ML20203K499

Boron Dilution by RCS Hot Leg Injection

ML20203K499
Person / Time
Site:	Crystal River
Issue date:	02/16/1998
From:	Klingenfus J, Wissinger G FRAMATOME
To:
Shared Package
ML20203K477	List: 3F0298-07, Forwards Topical Rept for Review & Approval,Which Describes Addl Active Method of Preventing Boron Precipitation Following Design Basis Loca.Issuance of SER Is Also Requested ML20203K480 ML20203K489 ML20203K499
References
51-5000519-06, 51-5000519-6, NUDOCS 9803050112
Download: ML20203K499 (33)

Text

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4 20440-7(12/95)

ENGINEERING INFORMATION RECORD

f. MGP.M Document ide "Ifler 51 - 5000519-06 f Title ' 9ron Dilution by Hot Leg injection i'REPARED BY:

REVIEWED BY:

Name G J Wissinger Name J A Klingenfus Signature _[rk M _Date 2/n.lw Signature ,. /IN Date)//d/M Tcchnical Managers tnatement: Initials Reviewer is Independent.

R: marks:

This revision replaces Revisions 05 entirely. This revision addruses customer comments.

During certain cold leg pump discharge loss-of-coolant accidents the core liquid through put will cease and boiling will cause the core boron concentration to increase. Control of the core boron concentration post-LOCA is a Nuclear Regulatory Commission issue for the B&W Owner's Group, of which Crystr.. River Unit 3 is a part.

This control can be provided by any passive mechanism or active method that results in a net liquid flow through the core. One of these methods is hot leg injection (HLI). This method provides flow from one low pressure injection pump backward through the other, shutdown LPI pump and through the decay heat drop line into the hot leg inducing a net reverse flow through the core to the break.

Evaluations of core boron concentratior' have been perfor.ned for LBLOCAs and SBLOCAs. Hot leg injection by re arse flows of 500 gpm through the decay heat drop line is sufficient to exceed the gap bypass flow with the remaining flow offering a positive and rapid means for reducing the core boron concentration. The calculations syporting this flow rate consider both 1.2 and 1.0 times the ANS 1971 decay heat standard and '

conservative core mixing volumes (i.e. 790 and 1200 ft' for large and small LOCA, respectively). FTl has reviewed the required flow patterns and hydraulic resistance within the reactor vessel and concluded that there are no problems using HLI for boron concentration control provided it is initiated before the hot leg reaches the boron precipitation mixing limit as defined in Reference 10.

9803050112 980227 Page 1 of M

, PDR ADOCK 05000302 P PDR

Frgr: w i Tcchnologiss, Inc. 51-5000519-06 BORON DILUTION BY RCS HOT LEG INJECTION ,

1 PREPARED FOR FLORIDA POWER CORPORATION BY FRAMATOME TECHNOLOGIES INC.

c FEBRUARY 1998 2

l 4

FremItoms Technologies, Inc.

51-5000519-06 4

Record of Revision Rev/Date DESCRIPTION Page No.

Sept. This Nvision replaces revision entirely.

1997 Section 4: Changes were made to the text discussing methods of 22-26 detection when boron is concentrating in the core. Bcron concentration measurement and incore temperature measurement uncertainty discussion was added to the text.

Tables 2 and 3 were modified and renumbered as were Figures 4 52 and 5. Boron concentration measurement and incore temperature measurement uncertainties were also added to Figures 4A,4B, SA,5B, and SC.

Section 5.2: Added discussion ofimpact of Hot leg Injection on 28 the reactor outlet piping, the reactor vessel and the internals Section 5.4: The parenthesis after 0.00202 should read 32 (cbout 0.2 % power) rather than (about 0.12 power).

Section 5.4: The word "only" was added after should, to read.... 33 "should only be used in the long term (about 34 days post event)", "Only" was added to clarify the intent of the sentence.

Section 6: A paragraph and a new figure (12 ) have been added 33 to clarify the dilution flow paths in the reactor vessel before and after the hot leg injection flow is large enough to reverse the direction of core flow, i

Section 7:The second paragraph was modified to read the same 35 '

as the last paragraph on page 20. These paragraphs discuss the sump boron concentration changes if boron is concentrating in the core. This change was made for clarity and continuity.

Section 9: References 13,14,15, and 16 were added. 37 The page numbers in all Appendices were changed from A1-1, consecutive text page numbers to A1-1, A2-1, A3-1, etc. A2-1, A3-1 3

. Framatoms Technologi:s, Inc.

