ML20203K152
| ML20203K152 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 02/28/1998 |
| From: | Klingenfus J, Pacheco K FRAMATOME |
| To: | |
| Shared Package | |
| ML20203K146 | List: |
| References | |
| 86-1266272-01, 86-1266272-1, NUDOCS 9803040473 | |
| Download: ML20203K152 (62) | |
Text
{{#Wiki_filter:_ _ _ _ _ _ _ _ _ __ 20697 3 (12/3$) CALCULATIONAL
SUMMARY
SHEET (CSS) f!M 9 M R Wi ._ DOCUMENT IDENTIFIER 266272 M TITLE Post LOCA Boron Concentration Management for CR 3 PREPAREoBY REVIEWED BY: NAuE J A KlingenfuS NAME K S Pacheco sloNATURE __ , , 4h , stoNATuRE ._ b &L- b TITLE suphisory Engineer hE pyg TITLE EnD neer IV cost CENTER 41010 REF. PAotts) 7 i TM STATEMENT: REVIEWE.R INoEPENDENCE DATE hW PURPOSE AND
SUMMARY
oF RLsuL1st This report summarizes boron concentration control methods and calculations needed for the CR 3 plant to meet NRC requirements for post LOCA boron concentration control. Specifically, the active boron dilution methods available at CR 3 were summarized, calculations to demonstrate compilance to Criterion 5 of 10 CFR 60.46 were provided, post LOCA boron concentration control guidance suitable for Technical Support Center uso was defined, and the time ranges over which changes in the sump boron concentration will be observed l f;llowing initiation of an active dilution method were quantified. The compliance calculations demonstrated that CR 3 can meet Criterion 6 of 10 CFR 60.48 by having at least one activo dilution method that can be initiated prior to reaching the solubility limit when a decay heat of 1,2 times ANS 1971 was used. These calculations used revised core mixing volurnes to define limiting times without credit for RVW overflow or gap flow. The DL RB-sump method was shown to be effective at lower RCS , pr ssures, but the method cannot be used at higher RCS pressures because of potential sump screen d. image. The flow rate that can be provided4#fgPS limits the time post trip that it is effective, but it has Wn shown to be adequate to cover the pressures above which the DL RB-sump method can be used. Conr,idered together, at least one of the methods can be effectively established prior to the core reaching the solub;1ity limit. This combination of methods meets the requirement to have an active boron dilution mechanism that is effective ov;r any RCS pressure range that core boron dilution could be needed. The TSC guidance includes a method for determining when and what form of activo boron dilution can be used based on RB mixed-mean to sump boronometer measurements, RCS saturation temperature from the average of the core exit thermocouples, and time post LOCA. The preferred dilution method is Via APS, because this method does not require an LPI pump to be shutdown. The guidance is comprehensive in that it provides information for use with and without sump boronometer indications, in the event that the boronometer is unavailable, time and saturation temperature can be used to inititte active boron dilution methods. THE FoLLOwtNo COMPUTER codes HAVE BEEN uSED IN THis DOCUMENT: CODE IVERSloNl REV CooE IVERsioN I REV THis DOCUMENT CoNTAINs Assumptions THAT MuST BE VERIFIED prior To uSE oN SAFETY RELATEDWoRK YES ( _ ) No t 8 i PAGE _1, OF 10 9003040473 980227 PDR ADOCK 05000302 P PDR
uvmu 303 os:si r.u 804 saa nas rr ,imit o o rectirioionie, gg3 Framatoma Tcchnologies Inc. 86-1266272 01 Summarv of Results Post-LOCA Boron Concentration Management for CR-3 Florida Power Corporation Crystal River Unit 3 FTl Document 88-1266272-01 February,1998 2
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86-1266272-01 Record of Revision Rev.No2 QbaAq9_S19VERLa a DucIlption/ChanaeAylhofization 00 Initial release, December 1997. 01 All New CR 3 boron concentration calculations with revised boundary conditions, non-uniform sump boron concentration gradients, sump transport delay times, and boronomotor indication delay times, February 1908. 3
~~ - G6/$b 0s CA2 00:01 UM 604 632 2531 l'tazutone Technologies 2 003 Framatome Tcchnologbs Inc. 86-1266272-01 Table of Contente Li s t o f T a b le s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L is t o f F ig u r e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Li st o f R e f e tc nce s. . . . . . .. . . . . . . . . . . . . . . . ......................7 .......................... 1. ABSTRACT.........................................................................................................8 2. A C TIV E B O R O N D IL U TIO N M ETH O D S ..... .. . .. ........ . ... ... . ... . .... ....... ....... 2.1 DECAY HEAT DROP llNE DUMP.TO SUMP (DL RB SUMP).................. .....................10 2.2 PRESSURIZER AUXILIARY SPRAY FLOW FROM THE.............12 LPI PUMP (APS)........... 2.3 Hoi LEO INJECTION (HLI) VIA REVERSE Flow THROUGH THE DHDL
.......................13 3.
S U MM A RY O F M ETH O D S . . . .. .... .. ...... .. ... . ....... .... ... . . . .. ..... . .... .... . ..... 3.1 List or K EY A S SUM PTION S . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .
- 3. 2 SUMMAR Y O F lNPUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . .
- 3. 3 AooiTioN AL C O N SIDE RATIO N S . . . . . . . . . . . . . . .... .. .. .. ........ .. ..... ... .. .. .. . .
4. COMPLIANCE WITH 10 CFR 50.46 REQUIREMENTS.................................... 36 5. EOP GUIDANCE FOR POST-LOCA BORON DlLUTION ................................ 40 5.1 MINIMUM TIMES FOR ACTIVE BORON DILUTION WITHOUT SUMP BORON SAMPLIN
- 5. 2 S UM P B ORON C o NC E NTRATION M ETH0 0. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .
- 5. 3 TS C G u lD AN C E . . . . . . . . . . . . . . . . .. . . ........ . . 4.5. . . . . . . . . . . . . . .
5.4 DEMONSTRATION OF BORON DILUTION METHoos ........... ........................................ 6. CONFIRMATION OF BORON DILUTION VIA SUMP CONC MEASUREMENT S .................................................................ENTRATION
. . . . . . . . . . . . . . . . . . . . . . . . . . . .57 7.
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- List of Tables 4
Table 1. APS Flow Rates and Time to Fill the Pressurizer......................................... 4 Table 2. APS Matchup Times for B LPI Pump Operation.............................................16
! Table 3. APS Matchup Times for A LPl Pump Operation.............................................16 Table 4. Key input Parameters for the Boron Precipitation Analyses........................... 31 Table 5. LPl Flow Rates with Suction from the BWST. ................................................ 33 Table 6. Approximate CR 3 CLPD HPl Flows to the Core. .......................................... 33 Table 7. CR 3 Auxiliary Pressur!zer Spray Flow Rates. ...............................................,34 Table 8. Minimum Solubility Time vs RCS Saturation Temperature and Pressure
] with 1.2 ANS 1971 Decay Heat. ............................................... ............. ...... 38 Table 9. Minimum Solubility Time vs RCS Saturation Temporture and Pressure with 1.0 AN S 1971 Decay Hee.t. ...... .......... .. .. .................... ...... ......... ........... 50 J O i i k i A 'I S 4 5
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Up dei se AU) U U J4 i M bu 4 8.12 2 5 31 l'ru!ato!U Tecimolosleh Q007 Frarnatome Tcchnologi:s Inc. 86 1266272 01 List of Figures i Figurs 1. CR 3 DHDL Dump to Sump Flow Paths with the A LPl Pump......................17 Figute 2. CR 3 DHDL Dump to Sump Flow Paths with the B LPl Pump......................18 i Figura 3. CR 3 Pressurizer Auxillary Spray Flow Paths with the A LPI Pump..............10 Figure 4. CR 3 Pressurizar Auxiliary Spray Flcw Paths with the B-LPI Pump.............. 20 : Figuro 5. CR 3 DHDL Hot Leg injection Flow Paths with the A-LPI Pump............... ... 21 Figure 0. CR-3 DHDL Hot Leg Injection Flow Paths with the B-LPI Pump. ........... . .. 22 Figure 7. APS Effective Boron Dilution Time Without Gap Flow .......... ...................... 23 Figuro 8. APS Effective Boron Dilution Time Without Gap Flow .................................. 24 Figuro 9. Coro Mixing Volumo Versus Time at 2568 MWt and 1.2 ANS 1971. ............ 35 Figure 10. Core Mixing Volume Versus Time at 2568 MWt and 1.0 ANS 1971. .......... 35 Figure 11. 2508 MWt Melchup Times and Times to Solubility without Gap Flow or Active Boron Dilution with 1.2 ANS 1971 Decay Heat. ........................... 30 Figure 12. Matchup Times and Temperatures for Active Boron Concentration Control (2568 MWt with 1.0 ANS 1971). ..................................................... 51 Figure 13. Core Boron Concentration Control Limits.................................................... 52 Figure 14. Minimum Boron Solubility and Mixing Limit Time versus RCS S a tu ra tion Temperatu re. . .. .. .. .. . . . . .. . .. . . .. . . . . .. .. .. .. . . . . . . .. . . . .. ... . ... . .. .... . . .. ....... .... 53 Figure 15. Demonstration of Boron Dilution with DL RB-Sump Flow............................ 54 Figure 16. Demonstration of Boron Dilution with APS Flow. ........................................ 55 Figure 17. Demonstration of Boron Dilution with HLI Flow. ..........................................,56 6
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vo u, w an v.i ~ ~ i aoos Framatome Technologics Inc. 86 1266272-01 i Llat of References 1.
