3F0187-14, Forwards Addl Info to Clarify Statements in Docketed Correspondence,Fsar & Tech Spec Bases as Result of Analyses Performed Subsequent to 851220 & s Re Generic Ltr 81-21 & NUREG-0737,Item II.E.1.1 Concerning RCS Cooldown

Forwards Addl Info to Clarify Statements in Docketed Correspondence,Fsar & Tech Spec Bases as Result of Analyses Performed Subsequent to 851220 & s Re Generic Ltr 81-21 & NUREG-0737,Item II.E.1.1 Concerning RCS Cooldown

ML20207Q238
Person / Time
Site:	Crystal River
Issue date:	01/15/1987
From:	Wilgus W FLORIDA POWER CORP.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.E.1.1, TASK-TM 3F0187-14, 3F187-14, GL-81-21, NUDOCS 8701270058
Download: ML20207Q238 (14)

Text

, , GL 81-21 Florida Power C C R P O # a T 8 0 es Walter S.Wilgus Mce President N aclear Operations January 15, 1987 3F0187-14 Document Control Desk U.S. Nuclear Regulatory Comission Washington, DC 20555

Subject:

Crystal River Unit 3 Docket No. 50-302 Operating License No. DPR-72 Generic Letter 81-21 and NUREG-0737, Item II.E.1.1

References:

1) NRC Safety Evaluation Reports (SERs) dated May 1,1984 and June 6, 1986.

2) FPC Letter to NRC, Simpson to Stolz (3F1285-12) dated December 20, 1985.

Dear Sir:

As a result of analyses performed by Florida Power Corporation (FPC) subsequent to the references above, we have determined various statements in docketed correspondence, the Final Safety Analysis Report (FSAR), and the Technical Specification bases require clarification. In clarifying i these statements, FPC has determined Crystal River Unit 3 (CR-3) is being operated within the intent of the SERs issued for the subject items.

These cl arified statements do not negate principal conclusions in the SERs. Most of the clarifications deemed necessary are based on our improved understanding of the length of time and amount of feedwater required for cooldown following a postulated loss of offsite power.

i Initial understandings were sometimes based on an assumption that when l

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January 15, 1987 3F0187-14 Page 2 cooling down with natural circulation, the initial high rates of cooldown could be maintained linearly from 604F to 280F (a condition for beginning operation of the CR-3 decay heat removal systen). Our current understanding is that below 350F, the rate of cooldown diminishes rapidly because the decreasing differential pressure - across the atmospheric dump valves reduces the steam mass flow rate through the valves.

Four attachments provide additional information. Attachment A includes a list of statements and clarifications. Attachment B includes a list of FPC letters to the NRC which contain statements requi ring cl ari fication .

Attachment C includes a technical discussion with related results from the calculations we performed. Attachment D lists water storage sources and capacities at the Crystal River power site, including fossil energy generating stations CR-1, CR-2, CR-4, and CR-5.

It is our intent that statements in the references of Attachment B which are identical to, or similar to, those contained in Attachment A, will be hereby considered clarified and amended by this transmittal. FPC continues to operate CR-3 within our licensed requirements and in a safe, legal, and efficient manner.

Please feel free to contact us for any further discussion on this subject.

Sincerely,

,/.

W. S. Wil Vice Pre ident Nuclear perations RMB:EHD/feb xc: Dr. J. Nelson Grace Regional Administrator, Region II Mr. T. F. Stetka Resident Inspector

~ ATTACHMENT A List of Statements and Clarifications The statements. and clarifications which follow are applicable ~ to reactor coolant system (RCS) cooldown by. natural circulation using the emergency feedwater (EFW) system at ' CR-3 'unless otherwise noted. In the natural circulation mode, the reactor is no longer critical. RC pumps and the main steam turbine are not operating. Heat is -being generated by fission

. product decay-and is also stored in the RCS metal and water . inventory. The operators are assumed to have several hours- in which to decide whether to continue to remove only decay heat or to also cool. the RCS metal and water inentory from about 555F (the. approximate operating temperature following a reactor trip) to 280F (the entry condition for operation of the decay -heat removal system). HOT STANDBY is the condition for which only decay heat is being actively removed and metal and water inventory heat are not.

C00LDOWN is .the approach to 280F.

The' heat removal path for natural circulation involves primary coolant flow from the RCS to the steam generators. Heat. is transferred to the emergency feedwater which flashes to steam and is subsequently discharged through two atmospheric dump valves. The ultimate heat sink is the atmosphere.

