ML20210T942

B Dilution by Hot Leg Injection

ML20210T942
Person / Time
Site:	Crystal River
Issue date:	08/29/1997
From:	Carlton J, Wissinger G FRAMATOME
To:
Shared Package
ML20210T939	List: 3F0997-28, Responds to Restart Issue Identified in Integrated Performance Assessment Process Final Assessment Rept 50-302/96-201 Re Boron Precipitation Following Design Basis LOCA ML20210T942
References
51-5000519, 51-5000519-00, NUDOCS 9709160185
Download: ML20210T942 (88)

Text

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FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3 DOCKET NUMBER 50-302/ LICENSE NUMBER DPR-72 3F0997-28 ATTACIIMENT H FTI DOCUMENT 51-5000519-00

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80440-7 (13/95)

- [ Nd.Oo^iT ,g,y ENGINEERING INFORMATION RECORD Document identifier 51 5000519 00

Title _ BORON DILUTION BY HOT LEG INJECTION PREPARED BY

,

REVIEWED BY:

Name 4 D. CARLTON Name ^G J. WISSINGER ,,

Signature Date _8/29/97 Signature , y .

DagQ29/97 Technical Man r Statoment: Initials M s i Reviewer is Independent.

Remarks:

THE ATTACHED DOCUMENT DESCRIBES THE ECCS REQUIREMENTS FOR MANAGEM

. CONCENTRATION POST LOCAS. HOT LEG INJECTION BY REVERSE FLOW THROU LINE IS EVALUATED AS ARE DUMP TO. SUMP AND NOZZLE GAP LEAKAGE.

PLEASE SEE ATTACHED DOCUMENT, Page 1A of I W W

/A! C) u i W 4 PAM ]$

51-5000519-00 BORON DILUTION BY RCS HOT LEG INJECTION PREPARED FOR FLORIDA POWER CORPORATION BY FRAMATOME TECHNOLOGIES INC, AUGUST 1997 l

l

51-5000519-00 TABLE OF CONTENTS 1,

1 N T R O D U C TI O N , , , , , , , , , , . . . . . . . . . . . . . . . . . . . . . . . . . . . , , , , , , , , , , , , , , , , , ,

2.

L

SUMMARY

...............................................................................................5 3.

l ECCS REQUIREMENTS FOR BORON DILUTION,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,8 4,

BORON CONCENTRATION CHARACTERISTICS ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,16 4.1 LeLOCA.......................................................................................17l 4.2 SBLOCA.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,................................................,,,,,18 1

- 5* l B OR ON DIL U TION - M E TH O DS ,, s. ... ... . ... ............,,,,,,,,,,,,,,,,,,,,,,,,,,,, e ,,,,, 23 4 1

5.1 D ump t o S um p , . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5,2 H o t L e g inje c t io n . . . . . . . . . . . , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,i , , , , , , ,

5,3 N ozz l e G a p s , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

5,4 _ Auxillary Spray to the Pressurizer,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 27

. 6, REACTOR VESSEL FLOW PATHf f *)R HOT LEG INJECTION,,,,,,,,,,29 7,

CONCLUSIONS,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,31 8,

M AJ O R A S S U M P TI O N S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.

REFERENCES,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,35 APPENDICES

1. HOT LEG INJECTION DILUTION CAL CULATIONS 2,-- REACTOR VESSEL HOT LEG INJECTION FLOW EVALUATIONS 2

c

51-5000519 00 List of Tables 1 Boron Solubility Limit I

2.

Caso 1: Spread Sheet for Determining the Sump Concentration Difference Allowed Versus RCS Tomporature 3.

Case 2: Spread Sheet for Determining the Sump Concentration Difference Allowed Versus RCS Temperature.

4.

LBLOCA Coro Boron Cuncontration for Dilution By Hot Leg injection: 400 GPM Not Hot Leg injection Flow 5.

LBLOCA Cere Boron Concentration for Dilution By Hot Leg injection: 100 GPM Not Hot Leg injection Flow 6.

SBLOCA Coro Boron Concentration for Dilution By Hot Leg injection: 400 GPM Net Hot tog injection Flow 7.

SBLOCA Core Boron Concentration for Dilution By Hot Leg injection: 100 GPM Net Hot Leg injection Flow 3

51 5000519 00 LIST OF FIGURES

1. LBLOCA Core Boron Concentration Versus Time

2. Reactor Vessel Artengement

3. RV Upper Plenum Mixture Levels

4. Case 1: BWST to Sump Concentration Difference Versus RCS Temperature i

5. Case 2: nWST to Sump Concentration Difference Versus RCS Temperature

6. LBLOCA Core Boron Dilution With Dump To Sump

7. Required Dump to Sump Flow versus Operator Action Timo

8. LBLOCA Core Boron Dilution With Hot Leg injection

9. SBLOCA Core Boron Dilution With Hot Leg injection

10. SBLOCA Core Boron Dilution With Hot leg injection

11. Hot Log Injection Flow Paths in the Reactor Vessel

12. Hot Leg injection Flow Paths in The ReactorVess91'rtor Reverse Core Flow 4

51-5000519 00

1. INTRODUCTION This document provides Florida Power Corporation (FPC)Information, evaluations and '

calculations to support emergency core cooling system (ECCS) ind reactor coolant system (RCS) hot leg injection flow for post loss of coolant accident (LOCA) boron control. Specifically, it: 1) places information supplied to FPC in July 1997 in a formal Framatome Technologies (FTI) format,2) provides information about boron concentration changes in the reactor building sump and the core with time as a function i

l of core bolling,3) provides information about the change in boron concentrations in i the core and sump after hot leg injection is initiated, 4) provides an evaluation of the hot leg injection water flow paths in the reactor vessel, and 5) evaluates possible log for actuation of Crystal River Unit 3's boron precipitation mitigation system (s).

Several sections of this report document the background information regarding ECCS flow rates required to either control or reduce core boron concentrations, provide boron concentration and solubility data for identification of steps to mitigate boron buildup, evaluate the hot leg injection natural circulation flow paths in the reactor vessel, and evaluate the auxillary spray as a potential boron concentration reduction method.

2.

SUMMARY

Evaluations of core and sump boron concentrations have been performed for both large- and small-break LOCAs. Under the most conservative assumptions [ ANSI 1971 Decay heat with 1.2 multiplier and the B&W heavy isotopes, no reactor vessel vent valve (RWV) liquid overflow or entrainment, no hot leg nozzle gap flow, and bounding 5

1 51-5000519-00 borated water storage tank (BWST), core flood tank (CFT), a3J reactor coo i

(RCS) boron concentrations), core boron concentrations could approach the limit within about 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post LBLOCA. The limiting SBLOCAs remain at elevated RCS temperatures and pressures, and hcyo higher boron solubility limits that pro i

additional time to detect the core concentration buildup and inillate the active dilution i

mechanisms. In either caso, the coro concentration cannot reach the solubility limit until after the BWST has emptied. While on sump recirculation, the core concentration

> buildup can be derived from periodic monitoring of the sump boron concentration. The simplest indication is the relationship of the difference between the initial BWST boron concentration and the current sump concentration versus RCS temperature. This method implicitly considers the solubility limit versus temperature and any passive dilution mechanism, such as RWV liquid overflow or entrainment, recirculation of the coro liquid directly out of the break, hot leg nozzle gap flow, and boron carryover in steam. If the difference between the initial BWST and sump concentration begins to grow, then the boron must be concentrating somewhere, most likely in the core. The maximum concentration difference, considering measurement uncertainties, can be used to indicate the conditions under which an active boron dilution mechan needed. By monitoring the sump concentrations, the operators will not have to perform u inecessary actions to terminate one train of low pressure injection (LPI) and realign the remaining ECCS flow paths.

If the post LOCA sump concentration reveals than an active boron dilution process is needed, then either hot leg injection or dump to-sump can be initiated by the operator as indicated in procedures to reduce and control the core boron concentration to well 6

S1-S000519-00 below the solubility limits. LBLOCAs have the smallest allowed sump concentration change that occurs over the shor'est post LOCA time interval (4 to 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />), if this interval is insufficient to monitor the sump concentration, then the operator must in the active method based on the time post LOCA. The same is true if the instrument uncertainty (sump boron concentration and RCS temperature measurement 1

uncerte~inties) does not provide an acceptable operating range and no other valid indicator of core boron buildup can be obtained. For SBLOCAs that remain at elev pressures and temperatures, additional time is available to monitor the sump concentration, and the cporational concentradon margin is larger. The EOPs must be structured to include aopropriate operator action times to bound any size LOCA with bounding operationallimits that consider instrument uncertainty during post-LOCA conditions.

FTl cobulations have shown that dump to sump or hot leg injenion is successful in rapidly reducing the core boron concentreuons. Any dump to sump flow in excess of approximately 10 gpm is adequate for controlling the core concentration once it is initiated, however, the initiation of dump-to-sump flow must not be performed at RC conditions that could compromiso the integrity of the sump screens. If the dump-to sump method cannot be used without possible damage to the sump screens, then hot leg injection by reverse flow through the decay heat drop line Et 500 gpm should be useo. IX, method also offers a positive and rapid means for reducing and contro core boron concentration buildup. In addition to protecting the sump screens, the ho leg injection can be established at higher RCS pressures and temperatures covering the SBLOCAs that hold up in pressures that could not use dump to sum 7

51-5000519-00 Hot leg injection could adversely effect the ability of the hot leg nozzle gaps to provide core boron dilution by reducing the concentrated boron flow through primarily one nozzle and possibly introducing debris entrained in the ECCS fluid at a different location. If the procedures that instruct the operator to initiate the hot leg injection are based on sump concentration change, then the hot leg nozzle gaps are not working effectively. In this case, hat leg injection is needed to provide boron dilution, and any adverse effect on gap how is inconsequential. Based on these considerations, the '

q activation for hot leg injection should be based only on indicated concentration, and not as a routine action, 1

I 3.

ECCS REQUIREMENTS FOR BORON DILUTION FTl has performed numerous analyses and provided licensing support for CR-3 and 'I the other B&W Owners to demonstrate adequate baron dilution following a postulated cold  ;

leg pump discharge (CLPD) loss of coolant accident (LOCA) (References 1 and 2).

During March of this year, a summary was sent to the NRC to report the latest set of generic analyses for small and large LOCAs (Reference 1). The largest LOCAs quickl depressurize and reach an equilibrium with the containment pressure within 20 to 25 seconds. These postulated break sizes in the CLPD pipe have the lowest long-term saturation temperatures and correspondingly the lowest boron solubility limit that could be achieved within 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post LOCA without credit taken for reactor vessel vent valve (RWV) liquid entrainment or hot leg nozzle gap flow. The NRC has been unwilling to allow credit for the hot leg nozzle gap flow dilution except as a backup to active dilution methods. Credit for RVWIIquid entrainment can be taken for the larges 8

51-5000519-00 LOCAs, but as the break size decreases, so does the liquid entrainment. Therefore, the LBLOCA analyses did not credit the RWV entrainment to bound the spectrum of possible break sizes. This conservative approach defined the minimum time for operator initiation of n active boron dilution mechanism at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post-LBLOCA. For the larger break size r in which the .eactor coolant system (RCS) and containment pressura are in near equlkbrium, the dump to-sump method through the decay heat drop line can be used without concern for sump screen integrity. Therefore, no ECCS flow is required for boron concentration control This is not the case for the smaller LOCAs with elevated RCS pressures.