'FPC Calculation S90-0134, Rev.1 " Fluid Volocity Analysts for the Reactor Bulldin9 Sump Screens.'
2.
'FPC Calculation M97 0097, Rev.1, " Low Pressure Auxillary Spray Flow Rate for Boron Precipitation."
3.
- interoffice Correspondence, S. K. Balliet to K. R. Campbell #NOE97 2696 dated 12/23/97.
- 4. FTl Document 32126622101, 'DHDL R5 Analyses for Boron Dilution,' 12/97,
- 5. FTl Document 321268263-00, ' Sump Delta Method for CR 3,' 12/97.
- 6. FTl Document 32-1266263 01, ' Sump Delta Method for CR 3,' 2/98.
- 7. FTl Document 321266110-00, 'B&WOG Post LOCA Core Boron Dilution,' 4/17/97.
- 6. FTl Document 321266110-01, 'B&WOG Post LOCA Core Boron Dilution."
- 9. FTl Document 321266110-02, *B&WOG Post-LOCA Core Boron Dilution.'
- 10. FTl Document 515000519 03, ' Boron Dilution by Hot Leg injection,' 12/97.
- 11. FTl Document 515000519-06, ' Boron Dilution by Hot Leg injection,' 2/96.
- 12. FT1 Document 321266312 00,'Charh , 'lzation of Boronometer Extracted Sample."
- 13. 'FPC Calculation M95 0044, Rev. O, 'RW/DC/DH Therinal Analysis - DC System Temperature Calc."
- 14. FTl Document 321266137 02,'CR 3 Containment Analysis for SBLOCA."
15 'FPC Calculation M08 0005, Rev. O, 'DHHE Outlet Temperature SensitMty Study."
- 16. FTl Calculation 321269013-02, ' Fluid to Wall Heat Transfor in A Pipe for CR 3 Decay Heat Drop Lino.'
- 17. FTl Document 32126622100, 'DHDL R5 Analyses for Boron Dilution,' 12/97.
- These documents are maintained and controlled by Florida Power Corporation. Per FTl procedures, use of these references are allowed in safety grade calculations with the approval of the cogntrant unit manager of contract mant,ger. The signature below authorizes the uso of these documents for input to this evaluation. .
(UnitTAanager/ Contract Manager) (Date) 7
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- 1. Abstract I l
Post LOCA boron concentration control is an issue being reviewed by the Nuclear Regulatory Commission (NRC) for Crystal River Unit 3 (CR.3). Florida Power Corporation (FPC) is committed to provide calculations to support license amendment request (LAR) #223, which describes their approach to boron concentration control. Framatome Technologies incorporated (FTI) has performed and recorded the required analyses in verified documents. This report summarizes the results of those calculations in a form that CR 3 can include in their records system to meet the commitment to the NRC. It describes the active boron dilution methods available at CR 3, provides calculations to demonstrate compliance with Criterion 5 of 10 CFR 50 46, gives post LOCA boron concentration control guidance nuttable for Technical Support Center (TSC) use, and identifies the time ranges over which changes in the sump boron concentration will be observed following initiation of an ective dilution method. The compliance calculations demonstrate the effectiveness of the auxiliary pressurizer spray (APS), the drop line to the reactor building (RB) sump (DL RB Sump), and hot leg injection (HLI) via reverse flow through the decay heat drop line (DHDL) as active boron concentration control mechanisms. The calculations demonstrate that at least one of these means will be effective in diluting the core boron for any loss-of-coolant accident (LOCA) scenario prior to the core boron concentration reaching the solubility limit. These results are based on conservative calculations that essume 1.2 times the American Nuclear Society (ANS) 1971 standard fission product decay heat to show compilance with 10 CFR 50.46 criteria for long term core cooling. The information developed for TSC guidance uses 1.0 times the ANS 1971 values for core decay host to define operator actions necessary for post-accident boron concentration contrcl managemont strategies. l 8 l
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- 2. Active Boron Dilution Methoda Criterion G of 10 CFR 50.46 requires that following a LOCA, long term core cooling must be assured. The Emergency Core Cooling System (ECCS)is designed to refill the core and provide continuous makeup to account for the decay heat bolloff rate for the duration of the event. Pumped ECCS injection is provided initially from the borated water storage tank (BWST) and later by recirculation from the RB sump. The post-LOCA core boiling will concentrate boron in the core. Precipitation could occur if the core boric acid concentration exceeds the solubility limit for the RCS conditions (specifically saturation temperature) resulting in the potential for blockage of the core
! cooling channels. This presents a potential challenge to long term cooling. Post-LOCA core boron concentration control can be provided by any active or passive mechanism that results in a not liquid flow through the core. The passive mechanisms available for core boron dilution are reactor vessel vent valve i (RVW) liquid overflow, hot log nozzle gap liquid recirculation, loop refill, and boron carryover in steam. The active methods are initiated and controlled by operator actions. The CR-3 active dilution methods include: - 1, Decay heat drop line dump to sump (DL RB sump),
- 2. Auxillary pressurizer spray (APS) flow via the low pressure injection (LPI) pump, and ;
- 3. Hot leg injection (HLI) via reverse flow through the decay heat drop line.
The plant configuration required for use of each method and the equipment availability nesded for each is described in the following sections. ' 9 'N 4
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86-1266272-01 1 i 2.1 Decay Heat Droo Lino Dur,o to Sumo fDL RB Sumo) t The decay heat drop lino (DHDL) is attached to the Loop B (loop without pressurizer) 3 hot leg piping at the bottom of the first elbow downstream of the reactor vessel. This line provides a direct flow path from the hct leg to the RB sump. The flow out of the hot leg carrios highly borated liquid from the core region to the sump. This Sow is replenished by diluto downcomer liquid, which has boration levels similar to those of the sump. The LPI / HPl flushing of emergency core coollng system (ECCS) water into the downcomer and out of the break during the long term cooling phase of the LOCA keeps the downcomer and sump boron concentrations approximately equal. Uso of the DL RB sump method requires one of the two LPl pumps to be taken off line and the valves in the DHDL to be configured such that the reactor cooMnt system (RCS) liquid can flow from the het leg into the decay heat drop line, backward through the non-operating LPl pump suction line into the sump. This dilution method is currently available at CR-3 via the piping configuration and flow paths shown in Figure 1 and Figure 2. Use of the DL RB sump method is restricted to RCS-to sump pressure differences that will not allow the Ilquid velocities through the LPI intake line to exceed the hydraulic loading limits calculated for the sump screens. Protection of the sump screens is important becauso they prevent debris in the RB from entering the sump and being entrained into an operating ECCS pump. The analyzed liquid velocity limit that protects the integrity of the sump screen is 30.5 ft/s (Ref.1). A REl.AP5 analysis performed by FTl determined that DHV42 or DHV-43 could be partially opened to an equivalent area of not more than 2.58 in' at hot leg pressures of 73 psia or below (Ref. 4) without, exceeding the velocity limit of 30.5 ft/s. This analysis credited coofing of the liquid as it traversed the hot tog piping. There are two methods available for determining the hot leg pressure. There is a pressure tap located in the vertical pipe of the hot leg that directly reads the RCS 10
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86 1266272-01 pressure. This pressure tap has an instrument uncertainty that is too large to be used to determine when the DHDL could be opensa. There are also sixteen qualified incoro thermocouples that can be read from the plant computer. An average of these readings will allow the operators to determine the coro exit temperature, and since the system is saturated, the RCS pressurk is thereby kncwn. An average of a minimum of fourteen incore thermocouples, using the plant computer, results in an uncertainty band of +9.0/- 19.3 F of indicated minus actual temperrsture (Ref. 3). The saturation temperature at 73 psia is 305.77 F. The Indicated average temperature at which the drop line shou:d be opened !s 305.77 19.3 = 286.47 F or a saturated pressure of 54 psla, if 4,1e DHDL is ' opened at this temperature, the actual conditions could be as low as 286.52 - 9 = 277.52 F, which corresponds to a minimum pressure of 47 psia. Therefore, the DHDL can be opened when the average of fourteen exit thermocouples is at or below 286 F (Indicated RCS pressure of 54 pala) to ensure that the hot leg pressure is actually below 73 psla. initiation of the dump-to-sump flow will result in flashing of the RCS liquid as it flows through the throttled dropline valve (DHV-42 or DHV 43). The steam that flows into the sump should not be drawn into the intake of the operating LPI pump suction piping because it could cause cavitation and adversely affect pump operation. The onset of potential adverse behavior could begin enytime between 2 minutes and 3 hours after the last valve is opened. This time period is the DHDL travel time for the saturated liquid in the hot leg to reach the sump (Ref, 8). For this reason, the operator should continuously monitor the operating LPI pump motor cur'uit for indication of cavitation once the DL RB-sump method is initiated. !! unusual behavior is dt.tected, flow through the DHDL should bo isolated immediately to protect the operating LPI pump. (A' different dilution method should be used if available, if not, reactivation of this method when the differential pressure between the RCS and the RB is less could be moro successful.) 11