51-5000519-06 The decay heat relationship should be 1.2 ANS 1971 with A1-1 the FTl heavy isotopes, rather than 102% ANS 1979 with FTl heavy isotopes.

The tabulation of the results of the hot leg injection dilution A1-7 calculations is identified as Table 4 in the main body of the document rather than in Appendix 1.

Table A-2 is corrected to Table 5 in the main body of the A18 document.

The units of core power are incorrectly identified as Btu /lbm. The A1-10 units are corrected to Btu /sec.

Table A-3 is corrected to Table 6 in the main body of the A1-12 document. '

Table A-4 is corrected to Table 7 in the main body of the A1-13 document. ,

i Appendix A3 was added to evaluate the Boronometer and incore A3-1 temperature measurement uncertainties.

/Oct 97 Minor editorial changes as requested by Florida Power Corp.

(David Rice) lOct'97 Corrected a calculation error and its results on page 32 and 33 in 4,32 &

Section 5.4. - Changes are on pages 4,32, and 33. 33

/Jan'98 This revision replaces Revisions 00 through 03 entirely, all The document was streamlined to include only information pertinent to HLI.

/Jan'98 Changed HL1 inlet temperature to 185 F. 17,18,20-27,31,32

/Feb'98 This revision replaces revision 05 completMr. Addresses CR-3 5,6.18, comments y21,26, 4

Fremitoms Technologits, Inc.

51-5000519-06 i

l l

\

d Table of Contents L i s t o f Ta b le s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lis t o f Fig u re s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

List of As s u mptio n s . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . . . .. . .

Li st o f R e fe re n ce s . . . . . . . . . . . . . . . . . . . . ..............................8 ..........................

1.

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

2. REACTOR VE S S EL FLOW PATHS FOR H LI...................................................... 10 3.

E C C S R EQ UI R EM EN TS F OR H LI .... ......................... ....................... ....... ............ 16 4.

VERIFICATION OF HLI EFFECTlVENESS .......................................................... 21 5.-

E FFECT OF H LI ON HOT LEG PIPING . . .......................................................... 26 5.1 WATE R H AM M E R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5. 2 TH E R MAL STRATIFICATIO N . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3 RATES O F TEM PERATU RE C HAN G E . .. . .. . .. . .. . . . . . . . .. . .. .. . . . . .. . . . . . . .. . . .. . . . .

5.4 PR E S S U R E-TEM P E RATU R E LIM ITS ... . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . ..

5. 5 R EVER S E FLOW lN TH E C O R E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.

S UMMARY OF RESULTS AND CONCLUSIONS ................................................ 29 Appendix 1: Reactor Vessel HLI Flow Path Pressure Losses ............................. 30 5

Fremstome Tcchnologias, Inc.

51-5000519-06 List of Tables Table 1: HLI Flow to Match Decay Heat and Suppress Core Boiling .......................... 20 1

List of Figures Figure 1: CR-3 DHDL Hot Leg injection Flow Patterns with the A LPI Pump..............12 Figure 2: CR-3 DHDL Hot Leg injection Flow Patterns with the B-LPI Pump .............13 Figure 3: HLI Flow Paths in the RV Before Core Boiling Suppression ........................14 Figure 4: HL1 Flow Paths in the RV After Core Bolling Suppression ...........................15 Figure 5: LBLOCA Core Boron Dilution with HLI,1.2 ANS71 DH ............................... 22 6 Figure 6: LBLOCA Core Boron Dilution with HLI,1.0 ANS71 DH ............................... 23 Figure 7: SBLOCA Core Boron Dilution with HLI,1.2 ANS71 DH ...............................,24 Figure 8: SBLOCA Core Boron Dilution with HLI,1.0 ANS71 DH ...............................,25 6

1

Framatome Technologies, Inc.

51-5000519-06 List of Assumptions

1. -

In order for hot leg injection to be initiated, the core exit must be saturated, and E

the decay heat removal /LPI system equipment must be accessible for alignment .

so that water can be injected in reverse flow through the DHDL to the nozzle on the RCS hot leg piping.

] 2. FTl considers 1.2 ANS71 decay heat plus B&W heavy isotopes to be conservative by 25 percent, so a value of 0.75 of this decay heat was used to represent some of the realistic decay heat levels in the calculation of the required HLI flows. Other calculations used 1.0 times ANS71 plus B&W heavy actinides.