1 ,

SBLOCA analyses performed for the boron dilution task identified that smaller break sizes (located on the bottom of tne CLPD ; ping) would result in a long-term RCS pressure holdup related to a quasi-steady balance achieved between the pumped emergency core cooling system (ECCS) flow and the break flow. The ECCS flow would enter the downcomer and condense the steam passing through the RWVs. The ECCS inflow rate would exceed the core boiloff rate with the excess ECCS flowing out of the break once the reactor vesselis refilled to the break elevation. Breaks of suffici can discharge all the excess ECCS not needed to match the core bolloff such that the system cannot refill any further. If the downcomer level cannot increase above the bothm of the CLPD nozzle elevation, RVW liquid overflow cannot occur because of the manometric balances established in the reactor vessel. Without RWV liquid overflow, core boiling removes the core decay heat with the RVW steam flow acting as the necessary energy transport mechanism to the break location. This boiling to remove decay heat concentrates the boron in the core and upper plenum region.

9

51-5000519-00 Although calculations showed that the hot leg nozzle gaps would be open and pass sufficient liquid flow to adequately dilute the core boron concentration post-LOCA, the NRC is unwilling to accept this gap flow except as a backup to an active dilution method that may be lost through a single active failure of the decay heat drop line valves or power supply.

Without credit for the hot leg nozzle gap dilution flow, the core boiling has the potentia to concentrate all the boron in the BWST, RCS, and CFT in the core region.

Comparison of the boric acid solubility in water with the total mass of boron available to the system, shows that the boron would not precipitate at saturation temperatures l

above 305'F (72 psla). Therefore, to preclude the possibility of boron precipitation, some active ollution method must be initiated prior to reaching these conditions, l Specifically, an active method may be initiated when the RCS is at approximately 100 psla (328 F) or a higher pressure consistent with the design conditions of the system selected for baron concentration control. A temperaturd of 328'F (100 psia )is above the design temperature (300*F) for the decay heat removal system (Reference 10), a operating the decay heat drop line with flow from the hot leg above 300 F will require further evaluation.

Another active dilution method may be available at CR-3 without significant hardware modification. This method uses one operating LPI pump in an alignment in which the LPI provides suction to one-high pressure injection (HPI) pump, ECCS injection th the CFT nozzle in the piping run of the operating LPI pump, and backflow through the LPI cross-connect line backward through the other idle LPI pump into the RCS hot 10

51-5000519 00 This alignment reverses the typical flow direction in the decay heat dropline. Since the LPI fluid that is injected in the hot leg has passed through the decay heat cooler and is cooled to about 140'F (Reference 10 ), there is no problem related to the design temperature in the decay heat drop line.

i To validate this boron dilution method, the hot leg injection alignment needs a definition of acceptable ECCS flow splits both for core cooling and boron dilution. At an RCS pressure of 72 psla, the LPI pump should be capable of providing at least 2700 gpm of flow (Reference 10), if a maximum flow of 600 gpm (Reference 11) is assumed for one HPl pump, the remaining 2100 gpm is split between the LPI nozzle and the hot leg injection path with allowances also made for instrument uncertainty and nozzle gap flow (also refer to Section 9, Assumptions).

The CR-3 total hot leg gap flow at isothermal conditions at 300*F post-SBLOCA is 14.1 lbcn/s or 103 gpm of ECCS liquid at 140 F. (Reference 1, Table 7A). Only one nozzle gap would pass the hat leg injection flow, so only one-half, or 51.5 gpm of gap flow should be considered. For a LBLOCA. one-half of the non-isothermal steam-cooldown is 22.5 lbm/s or 164 gpm ( Reference 1, figure SA).

The ECCS injection rates needed to match the 1.2 ANS 1971 decay heat boiloff rate and to totally suppress core boiling at 75 psia and 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />,24 hours, and 1 week post LOCA are as determined in the calculations below. (The five (5) hour time is the approximate time that the boron solubi'ity limit is reached for a LBLOCA assuming the

' core boiling rate corresponds to the conservative decay heat assumptions). The 11.

9-

51-5000519 00 necessary ECCS flow throughputs for more realistic decay heat levels are also calculated. i At 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, the decay heat is:

0.01131 (Reference 8)

• 2568

• 1.02

• 948 = 28,084 Blu/sec At 100 psia with an ECCS inlet temperature of 140*F, the ECCS flow needed to match core boitoff is:

W = (28,084)/(1187 - 108) = 26.0 lbm/sec = 190 gal / min Bulk core boiling could be suppressed with an LPI flow of:

W = (28,084)/(298 - 108) = 147.8 lbm/sec = 1081 gal / min At 75 psia with an ECCS inlet temperature of 140*F, the ECCS flow needed to match core boitoff is W = (28,084)/(1182 - 108) = 26.1 lbm/sec = 191 gal / min Bulk core boiling could be suppressed with an LPI flow of:

W = (28,084)/(278 - 108) = 165.2 lbm/sec = 1208 gal / min 4

At 14.7 psia with an ECCS inlet temperature of 140*F, the ECCS flow needed to match core boiloff is:

W = (28,084)/(1151 - 108) = 26.9 lbm/sec = 197 gal / min Bulk core boiling could be suppressed with an LPI flow of :

W = (28,084)/(181 - 108) = 384.7 lbm/sec = 2812 gal / min 4

12

51-5000519 00  :

At 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the decay hea is:

0.00703 (Reference 8)

• 2568

• 1.02

• 948 = 17,457 Btu /sec At 75 psia with an ECCS inlet temperature of 140* F, the ECCS flow needed to mat core bolloff is:

W = (17,457)/(1182 - 108) = 16.3 lbm/sec = 119 gal / min Bulk core boiling could be suppressed with an LPI flow of:

W = (17,457)/(278 - 108) = 102.7 lbm/sec = 751 gal / min At 14.7 psia with an ECCS inlet temperature of 140' F, the ECCS flow needed to ma core' bolloff is:

W = (17,457)/(1151 - 108) = 16.7 lbm/sec = 122 gal / min Bulk core boiling could be suppressed with an LPI flow of:

o W = (17,457)/(181 - 108) = 239.1 lbm/sec = 1748 gal / min At 1 week, the decay heat is:

0.00384 (Reference 8)

• 2568

• 1.02

• 948 = 9535 Blu/sec At 75 psia with an ECCS inlet temperature of 140 F, the ECCS flow needed to match core boiloff is:

W = (9535)/(1182 - 108) = 8.88 lbm/sec = 65 gal / min Bulk core boiling could be suppressed with an LPI flow of:.

13

51-5000519-00 W = (9535)/(278 - 108) = 56.1 lbm/sec = 410 gal / min l' At 14.7 psia with an ECCS inlet temperature of 140' F, the ECCS flow needed to ma core bolloff is W = (9535)/(1151 - 108) = 9.14 lbm/sec = 67 gal / min Bulk core boiling could be suppressed with an LPI flow of:

W = (9535)/(181 - 108) = 130.6 lbm/sec = 955 gal / min The ECCS injection rates needed to match the 1.2 ANS 1971 decay heat boiloff rate 75 psia and 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />,24 hours, and 1 week post-LOCA were calculated to be: 191 119 gpm, and 65 gpm, respectively. The calculations also show that core boiling coul be totally suppressed with core ECCS throughputs of 1208 gpm,751 gpm, and 410 gpm at 75 psia and 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />,24 hours, and 1 week, respectively. Using more realistic decay heat levels (0.75 times the 1.2 ANS 1971 fission product decay plus B&W h isotopes), the core boiling could be suppressed with ECCS throughputs of 75% of the 906,563, and 308 gpm flow rates, respectively. Suppression of core boiling eliminates the mechanism that concentrates the boron, thereby addressing the boron concentration control for the duration of the transient.

Based on these required flows, the hot leg injection flow must be 191 gpm plus 52 gp or approximately 250 gpm at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post-LOCA at 72 psia RCS pressure to match decay heat and gap flow through one nozzle. Additional flow, however, is needed to initiate a reverse core flow sufficiently large to totally suppress core boiling and to provide boron dilution. As noted above, a flow rate of 2812 gpm (at 14.7 psia and 5 14

51-5000519-00 hours post trip) is required to completely suppress core boiling. (Excess flow above 2812 gpm at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> is required to assure that flow is sufficient to cover potential nozzle gap by-pass). FTl believes that a hot leg flow with a 250 gpm excess above the decay heat and gap flow is adequate for core boron dilution with or without an operato assisted RCS cooldown. That is, a total hot leg injection flow of 500 gpm is adequate to provide boron dilution from 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post SBLOCA and beyond. If this were a LBLOCA,197 gpm (see above) is needed for core boiloff makeup at 14.7 psia and a maximum single gap flow of 27.25 lbm/s or 199 gpm (estimated CR-3 gap at 14.7 psia with Taw = 212*F and Tav = 400*F at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post-LOCA RV cooldown in steam)

(Reference 2) is needed.

{

1 in this LBLOCA case, tne recommended 500 gpm hot leg injection flow still exceeds the 197 gpm plus 199 gpm or approximately 400 gpm needed for boiloff makeup and g flow considerations, This example only has 100 gpm excess flow for boron dilution.

The excess willincrease with time as the decay heat boiloff and gap size and flow decrease. At 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the boiloff is 122 gpm (see above) and the gap flow is extrapolated from the nozzle gap data of Reference 1 to be less than 100 gpm. The excess hot leg flow at this time will be greater than 250 gpm. For LBLOCA the excess ECCS can be smaller, since the boron concentration does not have to be reduced to compensate for possible solubility decreases due to subsequent RCS depressurization after 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Therefore, the recommended 500 gpm is adequate for LBLOCA concentration control as well.

15

.a

51 5000519-00 With a minimum of 500 gpm of hot leg injection flovnd 600 gpm for HPI flow, approximately 1600 gpm of the 2700 gpm LPI pump flow is left for LPI nozzle flow and I

instrument uncertainty. Historically,1000 gpm per LPI nozzle has been assumed t the target value for securing the HPI pumps. When usinD the hot leg injection alignment, it is reasonable to target 1000 gpm for the one flowing LPI line, which lea 600 gpm of real pump flow for instrument uncertainty or flow imbalance at! 75 psi Below 75 psla, the pump flow will increase and additional flow may be available to the hot leg injection path, such that, once initiated, the flow may be adequate to su core boiling with best-estimate or realistic decay heat levels.

In summary, FTl recommends that the hot leg injection alignment provide flow for on HPl pump, a minimum reverse flow of at least 500 gpm through the decay heat line for boren dilution, and approximately 1000 gpm into one CFT nozzle, if possibl ,

the hot leg injection flow should be increased from a minimum of 500 gpm to rou I

900 gpm. This flow rate is capable of both suppressing core boiling and removin i core boron concentration mechanism when realistic decay heat contributions are considered.

4.

BORON CONCENTRATION CHARACTERISTICS

- Boron concentration effects have been reported by FTl for the B&WOG Boron Dilu project in Reference 1. Calculation of the boron concentration and dilution were k

. performed for the B&WOG plants, including CR-3. The cases of interest for CR-3~

2 include the LBLOCA ( break size > than 0.5 Ft ) and the Cold Leg Pump Dis (CLPD) SBLOCA of 0.05 Ft' area. The following sections describe the boron 16

51-5000519-00 concentrating and dilution processes for the large and small break LOCAs and discuss the several methods for dilution of core boron concentrations.

4,1 LBLOCA ,

The characteristic blowdown for the LBLOCA is rapid, and equilibrium between the RCS and the reactor building pressures can be expected to occur within about 30 seconds. The LBLOCA is ofinterest to deboration methods, because the LRLOCA thermal conditions offer early and vigorous core boiling such that the boron solu limit is rapidly approached. Avoidance of boron precipitation in the core requires

prompt recognition of the conditions and timely corrective measures.

I The saturation temperature and pressure for the LBLOCA will rapidly approach atmospheric conditions (212 'F /14.7 psia). The solubility of boron in reactor water is a function of the water temperature, and rat 212*F (saturated) the limiting solubility about 50,300 ppm boron. Table 1 gives boron solubility versus temperature (Reference 1). The core and sump boron concentrations with time for the LBLOCA assuming no dump-to-sump, hot leg injection or opening of nozzle gaps, is shown on Figure 1. The core boron concentration reaches the solubility limit at just over 5 hou post LOCA.