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86-1266272-01 2.2 Pressurizer Auxillarv Surav Flow from the LPI Pumo fAPS) The APS dilution method is also available at CR 3. The piping arrangements and flow paths are shown in Figure 3 and Figure 4. With APS, alignment of the ECCS piping to provide flow from the LPI pump to the APS nozzle provides a mechanism for core boron dilution. This alignment does not require termination of an LPl pump, but it may necessitate throttling of the LPI flow into the RCS to generate higher auxiliary spray flow rates. After the spray fills the pressurizer it begins to flow into the hot leg and finally to the core region. If the spray flow exceeds the core bolloff iste, the excess flow wil! raise the level in the hot leg and upper plenum. The static head difference between the downcomer and core regions will not support the higher level in the upper plenum. As a resu!!, a small net reverso liquid flow from the core mixing region into the lower plenum and back up the downcomer will be established. This reverse flow will provide core boron concentration controi when the boron outflow exceeds the boron inflow from the pressurizer spray. The core bolloff concentrates any boron in the spray. When the excess spray flow carries out more boron than is concentrated in the core, a long term dilution mechanism is achieved. The m!nimum availablo spray fiow as a functk,c. of RCS pressure (Ref. 2) is shown in Table 1 along with the pressurizer fill time. These flows consider throttled LPI flow with a resulting actual ECCS flow split of 800 gpm HFI and 1800 gpm LPl. FTl used these flows to calculate the time at which the pressurizer auxiliary spray flow matches decay heat and the time at which it provides excess flow (B gpm) such that boron dilution is achieved (Ref. 8). Table 2 provides the decay heat matchup times and effective boli dilution times for spray flow provided by the B LPI pump considering both 1.0 and 1.2 times ANS 1971 decav heat. Table 3 provides the same information for spray flow provided by the A-LPI pump. This information is presented graphically in Figure 7 and Figure 8. These results are appropriato once the pressurizer has filled and are valid for a quasi-steady RCS pressure without hot leg nozzle gap flow, if the nozzle gaps are 12
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86 1266272 01 open and liquid is flowing, the gaps can directly bypace some portion of the spray flow. However, if the gap flow is sufficient to bypass a significant fraction of the spray flow, pressurizer auxiliary spray flow dilution is not needed because the gaps will be providing adequato boron dilution. Onco the APS flow alignment is established, flow can be verified by the pressurizer level increase. Indication that the APS is providing coto boron dilution may be obtained via the sump boron concentration measurement described in Section S. 2.3 Hot lpAjale.chon (HLI) Via Reverse Flow Throunh the DED.L The DHDL can also be used to inject liquid into the hot leg to initiate a not core reverse flow with discharge through the cold leg pump discharge (CLPD) break. This process is similar to hot leg injection via APS oxcept that much higher flow rates can be achieved. In order to establish HLI, one LPI pump must be out of service, the LPl cross-connect line must be opened and have a quallfled flow indication, the operator must throttle the normal LPI flow to the core flood tank (CFT) nozzle, and the docay heat drop line valvos must be opened to the RCS. Flow is reversed through the idle LPI pump. This method is currently available for CR 3. (The application of this method at CR-3 will be reviewed by the NRC under a separate submittal. The method is presented in this document only for completeness, and adoquately describes the mechanics and principles behind the method.) The piping arrangements and flow paths for CR-3 are shown in Figure 5 and Figure 6. FTl has performed calculations to demonstrate boron concentration control with reverse, DHDL hot leg injection while assuring adequate core cooling (Ref.11). The results indicate that the hot log injection alignment must provide flow for one HPl pump (up to 600 gpm), a minimum hot leg injection flow of at least 500 gpm, and approximately 1000 Opm flow through one CFT nozzle. The flow splits demonstrate the capability of hot log injection to match decay heat and initiato a net reverso core flow to rnitigate the 13 y vi- w
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86 1266272-01 boron concentration bulldup at RCS pressures of 72 psia (the maximum pressuro in which the coro concentration could reach the solubility limit) or below and any timo after five hours. The required LPI flow considers all significant measurement and instrurnent uncertainties. The drawback of this method is that it requires one LPI pump to be deactivated, and the method must be initiated prior to exceeding the hot leg mixing limit described in Section
- 5. The required ECCS flow alignment is such that the flow from the lone operating LPI pump must provide flow to an HPl pump and the remaining flow is split between the one coro flood lino or LPI nozzle and the DHDL. The operator must throttle valves in the ECCS system to provido the targeted flow splits necessary to ensure adequate core cooling and provido adequate boron dilution via reverso flow through the DHDL.
14
e, # . aus v.a. c.u sua in asu rr a ato:o n,ci,,oionio, rug Framatome Technologies Inc. 88-1266272 01 Table 1. APS Flow Rates and Time to Fill the Pressurizer. B LPl Spray Flow A LPI Spray Flow Pressure Flow Rate Fill Time Flow Rate Fill Time (pala) (gpm) (gpm) (br) (br) 14.7 114.5 1,73 125.5 1,57 35 102.8 1.92 114.7 1.72 45 97.0 2.04 109.4 1.81 60 86.4 2.29 100.1 1.97 75 75.8 2.61 90.7 2.18 105 46.3 4.27 67.3 2.04 Note: These flows were calculated with throttled LPI flows and the assumed flow splits maximum of 600 gpmfloh is assure 3 bjpm LPI flow g a,ppJB,gp,y from eitherthe throttling the ALPl and flow B LPI pumps. to an This indicated flow gpm. 15 i
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Framatome Technologies Inc. 86-1266272-01 Table 2. APS Matchup Times for B LPl Pump Operation. 1.0 ANS uts1 Decay Heat 1.2 ANS 1971 Decay Heat Pressure Spray Decay Heat Effective Boron Decay Heat Effective Boron Flow Matchup Time Dilution Time Matchup Time Dilution Time (psla) (gpm) (br) (hr) (hr) (br) 14.7 114.5 19.1 22.5 32.8 39.0 35 102.8 26.3 31.7 45.0 53.6 45 97.0 31.9 38.5 53.9 83.6 60 86.4 40.4 55.8 75.6 88.9 75 75.8 68.9 82.2 107.8 128.6 105 46.3 271.9 378.1 483.6 644.7 (NOTE: APS initiation must occur three hours prior to the matchup t!mes listed on the above table to s!!ow for the APS fow to fill the pressurizer such that the effective times are accurate.) i Table 3. APS Matchup Times for A LPI Pump Operation. 1.0 ANS 1971 Decay Heat 1.2 ANS 1971 Decay Heat Pressure Spray Decay Heat Effective Boron Decay Heat Effective Boron Flow Matchup Time Dilution Time Matchup Time Dilution Time (psla) (gpm) (br) (br) (hr) (br) 14.7 125.5 14.3 18.4 23.5 27.6 35 114.7 17.9 21.0
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30.7 36.3 45 109.4 20.7 24.4 35.8 42.2 60 100.1 27,9 33.5 47.8 56.4 75 90.7 39.2 46.4 64.7 75.8 105 87.3 93.9 112.8 147.8 181.7 (NOTE: APS initiation must occur three hours prior to the matchup times listed on the above table to allow for the APS flow to fill the pressurizer such that the effective times are aceutate.) 18 i 9
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4 Framatom3 Tcchnologi s Inc. 86-1266272-01
- 3. Summary of Methods The core boron concentration was calculated as a funct!on of time for the LOCA transient using a Microsoft EXCEL spreadsheet. This model contains six control volumes and twelve junctions. It tracks the liquid and boron inventories in the coro, lower downcomer, RCS outside of the core and downcomer, CFT, sump, and BWST.
From the RCS pressure and temperature time histories provided by a RELAP5 RCS thermal-hydraulic model, core boiling and flashing rates, ECCS flows and condensation rates, RCS break flows, building spray flows, core and downcomer saturated liquid mass changes, core colubility limits, steam carryover, and hot leg nozzle gap sizes are calculated. These pressure- or time-dependent parameters determine the flows of liquid, steam, and boron between these six control volumes. The model includes I provisions for dump-to-sump flow through the decay heat drop line, nominal hot leg nozzle gap flows with user supplied multipliers, and excess ECCS spillage from the downcomer and core regions to containment. Further, the model considers liquid hold-up volumes in containment, a variable ECCS temperature during sump recirculation, and a boron transport delay between the core and the sump. 3.1 List of Kev Assumptionq The following list contains key assumptions used in determining the limits for the core boron concentration (Ref. 9). The first four assumptions apply to calculations used to determine the hot log nozzle gap size and have no bearing on analyses that do not use or credit hot leg nozzle gap flow.