] Both of these methods produce similar results, s

t 7

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www we w n m soa es: n a l -- Fra:ato:o Technotostes Q) oot -

Framatome Tcchnologi;s, Inc.

l 51-5000519-06 l

l List of References 4

1. FTl Document 32-1266110-00,"B&WOG Post-LOCA Core Boron Dilution."

2. FTl Document 51-1266113-00, " Post-LOCA Boron Concentration Management."

3. FTl Document 51-1212232-01, " Key Elevations for All Plants."

4. B&W Drawing 02142923E-04, " Lower Grid Top Rib Section."

5. B&W Drawing,02-142917E-04, " Upper Grid Rib Section."

6. FTl Document 51-5000396-00,"RVi Baffle Bolt Safety Assessment." I

7. B&W Drawing,02-27101F-02," Core Barrel Assembly."

8. FTl Document 32-1258134-00, " Decay Heat for LOCA Analysis."

9.* Florida Power Corporatior,, Nuclear Operations Engineering, Crystal River Unit 3,

" Enhanced Design Basis Document, Decay Hest Removal"

10. FTl Document 32-1266263-01, " Sump Delta Method for Cr-3."

11. FTl Document 32-5000185-01, "CR-3 Heatup and Cooldown PT Limits."

12. FTl Document 32-1266110-01, "B&WOG Post-LOCA Core Boron Dilution."

• These documents are maintained and controlled by Florida Power Corporation. Per FTl procedures,-

use of these references are allowed in safety-grade calculations with the approval of the cognizant unit manager of contract manager. The signature below authorizes the use of these documents for input to this evaluation.

NYY (Unit M(nager / Contract Manager

$/$h

'(Datb) 8

1 Framatomo Technologins, Inc.

51-5000519-06

1. Introduction During certain cold leg pump discharge (CLPD) loss-of-coolant accidents (LOCAsh the core liquid through put will cease and boiling will cause the core boron concentration to increase. Control of the core boron concentration post-LOCA is a Nuclear Regulatory Commission (NRC) issue for the B&W Owner's Group (BWOG), of which Crystal River Unit 3 (CR-3) is a part. This control can be provided by any passive mechanism or active method that results in a net liquid flow through the core (Ref. 2). One of these methods is hot leg injection (HLI). This method provides flow from one low pressure injection (LPI) pump backward through the other, shutdown LPI pump and through the decay heat drop line (DHDL) into the hot leg indt.citig a net reverse flow through the core to the break, f

This document presents an evaluation of hot leg injection as a means of core boron control. This evaluation includes ECCS flow requirements, plant confipeAn, HLI DHDL alignments, RV circulalbn patterns, and verification of boron d:lution with HLI.

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Frcmitoms Technologi s, Inc.

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2. Reactor Vessel Flow Paths for HLI The HLI method uses one operating LPI pump in an alignment in which the LPI provides suction to one-high pressure injection (HPI) pump, ECCS injection through the r, ore flood tank (CFT) nozzle in the piping run of the operating LPI pump, and flow 4

through the LPI cess-connect line backward through the idle LPl pump into the reactor coolant system (RCS) hot leg. This alignment reverses the typical flow direction in the DHDL. The piping arrangements and flow patterns for CR-3 with the A-LPI and B-LPl

. pumps operating are shown in Figure 1 and Figure 2, respectively.

A net HLI flow (injection flow minus nozzle gap leakage) into the reactor vessel upper plenum provides dilution of the coie boron in two ways. The minimum HLI flow rate to provide boron dilution rr .st match the core boil-off rate with an additional volume to facilitate some reverse flow through the core. This additional flow will mix with the concentrated fluid in the upper plenum, flow down through the core barrel-baffle region, s

up the downcomer, and out of the RV to the break. Figure 3 shows this process. At higher HL1 flows, it is possible to suppress core boiling entirely, thereby defeating the concentrating process. The core throughput is shown in Figure 4. The following discussion details the HLI boron dilution flow path in the reactor vessel prior to complete suppression of core boiling.