If boron is concentrating in the core region, the sump boron concentration for the LBLOCA will change about 600 ppm over the first five (5) hours post -LOCA.

Boronometer measurements along with reactor and reactor building pressure, incor temperature measurements and RCS temperature measurements, can form the basis 17

r 51-5000519-00 for actuation of dump to-sump, hot leg injection or auxillary spray methods of core boron dilution.

4.2 SBLOCA-A SBLOCA transient results in a rapid subcooleo primary system depressurization'until the hottest regions in the RCS saturate. Hot leg flashing causes steam to accumulate i in the top of the hot leg U-bends, which interrupts the loop natural circulation flows. The loss of RCS flow reduces the core inlet subcooling and intensifies the core boiling due

'to the decay heat generation in the fuel pins. The steam produced from flashing and bsiling accumulates in the upper portions of the reactor vessel, as shown in Figures and 3. The reactor vessel inventory quickly approaches a quasi-steady condition

-shown in Figure 3 in which the mixture level inside the plenum cylinder is slightly above-

. the bottom of the large holes in the upper plenum cylinder. The steam and liquid that flows through these holes separates in the outlet annulus region. The liquid flows downward and returns to the inside of the plenum cylinder through the small holes -

_ found opposite the two hot leg nozzles. The separated steam flows up and out of the RWVs to be condensed on the ECCS flows or lost out of the break. The downcome level remains near the bottom of the cold leg inlet nozzle. _The outlet annulus level remains below the RWV spillover elevation such that no liquid flows through the RWVs. Without liquid circuiration through the core region, the core boiling continues to -

l concentrate the boric acid contained in the initial RCS fluid or injected by ECCS flows .

There is some limited boron solubility in the steam (i.e., boron carryout with the RVW u

steam flow) but the rate of outflow is much less than the boiling production rate, thus i causing the concentration to increase.

18 i

51-5000519 00 l The break size and location dictates the rate of RCS pressure decline and ultimatel the maximum core boron concentration increase. A larger SBLOCA located on the bottom of the CLPD pipe at the elevation of the reactor vesselinlet nozzles will rapidly depressurize the RCS activating CFT and LPl flows. The break size is sufficient to discharge all the excess ECCS flow not needed to replace the liquid boiled by decay heat or lost by flashing during RCS depressurization and cooling to ambient conditions (14.7 psia). This loss of ECCS out of the break limits the downcomer level to slightly above the bottom of the cold leg pipe. This downcomer level produces an elevation head that supports a core and upper plenum mixture level (liquid and bubbles) that reaches the elevation of the large flow holes in the plenum cylinder. If the downcomer level could be increased significantly above the bottom of the cold leg pipe, there is a much better likelihood that some RWV liquid spillover would be predicted. This would be the case for a cold leg pump suction (CLPS) or a cold leg pump discharge (CLPD) break at an elevation above the cold leg nozzle centerline or the core flood tank (CF line break. The excess ECCS would refill the downcomer to a higher level which would allow RVW spillover and liquid recirculation out of the core region. The recirculation would begin to dilute the growth of the boron concentrations which had built up earlier in the transient. Similarly, a break in the hot leg pipe would allow the system to refill until liquid is discharged out the break. This break location would also allow core liquid circulation to restrict the maximum core concentration increase.

. From the previous discussions, it is concluded that a break on the bottom of the CLPD pipe will restrict the downcomer level to a maximum value such that the manometric 19

1 51-5000519-00 balances in the B&W-designed reactor vessel and RCS will not support re-i establishment of RWV overflow. This inventory distribution will tend to remain relatively constant for a very long time without operator intervention. The system will gradually depressurize as core decay heat drops. As long as the break can compensate for the core decay heat decrease by discharging the excess ECCS not boiled in the core and the core steam that is not condensed on the sub-cooled ECCS injection the system will remain in this state. This configuration can lead to extended J

periods of core boiling in which the core boron concentration will increase until a dilution mechanism is implemented.

For SBLOCAs that remain at RCS temperature above 305 F (72 psia), the solubility of boron in RCS water is such that all the boron in the system can be in the core water solution (up to 156751 ppm) and not precipitate. An indicator that the nozzle gaps or other core boron dilution means are not effective would be an indication of sump concentration of about zero ppm, or a BWST initial concentration to sump concentration difference of about 3000 ppm.

RCS cooling and pressure decline for small break LOCAs are determined by the size and location of the break. They also determine the path the must be established to vent the core steam from the system. The smaller small breaks are expected to refill and natural circulation will prevent core boiling so that boron concentration is not a concern.

2 Larger small breaks (<0.5 ft ) can remain in a core boiling mode for significant periods.

Those breaks that tend to remain at pressures greater than the cut in pressure for the LPI system are not likely to cool until the operator takes action (possibly1ith non-20

51-5000519-00 safety equipment) to depressurize and cool the RCS. It is these breaks that may require a means to control core boron concentration prior to cooldown.

1 As the system depressurizes and the core decay heat declines, the ECCS inflow will-increase and provide a mechanism for system refill. The refill will not occur if the break.

~

is large enough because it will compensate by discharging any core steam not condensed by the ECCS injection plus the excess ECCS and condensate not needed to makeup for the core boil off rate lf this is the case, then the system will remain in this stable vesselinventory configuration for extended periods of time. The core heat is adequately removed by saturated pool boiling which continues to concentrate boron in i

- the core until a liquid flow dilution mechanism is achieved.

i

{

System refill may be accomplished for tiny breaks where the HPI system flow can exceed the break discharge at higher RCS pressures, or cnce LPI flow is established at lower pressures. RWV liquid overflow may be established by system refill. (The refill Lcould be augmented by certain operator actions to depressurize the RCS. These actions to depressurize and cool the RCS may use non-safety grade equipment.) If1

- RWV liquid overflow cannot be established, the hot leg nozzle gaps can provide a reliable, passive core boron dilution floiv that is very effective at low RCS u press' res and temperatures.

2 The 0.05_ ft case represents the break size that does not depressurize rapidly and tends to " hang up" at or near the LPI injection pressure. The RCS leak flow rate from this break is maintained by one LPl pump for a relatively long period of time. Core 21

(-

51-5000519-00 t

l boiling and boron concentration persist for this SBl.OCA for a significant period: the RCS pressure is about 150 psia at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

The following paragraphs describe the concentrating effects of this SBLOCA. Two cases, both of 0.05 Ft' break area, were analyzed with different initial BWST, CFT j

i and RCS boron concentrations to evaluate the change in sump boron concentration, 1

and the core boron inventory and the solubility of the core boron inventory. These cases are developed to show the " delta" boron concentration and the boron solubility a limit as a function of temperature. The cases are:

Case 1 Case 2 BWST 3000 ppm 2270 ppm CFT 3500 ppm 2270 ppm RCS 3000 ppm 2270 ppm Tables 2 and 3 provide data to develop the delta function. The delta function relates the initial BWST boron concentration minus the sump concentration to the boron that is in the core and the solubility of the core boron. It is assumed that the boron not in the sump is concentrating in the core. The " delta" function is the difference in the initial BWST concentration and the sump concentration versus the solubility limit at RCS saturation temperature. The tabular data contain: the core liquid inventory, the core boron inventory, the sump liquid mass, the sump and downcomer boron inventory, and the BWST to sump concentration difference.

Figures 4 and 5 are plots of the delta function based on a core volume of 790 ft' for both cases. The plots almost overlay each other indicating that the " delta" function is a 22

51-5000519-00 stable characteristic and can be used to estimate core boron concentration. The tabular data indicate that the initial BWST concentration to sump difference at a solubility temperature of 212'F is about 600 ppm. This suggests that the " delta" plots I

can be used to evaluate the need to actuate dilution methods for the LBLOCAs.

Although the tables and plots are based on the smaller core volume for LBLOCAs, the data also show that the " delta" for higher temperatures are large, about 1800 to 2000 ppm, as expected for SBLOCAs (such as 300 F or greater). It is concluded from this data that the " delta" function is a viable means to evaluate the core boron concentration for LOCAs.

5. BORON DILUTION METHODS 5.1 Dump-To-Sump The dump to sump method of dilution of core born is an effective solution, provided the CR-3 sump screen issue can be resolved and/or for LBLOCAs that the LBLOCA reactor building pressure and the RCS pressure can be identified as equal or near equal so that b,

.down through the dump to sump line will not damage the sump screen. A dump-to-sump deboration for the CLPD LBLOCA is shown on Figure In 6.

this case, a 7.8 gpm dump to sump was initiated at 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The core boron concentration just reached the solubility limit from about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> until 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> and began a steady decrease thereafter. Earlier actuation of the dump to sump would have allowed the core boron concentration to decrease earlier. The amount of dump-to sump flow required for various times of actuation this dilution method is shown in Figure 7 (from 23

51-5000519 00 Reference 1). For example, a dump-sump-flow rate of 10 gpm allows a delay of abou 5.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> post event to actuate the system.

5.2 Hot leg injection RCS " Hot leg injection" provides an effective means of diluting core boron concentrations by aligning one decay heat (or LPI) pump to pump to the reactor vessel CFT nozzle as well as to pump flow backward through the other LPI pump to the heat pump. An evaluation using methods similar to the spreadsheet methods used in Reference 1 (see Appendix A) has been used to estimate the change in core an boron concentrations after the hot leg injection is initiated.

The major assumptions associated with hot leg injection are:

i .

The Decay Heat Removal /LPI system equipment is accessible for alignment so that water can be injected in reverse flow through the decay heat dropline to the nozzle on the RCS hot leg piping.

The Hot leg injection flow is 500 GPM at 140 'F.

The LPIinjection flow to the reactor vessel (CFT) is 1000 gpm at 140 F.

Hot leg injection dilution of high concentration core boron has been evaluated for two cases as follows :

Case 1:

The first case is the CLPD LBLOCA. The core boron buildup for this case is also t,hown in Figure 1.

The saturation temperature for this case is assumed to be 212'F and the solubility limit at 212 F is about 50,300 ppm (Reference 1). The core 24

51-5000519 00 boron concentration approaches the saturation limit at just over 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Core boron dilution by hot leg injection is assumed to begin at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and the boron concentration reductions in the core and the boron buildup in the sump are shown on Figure o and Tables 4 and 5. It is assumed that some of the hot leg injection flow leaks through the nozzle gaps and is not available for core boron dilution. The core boron dilution rates given on Table 4 assume that 100 gpm injection flow is by-passed through the nozzle

(

gaps, leaving 400 gpm for core boron dilution. A net hot leg injection flow rate of 100 gpm (400 gpm by pass through the RV nozzle gaps) is also analyzed for this LBLOCA and reported in Table 5. The results of these cases indicate that the core boron i

, concentratiqn is rapidly reduced and approaches the sump boron concentration levels within about one-half hour after 400 net gpm hot leg injection was initiated. The lower net hot leg injection flow rate of 100 gpm also reduces the core boron concentration, but at a slower rate.

Case 2: The second case of hot leg injection core boron dilution was evaluated for the

" limiting" 0.05 Ft' CLPD SBLOCA. This SBLOCA case tends to remain at or above 72 psia /304'F for a significant period. The boron saturation limit is approached at just over 159 hours0.00184 days <br />0.0442 hours <br />2.628968e-4 weeks <br />6.04995e-5 months <br /> (Reference 1). Hot leg injection was assumed to be initiated at 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> post trip for this case when the core boron concentration was about 122,000 ppm. The core boron concentration reduction case was also analyzed with net hot leg injection flow rates of 400 gpm (100 gpm by-pass) and 100 gpm,400 gpm by pass.

The reduction in core boron concentration again was relatively rapid for the rapid 400 gpm net hot leg injection flow rate and slower for the net hot leg injection flow rate of 100 gpm (Figure 9). The boron concentration approached the initial concentration 25 J

51-5000519-00 within about an hour after net hot leg injection flow of 400 gpm was initiated. The core boron concentration di'ution rate with 100 gpm net hot leg injection was slower but steady requiring about 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to reduce the core boron concentration from 122,000 ppm to about 9000 ppm. These evaluations indicate that hot leg injection is a valid and efficient deboration methods.