- 1. The hot leg nozzio gap is calculated with methods that assume an isothermal temperature in the RV shell. The calculations are also conservative if the temperature gradient is positive from the inside to the outside (i.e. Inside is colder from steam or liquid cooldown). The calculations are non-conservative if the inside of the shell is hotter.
25 e
uz mun sususua m soi333 n33 n. , m o .rce wi nie. Framatomo Tcchnologins Inc. 86-1266272-01
- 2. There are no plastic deformations of the original measured as-built gap sizes that have reduced both gap sizes. Shifting of the RV internals may reduce one gap but the other should open up accordingly. It is the average gap size that is important for the gap flow calculations.
- 3. The dead weight of the vessel and water, the hydrostatic pressure acting on the internals, and the pipe loads on the hot leg nozzles have been neglected for these calculations. These contributions are expected to be negligible with some contributions opening the gap and others closing the gap.
- 4. The RV deflection at the nozzle belt due to pressure and temperature can be approximated by equations valid for a thick-walled cylinder. There are four cold leg nozzles, two hot leg nozzles, and two CFT nozzles attached to the shellin this region. The reinforced nozzle forgings add stiffness to this region, such that the thermal expansion can be represented as a thick-walled cylinder without any openings or attachments.
- 5. The boron concentrations in the core, upper plenum, core baffle, and outlet annulus regions are uniform. The vesselintemal circulation due to the core boiling keeps these regions well-mixed and uniform in temperature.
- 6. The boron solubility in water is representative or conservative for use in determining the solubility limit when the sump pH control additives are injected back into the core during the sump recirculation phase.
- 7. The sump pH additives that are concentrated in the core will not result in any other compounds that could precipitate and block core flow or totally obstruct the gap flow.
B. The LPI flow must be throttled to an actual flow of 1600 gpm or less for the APS effectiveness calculations summarized in this document.
- 9. The DHV-42 or DHV-43 valve open areas are based on a nominal stroke time of 6.0 seconds. The sump screen analyses were performed with a stoke time of 6.5 seconds (A,,, = 2.56 in 2). The minimum stroke of 5.5 -
seconds (A, = 0.0884 in )2provides adequate flow for boron dilution. 26
ii7p F id H ai44 rh 804 asa u si o ribow reiriotono d Fram; tom] Tcchnologi:s Inc. 86-1266272-01
;L2_Symmary of inouts The inputs used in the analyses are summarized on Table 4.
3.3 AdditionalConsiderations NRC reviews and discussions with FPC have led to the inclusion of certain specific considerations beyond the basic inputs in the boron dilution cnalyses. This section presents a summary of these concerns and the approach taken in the analysos to address them. 3.3.1 ECCS Temoerature Durino Sumo Recirculation The original boron dilution analyses (Refs, 7 & 8) used a constant ECCS inlet temperature of 140 F during sump recirculation. An analysis performed by FPC suggested that the ECCS temperature on sump recirculation could be closer to 180 F (Ref.13). The increased temperature results in additional boiling to remove the decay I heat and delays the time at which a given flow rate (such as with APS) will match com decay heat. 1 FTl reviewed several long-term containment analyses and observed that the sump liquid temperature reached a maximum at the time that the ECCS flow had matched the decay heat boiloff rate and the excess had refilled the vessel to the elevation of the break. Subsequentlydhe excess ECCS flow would spill out of the break and begin the' slow but steady cooldown of the sump liquid temperature. Several LBLOCA and SBLOCA containment analyses were performed to define a bounding time-dependent sump liquid temperature that could be used to determine the ECCS inlet temperature (Ref.14). FPC performed a variety of decay heat cooler analyses with different sump inlet temperatures to define a time-dependent ECCS temperature curve for use in 27 i
)
u nia/ss mui usi45 jeA.( 804 632 2b31 Fra:ato:o Tucimologlou Qogg Framatoma Technologies Inc. 86-1266272-01 boron precipitation analyses (Ref.15). As a result, the following equation (Ref. 9) was used to determine the ECCS liquid temperature with time for the boron dilution analyses. Toces = max (140,{0.55
- min [250,(493*t*2')) + 47.5))
As this equation suggests, early in the event (t < 11.3 hours), the ECCS temperature is 185 F. As the transient progresses, however, the ECCS temperature decreases untilit reaches 140 F (t > 46.6 hours). 3.3.2 Core Mixino Volume A large LOCA depressurizes the RCS to the containment pressure within an hour or two. At low RCS pressures and high core decay heat contributions, the combination of the high bolling rates and large specific volume ratios leads to significant volding in the core mixing region. As a result, the core liquid mixing volume is minimized (790.5 ft*). With time, the core decay heat declines and the mixture level swell decreases and allows the core liquid mixing volume to increase to approximately 1200 ft*. This transition evolves gradually after the core refills until a relatively constant liquid volume of 1200 ft* is reached. FTl has reviewed RELAP5/ MOD 2 analyses to determine the core mixing volume evolution with pressure and time after trip. The results are included in Reference 5 and shown in Figure 9 for 1.2 ANS 1971 decay heat and in Figure 10 for 1.0 ANS 1971 decay heat. Previous caiculations performed in Reference 7 with 1.2 times ANS 1971' decay heat identified that the solubility limit could be reached within 5 to 6 hours when a 2 mixing volume of 790.5 ft is used. At the time the solubility limit is reached, the core liquid volume is actually larger. Using the larger core mixing volume delays the time that the solubility limit is reached, which leads to a larger mixing volume, etc. This 28 _ _ . . . . . . _ . . . - '" ~
wwee corono ru sousa ust rr aratore Technotodo. f,3,_ Framatome Tcchnologi s Inc. 86-1266272-01 iteration process can be used to determine the appropriate core mixing volume for use in the solubility calculations. 3.3.3 Uniformity of Sumo Boron Concentration The NRC has asked whether operator actions based on sump boron concentration measurements may be performed at an inappropriate time, because the reactor building (RB) baron concentration might be non-uniform. Specifically, the major concems relato to (1) sump transport delay times and (2) the possibility that liquid and boron mass could be retained in isolated regions in the reactor building. These issues are discussed separately in the following paragraphs. During sump recirculation, tM 9xcess ECCS injected into the RCS condenses steam, mixes with the downcomer e id, spills out of the break, and flows back to the RB sump. The spilled flow has a certain boron concentration that can be used to indicate core boron concentration. With time, the core boron concentration can continue to
. grow until an active dilution method is established. The core concentration increase causes the spilled liquid to have a continuously declining boron concentration trend, This decreasing trend will establish a non-uniform gradient in the RB liquid as it travels back to the sump. The spilled liquid should have a lower concentration than the RB mixed-mean value. The mixed-mean value would also be less than the concentration that is being recirculated though the ECCS or building spray pumps. Inclusion of this gradient in the core boron calculation method results in faster increases in core concentration following a LOCA.
The method-used by FTl for including this contribution is to adjust the ECCS inlet concentration to that of the mixed mean sump boron concentration at the post-LOCA time minus the time it takes for one complete sump exchange at the given ECCS and building spray flow rates, f 29
ui7ssTvs % oE W i K ion ass asst lera:ato e Technolostes
. 0 03:
Framatome Tcchnologi:s Inc. 86-1266272-01 BCeces (@ t) = BCu (@ t - At ,,,) where: BCeces is the boron concentration of the ECCS at the time post-LOCA, BCu is the boron concentration of the RB, t is the time post-LOCA, and At.,,,%,is the sump exchange time interval. This is a relauvely simple yet effective method of including the non-uniform RB concentration padlent. The consideration of liquid and boron hold up in isolated regions of the RB is important in determining operator actions based on the indicated sump boron concentration. If dilute liquid is held up in the RB, the sump boron concentration measurement will indicate a boron concentration that is higher than the RB mixed-mean value. A higher sump boron concentration indication implies a lower core boron concentration, which , may result in a delayed initiation of an active dilation method when it was truly needed. Conversely, lower sump concentration will imply a higher core concentration, which will l lead to earlier initiation of an active dilution method. Early initiation of an active method is acceptable, so long as it does not compromise the ability to provide continuous long-term ECCS flow for core cooling. The maximum RB liquid holdup volume was calculated to be 12300 ft* (Ref. 6). The possibility of dilute liquid hold up has been considered in the development of the sump delta curves. Borated liquid hold up has been conservatively neglected, because it-removes baron from the analysis that could otherwise find its way into the core. 30
uge go va sua us:4I tM 804 832 2531 leruratore Technologleh
@ 032 Framatome Technologics inC.