The DHDL is connected to the RCS hot leg pipe 4.7 inches above the bottom of the ho!

leg pipe (Ref. 3). The inner cylinder of the upper plenum assembly directly opposite the hot leg nozzle has 24 three-inch flow holes in addition to the larger flow holes (six 34- >

inch and four 22-inch) located in the upper parts of the plenum cylinder (Ref. 3). From the small holes opposite the hot leg nozzles, the hot leg injection fluid flows to the upper plenum where it mixes with core outlet steam and water. The resulting saturated, boron rich 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 10

4 Framatomo Technologies, Inc.

51-5000519-06 former plates. There are 24 flow holes (8-3", 8-2", & 8-4") spaced around the periphery i-of the upper core plate (Ref. 5) that provide for downflow of the fluid to the core barrel / baffle region. Within the core barrel / baffle region there are eight former plates, each with 80,1.312-inch flow holes (Ref. 6). From the barrel / baffle region the flow can either exit to the periphery of the lower core plate where there are 64 flow holes (8-3",

8-2.5", 8-2", 8-6", 8-3.5",16 1.75", & 8-5") arranged around the periphery of the plate (Ref. 4) or exit to the barrel / baffle region through 30, 0.75-inch flow holes in the core barrel wall to the thermal shield annulus (Ref. 7). The fluid needed to remove the core decay heat circulates back into the core. The excess liquid travels to the break via the thermal shield annulus or the downcomer, providing a boron dilution flow path. The dynamic pressure drop through the flow path described above is about 5.4 inches of water (see Appendix 1) for an HLI flow of 500 gpm (the minimum flow identified in Section 3). The head to prov!de this flow is developed by the injection fluid in the hot leg and the entrance to the upper plenum.

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Framatome Technologies Inc. 51-5000519-06 -

Figure 1: CR-3 DHDL Hot Leg injection Flow Patterns with the A-LPI Pump.

Ilot Leg l

{RB l

DlIV-3[A !

DIIV-4[ f i  ?

2 l ~

DIIV-41 From BWST l

ToIIPI To PZR Aux Spray 3 g DIIV-34 j g DIIV-110 DIIV-1I [

DilV-42 DIIP-1A DIIV-S T v

. .g.o MNode

^ '

_ -, 7 DH-1-FEl DHV-8 '

l DlIV-39] (:

- p t DM-120 N RB Sump DH-3m I'

I DIIV-7 DIIV-40 . : DII-1-FI:2 l DIIV-43 v LJ

! LJ m ' To CFTNozzle FT

! FT "

DIIV-111 DIIV-6 l DIIP-1 lRB y l DHV-353 jg

][DHV-12 ,

To HPI From BWST 12

Framatome Technologies Inc. 51-5000519-06 -

Figure 2: CR-3 DHDL Hot Leg injection Flow Patterns with the B-LPI Pump .

Ilot Leg l

lRB DIIV-3[ A j DHV-4[

! N- ,

DlIV-41 .

Fr9m BWST j To HPI To PZR Aux Spray

a n l DIIV-34V l '

~ DHV-110 DHV-5 l DilV-42  % v LJ e LA ,

m  : ToCFTNozzle Fl

, Y3 j

e DIIV-39 :DlIV-120 d DH-t-FEl j DlIV-8 I

RB Sump l - w )

r

/ (DII-38-FE DTIV-40' y DH-t-FE2 l y

• DlIV-43 J L: Df!V-121 U

To CFT Nozzle m

• w DHV-III Dl W

7 DHP-1B DHV-12

(

j DHV-35 '

To HPI Fron BWST 13

-i...,,,,,,,..-.,, . . . .

Frcmatom] Tcchnologi:s, Inc.

51-5000519-06 i

Figure 3: HLl Flow Paths in the RV Before Core Bolling Suppression Q Control Rod

Drive Mechanism c>c=,c-sbc=,c=,c, c 2= = = = = = = =x s

~ S- ? -

Qs l

-$g f~

- '$ L RkA Reactor Vessel p

,Md I f Plenum Cylinder ht - M t sj ja inner T

.JC$  % I Plenum f O o a . o ,. .

[i i Cylinder Hot M. o ,o,c o, o c

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6

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Hot t.eg 1 11  % Injection Thermal Shield I*  : ..

n ... .. ... A }x Core Barrel --

T d i- ... .. ...

'll 4

1 g

Downcomer Fos.ner Plates  :. . . . ... ... .. ... ... . . . .

s 3 - h '. %

Baffle Plates -  ; q

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g Flow Holes

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~

A '

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Fram toma Technologins, Inc.