5.3 Nozzle Gaps Hot leg to plenum cylinder nozzle gaps provide a passive means for dilution of core boron. Figure 10 shows the reduction in core boron concentration after the nozzle gaps are assumed to open.

The nominal nozzle gaps in CR-3's reactor vessel range from 0 inches up to 0.90

~

inches (Reference 1T ThICR-3 sump has % inch mesh wire screen to prevent large debris from entering the sump (Reference 9). The largest pieces of debris that could reach the sump is % inch square. The center line of the horizontally mounted suction nozzles for the LPllDHR pumps are located 1 Ft-9 inches (21 inches) above the bottom of the sump liner (Reference 9). The LPI pump suction nozzles in the sump are 16 inches in diameter (ID) (Reference 9). This gives a clearance of 13 inches (21 inches -

8 inches) between the bottom of the sump and the bottom of the LPl suction nozzle. It is unlikely that any particles % inch square or less in size; and heavier than water will reach the suction of the LPI pumps. Any material % inch square of less that reaches the suction cf the LPI pumps floats or is of neutral buoyancy. Assuming floating particles of this size reach the RCS hot leg through the decay heat drop line, such i particles will float or be slowly swept by the hot leg injection stream to the react .

26

~ _ . _ _ _ _ _ _ . . - _ _ _ _ _ . . _ _ . _ _ . _ _ . . _ . _ _ . _ _ . _ __ _ _ _

i h

51-5000519 00 vessel and into the upper plenum. Particles of this size can be drawn into the nozzle -

gaps and potentially clog shem, i

! +

Calculations (Reference 1) have shown that the hot leg nozzle gaps will be open and I

provide sufficient dilution flow in the absence of debris collection in the gap itself.

Various studies were used to evaluate the variations on gap size and flow and its effect on the boron dilution mechanism, it was confirmed that a reduction of the - '

i smallest as built gap area by ninety percent (90%) during the long term cooling phase l '

does not preclude gap flow from providing adequate core boron dilution. The gap flow i

[ mechanism was also shown to provide adequate flow for a small range of non-isothermal temperatures. The shell temperature can be up to 25'F cooler th'an the RV internals without totally closing the gap and inhibiting the dilution flow, i

E 5.4 . Auxiliary Spray to the Pressurizer -

Auxiliary Spray (by the decay heat or LPI pumps) is a possible means to achieve hot L

leg injection (about 40 gpm) for boron dilution in the longer term _(about 46 days post-event). A minimum time for operator action to initiate an active baron dilution flow path is identified in Reference 1. The decay heat drop line method (dump-to-sump) for roost of the B&W-designed plants is not single failure proof until after the decay heat drops 4

]- below the value where 40 gpm (assumed flow rate) of pressurizer auxilicry spray can

{ offset the core decay heat and initiate a reverse flow through the core. This limited auxiliary spray flow rate will be successful at matching the core decay heat at very long i.

times after reactor shutdown. If the core power exceeds the auxiliary spray absorption, 4- it will be totally boiled away leaving th be oron that was injected with this flow, thereby 27

51 5000519 00 contributing to the core concentration increase at a rate similar to that obtained via the core inlet ECCS flow.

The maximum core power that 40 gpm can absorb for an initia! power level of 2565 MWt at an inlet erdhalpy of 108 Btullbm is:

P/P o me um = (5017 Btu /s)/[(1,02)*(25GB MWt)*

(948 Btu /s/MWt)) = 0.00202 (about 0.2 % power) which occurs at 3,950,000 seconds (45.7 days)(Reference 8). These calculations define the match point at which all the pressurizer auxiliary spray is boiled off. There is a longer timo period required for the coro power to drop below this match point such that there is excess flow that can initiate a small reverse core flow sufficient to dilute 3 the core concentration.

Credit for reverse core flow initiated by the pressurizer auxiliary spray is not guarantcod even though the flow rate is sufficient to remove the core decay heat. The auxiliary spray enters the pressurizer, and flows into the hot log pipe. This flow must pass over the hot leg nozzle gap before it enters the upper plenum and reaches the core. If the hot leg nozzle gap is open, it will possibly pass some or all of this injection flow rate out of the hot leg nozzle gap. In most cases the flow from one hot leg nozzle gap may be sufficient to bypass nearly all of the flow that was intended to dilute the core boron concentration. In fact, the pressurizer auxiliary spray may hinder the boron dilution that was available prior to the initiation of the spray injection. For these reasons, the pressurizer auxiliary spray method should only be used in the long term 20

51-5000519-00 (about 46 days post event) on indication that coro boron dilution methods are n diluting the core boron concentration.

If tho .tump concentrations and or other measurements indicate that the reactor v nozzle gaps dilution flow is not working and the auxiliary spray flow is equal to or greater than the decay heat boil off of all of the pressurizer auxiliary spray then the auxiliary spray method may be effective in controlling the core bcron concentration.

6. REACTOR VESSEL FLOW PATHS FOR HOT LEG INJECTION Hot leg injection can be performed by reverse flow through the decay heat drop line described in Sections 2 and 3 above and also pctentially by the auxiliary spray. A net hot leg injection flow (injection flow minus nozzle gap leakage) into the reactor vessel upper plenurn can provide dilution of the boron by mixing with the boron rich upper plenum fluid. Reverse flow of boron rich fluid down through the core barrel-baffle region or cold fuel channels and up the downcomer and out of the reactor vessel as shown in Figure 11 will provido dilution of core boron. This is the dilution flow path when the hot leg injection flow is not large enough to overcome core boiling. Net reverse flow through the core as shown in Figure 12 is expected when hot leg injection flow is sufficiently large to exceed bciloff. The net reverse flow through the core controls the boron concentration by dilution of existing boron concentration, if any, at the time of core flow reversal.

The following discussion relates to the het leg injection /coron dilution flow path in the reactor vessel (Figure 11) prior to complete suppression of core boiling.

29

l 51-5000519-00 y- A sketch of the flow path of the het leg injoction by backflow through the decay heat dropline is shown in Figure 11. The decay heat dropline is connected to the RCS hot log pipe at an elevation slightly above (4.7 inches) the elevation of the bottom of the hot log pipe (Reference 3). (The hot leg injection no=le is located within the start of the bend of the hot leg 90

• elbow).

Do inner cylinder of the upper plenum assembly directly opposite the hot leg no=le has 24 - 3 inch ID flow holes in additica to the larger flow holes (6 34 inches ID and 4-22 inches ID) located in the upper parts of the plenum cylinder (Reference 3). From the small holes opposite the hot leg no=les, the het leg injection flows to the uppor plenum where it to mixes with core outlet steam and water. The saturated, boron rich injection fluid then flows down, by virtue of static head, to the top of the core where it enters the flow holes that direct flow into the region formed between the core barrel and the former plates. There are 24 flow holes spaced around the periphery of the upper core plate that provide the flow area for downflow of the injection fluid to the core barrel / baffle region. Within the core barrel / baffle region there are 8 former plates, each with 80 flow holes (Reference 6). From the barrel / baffle region the flow exits to the periphery of the lower core plato where there are 64 flow holes arranged around the periphery of the plate (Reference 4). From the lower core plate the fluid enters the lower sections of the reactor vessel and then flows up the downcomer to exit the reactor vessel by way of the affected cold leg. At 500 gpm the dynamic pressure drop through the flow path described above is about 5.4 inches of water as calculated in Appendix B. The head to provide this flow is developed by the injection fluid in the hot leg and the entrance to the upper plenum.

30

_ .._m._____.____.___.. . _ _ _ _ . _ _ . _ _ _ _ _ . _ _ _ _ _

4 5105000519 @ >

7.- CONCLUSIONS Evaluations of core and sump boron concentrations have been performed for LBLOCAs and SBLOCAs. Under the most conservative assumptions (ANSI 1971 Decay beat with 1.2 maittiplier and the B&W heavy Isotopes), boron corr.entrations can l reach the solubility limits within about 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> for LBLOCAs. An active mitigation process such as hot leg injection or dump-to-sump can reduce and control the boron -

concentratiorito well below the solubility limits.

if boron is concentrating in the core region, the sump boron concentration for the LBLOCA will change about 600 ppm over the first five (5) hours post -LOCA.

Boronometer measurements along with reactor and reactor building pressure, incore

] temperature measurements and RCS temperature measurements, can form the basis -

for actuation of dump-to sump, hot leg injection or auxiliary spray methods of core

[

boron dilution. -

a The limiting SBLOCAs, by virtue of longer (than LBLOCA) time at elevated RCS temperature and pressure have higher boron solubility limits and have more time e

available to detect concentration of boron in the core, For the SBLOCAs change,7 in sump boron concentration appear to be a valid indication of core boron buildup, The -

relationship of the difference between the initial BWST boron concentration and the .

sump concentration versus RCS temperature, subject, to measurement uncertainties, offers a valid core boron concentration indicator.

Hot leg injection by reverse flow through the decay heat drop line at 500 GPM offers a

- positive and rapid means for reducing and controlling core boron concentration buildup.

> The flow areas within the reactor vessel for the hot leg injection flow are sufficiently-M 4

, _ . ~ . _ .-. -

51 5000519-00 large to offer little resistance to the injection flow paths. Dump-to-sump is also a viable means to provide positive and rapid control of core boron concentration.

Hot leg nozzle gaps offer a passive means for post-LOCA core boron control. The performance of the r.czzle gaps for boron dilution can be inferred by indirect observations, such as long term changes in the sump concentration. Initial reliance on nozzle gap dilution control can be used for SBLOCAs because of the higher temperatures and the longer time required for core boron concentration to reach boron solubility limits.

32

51-5000519 B; MAJOR ASSUMPTIONS'

-The major assumptions used include:

• . -The BWST volume is 350000 gallons.

-The'BWST boron concentration is 3000 ppm This is the Improved Technical j Specification' (Reference 12) upper limit for BWST boron concentration. Larger values of boron concentration are used to determine conservative boron concentrations in the core.

• The RCS volume is 11500 ft',

- The RCS initial boron concentration is 3000 ppm.

The CFT volumes are 8005 gallons each (1070 Ft* each). This value is the maximum water inventory from the CR-3 Improved Technical Specifications (Reference 12).

The CFT boron concentration is 3500 ppm. (This is the CR 3 Improved Technical Specification (ITS) (Reference 12) upper limit for CFT boron -

concentration.-

The core volume for LBLOCA boron concentration is 790 Ft'. FTl will use this value for all cases unless requested to use the SBLOCA core volume. This is a relatively low core volume used to conservatively predict core baron concentrating rates during core bolling following'LOCAs.-

Boron solubility versus temperature is as given on Table 1 from page 81, table 10 of Reference 1.

The hot leg injection flow rate (reverse flow through the decay heat drop line) is assumed to be 500 GPM. !(This value is believed to be slightly conservative in -

that it provides a minimum of about 100 gpm net hot leg injection flow assuming '

33 --

l

51-S000519 00 the hot leg nozzle gaps are flowing up to about 400 gpm.

The injection flow to a core flood nozzle is assumed to be 1000 GPM. (This value is used as an indicator that the HPl injection pumps can be secured. This value is conservative because during a LOCA a significant amount of this flow can flow out the cold leg nozzle back to the sump. Decay heat removal is by core boiling. The HPl pump flow requirements for SBLOCAs are defined in Reference 11.)

The injection weter temperature to either the core flood nozzle or the hot leg is assumed to be 140 'F (from Reference 10).

The decay heat relationship is assumed to be 102% of 1.2 times ANS 1971 plus FTl heavy isotopes. This decay relationship is believed to be very conservative because of the long term operation assumptions and the heavy isotopes. FTl believes that a value of decay heat of 70 to 90 percent of this relationship is more correct.