86-1266272-01 Table 4. Key input Parameters for the Boron Precipitation Analyses. Parameter Value Source RCS Power Level 2568 MWt - RCS Power Uncertainty 1.02 NRC requirement. Occay Heat 1.2 ANS 71 for compliance cases. NRC requirement. 1.0 ANS 71 for EOP guidanca cases Reasonable bound. Actinide Decay Heat B&W Heavy isotopes Reasonable bound. RCS Initial Temperature 579 2 F - RCS Boron Concentration 5 2400 ppm BWST Boron Concentration 5 3000 ppm CFT Doron Concentration 5 4000 ppm See Note 1. RCS Liquid Volume 11500 ft3 CFT Inventory 1070 ft'l CFT BWST Inventory 5 350000 gal RB Spray Flow (1 pump) 1500 to 1600 gpm from BWST - 1200 gpm during sump recirculation (Recirc) BWST Temperature $ 120 F - ECCS Temperature dunng Sump Variable 185 - 140 F See Note 2. Recirculation LPI Flow CR 3 typleal flows from BWST (See Table 5) - 2000-2400 gpm during recire iir'l Flow CR-3 typical flows (See Table 6) - A-LPI APS Flow 2 Table 7 Flows Ref. 2. B-LPI APS Flow 2 Table 7 Flows Ref. 2. Sump Boron Conc. Gradient in 2 hr gradient for 1.2 ANS 1971 cases Ref 9. the Concentration Ca!culations 3.5 hr gradient for 1.0 ANS 1971 cases Maximum Sump Holdup Volume 5 12300 ft* Ref. 6. Sump Detta Temperature 5. +0 F Ref. 3. Uncertainty Core Saturation Temperature +9 / -19.3 Ret 3. Uncertainty (T.,mu - T.u) Sump Delta Boron Concentration 0.8 hour Ref.12. Measurement Delay Time See Note 3. Sump Difference Safety 25% applied to limiting sump difference with NRC requirement. Margin 12300 ft' holdup volume with the boronometer concentration Indicated time delays that will be calculated by FTl Ave As Built Hot Leg Nozzio Gap 0.092 in Ref. 7. Hot Leg injection Flow 500 gpm HLt Ref.11. 1 HPI pump (up to 600 gpm) 1000 ppm LPI to one CFT Nozzle SBLOCA Core Mixing Volume 1200 ft3 Ref. 9. Downcomer Mixing Volume 1285 ft3 Ref. 7. 31
- - - _ _ _ - - - - - I
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u >id/W Wuana u.noi asa issi ir r union wimoio% % Frcmatoma TcChnologics Inc. 86-1266272-01 Paramotor Value Source Core Mixing Volume Figure 9 & Figure 10 Ref. 8. DHV 42 or DHV43 Max Valve 2.56 in' Ref. 4. Open Area to protect sump screen DHV 42 or DVH-43 Min Velve 0.0864 in' Ref.17. Open Area to protect sump screen DHDL Pipo Temperatures at 306 F Hot Leg and vertical fall Ref.16. Initiation of dilution flow 270 F from vertical to containment wall 212 F in Aux Building Minimum Sump Level 98 to 102 ft Ref. 4. Notes: (1) The total mass of boron available in the system is the important parameter. The initial distribut.on of the boron may be different than the values used depending upon other plant requirements (i.e. Tech Spec limits, NPSH concems, etc.). Provided that the total boron mass rcmains similar to the values used here, the results will not change substantially. (2) The ECCS inlet temperature curve during the sump recirculation phat.o has been characterized as a function of time (Ref 9) by Ti ce. = max (140,{0,55
- min [250,(493*t *)) + 47.5})
The CR-3 ECCS inlet temperature should be less than or ecual to the value computed by th!s equation. (3) The delay time is determined by the boronometer flow split and the sump boron lag time for each of the three boronometer inlet locations. Engineering judgement and characteristic 3-D mixing analyses performed by FTl were used in Reference 12 to determine an appropriate sump concentration to boronometer concentration measurement lag time. A bounding time of 0.8 hours was used. 32
~ uu Fh iis us:6 ru soi as assi Frantow rechnotories co3 Framatome Technologies Inc.
86-1266272-01 Table S. LPl Flow Rates with SucJon from the BWST. RCS Pressure LPI Fid (psla) (gpm) 175 0 100 -2200 50 -2880 14.7 ~3060 These flows rates are representative of those used for core boron precipitation analyses. , Variations in these flow rates will not invalidate the boron concentration calculations performed for CR 3, but it could have a small effect on the range of break sizes for which boron concentration management may be required. 4 I Table 6. Approximate CR-3 CLPD HPl Flows to the Core. RCS Pressure HPi Flow (psla) (gpm) 1815 ~260 1215 -320 l 615 ~350 14.7 ~350 These HPl flows rates are representative of the flow that reaches the vessel in the t' ore boron
- precipitation analyses. Variations h these flow rates wih not invalidate the boron concentration calculations performed for CR 3, but they can have a slight effect on the break size of interest.
33
Ud/dd/WO M U.4 08*4W PAA 604 832 2331 Framatomo 'rectirtologieh
. i,j a 33 Framatom3 Technologts Inc.
86-1266272-01 Table 7. CR 3 Auxiliary Proesurizer Spray Flow Rates. RCS CR 3 APS Flow CR-3 APS Flow P From the From the B - LPI Train A- LPI Train (osla) (gpm) (gpm) 14.7 114.5 125.5 35 102.8 114.7 45 97 109.4 60 86.4 100.05 75 75.8 90.7 105 46.3 07.3 The APS spray flow rates were supphed by CR-3 Calculation M97 0097 Rev.1 (Ref. 2) for a throttled LPI flow of 1600 gpm. The CR 3 APS flow must be greater than or equal to these values to support the operator action times in the boron precipitation ana!yses. t 6 34
02/23/95 auN 06:49 FA1 604 632 2531 Frasatoso Technologie"
@ 036 Framatoma Tcchnologhs inC.
86-1266272-01 1 l Figure 9. Core Mixing Volume Versus Time at 2568 MWt and 1.2 ANS 1971. 1 1 1 1500 RCS Pressure 1400 ------
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- 40-50 psia g
. 900
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e 30-40 psia 800 ---------;---------
;-----------l------------
+ <30 psia 700 - LOCA 100 1000 10000 100000 1000000 Time, a Figure 10. Core Mixing Volume Versus Time at 2568 MWt and 1.0 ANS 1971.
i 1400 RCS Pressure i . . .
, , i 1300 ---------'---------d '
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. 1200
-----------{-----A---' ,;
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100 1000 10000 100000 1000000 Time, s 35
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- 4. Complianca With 10 CFR 50.46 Requirements Compliance with Criterion 5 of 10 CFR 50.46 was demonstrated for the CR-3 plant by calculations that show an effective active boron dilution method can be initiated before the core can reach the solubility limit. These calculations have been performed using Appendix K decay heat rates (1.2 ANS 1971 DH standard) to define the minimum time for operator actions to initiate an active dilution method (Ref. 9). lhe core boron concentrations can be maintained below the solubility limit by using two separate methods at CR 3, namely flow via DL RB-Sump and APS. Compliance is demonstrated by showing that at least one of the active dilution methods can be established prior to the time that the core reaches the solubility limit without crediting hot leg nozzlo gap or l
RVW entrainment or liquid overflow. (It should be noted that credit is only taken for RW/ liquid overflow for smaller RCS break sizes that can be refilled.) In the event that : Wu failure renders the active methods inoperable, calculations performed in References 7 and 8 have shown that the hot leg nozzle gaps are an effective backup dilution mechanism that prevents the core from reaching the solubility limit until an active method can be established. The time that it takes for the boron concentration to reach the solub;ity limit is govemed by the core concentration increase and the RCS pressure or temperature. The core concentration increases because of the core bolloff, which is governed by the integrated core decay heat rate. The core concentration is relatively independent of break size or RCS cooldown rate other than the effect of the core mixing volume and RCS temperature, which dictate the baron solubility limit. The time-dependent core mixing volume was used in simulations of the spectrum oflimiting CLPD LOCAs (from a' full double-ended guillotine LBLOCA to 0.05 ft: SBLOCA) to define the limiting core boron concentration versus time (Ref. 9). An iterative approach was used to converge on the mixing volume that coincided with the time that the core boron concentration reached the solubility limit. Iterations were performed with RCS saturation pressures 36
ua/giin 305 Uhi3 U [ 804 832 2531 Framatomo Technologies Qoss Framatoma Tcchnologi s Inc. 86-1266272-01 from 14.7 to 40 psia to define the minimum time to reach the solubility limit during the time-dependent portion of core mixing volume curve. Figure 11 and Table 8 present the converged results of these analyses as well as the minimum solubility times at higher pressures where the mixing volume is at 1200 ft'. Figure 11 also shows the RCS pressures at which the DL RB-sump method is available and the APS matchup times (not including the pressurizer fill time) from the A. and B LPI tra!ns. Based on this figure, boron dilution can be initiated via the DL RB-sump method if the RCS pressure drops to an indicated value of 54 psia (error corrected 47 psla) prior to the APS matchup time. If the A-LPI pump is operating, the matchup time at 54 psia is as early as 44 hours, while it is 67 hours if the B-LPI pump is operating. (Note: The A LPI APS can provide adequate core boron dilution at any time after 38 hours.) The compliance calculations show that APS or DL RB-sump flow can be initiated to control the core boron concentration at or before the time that the core could reach the solubi;ity limit. Once activated under conditions at which the methods can be used, they are effective in proventing the core from reaching the solubility limit. This combination of methods is not single failure proof. That is, one failure could take out-one (with a valve, valve motor, cr power source failure) or both active dilution methods (MCC-3AB failure). With a failure of this type, calculations have shown that the hot leg nozzle gap flows are an adequate backup to provide effective core boron dilution until the activo method can be established (Ref. 7 & 8). 37
02/23/98 XU.N 08:31 FAX 804 832 2531 Frn:atore Tecimologies Qo39 Fremi.toma Tcchnologi:s Inc. 86-1266272-01 Table 8. Minimum Solubility Time vs RCS Satrition Temperature and Pressure with 1.2 ANS 1971 Decay Heat. RCS Saturation Pressure RCS Saturation Timo to Reach the (psla) Temperature (F) Solubility Limit (hr) 14.7 212 7.6 20 228 10.4 25 240 14.1 30 250 26.9 40 2#, / 47.2 47 277 67.2
~~
!. . 281 79.4 90 293 148, 67 300 345.
