below the pressure of the safety injection tanks. This initial surge of water into the core provides the initial cooling

0 St. Lucie Unit 2 L-98-115 Docket No. 50-389 Attachment 1

, Proposed License Amendment Page 2 of 4 Safet In'ection Tanks-MODE 4 mechanism during large RCS pipe ruptures. TS 3.5.1 establishes SIT operability requirements for MODES 1 through 4, and allows reduced minimum values of nitrogen over-pressure and contained water volume when pressurizer pressure is less than 1750 psia.

The development of SIT operability requirements when pressurizer pressure is below 1750 psia involved calculations to determine the minimum SIT pressure and inventory necessary to ref lood the reactor core, assuming a large break loss of coolant accident (LBLOCA) occurs in an RCS cold leg while in MODE 3 (average coolant temperature ~ 325 'F).

Explicit transient calculations were not performed to analyze the system response, but it was conservatively assumed that partial core uncovery would occur early in the event due to blowdown and that safety injection tanks would be required for ref lood. The reduced SIT requirements (shown in Footnote" of TS 3.5.1) were also conservatively extended to MODE 4, conditioned with the statement that the safety injection tanks may be isolated in MODE 4 with pressurizer pressure less than 276 psia, which is the maximum pressure for aligning the shutdown cooling system to the RCS. The SIT isolation valves are motor operated valves that automatically open, if closed, when RCS pressure exceeds 500 psia or upon receipt of a safety injection actuation signal (SIAS):

When considering the impact from large break RCS pipe ruptures, the pressure at the top of'the core after initial depressurization will be equal to the pressure at the break (close to the containment pressure) plus the pressure drop in the system corresponding to the rate of steam flow through the loops toward the break location. This pressure, acting against the reactor vessel downcomer head, will determine the potential for core uncovery.

In the presence of significant steam binding effects which are expected in the MODE 1 LBLOCA scenario, the pressure above the core will remain sufficiently high to force coolant from the core into the downcomer and out through the cold leg break, uncovering the active fuel.

Assuming the maximum cooldown rate of 100 'F/hour allowed by TS, the elapsed time to enter MODE 4 (defined by 325 'F > average coolant temperature > 200') following a shutdown from MODE 1 conditions will be greater than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, and the decay heat will only be about 1% of Rated Thermal Power. In the event of a LBLOCA in MODE 4, the reactor coolant system would depressurize quickly due to the large mass and energy releases through the break. By the time reactor vessel level falls below the hot/cold leg

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elevation, RCS pressure would be sufficiently low for high pressure safety injection (HPSI) pump(s) to inject borated water into the cold legs from the refueling water tank (RWT). Per TS 3.5.3, at least one HPSI pump is required to be operable in MODE 4.

When HPSI flow begins (-30 seconds following break initiation) and conservatively assuming an initial pressure of 2250 psia, the total RCS flashing and boil-off in the vessel

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St. Lucie Unit 2 L-98-115 Docket No. 50-389 Attachment 1 Proposed License Amendment Page 3 of 4 Safet'n'ection Tanks-MODE 4 resulting from system depressurization, release of initial stored energy, and decay heat generation is calculated to be about 462 ft'. This is a small fraction of the initial RCS liquid inventory (> 4600 ft'),in the vessel. The volume of coolant in the vessel below the hot/cold legs bottom elevation and above the active core is approximately 480 ft'.

Therefore, the remaining RCS inventory is sufficient to keep the core covered.

The pressure at the top of the core will not be sufficient to prevent the safety injection flow from entering the core via the vessel downcomer. At the time safety injection begins, the boil-off rate due to decay heat and the initial stored energy is estimated to be about 34.4 Ibm/sec (< 260 gpm), which is small compared to that in the MODE 1 LBLOCA scenario

(>130 Ibm/sec). The minimum three loop flow rate of one HPSI pump in this event will be approximately 450 gpm. Since the HPSI flow rate is significantly greater than the rate of inventory loss, the boil-off rate and the accompanying steam binding effects in MODE 4 will not be sufficient for core uncovery to occur.

A conservative adiabatic heat-up calculation shows a fuel/clad temperature rise of less than 115'F/min for the MODE 4 scenario. At this heat-up rate, the core uncovery must be substantial to challenge any of the 10 CFR 50 46 limits. In the absence of substantial core uncovery, the cladding temperatures and the clad oxidation will remain at low levels, and long term cooling will be maintained. It is thus concluded that all the 10 CFR 50.46 acceptance criteria will be met.