Enthalpy, temperature and pressure relationships will be obtained from the 1967 or later ASME Steam Tables.

4 34

1 51 5000519-00  !

1

9. REFERENCES

(

! 1.

1 FTl 32-1266110 00:'B&WOG Post LOCA Core Boron Dilution

• 2.

t FTl 51 1266113 00:

• Post LOCA Boron Concentration Management'

3. FTl 51-1212232-01: " Key Elevations for All Plants" 4.

FTl (B&W) Drawing : 02142923E-04: ' Lower Grid Top Rib Section" i

S.

FTl (B&W) Drawing : 02142917E-04: ' Upper Grid Rib Section" G.

FTl 51-5000396 00: 'RVI Baffle Bolt Safety Assessment" 7.

Meyer, C.A., McClinteck, R B., Silvestri, G.J., and Spencer, R.C. Jr.;

" Thermodynamic and Transport Proporties of Steam", ASME,1967, i 8.

FTl 32-1258134-00: " Decay Heat for LOCA Anelysis" l 'O. Florida Power Corporation Drawing s 521-030: ~3eactor Building Sump, Liner, Screen and Covers Plan, Sections and Details".

• 10.

Florida Power Corporation, Nuclear Operations Engineering, Crystal River Unit 3, " Enhanced Design Basis Document, Decay Heat Removal"

11. FTl 51-1229115 03: "CR-3 HPI Flow Requirements"

• 12. Florida Power Corporation, C,ystal River Unit 3, improved Technical Specification B,3.5 Emergency Core Cooling Systems,- B.3.5.1 Core Flood Tanks (CFTs).

The documents marked with an asterisk are maintained and controlled by Florida Power Corporation. Per FTl procedures, use of the references are allowed in safety-grade calculations with the approval of the cognizant unit manager or contract manager. The signature below authorizes the use of these documents for input to this evaluation.

2 h h /) 0 r L(El C Y ff U$if Manager / Contract Manager Dafe 35

51-5000519-00 TABLE 1 BORON SOLUBill1Y LIMIT TEMPERATURE BORON SOLUBILITY LIMIT (F)

(PPM WATER) 68.0

. 1438 104.0

{

7363 140.0 16785 176.0 29592 212.0 50314 226.0 58467 242.0 l 72089 l

260.1 87930 277.3 108128 289.9 128548 304.7 156751 318.9 193721 326.1 >

231771 333.1 280489 36

- - - . . . - . - - - . ~ - - . - - . - - - . - . . - - - - - . - _ . - - . - _ -

m2 51 5000519 00 -

Spread Sheet for Determining the Sump Con;entration Difference Allowed Versus RCS Temperatu j inputs 1

DWST Concenttation 3000 ppm boron / water I

Core Mixing Volume CFT Concentration 3500 ppm boron / water 79dfft3 4

DC Uguld Volume RCS Concentration 3000 ppm bororVwater 1285 ft3 i

BWST Uguld Volume 350000 gal 4 RCS Uguld Vclume ' 11500 ft3 CFT Uquid Volume 2140 ft3 RCS Avera9e Uguld Density 41.bObm/ft3 i CFT Uquid Density 61.5 tom /ft3 BWST Uquid Density _62 4 lbm/ft3 i

Calculations Uquid Doron Mass Mass TotalMass Conwrvation (Ibm) (ibm)

DWST Initial Mass, Ibm 2919786 B759 RCS Initial Mass, Ibm 225283 max ppmin core at 14.7 psia 477250 1432 CFT Initial Mass, Ibm 47282 lbm core water et 14.7 psia '

131610 461 Totat Mass 10652 352B046 3019 average boron concentration. ppm RCS Saturated Core Sat Ccre Saturation Uquid Core Boron DC Sat Sump DC and DWST to Uguld Solubility Mass at Uquid Uquid Sump Sump Cone Temp Spec Vo! Mass Umit Sol umit Mass Mass F (ft3.1bm) (ppm) Concen Differenco (Ibm) (Ibm) (ibm) (Ibm) (ppm) (ppm) 180 0.01651 47880 32765 1569 200 0 016637 77832 3402934 2609 391 47515 43339 2059 212 0 016719 77237 3403894 2468- 532 47282 50404 2383 220 0 016775 76859 3404506 2375 625 47124 -54352 1561 240 0 016920 76602 3404920 2324 676 46703 67990 3176 260 0 017089 75919 3406024 2147- 653 46258 88467 4092 280 0 01726 75195 3407194 1884 1116 45800 113730 $209 300 0.01745 74450 3408397 1563 1437 45301- 144554 6548 73639 3409706 320 0 01766 1178 1822 44762 200898 8993 330 001h6 72763 3411121 476 2524 44510 256156 11402 340 0 01787 72354 3411782 0 3000 44236 200000 12386 71908 3412502 0 3000-37

TABLE 3 51-5000519 00 Spread Sheet for Determining the Sump Concentration Difference Mowed Versus RCS Temperature inputs l

DWST Cone:ntraten 2210 ppm boron / water Core Mixing Volume 790.b ft3 CFT Concentration 2270 ppm bororVwater DC Uquid Volume 1285 ft3 RCS Concentration 2270 ppm bororVwater BWST Liquid Volume 350000 gal RCS Liquid Volume 11500 ft3 l

CFT Uquid Volume 2140 ft3 I

RCS Average Uguld Density 41.5 lbm/ft3 CFT Liquid Density 61.5 tbm/ft3 DWST Uquid Densit/ 62Mbm/fl3 Calculations Liquid Boron Mass Mass Tctal Mass Conservation (Ibm) (Ibm)

DWST Initial Mass, Ibm 2919786 6628 169411 max ppm in core at 14.7 psia RCS Initial Mass, Ibm 477250 1083 47282 lbm core water at 14.7 psia CFT Initial Mass. Ibm 131610 299 Total Mass 8010 3528646 i 2270 average boron concentration. ppm RCS Saturated Core Sat Core Core Boron DC Sat Sump DC and BWST to Saturation Uquid Uquid Solubility Mass at Uquid Uquid Sump Sump Cone Temp Spec Vol Mass Limit Sol umit Mass Mass Concen Difference F (ft3/lbm) (ppm)

(Ibm) (lbm) (lbm) (ppm)

(1bm) (ppm) 160 0 01651 47880 32765 1569 77832 3402934 1851 419 200 0 016637 47515 43339 2059 -77237 3403894 1709 561 212 0 016719 47282 50404 2383 76859 34045C6 1616 654 220 0 016775 47124 54352 2561 76602 3404920 1565 705 240 0.016926 46703 67998 -3176- 75919 3406024 1398 882 260 0.017089 482C8 88467 4092 75195 3407194 1125 1145 280 0 0$726 45000 113730 5209 74450 3408397 804 1466 300 0 01745 45301 144554 6548 73639 3409706 420 1850 320 0 01766 44762 200898 8993 72763 3411121 0 2270 330 0 01776 44510 256156 11402 72354 3411782 0 2270 340 0.01787 44236 280000 12386 71908' 3412502 0 2270

-38

51-5000519-00 i

TABLE 4 LBLOCA CORE BORON CONCENTRATION FOR DlLUTION BY HOT LEG INJECTION 400 GPM NET HOT LEG INJECTION Fl.OW I

Ccore '

DCMB MCB Core Boron Time Delta Core Mass Mass of Core Boron Concentration (seconds) (Ibs) (Ibs) (ppm) 18000 ------------

2376.8 50300.0 18500 1254.6 1122.2 23750.3 19000 528.5 593.7 125G4.6 19500 222.5 371.2 7855.7 20000 95.8 277.4 5870.6 20500 39.5 247.9 5246.3 21000 22.4 225.5 4772.3 21500 9.4 216.1 4573.4 22000 4.0 212.1 4488.7 39

51-5000519 00 l

. 1 TABLE 5 LBLOCA CORE BORON CONCENTPATION j FOR DILUTION BY HOT LEG INJECTION:

100 GPM NET HOT LEG INJECTION FLOW Ccore DCMB MCB Time Core Boron

Delta Core Mass Mass of Core Boron Concentration (seconds) (Ibs) (Ibs) (ppm) 18000 ------------

2216.8 50300.0 19000 570.0 1646.8 34851.4 i

20000 358.4 1288.4 27266.6

21000 254.5 1033.9 21880.6 22000 180.7

853.2 18056.4

) 23000 128.2 725.0 15343.3 24000 91.1 1 633.9 13415.3 25000 64.7 569.2 12046,0 40

51-5000519 00 TABLEG SBLOCA CORE BORON CONCENTRATION FOR DlLUTION BY HOT LEG INJECTION:

400 GPM NET HOT LEG INJECTION FLOW l

Ccore DCMB MCB Core Boron Time Delta Core Mass Mass of Core Boron Concentration (seconds) (Ibs) (Ibs) (ppm) 360000 - - - - - - - - - -

8228.2 '

120000.0 360500 3183.9 504403 73566.4 '

361000 1913.9 3130.4 45653.4 361500 1150.5 1980.9 28889.3 362000 691.4 1289.5 18805.8 362500 416.2 873.3 12736.3 363000 250.2 623.1 9087.3 363500 150.4 472.7 6893.9 364000 90.4 382.3 5575.5 364500 54.4 327.9 4782.1 41

. . . _ . ~ _ _ _ _ . . _ . _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ . .

51 5000519 00 TABLE 7 2

SBLOCA CORE BORON CONCENTRATION FOR DILUTION BY HOT LEG INJECTION:

100 GPM NET HOT LEG INJECTION FLOW Ccore

' DCMB MCB Core Boron Time Delta Coro Mass Mass of Core Boron Concentration (seconds) (Ibs) (Ibs) (ppm) 360000 ---- ---------

8228.2 120000 3,61000 15780.8 6657,4 97091.9 362000 1257.0 5400.4 78759.8

363000 1005.8 4394.6 64091.1 364000 804.8 3589.8 52353.9 365000 644.0 2945.8 42961.7 366000 515.4 2430.4 35445.1 367000 412.4 2018.0 29430.6 368000 320.0 1688.0 24617.9 369000 264.1 1423.9 20766.2 370000 211.3 1212.6 17684.6 371000 169.1 1043.5 15218.5 372000 135.3 908.2 13245.2 1

42 1

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1 51 5000519 00 FIGURE 3 REACTOR VESSEL UPPER PLENUM MIXTURE LEVELS I

, Large S cam Upper . iteam Plenum f- -

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FIGURE 4

{

BWSTTO SUMP BORON CONCENTRATION DIFFERENCE Vs RCS TEMPERATURE BWST & RCS INITIALLY AT 3000 PPM. CFT INmALLY AT 3500 PPM 3000 2500 .. - . - . . . -. - ..

p 2000 . _ - - - -

. Unacceptable aton.

@ Ininate Actue Bo'ron Dduton l E 1500 -

0 .----- -

+

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Acceptab% Operaten

$00 /

/

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180 200 220 240 260 280 300 320 340 8

RCS Saturation Temp (F) O

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8

FIGURE 5

~

BWST TO SUMP BORON CONCENTRATION DIFFERENCE Vs RCS TEMPERATURE BWST, CFT & RCS INmALLY AT2270 PPM 3000 2500 -

0 y 2000 _ _ _ _ . - . . _ . - . . - . ...._. . - - - -

E p Unacceptabte gWration, a e Initiate Active Doion Dilut.b n

{1500 u

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RCS Saturation Temp (F) $

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FIGURE 8

. LBLOCA CORE BORON DILUTION WITH HOT LEG INJECTION 10000 --

14000

,,,noo . _ >

0 -5*IIOURS FROM FIGURE I

_ 10000 8-E .'.

a-3 8000

• DILUTION DATA FROM APPENDIX 1

.R c .

5 I I

O sooo _{

_CORFJ10 - 400 GPM NET IIOT LEG INJECTION i

p.