73 306 Never - 38
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M; to ' N, Framatome Technologies Inc. 86-1266272-01 :l w S: Figure 11. 2568 MWt Matchup Times and Time to Solubility ;\
,, Without Gap Flow or Active Boron Dilutioj with 1.2 ANS 1971 Decay Heat.- :::
. . . . :- i
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.; _ _ _ _ _ 4. _ _ _ _ . ..
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20 ----- --- I- ------- I--------- ===*=== Min Uncertainty Adj P for Dump to Sump E
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, @ 041 Framatom3 Technolo0ies Inc. 86-1266272-01
- 6. EOP Guidance for Post LOCA Boron Dilution Compliance with 10 CFR 50.46 requirements was demonstrated by calculations that established initiation times fer active boron dilution methods with a decay heat of 1.2 times the ANS 1971 standard, Due to the additional decay heat contribution, these times are very conservative and could prompt premature realignments of the ECCS system to manage core boron concentrations in the unlikely event that a CLPD LOCA of the critical size occurred at CR-3. In order to preclude premature realignment, a more realistic, yet still conservative, decay heat (1.0 times the ANS 1971 standard) was used to develop minimum times for act.' v ation of boron dilution methods. In addition, a method was developed to calculate the limiting coro boron concentration based on the measured sump boron concentration. The minimum times to reach the solubility limit and the sump sampling methods can be integrated into the CR 3 TSC guidance for post-LOCA boron concentration control.
51 Minimum Times for Active Boron Dilution without Sumo Boron Samolina The TSC guidanco calculations were performed with the realistic decay heat levels (1.0 times ANS 1971) to determine the rate at which the core boron concentrat!on would increase and to define active boron dilution initiation times for casos when the sump sampling method is not available. These analyses were similar to the compliance calculations in that conservative boundary conditions were used that maximized the core boron concentration based on the most restrictive combinations of break size and break location. Like the compliance calculations, no credit was taken for passive boron dilution mechanisms such as RWV liquid entralnment or hot leg nozzle gap flow,' because both mechanisms are transient-specific and time-dependent for which the magnitude or effectiveness of the flows cannot be directly measured or validated without sump boron sampling. These calculations determined the minimum times for operator actions to reconfiguro ECCS flow paths, to shut down an operating LPI pump, 40 i
useus m n ua:ss m m usz assi rnato:e wctmotuim, goy Framrtom3 Tcchnologl:s Inc. 86-1266272-01 or to throttle ECCS flow rates in the event that the core concentration could not be determined. Figure 12 and Table 9 show the minimum time to reach the solubility limit versus the uncertainty-adjusted saturation temperature. That figure shows the APS effectivo times versus the uncerte!nty-adjusted saturation temperature. For all three curves, the actual saturation temperature is increased by the maximum uncertainty of
+9 F, 5 2 Sumo Boron Concentration Method The post-LOCA management of core boron concentration has typically been demonstrated with time-based initiation of active boron dilution methods. While this method is effective, it does not take into consideration the effectiveness of the hot leg nozzle gap flows or the RWV liquid overflow. A method has been developed to identify appropriate times to initiate an active boron dilution method in the event that the passive mechanisms are not effective (Ref. 6). This method allows the TSC and the operators to infer the core boron concentration using measurements of the sump boron concentration during the sump recirculation phase. The underlying premise is that if boron is depleting in the sump, it must be concentrating in the RCS or core. The break location that could result in significant core boron concentration build up must be located in the cold leg pump dischargo region and must be of sufficient size that the RCS loop piping cannot refill. Under these conditions, liquid could be retained in the reactor vessel or cold leg pump suction (CLPS) regions. The liquid that is trapped in the CLPS regions will be isolated from the reactor vessel and its boron mass content will not change significantly during the transient. Therefore, the only regions that will have variable boron concentrations are the reactor vessel or reactor building regions. If' the sump concentration can be measured, then the core boron concentration can be determined from bounding calculations that take into consideration limiting boron concentrations and measurement uncertainties.
41
mainocu.n a< 4.tnoi sai'sai~ ~ i:G e i n 5 ci; ; G i i n ? ~ ^ ~ ~ u
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Framatoma Tcchnologies Inc. 86-1266272-01 CR-3 has the capability to sample the boron concentration of the recirculating sump liquid using a boronometer and a sample lino that is located in the sump. Once the sump concentration is known, calculations can be performed to determine if the core !s approaching the solubility limit. These calculations require that the entire liquid and boron mass contained in the RCS, CFT, and BWST are known, such that a system mixed-mean average initial boron concentration can be. calculated. The difference between the initial mixed-mean average value and post-LOCA sump concentration will be used to evaluate the margin between the solubility limit and the core baron concentration. This margin can then be used with the RCS saturation temperature to determine if boron dilution methods are needed and which methods can be used. The sump difference method calculates an RB mixed mean boron concentration (ppm liquid), BC ,,,,,,, by taking the ratio of the total boron mass (Ibm B), B , to the total liquid mass (10' lbm), M., BCo m =B./M . The totalliquid mass is calculated by the sum of the RCS, CFT, and BWST liquid mass injected Mew = Macs + Mer1 + Mawsti,3 The total boron mass is determined by the sum of the products of the liquid mass and the boron concentration B = Macs
- BCac3 + Men
- BCen + M,wsm*BC,wsr.
The boron and liquid mass during the sump recirculation phase of a LOCA will be distributed in the core, downcomer, and reactor building. 42
[~ 48/89/60 00% 06:55 FAX 604 832 2531 Fra:ato;u Tecimologies
. Qo44 Framatome Technologies Inc.
86-1266272-01 f B. = B + Boe + Bn, l The boron and liquid mass retained in the core at the boron solubility limit can be calculated as a function of RCS temperature Using these core masses, the total boron and liquid mass in the downcomer and sump can also be determined as a function of RCS temperature. The core boron mass at the solubility limit is calculated as the - product of the boron concentration at the solubility limit (ppm), saturated liquid density (ibm /ft*), and core mixing volume (ft'). Bn. . oc = B., - B. = B., - (BC %. *V .*p,,,J. M,. . oc = M. - M = M. - (Vm un, o *p,). The appropriate core liquid volume for the boron concentration calculations with realistic decay heat remains approximately constant at 1200 ft' over the post-LOCA time period ofinterest. The boron wncentration in the downcomer and sump will be similar because of the high ECCS recirculation rates that keep the downcomer and sump relatively well mixed. With this consideration, the RB and downcomer boron concentration when the core is at the solubility limit is then calculated by BCps.oc = Bas.oc / Man.oc - This calculation can be repeated at a variety of temperatures to define a sump' concentration at which the core would be at the solubility limit. This curve could then be developed for a specific combination of BWST volumes and RCS initial concentrations at the time of the LOCA. However, a single curve can be devised to cover all combinations of mixed-mean liquid and boron masses by changing the basis of the limit to a difference curve. A variety of cases were evaluated with different RCS, CFT, and 43 i
ovasiiriis on:su m 8o4 a : 233: n. mum, .rieiiiss,
%3 Framatome Technologies inc, 86-1266272-01 BWST liquid masses and boron concentrations to define a bounding sump boron difference curve that can be used to establish operator action times considering instrument uncertainties and reactor building holdup volumes (Ref 6). Figure 13 demonstrates these results. Concentration differences below and to the right of this curvo identify acceptable operation. Concentration differences above and to the left of this curve indicate that core boron precipitation could result if an active dilution mechanism is not established.