51-5000519 06 Figure 4: HLI Flow Paths in the RV After Coro Boiling Suppression 0

~

Control Rod

_. Drive Mechanism e=se=,c=> r=2 e=, e= 2 e:= = = = = = = =r

$_INA /

f '

1. ~

• ^ gg Reactor Vessel y 7 M Q Plenum Cy!!nder

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na tea injection Core Barrel -- 6 ,

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< Downcomer V

Former Plates g "n . . . . . ..- -

V T

Baffle Plates -

x g

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Fuel Assembly b ~

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$j 11L[LR11i Lig, ., tower Core piate q

y 4  %

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15

Framatoma Tcchnologi:s, Inc.

51-5000519-06

3. ECCS Requirements for HLI The HLI method involves either shutting down an operating LPI pump if both are available or throttling the only available LPI pump (if the other one was lost because of a single failure). Use of this method therefore requires a definition of an acceptable ECCS flow-split that will provide both core cooling and boron dilution. Since the pumped injection flow increases with decreasing system pressure, this evaluation should be performed at the highest appropriate pressure. The solubility limit increases with temperature, and since the system will be saturated, the limit will increase with pressure. At an RCS pressure of 72 psla, calculations have shown that boron precipitation will not occur, even for a scenario with all of the available system boron in the core (Ref.1), At this pressure, the LPI pump is capable of providing at least 2700 gpm of flow (Ref. 9) for all of the ECCS and HLI.

ECCS flow = 2700 gpm = Wagi + W tpi + Wau .

If a maximum flow of 600 gpm is assumed for one HPl pump, the remaining flow is-available to be split between the LPI nozzle and the HLI path.

W tpi + Wau = Weces - Wapi = 2100 gpm.

Some of the HLI flow may bypass the core via the hot leg nozzle gaps. The remaining flow is used to match core decay heat and provide an excess flow for boron dilution via throughput to the break, if the excess throughput is sufficiently large, it can possibly suppress core boiling and eliminate the concentrating mechanism entirely. So, Wnu = W,, + Won + W, . .

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i Fiamatoms Tcchnologi:;s, Inc.

51-5000519 00 Post small break LOCA, the system cool down is slow such that the internals and RV shell remain nearly isothermal. At 300 F, the CR 3 total nozzle gap flow was calculated to be 103 gpm (Ref.1, Table 7A). Only one nozzle gap would directly bypass the hot leg injection flow, so only one half of gap flow should be considered.

W,,mtou = 0.5 (103 gpm) = 51.5 gpm .

Post large break LOCA, the cooldown is more rapid +,nd the thick RV shell will remain hotter than the intemals (i.e. non isothermal). The internals are at the RCS saturation temperature, while the reactor vessel is still at a higher temperature. At 14.7 psia with the RV internals at 212 F and the RV at 400 F five hours post LOCA, the maximum single gap flow is estimated to be W,<.,, taoa = 199 gpm .

The ECCS injection' rates needed to match the decay heat bolloff rate and to totally suppress core boiling can be determined with the following equations.

Wos,m.icn = DH / (h,- h ) and Wonu = DH / (h,- h )

where DH is the decay heat, h, is the saturated steam enthalpy, h, is the ECCS liquid enthalpy, and h,is the saturated liquid emhalpy. Calculations were performed using 1.2 times the 1971 ANS decay hea mandard (tabulated in Ref. 8) at 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 for various RCS pressures. The calculation was repeated for best-estimate decay heat. (FTl considers 1.2 ANS71 decay heat to be conservative by 25 percent, so a decay heat of 0.75 times 1.2 ANS71 was used.) The results are shown in Table 1.

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Framatome Technologies, Inc.

i 51 5000519-06 For small break loss of coolant accidents (SBLOCAs), the required HLI flow to overcome the gap flow and to match 1.2 times the ANS 1971 decay heat at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post-LOCA and 72 psia !s 52 gpm plus 202 gpm, or approximately 255 gpm. An additional hot leg flow of 245 gpm in excess of the decay heat match up flow plus gap flow should be adequate for core borc^ dilution. That is, a total not leg injection flow of 500 gpm is adequate to provide boron dilution 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post SBLOCA and beyond.

For large break loss of coolant accidents (LBLOCAs), the required HLI flow to overcome the gap flow and to match 1.2 times the ANS 1971 decay heat at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> post LOCA and 14.7 psla' is 199 gpm plus 200 gpm, or approximately 410 gpm. In this cas.o. the recommended 500 gpm HLI flow still exceeds the flow needed for bolloff and gap flow considerations. This example only has 90-gpm excess flow for boron dilution ersus the 245 gpm recommended previously. The excese will increase with time as the decay heat bolloff 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 130 gpm 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 245 gpm.