3.0 Environmental Consideration The proposed license amendment changes requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes the surveillance requirements. The proposed amendment involves no significant increase in the amounts.and no significant change in the types of any effluents that may be released offsite, and no significant increase in individual or cumulative occupational radiation exposure. FPL has concluded that the proposed amendment involves no significant hazards consideration and meets the criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9) and that, pursuant to 10 CFR 51.22(b), an environmental impact statement or environmental assessment need not be prepared in connection with issuance of the amendment.

St. Lucie Unit 2 L-98-115

'ocket No. 50-389 Attachment 1 Proposed License Amendment Page 4of 4 Safet In'ection Tanks-MODE 4 4.0 Conclusion Based on low decay heat level and initial stored energy in MODE 4, FPL has performed calculations to show that a LBLOCA occurring in this operational mode would not result in core uncovery and safety injection tanks would not be required in the success path to mitigate the consequences of the event. The proposed elimination of MODE 4 applicability from TS 3.5.1 is consistent with NUREG-1432 (Standard Technical Specifications for Combustion Engineering Plants) as well as the corresponding TS for St. Lucie Unit 1.

St. Lucie Unit 2

'ocket No. 50-389 Proposed License Amendment .

Safet In'ection Tanks-MODE 4 ATTACHMENT2 to L-98-115 DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION

St. Lucie Unit 2 L-98-115

'ocket No. 50-389 Attachment 2 Proposed License Amendment Page1 of 2 Safet In'ection Tanks-MODE 4 DETERMINATIONOF NO SIGNIFICANT HAZARDS CONSIDERATION Description of'mendment request: The proposed amendment will revise Technical Specification (TS) 3.5.1, Emergency Core Cooling Systems (ECCS) - Safety Injection Tanks (SIT), to remove the requirement for safety injection tanks to be operable in MODE 4.

Pursuant to 10 CFR 50.92, a determination may be made that a proposed license amendment 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. Each standard is discussed as follows:

(1) Operation of the facility in accordance with the proposed amendment would not involve a significant increase in the probability or consequences of an accident previously evaluated.

The proposed amendment does not involve changes to previously evaluated accident initiators. The proposed TS changes related to removal of the requirement for safety injection tanks to be operable in MODE 4 do not impact the results of existing accident analyses, and have no adverse impact on any plant system performance.

The function of each SIT is to provide early reactor core reflood in the event of a LBLOCA.

Safety injection tanks are not required for mitigating the consequences of large RCS pipe ruptures in MODE 4, and the proposed change to TS 3.5.1 will delete the requirement for SIT operability when in this mode. Due to the reduced initial stored energy and decay heat generation rate consistent with operation in the shutdown modes, the required operable HPSI pump is sufficient to perform the function of reactor vessel ref lood and coolant inventory make-up. Therefore, 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.

St. Lucie Unit 2 L-98-115

'ocket No. 50-389 Attachment 2 Proposed License Amendment Page 2 of 2 Safet In'ection Tanks-MODE 4 (2) Operation of the facility in accordance with the proposed amendment would not create the possibility of a new or different kind of accident from any accident previously evaluated.

The proposed amendment will not change the physical plant or the modes of operation defined in the facility license. The changes do not involve the addition of new equipment or the modification of existing equipment, nor do they alter the design of St. Lucie plant systems described in the Updated Final Safety Analysis Report (UFSAR). There are no adverse effects on any system performance due to the proposed TS changes, and the plant configuration will continue to remain consistent with assumptions used in the existing accident analyses. Therefore, operation of the facility in accordance with the proposed amendment would not create the possibility of a new or different kind of accident from any accident previously evaluated.

(3) Operation of the facility in accordance with the proposed amendment would not involve a significant reduction in a margin of safety.

The proposed TS changes have been evaluated with respect to the applicable safety analyses. FPL determined from this new evaluation that safety injection tanks are not required to prevent core uncovery during a loss of coolant accident initiated in MODE 4.

Due to the reduced core heat removal requirements in this lower mode and in the absence of substantial core uncovery, fuel cladding temperatures and clad oxidation will remain at low levels, long term cooling will be maintained, and 10 CFR 50.46 acceptance criteria will be satisfied. Therefore, operation of the facility in accordance with the proposed amendment would not involve a significant reduction in a margin of safety.

Based on the discussion presented above and on the supporting Evaluation of Proposed TS Changes, FPL has concluded that this proposed license amendment involves no significant hazards consideration.