Note that some of the statements are several years old. The clarifications are based on analyses performed by FPC during 1986.

1. Statement in FSAR, page 14-25 The . condensate storage tank and condenser hotwell provide cooling water to the steam generators. The minimum condensate storage inventory is 200,000 gallons. This inventory provides sufficient water. for decay heat cooling (assuming infinite irradiation at 2,544 MWt) for a period in excess of one day.

Clarification This statement is correct for HOT STANDBY cooling.

2. Statement in Technical Specifications, Limiting'- Condition for Operation, page 3/4, 7-6 3.7.1.3 The condensate storage tank (CST) shall be OPERABLE with a minimum contained volume of 150,000 gallons of water.

Clarification The OPERABLE inventory is sufficient for H0T STANDBY cooling for a period of about 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />, using conservative decay heat generation rate assumptions.

A-1

3. Statement in Attachment B, Letter 5, page 1 The condensate storage tank in conjunction with the auxiliary

'feedwater system -has - been designed to sprovide a seismic Category I auxiliary feedwater source to the steam generators for required heat removal from the reactor coolant system during the . loss of off-site power conditions. The outdoor storage tank has been designed to seismic Category I requirements. In addition, this tank can withstand the effects of design level tornadic wind forces and associated missiles so that a minimum of 112,000 gallons of condensate will be available for removal of the reactor coolant system heat to achieve a safe shutdown condition.

Clarification The basis for the 112,000 gallons is contained in FSAR Section 10.2.1.2. This is the quantity of condensate required to effect a cooldown assuming none of the resulting steam .is recovered. This assumes a linear cooldown to decay heat system entry condition can be achieved. The 112,000 gallons would be sufficient for operation at HOT STANDBY for about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, assuming conservative decay heat. The 112,000 gallons is insufficient for cooldown to 280F as we now calculate it.

4. Statement in Attachment B, Letter 12, page 2 Crystal River Unit 3 Technical Specification 3.7.1.3 requires the condensate storage tank to have a minimum contained water volume of 150,000 gallons.

Clarification The OPERABLE inventory is sufficient for HOT STANDBY cooling for a period of about 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />, using conservative decay heat generation rate assumptions.

Statement in Attachment B, Letter 16, page 1 of Attachment Assuming that the amount of capacity listed in the Technical Specifications (150,000 gallons of which 139,000 gallons is usable) is the only emergency feedwater (EFW) source, cooldown of the P.CS would need to be completed in about 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> to avoid depletion of the capacity prior to reaching the decay heat removal system entry condition of 280F.

Clarification We now understand that cooldown to 280F cannot be accomplished with 150,000 (or 139,000) gallons using natural circulation. The 15 hour1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> number assumed linear cooldown, l

A-2 L

'7. Statement:in Attachment B, Letter 16, page 2 of Attachment Under assumptions which include availability of EFW from the primary source (condensate. storage tank) plus other CR-3 site and nearby fossil electric generating plant sources, the supply of EFW is adequate to assure natural circulation cooldown to DHR conditions at small cooldown rates.

j Clarification This statement is correct.

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ATTACHMENT B FPC Letters to NRC Identified to Contain Statements Requiring Clarification

~(1)' Letter, P. Y. Baynard ~ (FPC) to - R. W. Reid (NRC), "NUREG-0737, Item II.E.1.2 - Emergency Feedwater System Upgrade", December 19, 1980.

(2) Letter, P. Y. Baynard (FPC) to J. F. Stolz (NRC), "NUREG-0737, Item II.E.1.2 - Emergency Feedwater System Upgrade", April 1,1981.

(3) Letter, W. A. Cross .(FPC) to J. F. Stolz- (NRC), "NUREG-0737, Item II.E.1.2 - Emergency Feedwater System Upgrade," August 11, 1981.

(4) - Letter, W. A. Cross (FPC) to . J. F. Stol z (NRC), "NUREG-0737, Item II.E.1.2 - Emergency Feedwater System Upgrade," ' September 16, 1981.

(5) Letter, W. A. Cross (FPC) to J. F. Stolz (NRC), "NUREG-0737 Item II.E.1.2 - Emergency Feedwater System Upgrade," October 19, 1981.

(6) Letter, W. A. Cross (FPC) to D. G.. Eisenhut (NRC), " Generic Letter No. 81 Natural Circulation Cooldown", November 18, 1981.