400o . _

_ \ / COREn0 - 100 GPM NETIfOTLEG INIECHON

\ V 2000 - -

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e -

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~ - - - ^ '

-.w_4-w e _ _ . - _ _ _

• _ _ ._*________-___.___m_m_ _ _ _ _ _ _ . _ _ _ _ _ _ .

FIGURE 9 51-5000519 00 SBLOCA CORE BORON DILUTION WITH HOT LEG INJECTION

, , .,a.

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51

51-5000519-00 FIGURE 10 SBLOCA CORE BORON DlLUTION BY REACTOR VESSEL NO7.ZLE GAP FLOW R

e I

-R

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(Wdd) tuonstnuesues 52

51-5000519-00 FIGURE 11 HOT LEG INJECTION FLOW PATHS IN THE REACTOR VESSEL

() Control Rod

Drive Mechanism i

h--- = =

\ "7== " [ ==P s-

~

_ Q-%s l" f .

gkg

, 4 '

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o o o, ,ox ,, . )

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lli

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l Lower Core Plate Flow Holes

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0 i i 96C123G 53

51-5000519-00 FIGURE 12 HOT LEG INJECTION FLOW PATHS IN THE REACTOR VESSEL FOR REVERSE CORE FLOW D ControlRoo 0,tve Mechanistn

{

m r=s r=s r=3 r, m ex: = = = = = = =xs 6 NA % }

f" l Reactor Vessel

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Downcomer l- .. ...

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)

t > <

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wm 53 at

51-5000519 00 APPENDIX 1

{

HOT LEG INJECTION DILUTION OULATIONS This Appendix contains calculations of CR 3 core boron concentrations following assumed actuation of hot tog inJoction at 500 gpm Hot log injection is twomplished by  !

reverso flow from one running LPI pump, pumping through the LPI cross connect piping, backward through the idio LPI pump through the decay heat drop line, and into the hot leg.

l These deborating calculations are for two cases:

Case 1: A LBLOCA where the RCS is assumed at 14.7 psla and the boron solubility limit is about 50300 ppm boron.

Caso 2: A SOLOCA that hangs up at about 72 psla/305 F saturated. The boron solubility limit for these conditions is about 156 750 ppm boron (Table 1).

The major assumptions common to both casos include, e Hot log injection flow is asscmod to bc 500 gpm Decay heat is 102% of 1.2 ANS 1971 with the FTl heavy isotopes

. The BWST volumo is 350,000 gallons at 3000 ppm boron

. Tho CFT volume is 8005 gallons each at 4000 ppm boron

. Total CFT volumo is 2140 ft'

. The RCS volume is 11.500 ft', at 3000 ppm boron The core / plenum volume used for borating/deborating calculations is 790 ft' 54

51 5000519 00 The initial temperature of the BWST and CFT water is 140'F e

The RCS pro trip conditions are assumed to be 580 F/2200 psia e

The temperature of the hot leg injection water is 140'F e  !

The LDLOCA thermal conditions are assumed saturated at 212*F/14.7 psia The SBLOCA thermal conditions are assumed saturated at 72 psla/305'F

=

Nozzle gap flow is conservatively assumed to be 100 gpm of the hot leg injection I flow that bypasses the reactor vessel upper plenum and core outlet.

Oth tr data used in the deborat ng calculations are:

4 Water specific volume at 140'F (Reference 7) = 0.01629 ft'/lb e

Water specific volume at 14.7 psis sciurated =0.016719 ft'llb e

Core water volume is 790 ft' Core water mass inventory at 790 ft' and 14.7 psia = 790 ft'/0.016719 ft'/lb =

47252lbs Case 1: LBLOCA The general calculation process will be to conservatively calculate the core boron mass and concentrations at each time step. The sump boron mass and concentration will be assumed to be constant , consistent with a surnp Doron concentration of 3000 ppm.In addition, the core boiling flow rate over the time of interest will be assumed constant at 26 lb/sec. (The boiling flow rate is nearly constant at about 26 lb/sec over the 2000 second time of interest for the deborating calculations). The core boron mass calculation will be performed as described below.

55

51 5000519-00 The boron mass change for each time step will be calculated as:

i) boron mass into the core from the core bolling flow times the sump concentration, plus,

2) the not hot leg injection flow of 400 gpm (500 gpm hot leg injection minus the assumed reactor vessel nozzle gap flow of 100 gpm) times the sump concentration of 3000 ppm, and,

3) minus the net hot leg injection flow of 400 gpm times the core boron concentration at the beginning of the time step.

l Core boron concentration is calculated from the core boron mass at the end of each time step divided by the core water mass, in equation form the boron mass change is:

DMCB= delta mass core boron, Ibs DMCB= [Wb

• Csump + Nhil

• Csump - Nhli

• Ccore]

• Dt/10' Where:

Wb = core boiling flow rate, assumed constant at 26 lb/sec Csump = sump boron concentration, ppm boron, assumed constant at 3000 ppm Nhli = Net hot leg injection flow of 40^ apm (500 gpm flow into the hot leg pipe from the decay heat drop line minus assumed 100 gpm leakage through the reactor vessel inlet nozzle to the downcomer, Ccore = Core boron concentration, ppm boron Dt = Time step, seconds '

- 10' = ppm per Ib 56

51 5000519 00 By assuming that the bolling flow rate is constant, that the sump boron concentration is constant, and that the time step is 500 seconds, the equation for change in core boron mass:

DMCB= [Wb'Csump+Nhii*Csump-NHil*Ccore}*Dt/10' , reduces to:

DCMB = [26lb/sec

• 3000 ppm + 54.7 Lb/sec

• 3000 ppm - 54.7 lb/sec

• Ccore], or DCMG = [121,05 lb 0.02735 lb/ ppm

• Ccore]

The initial core boron concentration is assumed to be 50300 ppm, the boron solubility limit at 212 F/14.7 psia (Reference 1). The corresponding initial core boron mass is:

50300 ppm

• 47252 lb /10' ppm /lb = 2376.8 lb.

The core boron mass with time is the core mass at the beginning of the time step time minus DCMB of the time step. The initial core boron inventory is 2376.8 lb at 18000 seconds The core boron concentration is:

Ccore = (Core boron mass, Ibs / Core water mass, Ibs)*10' ppm /lb,ppm Using the DCMB equation above: DCMS = (121.1-0.02735

• Ccore)

The results of the first time step 18000 to 18500 sec is shown below:

DCMB = (121.1 ppm - 0.2735 lhlppm

• 50300 ppm) = 1254.6 ppm

-57

51-5000519-00 Core boron mass = 2376.8 lb 1254.6 lb = 1122.2 lb and the core boron  !

concentration is: '

Ccore = 1122.2 lb / 47252 lb

• 10' ppm /lb = 23750.3 ppm a

Following this process, the core boron mass and concentration with time are calculated as follows:

1 2"d Time step,18500 to 19000 sec i

DCMB = (121.1 lb - 0.02735 lb/ ppm

• 23750.3 ppm) = 528.5 lb

. CMB = 1122.2 lb - 528.5 lb = 593.7 lb Ccore = 593.7 lb /47252 lb *10' ppm /lb = 12564.6 ppm

\

3'd Time step,19000 to 19500 sec DCMB=(121.1 lb - 0.02735 lb/ ppm

• 12564.6 ppm) = 222.5 lb I

CMB= 593.7 lb - 222.5 lb = 371.2 lb Ccore = 371.2 lb / 47252 lb

• 10' ppm /lb = 7855.7

.I 4

4* Time step,19500 to 20000 sec DCMB= (121.1 lb - 0.02735 ppm /lb

• 7855.7 ppm) = 95.8 lb CMB = 371.2 lb - 95.8 lb = 277,4 lb Ccore = 277,4 lb /47252 lb

• 10' ppm /lb = 5870.3 ppm 4

58

51oS000519-00 s

5* Time stop,20000 to 20500 see DCMB = (121.1 lb . 0.02735 ppm /lb '5870.3 ppm) = 39.5 lb CMB = 277.4 lb 39.5 lb = 247.9 lb Ccore = 247.9 lb / 27252 lb

• 10' ppmnb = 5246.3 ppm 6* Time step,20500 to 21000 see DCMB= (121.1 Lb . 0.02735 lb/ ppm

• 5246.3 ppm) = 22.4 LB I CMB = 247.9 lb 22.4 lb = 225.5 lb Ccore = 225.5 !b / 47252 lb

• 10' ppm /lo = 4772.3 1

7* Time step,21000 to 21500 see DCMB = (121.1 lb - 0.02735 lb/ ppm

• 4772.3 ppm ) = 9.4 lb CMB = 225.5 lb 9.4 lb - 216.1 lb Coors = 216.1 lb / 47252 lb

• 10' =4573.4 ppm 8* Time step,21500 to 22000 see DCMB = (121.1 lb - 0.02735 lb/ ppm

• 4573.4 ppm) = 4,0 lb CMB = 216.1 lb-4.0 lb = 212.1 lb Ccore = 212.1 lb / 47252 lb

• 10' ppmab = 4488.7 ppm The chan9es in boron concentration and mass with time as shown above indicato that hot leg injection is a valid core deboration method. A tabulation of the results are shown in Tables 4 7 in the main body of this document. Table 4 shows the results of 400 gpm net hot leg injection flow for a LBLOCA.

59

51-5000519 00 in addition to this caso, it is assumed that 400 gpm of the 500 gpm hot log injection flow bypasses the upper plenum by flowing to and through the reactor vessel nozzle gaps.

The following deboration case uses 100 gpm hot leg injection dilution flow and the core bolling flow rato is assumed to be constant at 26 lb/sce as used for the 400 gpm hot leg injection case.

The not hot leg injection mass flow rate at 100 gpm is:

100 gpm/7.48 Ft* / gal /0.01629 Ft*'/lb (@ 140 F: Reference 7).=13.7 lb/soe i

\ .

The DCMB equation becomes:

[26 lb/sec *3000 ppm + 13.7 lb/sec* 3000 ppm 13.7 lb/sec

• Ccore}

• 1000 sec/10' ppm /m]

DCMB=[78 lb + 41.1 lb + 0.0137 lb/ ppm

• Ccore), Ib = [119.1 lb - 0,0137 lb/ ppm

• Ccore)

Two time steps will be used to illustrate the boron dilution calculation process:

1 Time Step DCMB= 119.1 lb - 0.0137 lb/ ppm

• 50300 ppm = 119.1 lb 689.1 = -570 lb MCB= 2216.8 lb - 570 lb = 1649.8 lb Ccore = 1646.8 lb /47252 lb

• 10' ppm /m =34851.4 ppm 60

51 5003519 00 2* Time Step DCMB= 119.1 lb 0.0137 lb/ ppm

• 34851.4 ppm = 119.1 lb 477.5 lb = 358.4 lb

MCB =1646.6 lb 356.4 lb = 1288 4 lb Ccore = 1288.4 lb /47252 lb *10' ppm /m =27266.6 ppm

~

Following this calculation method boron dilution for 100 ppm not hot leg injectiot, is developed as shown in Table 5 in the main body of this document.

r Case 2: SBLOCA

, - Deborating calculations are performed for a SBLOCA, assumed to be at 72 psia /305'F to show the capability of hot leg injection. The hot leg iriection flow assumptions are the same as those for the LBLOCA described above. (The hot leg injection flow is assumed to be 500 gpm, but 100 3pm is assumed to flow through the reactor vesWi

. nozzle gaps to the downcomer). The SBLOCA deboration calculation will be storied at i

100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (360000 seconds) post trip with an initial core boron concentration of 120000 ppm. This case is chosen to be well out in time with a signmcant core boron 4

conce stion. The case will show that hot leg injection can rapidly arrest core boron conces don buildup and reduce the concentration to values wall below the solubility a

limit. This case will also assume that the core boiling flow is constant, the sump boron concentration is constant at 3000 ppm, and the deborating equations are the same as those for the LBLOCA.