A calculation was also pensmed to define conditions under which hot leg injection via reverse flow through the DHUL could be initiated (Ref.11). This limit, also shown in Figure 13 and Table 9, ensures that HLI will not induce boron precipitate due to the mixing of hot borated liquid with cold deborated liquid. If HLI is not established prior to reaching this limit, one of the other forms of concentration control should be used (APS or DL RB-cump). Concentration differences below and to the right of this curve identify acceptable times for initiation of the HLl method. Concentration differences above and to the left of this curve indicate sump concentrations that could cause boron precipitation in the hot leg piping. Figure 13 provides TSC guidance for HLI based on sump concentration. If the sump concentration is unavailable, the TSC needs guidance for establishing this method based on time. Reference 9 gives the time versus uncertainty-adjusted saturation temperature shown in Figure 14. This additional TSC guidance, when combined with Figure 12 and Figure 13, provides a composite set of instructions that can be used with or without sump boron concentrations to manage the core boron concentration post-LOCA. - 44
~
7 $W56 00k 08:57 FAf 804 832 2531 Frasato2e Tecimologies - @ 046 Framatome Technologi:s inc, 86 1266272-01 5.3 TSC Guidance All of the methods for monitoring and managing the core boron concentration post-LOCA have been presented in the previous sections. This section integrates them into a set of instructions for EOP or TSC guidance during the long-term cooling phase of a , LOCA. These instru.,tions should be followed whenever inadequate subcooling exists, or has existed for greater than five hours, and the core exit temperature is less than 305 F (314 F error corrected). Cexulations have shown that even if all the boron in the RCS, BWST, and core flood tanks were concentrated in the core region, the boron would remain soluble at temperatures above 305 F (saturation at 72 psla). Core boiling is the concentrating mechanism that will continue until core exit subcooling is tastored. The restoration of core exit subcooling is assured by establishing a liquid flow through the core that not only suppresses core boiling, but also effectively dilutes the core boron accumulated during the period of inadequate subcooling. At lower temperatures, the boron concentrations could result in precipitation and possible blockage of core cooling channels. Therefore, if core exit subcooling margin is lost for an extended time period (greater than 5 hours), then this guidance must be followed to prevent boron precipitation. The post-accident core boron concentration monitoring and management strategies are based on Figures 12 through 14. These strategies use core exit temperatures, time, and sump boron concentration to track the transient evolution and determine when an active dilution method is required and which of the three active methods (APS, dump to sump, or HLI) are appropriate for use. The preferred active dilution method is APS, because it does not require significant realignment of the EOCS flow paths (needed for' HLI use) or tight control of DHDL valve positions to protect the sump screens (needed for dump to sump use). - Once in this procedure, the sump mixed-mean concentration must be calculated, the boronometer measurements must be taken, and the transient temperature-time histories must be recorded for use in this guidance as outlined. 45
of m us mu.s ca:s7 v.u aos as: assi rmwoxo reemosm.. w Frarnatoms Technologizs Inc. . : 86-1266272-01 . Figure 14 presents the minimum time post-trip that the core could reach the solubility I limit (or mixing limit for HLI) as a function of saturation temperature. This curve is used j exclusively if sump boron sampling is not available. It is used to determine the time for
- initiation of an active method or to make a decision on the use of hot leg injection. An active method should be initiated before crossing the lines identified in Figure 14.
i if sump boron sampling is available, the sump delta concentration should be plotted against the core exit temperature on Figure 13 with time noted at each data point. If the curve stays flat (i.e. near zero delta concentration), some passive dilution mechanism :s working (RCS refill, RWV liquid overflow, or hot leg nozzle gaps) and an active dilution method is not needed at this time. If the curve begins to approach the solubility or mixing limits, an active boron dilution method may be needed. The methods that are
- effective for boron dilution can be derived from Figure 12, j.
- Figure 14 con be used along with Figure 13 to delay the initiation of 4.n active method based on the sump-delta limit. The sumo-delta method provides a very conservative -
l limit that prevents the core from reaching the solubility limit.' These conservatisms may prematurely indicate that active boron dilution is needed. That is, if the sump-delta
- . method indicates that an active method is needed by 10 hours, but the minimum time to solubility at a given temperature is 20 hours, then active dilution may be delayed until h just before the later of the two, or 20 hours. By the same token, the time-based actions
- - do not have to be used if the sump delta concentration indicates passive dilution is l occurring. In other words, initiation of active boron dilution is acceptable and adequate i
; at the latest activation time derived from the combination of sump-delta and time-based- -
limits at the given core exit temperature. 46
,,.m r _ . . , y _ w - --
n> u s co rosiss T, W sor isi i gi o n.sm, .rwimoie. 6 Framatome Tcchnologies Inc. 86-1266272-01 5.4 Demonstration of Boron Dilution Methods Three cases are provided as examples of each of the three CR-3 active dilution methods to assist in the understanding of how the three sets of EOP guidance curves can be used together to determine when boron dilution is needed end which methods can be used. The examples further demonstrate the significant conservatism included in the sump-delta curves, it is clear that the margin between the indicated and real solubility limit is significant and adequate to ensure initiation of active dilution methods before the core reaches the solubility limit. 5.4.1 Case 1. Boron Dilution via Dumo to Sumo Case 1 is a begl. ning-of-life (80L) CLPD LOCA with a break size of 0.12 ft'. It simulates a single failure of the A-emergency diesel generator (EDG). The progression is shown in Figure 15. The long-term core exit temperature drops below 280 F within 5 hours post LOCA. At this time, the operators enter the post-accident EOP guidance criteria, because inadequate subcooling has persisted for at least five hours and the core exit temperaturo is less than 314 F. They calculate the system mixed-mean boron concentration, Degin to measure the sump boron concentration with the boronometer, and plot transient progress on Figures 12 through 14. The first several boronometer measurements indicate that the sump detta concentration difference is increasing. At approximately 9 hours, the sump delta reaches the HLI j mixing limit. A cross reference with the time-based HLI mixing limit on Figure 14, reveals that the real decision to initiate HLI does not have to be made until approximately 30 hours post LOCA. Therefore no active dilution is initiated at this time. They continue to measure the sump concentration and plot the course on each figure. At 15 hours, the sump delta concentration has approached the sump-delta solubility limit, but the time-based limit is still 15 hours away at the current RCS temperature 47 l
ub 4Jiv6' un uniiWiAn 604 832 2531 l~ramat ome Techtiologien
@o4g Framatome Technologies Inc.
86-1266272-01 trajectory. At the end of the first day, the TSC staff concludes that detive dilution is needed and the preferred option of APS with the B-train is not effective at this time. However, the temperature is in the acceptable range for dump to sump, plus HLI is still a viable option because the time based mixing limit has not been reached. The dump-to sump mathod is selected and the operators are instructed to initiate it by 25 hours. Onco this methoo is initiated, the core concentration turns over quickly as confirmed by the sump concentration increase. The minimum solubility margin was in excess of 27000 ppm at 25 hours. 5.4 2 Case 2. Roton Dilution via Auxiliarv Pressurizer Sorav The second example is a slightly smaller 01.PD break,0.08 ft', at BOL with a single failure that prevented use of the A LPI pump. The progression is shown in Figure 16. This break plateaus at a higher pressure and temperature than the previous case. At five hours tho operators begin to measure the sump boron concentration and monitor the t e . lont progress on the time-temperature curvos. By 15 hours, the HLI mixing limit is approached on the sump delta curve. By cross-reference to the time based limit, the TSC concludes that the timo based mixing limit is still 30 hours away, so no action is required at this time. The sump delta differenro continues to increase toward the solubility limit. At approximately 40 hours, the TSC determines that the D train APS methed would be offective by 45 hours. Since APS la the preferred dilution method, the TSC instructs the operators to initiate APS at 42 hours, allowing three hours for the pressurizer to fill Once the pressurizer is full, the APS flows into the hot leg and begins a not reverse liquid flow through the core. The liquid flow slowly but steadily reduces the core concentration. The minimum core solubility margin calculated for this case' was greater than 37000 ppm at 45 hours. 48
og/gaiva suA 09:00 4A1 604 432 2831 Fra:atonio Technotosten gogo j i Framatome Technologies Inc. 86-1266272-01 53.3 Cate 3. Boron Dilution via Hot Lea Inloction The final case also simulates an 0.08-ft' case but with end of-life (EOL) RCS boron concentrations. Tne prcr tssion is shown in Figure 17. This case usos a dilute liquid holdup volume in excess w,' 9900 ft', with a single failure of a valve In the APS piping l that is not dia: overed until the preferred APS method is attempted at 30 hours. With the failure of APS, the TSC instructs the operators to use HLI. Use of this method is not restricted because the time-bated mixing limit has not been exceeded. At 40 hours, the operators initiate HLI to manage the core boron concentration. The minimum core solubility margin for this case was 56662 ppm at the time of the HLI initiation. (NOTE: The application of HLl at CR 3 is currently under rev!ew by the NRC under a separate submittal. This demonstration is presented only for completeness and to demonstrate the mechanics and principles behind the method.) l 9 1 49
~on;asin m os:oo r.u soi ass assi r,e a m , w iinoton <,. g o3, Framatome Technologies Inc. 86 1266272-01 Table 9. Minimum Solubility Time w 'CS Saturation Temporture and Pressure with 1.0 ati. 1971 Decay Heat.