(7) Letter, P. Y. Baynard (FPC) to J. F. Stolz (NRC), "NUREG-0737, Item II.E.1.1 - Auxiliary (Emergency Feedwater System Evaluation", November 19, 1982.

(8) Letter, G. R. Westafer (FPC) to J. F. Stolz (NRC), "NUREG-0737, Item II.E.1.1 - Auxiliary (Emergency) Feedwater System Eval uati on",

December 17, 1982.

(9) Letter, G. R. Westafer (FPC) to H. R. Denton (NRC), " Technical Specification Change Request No. 82", June 22,1983.

(10) Letter, G. R. Westafer (FPC) to J. F. Stolz (NRC), " Generic Letter No. 81 Natural Circulation Cooldown", July 28, 1983.

(11) Letter, G. R. Westafer (FPC) to J. F. Stolz (MC), " Emergency Feedwater System Program", November 18, 1983.

! (12) Letter, P. Y. Baynard (FPC) to - J. F. Stolz (NRC), " Generic Letter 81-21 -Natural Circulation Cooldown", May 23, 1984.

(13) Letter, G. R. Westafer (FPC) to G. W. Rivenback (NRC), "NUREG-0737, i Item II.E.1.1 - Turbine Driven Emergency Feedwater Pump Missile i Potential", August 8,1984.

(14) Letter, G. R. Westafer (FPC) to J. F. Stolz (NRC), " Response to NRC Generic Letter 81 Natural Circulation Cooldown", January 25, 1985.

(15) Letter, W. S. Wilgus (FPC) to H. R. Denton (NRC), " Emergency Feedwater System Reliability", October 29, 1985.

l (16) Letter, E. C. Simpson (FPC) to J. F. Stolz (NRC), " Response to NRC

! Generic Letter 81 Natural Circulation Cooldown", December 20, 1985.

ATTACHMENT C Technical Discussion and Results of Analyses Because FPC wanted to establish the options available to the operators of CR-3 during natural circulation cooldown and the impact of these options on feedwater availability, we modelled mathematically the heat sources available and the principal heat sink, assuming a loss of off-site power at CR-3. (The most likely scenario leading to natural circulation cooldown is a loss of off-site power.) Heat sources modelled include 1) decay power,

2) stored heat in the primary system metal, and 3) stored heat in the water inventory. The principal heat sink is the feedwater change-of-state occurring in the steam generator and subsequent exhausting of steam to the atmosphere through the two atmospheric dump valves (ADVs), as designed to occur during a natural circulation cooldown with a loss of off-site power scenario. The model also includes heat losses to containment atmosphere, incorporates dump valve coefficients from the manufacturer, and includes effects of the dump valve exhaust pipes in determining flow through the valves.

The analyses assumed the following principal conditions for CR-3.

Power (Po) 2544 thermal megawatts Prior operating time Infinite Initial hot leg temperature 604F Initial cold leg temperature 554F Loss of offsite power Trips reactor and reduces Po to decay power at time t = 0 Decay power generation rate As in NRC Standard Review Plan Branch Technical Position ASB 9-2 Natural circulation cooling Initiated at t = 0 Cooled down condition (DHR cut-in) 284 psig and 280F Significant results of the CR-3 loss of off-site power analyses are shown below.

1) Feedwater requirements and the time to cooldown are controlled primarily by the characteristics of the ADVs and the cut-in conditions for the DHR system.

2) The minimum time to cooldown from t = 0 is about 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br />.

3) The minimum feedwater requi rement to cooldown is about 350,000 gallons.

4) The minimum cooldown rate (C) consistent with 2) and 3) above is about 8.5F/hr.

5) Cooldown rates in excess of 8.5F/hr do not decrease the feedwater or time requirements for cooldown.

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6) Cooldown rates less than 8.5F/hr increase both the feedwater and the time requirements for cooldown.

7) A time delay from t = 0 to t = 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> in initiating cooldown will not significantly affect feedwater or time requirements if a cooldown rate of 50F/hr is then utilized. For smaller delays (t < 28 hrs) smaller cooldown rates (C < 50F/hr) may be utilized.