61

51-5000519-00 in equation form the boron mass change is:

DMCB= dolta rnass core boron, Ibc

)

DMCB= [Wb

• Csump + Nhli

• Csump - Nhli

• r' core]

• Ot/10' Where: i Wb = core boiling flow rete, assumed constant I Csump = sump boron concentration, ppm boron, assumed constant at 3000 ppm i i

1 Nhli = Net hot leg injection flow of 400 gpm (500 gpm fiow into the hot leg pipe from the decay heat drop line trinus assumed 100 gpm leakage through the reactor vessel inlet nozzle to the downcomer, Ccore = Core boron concentration, ppm boron Dt = Time step, seconds 10' = ppm per Ib The initial thermal hydraulic conditions for the SBLOCA case are listed below:

The reactor is operating at 72 psia /303 F saturated conditions The initial time is 360000 seconds (100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> post trip)

Hg at 72 psia is 1181.1 Btu /lb (Reference 7)

The enthalpy of the hot leg injection water at 140 F is 108 Btu /Lb (Reference 7)

The density of saturated water at 72 psia is 1/0.017501 ft'/lb (Reference 7)

The core volume is assumed to be 1200 tt' The core water inventory is 1200 Ft'/0.017501 ft lib = 68568 lb The initial core boron inventory, MCB=120000 ppm *C8568tb /10' ppm /m=8228.2 lb The decay heat fraction at 360000 seconds is 0.00461 (Reference 8). This fraction is the average of the fraction at 350000 seconds (0.00466) and the fraction at 62

. ~ = _

l 51 5000519-00 l l

370000 seconds (0.00456): (0.00466 + 0.00456)/2 = 0.00461  :

.~ The core decay heat is 0.00461

• 2483299 Blu/ soc = 11448 Blu/Sec

. The core boiling flow is 11448 Stu/sec / (1181.1 Btu /lb - 108 btullb) = 10.7 lb/soe

. Although the hot leg injection flow is assumed to mix with the core cuitet and upper plenum fluid , no credit is assumed for heat transfer to the het leg injection fluid.  ;

By assuming that the belling flow rate is constant, that the sump bcron concentration is constant, and that the tir.ie step is 500 seconds, the equation for change in core boron l mass is:

OMCB= delta mass core boron, Ibs l.

4 j DMCB@Vb

• Csump + Nhil

• Csump - Nhli

• Ccore]

• Dt/10' ppm /m l- reduces to:

DMCB = [10.7 lb/sec

• 3000 ppm +54.7 lb/sec

• 3000 ppm 54.7

• C core )

• 1 500 sec/10' ppm /lb 4

! DCMB= [16.05 lb +82.05 lb -0.02735 lb/ ppm

• Ccore).

l

DCMB = [98.1 lb - 0.02735

• Ccore]

i-The deboration calculat!ons for the SBLOCA follow:

l 1" Time step: 360000 to 360500 seconds -

DCMB = 98.1 lb - 0.02735 lb/ ppm ? 120000 ppm = 3183.9 lb CMB, Core boren mass = 8288.2 lb 3183.9 lb = 5044.3 lb l

j Ccore, core boron concentration =-73566.4 ppm i

1 63 l

. . - . . . . , . ~ - -

51 5000519 @

2" Time step:

DMCB 98.10.027.5 lb/ ppm '7Wa6.4 ppm =1913.9 lb CMB= 5044.3 Lb.1913.9 Lb=3130.4 lb Ccore = 3130.4 lbl68568 lb

• 10' ppm /m =45633 ppm 3" Time step DCMB-98.1 l'b .02735 lb/ ppm

• A5653.4 ppm =1150.5 lb MCB= 3130.4 lb 1150.5 lb = 1980.9 lb l

Ccore = 1980.9 lb / 6B568 lb *10' ppm /m = 2BB89.3 l

4* Time step

[ DCMB= 98.1 lb - 0.02735 lb/ ppm *28BB9.3 ppm =691.4 lb MCB = 1980.9 lb - S91.4 lb = 1289.5 lb Ccore = 1289.5 lb / 68568 lb *10' ppm /m = 18805.8 Following this calculation for 6 more time steps (11 total time steps) produces the data -

for Table 6 in the main body of this document. =

In addition to this case, it is assumed that 400 gpm of the 500 gpm hot leg injection flow bypasses the upper plenum. A second case of SBLOCA deboration is evaluated, assuming that the net hot leg injection flow to the upper plenum is inly 100 gpm of the

.- 500 gpm injection flow entering the hot leg through the decay heat dropline. In this case flow through the reactor vessnl nozzle gaps is assured to be 400 gpm. The 1

64

51-5000519-00 purpose of this case is to provide further evidence that hot leg injection can control

' and reduce the bore boror, conuntration.

1 As noted above the net hot leg injection flow is assumed to be 100 gpm. This is 100 gpm/7.48/0.01629 Ft'llb/60 sec/ min =13.7 Lb/sec. This case will use time steps of -

[ 1000 seconds. The DCMB equation becomes :

f-l DCMB= [Wb *Csump + Nhli

• Csump - Nhli

• Ccore]*1000 sec/10' ppm /m l DCMB= 10.7 lb/sec

• 3000 ppm + 13.7 lb/sec

• 3000 ppm - 13.7 lb/sec

• Ccore)'1000 sec/10' ppm /m DCMB= [32.1 lb + 41.1 lb- 0.0137 lb/ ppm

• Ccore]

The initial core boron mass is 8228.2 lb, the initial core concentration is assumed to be 120000 ppm, and the core volume is conservatively assumed 1200 fT', and the core water inventory is 1200 Ft* / 0.017501FT (Reference 7) = G8568 lb. Calculation for the -

first two time steps will be shown.

1" Time Step DCMB= 73.2 lb-13.7 lb/ ppm *120000 ppm =1570.8 lb MCB = 8228.2 lb - 1570.8 lb =6657.4 lb Ccore = 6657.4 lb /68568 lb *10' ppm /m = 97091.9 2"d Time Step _

65

51-500051EK)0 DCMB: 73.2 lb - 0,0137 lb/ ppm

• 97091.9 ppm =1257.0 lb MCB = 6657.4 lb .1257.0 lb =5400.4 lb ,

Ccore = 5400.4 lb /68568 lb *10' ppm /m = 78759.8 Continuing the calculations for 13 more time steps, (15 time steps total) provides the deboration data for Table 7 in the main body of this document.

The results of these calculations suggest that het leg injection provides a rapid means of deborating boron build up in the core and outlet plenum.

l t

+

l

51-5000519-00 APPENDIX 2 REACTOR VESSEL HOT LEG INJECTION FLOW EVALUATIONS

1. INTRODUCTION A sketch of the flow path of the hot leg injection by back flow through the decay heat dropline is shown in Figure 11. The decay heat dropline is connected to the bottom of the RCS hot leg pipe at an elevation of 20.14 ft. (00 ft elevation is taken at the upper '

face of the lower tube sheet of the steam generators). The bottom of the 36 inch ID hot i

leg pipe is at elevation 19.75 ft. The hot leg injection nozzle is located within the start i

L of the bend of the hot leg 90

• elbow, about 4.7 inches above the bottom of the hot leg-pipe (Reference 3). The inner cylinder of the upper plenum assembly directly opposite the hot leg nozzle has 24 - 3 inch diameter flow holes in addition to the larger flow holes (6 34 inches ID and 4- 22 Inches ID) located in the plenum cylinder (Reference .

3). The area of these small flow holes directly opposite the hot leg nozzles is 1.182ft per nozzle (see below). _ From the small holes opposite the hot leg nozzles, the hot leg -

injection flows to the upper plenum _where it continues to mix with core outlet steam and water. The saturated, boron rich injection fluid then flows down, by virtue of static -

head, to the top of the core where it enters the flow holes that direct flow into the region formed between the core barrel and the former plates. There are 24 flow holes (8 each of 2 inches,3 inches and 4 inches diameter) spaced around the periphery of the 2

upper core plate that provide a flow area of 1.26 ft for downflow of the injection fluid to the core barrel / baffle region (Reference 5). Within the core barrel / baffle region there --

are 8 former plates, each with 80 - 1.312 inch diameter flow holes (Reference 6). '

These former plate holes make up a flow area of 0.75 ft'. From the barrel / baffle region 67

51-5000519-00 the flow exits to the periphery of the lower core plate where there are 64 flow holes ranging in diameter from 1.75 inches to 6 inches (Reference 4). The total flow area for the injection fluid at the lower core plate is 4.30 ft'. From the lower core plate the fluid enters the lower sections of the reactor vessel and then flows up the downcomer to exit the reactor vessel by way of the affected cold leg. At 500 gpm the dynamic pressure drop through the flow path described above is about 5.4 inches of water (see calculation below). The head to provide this flow is developed by the injection fluid in the. hot leg and the entrance to the upper plenum.

a The argument to support the hot leg injection is that the pressure drop in the hot leg injection flow path is small because of the low flow rate (only 500 gpm) and the flow areas, except for the flow area of the reactor vessel internals former plates, are large. If the pressure drop in the flow path is relatively small that indicates that a small driving head in the hot leg pipe or the upper plenum will support the hot leg injection flow path.

The fluid in the reactor vessel is assumed to be saturated at 14.7 psia or the RCS pressures of the SBLOCAs (The incoming injection fluid from the LPI or HPl is heated to saturation by the vent valve steam flow. The boiling flow rates through the downcomer, the core and the upper plenum are low because of the relatively low flow core boiling flow rates and the large flow areas. The driving head for the boiling flow is the gravity head formed by-the density difference between the boiling in the upper core and the saturated water downcomer.)

68

51-5000519-00 The water density in the hot leg injection flow path is expected to be saturated water throughout the flow path.

2.

CALCULATION OF HOT LEG INJECTION FLOW PATH PRESSURE LOSSES Calculation of the pressure losses through the several plate flow holes in the hot leg injection flow path is performed below.

2.1 Identification of Flow Holes

, a) Plenum Cylinder FlowHoles (Reference 3)

There are 24- 3 inch flow holes in the plenum cylinder adjacent to the hot leg nozzle. These holes are arranged in rows as follows:

Row Number of flow holes 1 2 2 2 3 4 4 2 5 4 6 2 7 4 8 2 9 2 24 The flow area of these holes is:

24*0.785*(3.0 in)'/144 in'/ft 2=1.1775 ft', Use 1.18 ft' b) Upper Core Plate Flow Holes (Reference 5 )

There are 24 flow holes in the upper core plate. Their numbers and dimerisions are:

2 2 2 8-3 inch dia holes: 8*0.785*(3.0 in)2/144 in /Ft = 0.392 ft 2

8-2 inch dia holes: 8*0.785*(2.0 in)'2/144 2 2 n /Ft'= 0.174 ft' 8-4 inch dia holes: 8*0.785*(4.0 in) /144 in /Ft = 0.70 ft' 1.266 ft' 69

51-5000519-00 c) Fo mer Plate Flow Holes (Reference 6)

The former plates have 80-1.312 in dia flow holes.