r RCS Saturation Actual Indicated Time to Reach Pressure RCS Saturation RCS Saturation the Solubility Time to Reach (psla) Temperature Temperature Limit HLl Mixing Limit (F) (F) (hrs) (hrs) 14.7 212 221 13.06 13 ; 20 228 237 17.00 17 25 240 249 23.69 23 30 250 259 32.22 28 ; 40 267 276 56.94 40 ' 47 277 286 81.67 48 49.1 280 289 93.06 51 50 281 290 98.61 52 60 293 302 193.61 64 63.1 296 305 348.89 68 65.4 299 308 >350 72 73 306 315 Never 83 1 j i \ 9 i 1 50
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.o Control (2568 MWt with 1.0 ANS 1971). ;;
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D . 200 223 240 250 280 300 320 340 360 RCS Saturation Temperature,(F) Note: APS initiation must occur three hours pner to the matchup times to allow time for the APS to fi2 the pressuizer 51 g a es M
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ei i Figure 13. Core Boron Concentration Control Limits. 5! ssee . .u _1 , 3000 .________
.__s___________a___ ___
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Figure 14. Minimum Boron Solubility and HLI Mixing Limit Time Versus RCS o Saturation Temperature. g im -
-+-Max SorubiMy Temp (314 F) ; ; ; l l i20 ----______
-_;_____--__-_z_--__-______
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o . Be needec . e Q e . . . . . 9 i : . . : : Boron Deutioa [ g Go ___________;.___________l____________: _________ _;__________ ,________ __..:_______. g% g
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. s . . . . e 20 - - - - - - - - _ - _ ' - - _ - _ - - - - - - _-_-_-__'-_-_--_--_._---------- .-_--__-- _-_.---___----- ---_-.--_-
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0 200 220 240 260 280 300 320 343 360 RCS Saturation Tenperature,(F) 53 G a t.s an.
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@2/2346 00% 09:03 FM 604 632 2531 Ita ato:o 'lechnologies
@ 055 Frambtome Tcchnologies Inc.
86 1266272 01 Figure 15. Dernonstration of Boron Dilution with DL RB. Sump Flow. Sump Delta Boron Concentration Limits, poo
' .... .. T--k --Hu ue s t C ro opm ei n o hr l
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200 22o 240 teo reo 300 sto 90 seo RCS Saturatlon Temperature,(F) l l goo Minimum Baron Solubility and HLI Mixing Time Temperature Limits. su ......-.
, , , -+- ues solub My Tomo in ........l.........:...
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~ 0N23 rp6 MON 09iO4 l'AI 604 632 2531. _ - lernsato::o Technologleh
. 0 030 Frcmatomo Technologics Inc.
86 1266272 01 . Figure 16. Demonstration of Boron Dilution with APS Flow. Sump Delta Boron Concentration Limits. 3000 -
, . . --. . - nu u . ,0 um.
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02/23/ph MON 09:03 FA.\ 604 632 2531 friciatomo Tecimologi""
. B057 Framatomo Tachnologies Inc.
86 1260272 01 Figure 17. Demonstration of Boron Dilution with HLI Flow, Sump Delta Boron Concentration i.imits. 3000
, . . . . -.-to-e ' ' ' ' '
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6 tv ; 0 - 300 220 340 260 260 300 320 340 360 RC6 Saturation Temperature,(F) Minimum Boron Solubility and Hl.1 Mixing Time. Temperature Limits. 200 i 100 ........'....... ....-.. . , =+=. Man Boub44 Temp 6.-..... .6........-- ...... .*.. 160
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APS and Dump to Sump Time Temperature Effectiveness Limits. 120
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.......{.......,'. .
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02/23/96 NON 09:06 FA% 604 632 2531 Ira:ntoru Technologiuk
@ 056 Framatome Tcchnologi:s Inc. 86-1266272-01
- 6. Confirmation of Boron Dilution via Sump Concentration Measurements Once an activo boron dilution method has been initiated, a positive confirmation that it la offective can be obtained by continuous monitoring of the sump boronometer. The amount of time required to obtain feedback togarding effectivenirss of dilution is a function of which active boron dilution method is used. Calculations were dono to examine the time that it takes to obtain changes in the boron readings at the boronometer for the APS, DL RB ., ump, and HLi boron dilution methods (Ref. 8).
The boronometer at CR 3 is located near the ECCS sump suction piping. For the APS method, the time it takes liquid to reach the boronometer includes the time to fill the pressurizer, the time for the concentrated boron to traverse the lower plenum and downcomer, and the time it takes to make its way from the break to the boronometer. The calculations demonstrated that feedback could be obtained before approximately g hours plus the time it takes to process the samplo from the boronometer. For the DL RB Sump method, the time that it takes the boronometer to register a chango in the sump concentration is dependent upon the valve open area and the hot leg pressure. The longest timo to register is consistent with the smallest opening and the lowest hot leg pressure (gravity feed post LBLOCA). The shortest time is consistent with the maximum opening and the highest hot leg pressure. The calculations demonstrated that feedback could be obtained as quickly as three minutes, but no later than nine hours, plus the time it takes to process the sample from the boronometer. For the HLI method, the timo that it takes the bcronometer to register the concentratiori change is shorter than the APS because there is no filling time and the excess flow rato is much higher. Tha calculations demonstrated that feedback after initiation of HLI should be obtained between approximately 2.5 and 0,5 hours plus the time it takes to 57
on/ aves nos osion ru 804 aan assi re,i m ozo Tectitioionic. g ,3, Framatome Technologbs Inc. 86 1266272-01 process the sample from the boronometer. (Note: When using HLI it is possible to subcool the core exit fluid, either continuously or cyclically.) The material in this section is provided to highlight the fact that positive feedback of core boron dilution will not be Instantaneous. Somewhat continuous monitoring of the sump boronometer is required both prior to and after the active mechanism is initiated to verify that dilution is occurring. It also highlights that cyclic or continuous core exit subcooling may be observed following the use APS and HLI, although it is most likely with HLI because it provides the highest flow rate into the upper plenum regien. I i i r 58
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~ oajmen m os:ov ru sea as ssi tra:atos h ennotoni n easo Framatome Technologts Inc. 86 1266272-01
- 7. Summary and conclusione l
This report summarizes boron concentration control methods and calculations needed for the CR 3 plant to meet the NRC requirements for post-LOCA core boron concentration control. Specifically, the active boron dilution methods available at CR-3 were summsrized, calculations to demonstrate compliance to Criterion 5 of 10 CFR 50/,8 were provided, post LOCA boron concentration control guidance suitable for Technical Support Center use was defined, and the time ranges over which changes in the sump boron concentration would be observed following initiation of an active dilution method were quantified. The compliance calculations demonstrated that CR 3 can meet Criterion 5 of 10 C!T1 50.46 by having at least one active dilution method that can be initiated prior to reaching the solubility limit when a decay heat of 1.2 times ANS 1971 was used. These calculations used revised core mixing volumes to define limiting times without credit for RWV overflow or gap flow. The DL RB sump method was shown to be effective at lower RCS pressures, but the method cannot be used at higher RCS pressures because of potential sump screen damage. The flow rate that can be provided to the core via APS, limits the time post trip that it is effective, but it has been shown to be adequate to cover the pressures above which the DL RB sump method can be used. Considered together, at ieast one of the methods can be effectively established prior to the core roaching the solubility limit. This combination of methods meets the requirement to have an nctive boron dilution mechanism that is effective over any RCS pressure range that core boron dilution could be needed. The TSC guidance includes a method for determining when and what fonn of active boron dilution cu be used based on RB mix 9d-mean to sump boronometer measurements, RCS saturation temperature from the average of the core exit thermocouples, and time post LOCA. The preferred dilution method is via APS, because this method does not require an LPl pump to be shutdown. The guidance is 59
or/sa m - ma3 osioi is so4 ::: sui ira:ato:o Technutonin coot Framatoma Tcchnologics Inc. 86-1266272-01 comprehensive in that it provides information for use with and without sump boronometer indications. In the event that the boronometer is unavailable, time and saturation temperature can be used to initiate activo boron dilution methods. t 9 60 E
U.S. Nuclear Regulatory Commission Attachment C 3F029812 Page1 of1 ATTACHMENT C l ACRONYMS AND ABBREVIATIONS l l APS . . . . . . . Auxiliary Pressurizer Spray (mitigation method) IlWST . . . . . . llorated Water Storage Tank CFT . . . . . . . Core Flood Tank CR 3 . . . . . . . Crystal River 3 DL RH Sump . . Drop Line to Reactor fluilding Sump (mitigation method) ECCS , . . . . . Emergency Core Cooling Sys:em ES . . . . . . . . Engineered Safeguards FPC . . . . . . . Florida Power Corporation Fri . . . . . . . . Framatome Technologies Incorporated j llL1 RF . . . . . Ilot leg injection via Reverse Flow (mitigation method) - LAR , . . . . . . License Amendment Request LOCA . . . . , less of Coolant Accident LPI . . . . . . . . law Pressure Injection system MCC . . . . . . Motor Control Center NRC . . . . . . . U.S. Nuclear Regulatory Commission RB . . . . . . , Reactor fluilding RCS . . . . . . Reactor Coolant System TSC . . . . . . . Technical Support Center}}