The above results are consistent with conservation of energy. The energy sources include: a) decay heat, b) stored metal heat, and c) stored heat in the primary system water inventory. Source a) is a time-dependent variable. Sources b) and c) are constants. The principal energy removal mechanism requires steaming through the atmospheric dump valves. Although initial systen cooldown rates may be high and pressure reductions may be rapid, the dump valve steaming rate is limited by the differential pressure across the valve. At t = 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br />, approximately the same amount of energy has been removed for all cooldown rates in excess of 8.5F/hr. Therefore, the same amount of feedwater is required for all such cooldown rates. If the cooldown rate is lower than 8.5F/hr, a temperature of 280F cannot be attained within 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> and more feedwater will be required to remove the additional energy generated beyond 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br />.

Figures 1 and 2 are graphical representations for three cooldown cases.

1) C = 50F/hr with cooldown initiated at t = 0.

2) C = 8.5F/hr with cooldown initiated at t = 0.

3) C = 50F/hr with cooldown initiated at t = 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br />.

Figure 1 illustrates that the three cases all are calculated to require about 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> to reach the cooled-down condition. The plot also shows the calculated non-li neari ty of behavior for cases 1) and 3) and the near-linear behavior for case 2).

Figure 2 shows the feedwater requirements are calculated to be approximately the same for all three cases. Note that the requirement for case 1 exceeds the other cases because less heat is lost to the containment a tmosphere.

Figure 3 shows the time required to reach cooldown conditions if realistic decay heat conditions are assumed, i .e., the multipliers 1.2 and 1.1 used in the conservative decay heat equations are replaced by 1.0. The minimum time to cooldown is reduced from about 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> to about 34 hours3.935185e-4 days <br />0.00944 hours <br />5.621693e-5 weeks <br />1.2937e-5 months <br /> as shown by curves 2, 3, and 4. As shown in curve 3, the operator needs to initiate cooldown no later than 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> after t= 0 to attain cooldown by 34 hours3.935185e-4 days <br />0.00944 hours <br />5.621693e-5 weeks <br />1.2937e-5 months <br />. The linear cooldown rate has increased to 11.4F/hr, as shown in curve 2.

Figure 4 indicates the EFW requirements for CR-3 cooldown as calculated using realistic decay heat assumptions are less than 275,000 gallons.

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ATTACHMENT D SOURCES OF EMERGENCY FEEDWATER (EFW) AT THE CRYSTAL RIVER I. Condensate - Grade Sources Source Volume (gal) Remarks Dedicated EFW Tank 150,000 Seismic I, tornado hardened

~ (EFT-2) tank. Volume to be controlled by Technical Specifications.

Will install during Refuel VI.

Condensate Storage 139,000 Tank (CDT-1)

Seismic I tank. Hard-piped to EFW pump suctions. Volume now controlled by Technical Speci.

fications.

Condenser Hotwells 150,000 Hard-piped to EFW pump suctions.

Auxiliary Building 5,000 Hard-piped to condensate Condensate and De- hotwells.

mineralized Water Storage Tank (DWT-1)

Demineralized Water 450,000 Used to refill EFT-2. Requires Storage Tank, Unit 3 portable pump and hose given (WTT-1) LOOP.a Demineralized Water 147,000 Used to refill EFT-2. Requires Storage Tank, Unit 1 portable pump and hose given LOOP.

Demineralized Water 147,000 Used to refill EFT-2. Requires Storage Tank, Unit 2 portable pump and hoss given LOOP.

i Demineralized Water 250,000 Used to refill EFT-2. Requires Storage Tank, Unit 4 portable pump and hose given LOOP.

a The term " LOOP" means loss of off-site power.

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Condensate - Grade Sources (cont'd.)

Source Volume (gal) Remarks Demineralized Water 250,000 Used to refill EFT-2. Requires Storage Tank, Unit 5 portable pump and hose given LOOP.

Total Condensate Grade Sourcesb 1,699,000 II. Other Sources .

Source Volume (gal) Remarks -

Treated Water 1,000,000 Storage Tank, Used to refill EFT-2. Requires Units 1, 2, and 3 portable pump and hose given LOOP.

Treated Water 1,000,000 Used to refill EFT-2. Requires Storage Tank, portable pump and hose given Units 4 and 5 LOOP.

Unit 3 Fire Pro- 720,000 Used to refill EFT-2. 360,000 tection System per tank (2 total). Water can Water Tanks be removed via one of two diesel-driven fire pumps using a hose.

Total Other Sources 2,720,000 b

Does not include sources within the fossil units feedwater or condensate systems (e.g., condensate storage tanks, condenser hotwells, etc.). These have been excluded by an assumption that these sources will be needed to shutdown the fossil units following a LOOP.

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