The flow area per former plate is:

2 80*.785*(1.312 in)'/144 in /ft'=0.75 ft' d) Lower Core Plate flowholes:(Reference 4)

There are:

8-3 in dia holes 8*.785*(3 in)2/144 n'/ft'= 0.392 ft 2 8-2.5 in dia holes 8*.785*(2.5 in)'/144 in*/ft'= 0.273 ft'

, 8-2.0 in dia holes 2 S*.785*(2.0 in)'/144 in'/ft = 0.174 ft' i

8-6.0 in dia holes 8*.785*(6.0 in)'/144 in'/ft'= 1,57 ft 2 8-3.5 in dia holes 8*.785*(3.5 in)'/144 in'/ft'= 0.534 ft2 2

16-1.75 in dia holes-16* 785'(1.75 in)'/144 in'/ft = 0.267 ft' 8-5.0 in dia holes 8*.785*(5.0 in)2/144 in'/ft* = 1.090 ft2 Total d.30 ft' e) Summary of Flow hole areas in the hot leg injection flow path Plenum cylinder adjacent to hot leg nozzle 1.18 ft' Upper core plate inlet to core barrel / baffle area 1.26 ft 2

Former Plate 0.75 ft 2

Outlet holes in lower core plate d.30 ft' 2.2 Calculation of Velocities in the Flow Holes velocity = flowlarea/ density Flow = 500 gpm Density of water at 140 F=1/0.01629 ft'/lb=61.39 lb/ft' Mass flow =500 g/ min *61.4 lb/ft'/7.48 gal /ft'/60 sec! min =68.4 lb/sec a) velocity in plenJm cylinder flow holes =

68.4 lb/sec/1.18 ft2/61.4 lb/ft'=0.944 ft/sec 70

I 51-5000519-00 b) velocity in upper core plate flow holes =

68.4 lb/ sed 1.26 ft2/61'.4 lb/ft'=0.88 ft/see c) velocity in former plate flow holes; 68.4 lb/ sed 0.75 ft2/61.4 lb/ft'=1.49 ft/sec '

d) velocity in lower core plate flow holes; 68.4 lb/ sed 4.30 ft2/61.4 lb/ft'=0.26 ft/sec 2.0 Calculation of pressure drops in the several flow holes:

delta p= DP = k* rho *v'/144/2g:

L k = is assumed to be 1.5 velocity heads entrance (k=0.5) and exit loss (k=1.0) at each plate (Total loss factor =0.5 +1.0 velocity heads) rho is water density = taken as 61.4 lb/ft' as above. This value of density is used for conservatism (higher DP) of the pressure losses in hot leg injection flow path, g= gravitational constant =32.2 ft/sedsec a) DP plenum cylinder flow holes =

2 1.5*61.4 lb/ft *(0.944 ft/sec)*/(144 in'/ft2'2*32.2 ft/sec )=0.00885 psi b) DP upper core plate:

- 1.5*61.4 lb/ft *(0.88 ft/sec)'/(144 in'/ft'*2*32.2 ft/sec')=0.00769 psi c) DP former plates:

2 2 8 plates *1.5*61.4 lb/ft'*(1.49 ft/sec)2 / (144 in /ft '2*32.2 ft/sec')=0.176 psi d)  : DP lower core plate:

1.5*61.4 lb/ft'*(.026 ft/sec)2/ (144 in /ft'*2*32.2 ft/sec')=0.0000067 psi 2

71

51-5000519-00 e) Sum of DPs =(0.00885+0.00769+0.176+0.00067)=0.193 psi Convert DP in psi to inches of water 2

one psl=lblin *144 in'/ft 2/61.4 lb/ft'=2.345 ft or 1/2.345=.4264 psilft then 0.193 psi /0.4264 psi /ft= a water column 0.453 ft or 5.4 inches high. This is a small head required to drive the hot leg injection flow through the flow path described above. This head can be easily created in the reactor vessel upper plenum by the hot leg injection.

3.0 REFERENCES

The references list for this Appendix is the same as that identified in Section 9 of

! the text.

l 72

FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3 DOCKET NUMBER 50-302/ LICENSE NUMBER DPR-72 3F0997-28 ATTACHMENT C l

i SUPPORTING INFORMATION I

1 U. S. Nuclear Regulatory Commission Attachment C 3F0997 28 Page 1 of 8 ATTACHMENT C SUPPORTING INFORMATION Figure 1...... ........... Decision Matrix Figure 2.......... ....... Drop Line to RB Sump (Reactor Vessel Flow Peth)

Figure 3.................. Drop Line to RB Sump (Flow Schematic)

Figure 4............ ..... Hot Leg Injection - Auxiliary Pressurizer Spray / Reverse Flow through LPI (Reactor Vessel Flow Path)

Figure 5. .... . .. ..... Hot Leg Nozzle Gap Flow (Geometry)

Figure 6... . ... .. .... Hot Leg Nozzle Gap Flow (Reactor Vessel Flow Path)

Figure 7.................. Hot Leg Injection via Reverse Flow through LPI(Flow Schematic)

i I

U. S. Nuclear Regulatory Commission Attachment C 3F0997-28 . Page 2 of 8 Figure 1. Decision Matrix Sample RB Sump Is RCS Saturated? IF Concentration < Predetermined Value, THEN Establish Active Method No Default -If sampling unavailable, Then establish active method ~

Is RCS Pressure = RB Pressure?

Continue Cooldown Yes No and Establish DHR Align Dropline Establish Hot to RB Sump Leg Injection If Active Method can not be Established, Then Reliance on Passive Method (Gap Flow).

i i

t__

U. S Nuclear Regulatory Commission Attachment C 3F0997-28 Page 3 of 8 Figure 2. Drop Line to Ril Sump (Reactor Vessel Flow Path) z nt>7annn 6 _ = = = = = = _a

,, r c - 2

'_ / I I . _ _ II . ! _B /

,UQ ' '

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_, c-r- , ,

g wxN II

U. S. Nuclear Regulatory Commission Attachment C 3F0997-28 Page 4 of 8 Figure 3. Drop Line to RB Sump (Flow Schematic)

• B' Hot leg Reactor

, Vessel

________________I

Drop Line e <  ;

I O 4 A 8 e 8

CFT l CFT 1A i 18 l

CFV 5 l CFV-6 HV 3 ,,,,,,,,,,,,,,)

DHV5 I DHV 6 e

< I DH 38 Fl DHV4 I Ls V'

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l i

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i I s Y e

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s 8

To HPl umps 8 A ' DHP 1 A DHP 1B s e DHV 39 DHV-40 l l >< ________ w __'

t _ _ _ _ _ _ _ ,j , _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _43_,.

DHV DHV-42 r----------~~----------------______e i Reactor Tl le l Building Sump l l j i 8 I

g i B I___________4 lp g t

U. S. Nuclear Regulatory Commission Attachment C 3F0997 28 Page 5 of 8 Figure 4. Hot Leg Injection Auxiliary Pressurizer Spray / Reverse Flow through LPI (Reactor Vessel Flow Path) mm~v mm

, _ = = = = = = _.

[sf E 3 W

i

,a s :

s t- - un /5

: an v

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• -Steam Flow n

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101 l il D 2:4 D  ! i .M 1 I lbs m, *e r s -I xxx I I

'E"I* tory Commission Attachment C; 3 92 Page6ofg II R"'* 5. Ilot Leg som cometry)

Leakage pagy W/

/

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a

U. S. Nuclear Regulatory Commission Attachment C 3F0997-28 Page 7 of 8 Figure 6. Hot Leg Nozzle Gap Flow (Reactor Vessel Flow) onnanno 6 = = = = = = _. a t 2

/ .

~

/ I I _ _ __

_ 8 .1_'t

,U.Q s .

l l ..

- ),U.

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__i

U. S. Nuclear Regulatory Commission Attachment C 3F0997-28 Page 8 of 8 Figure 7. Ilot Leg injection via Reverse Flow through LPI (Flow Schematic) s r 7

=B' Hot Leg Reactor

, vessel

___________J p_

e __ __ Drop Line l i

A 4 o 8

1

! CFT l CFT

' 1A e IB FV CFV 6 DHV 3 ,,__________5., _ Jl j 1 DHV 6 DHVS

! DH 38 Fi

,, j M______@____w DHV 7 DHV 8 i e e i

! e DHV 11 DHV 12  !

l t-----+C)<3- ; >< j DH Cooler l DH Cooler DHV 41 j

, j

, s y a

! To HPl  !

l ump 5 8 A ' DHP 1 A DHP 1B y i DHV 39 DHV 40 l l >q ,_ _ _ _ _ _ _ _ _ _ .p<:p _ _ .

t _ _ _ _ _ _ _ ,j , _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ + y,gy ,3 AN DHV 42 -

l Reactor j j Building e i Sump e i l 1 I l l___________ ____.

t +-- Screen 9

FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3 DOCKET NUMBER 50-302/ LICENSE NUMBER DPR-72 3F0997-28 ATTACHMENT D l

LIST OF COMMITMENTS I

U. S. Nuclear Regulatory Commission Attachment D 3F0997-28 Page 1 of 2 ATTAcilMENT D LIST OF COMMITMENTS

1. Auxiliary Pressurizer Spray A change to the Final Safety Analysis Report (FSAR) to add the auxiliary pressurizer spray method will be initiated prior to plant restart.

Due: Prior to plant restart

2. Hot Lee triection via Reverse Flow throuch Low Pressure Iniection (L.PD FPC is currently evaluating this method and plans on providing a submittal containing a description of change in system operation and safety analysis by September 30,1997. At that timc, CR-3 will request NRC review and approval of the hot leg injection method for post loss of coolant accident (LOCA) boron dilution.

Due: Sentember 30.1997 l

3. Procedures The decision matrix and guidance on the implementation of the hot leg injection via reverse flow through LPI method will be proceduralized in Emergency Plan Implementing Procedure EM-225, " Duties of the Technical Support Center Accident Assessment Team."

The Emergency Operating Procedures (EOP) will provide guidance on the use of the drop line to the RB sump and hot leg injection with auxiliary pressurizer spray methods and require TSC approval prior to implementation of an active boron dilution method. The affected procedures will be appropriately validated to ensure that the actions are reasonable and can be performed adequately in the control room and TSC. This will ensure that operator actions required for boron dilution can be performed and can be completed within the required time frame under expected post LOCA conditions.

Due: Prior to plant restan

4. Instrumentation The instrumentation required for post LOCA boron precipitation control will be determined and evaluated as necessary against Regulatory Guide 1.97 requirements for post accident instrumentation. If a change to the instrumentation listed in Technical Specification 3.3.17,

" Post Accident Monitoring (PAM) Instrumentation," is identified, a Technical Specification Change Request will be submitted prior to plant restart.

Due: Prior to niant restart

U S. Nuclear Regulatory Commission Attachment D 3F0997-28 Page 2 of 2

5. Operating License Condition Florida Power Corporation (FPC) will provide a revised amendment request for Operating License Condition 2.C.(5) that reflects the post LOCA boron dilution methods discussed in this submittal. The revised amendment request will be submitted by October 3,1997.

Due: October 3.1997

_J

a l

FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3 DOCKET NUMBER 50-302/ LICENSE NUMBER DPR-72 3F0997-28 ATTACHMENT E .

Acronyms and Abbreviations i

- U. S. Nuclear Regulatory Commission Attachment E 3F0997-28 Page1ofI e

ATTACHMENT E ACRONYMS AND ABBREVIATIONS B&W------------- Babcock and Wilcox B&WOG ------------ Babcock and Wilcox Owners Group BWST------------ Borated Water Storage Tank CFR -------------Code of Federal Regulations CFT --------------- Core Flood Tank CR 3 ----------------- Crystal River Unit 3 dP--------------------- differential pressure ECCS --------------Emergency Core Cooling System EOP ----------------Emergency Operating Procedure F -------------------- Fahrenheit FPC----------------- Florida Power Corporation FSAR ----------- -- Final Safety Analysis Repon 2

ft ----------------- square feet FTl ------------------ Framatome Technologies Incorporated gpm---------------- gallons per minute llPI ------= ------ High Pressure Injection IPAP --------------Integrated Performance Assessment Process LBLOCA--------Large Break LOCA LOCA-----------Loss of Coolant Accident LPI ---------------- Low Pressure Injection MWt---------------- Megawatt (Thermal)

NRC------------ Nuclear Regulatory Commission PAM -------------- Post Accident Monitoring PASS --- ------Post Accident Sampling System psia ---------- pounds per square inch absolute i RB --------------- Reactor Building

- RCS --------- -Reactor Coolant System RVVV -------------- Reactor Vessel Vent Valve SBLOCA- ----Small Break Loss of Coolant Accident TSC ------ ------Technical Support Center

.,,,,,_____--_m.__. . - - _-_