For LBLOCA the excess ECCS f'ow can be sinaller, since the boron concentration dce ,

not have t< 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.

With a minimum of 500 gpm of HLI flow and 600 gpm for HPl flow, the flow available for LPI nozzle flow and instrument uncertainty is Wop, = ECCS flow - Wapi- Wsu .

= 2700 - 600 - 500 = 1000 gpm.

i The LBLOCA is expected to depressurize to 14.7 psia by five hours post '.OCA. The difference in the LD1 flow between 72 psia and 14.7 psia is not considered in this calculation, but the result preser,ted is conservative.

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. Frcmr.toma Technologias, Inc.

51 5000519 06 '

Historically,1000 gpm per LPI nozzle has been assumed to be the target value for securing the HPI pumps. When using the HLI alignment, it is reasonable to target 1000 gpm for the one flowing LPI line, which leaves 600 gpm of real pump flow for instrument uncertainty or flow imbalance at 72 psia. Below 72 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 suppress core boiling with best-estimate or

realistic decay heat levels.

in summary, FTl recommends that the HLI alignment provide flow for one HPl pump (up to 600 gpm), a minimum reverse flow of at least 500 gpm through the decay heat drop line for boron dilution, and approximately 1000 gpm into one CFT nozzle, it should be l emphasized that the suppression of core boiling eliminates the mechanism that <

concentrates the boron, thereby addressing the boron concentration control for the duration of the transient. Therefore, the highest possible HLI flow rates should be targeted. For examplo, if hot leg injection flow is 900 gpm, core boiling will be suppressed and the core boron concentration mechanism will be removed if realistic decay heat contributions are considered.

i l

i

, = __

l 9

Frcm:toma Technologi:8, l.ic.

51 5000519-06 Table 1: HLI Flow to Match Decay Heat a.. Suppress Core Bolling l

1.2 ANS71 DH I 0.75'(1.2 ANS71 DH)

Time Pressure, Decay- Won ., Wo .w, Post Decay Woam... Wo w, psia Heat, gpm gpm Heat, gpm gpm LOCA Blu/s Blu/s  ;

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 100- 28,084 201 1437 21,063 151 1078 72 202 1708 102 1281 14.7 209 7717 157 5788 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 72 17,457 l 126 1062 13,093 94 796 14.7 130 4797 97 3596'  ;

1 week 72 9535 69 580 /151 52 -435 14.7 71 2620 53 1965 NOTE: The HLIliquid is injected at 185 F.

l l

20

Frcmrtoma Tcchnologi:s, Inc.

51 5000519-06

4. Verification of HLI Effactiveness The previous sections have identified the HL1 flow paths and minimum required flow

-rate for core boron dilution. Tha effectiveness of HL1 as a boron dilution mechanism has also been demonstrated by analyses performed in Reference 12 for both large and small LOCA scenarios. These analyses do not necessarily represent the most limiting '

r, eses or identify necessary HLI activation times. They simply demonstrate the effectiveness of the HLI method in reversing the core borors concentration buildup.

The LBLOCA cases were run with 100 gpm of net HLI flow (at 185 F) beginning five hours post-LOCA. Two cases were examined, the first case using 1.2 times ANS 1971 -

decay heat, and the second us!ng 1.0 times ANS 1971 decay heat. The results from Appendix G of Reference 12 are shown in Figure 5 and Figure 6. It can be seen from the figures that even this small amount of HLI is effective in diluting the core boron concentration very quickly.

The SBLOCA ccses were run with 100 gpm of net HLI flow (at 185 F) beginning 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> post LOCA. Two cases were examined, the first case using 1.2 times ANS 1971 decay heat, and the second using 1.0 times ANS 1971 decay heat. The results from Appendix G of Reference 12 are shown in Figure 7 and Figure 8. Again, it is obvious that HLI is an effective core boron dilution mechanism once it is initleted.

The core boron dilution flows used in these analyses were very conservative (i.e. high gap bypass flow). If the gaps were open and passing liquid, the core concentration at the beginning of the dilution would be much lower, although the dilution mechanism would be as effective. Further, if the gaps were closed, the net core throughput would _.

be significantly higher. With larger core flows, the core boron concentration decrease would be faster.

21

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51-5000519-06 I

Figure 6: LBLOCA Boron Concentations Versus Time for the 2568 MWt LL Piant.

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51 5000519-06 5, Effect of HL1 on Hot Leg Piping In addition to the boron dilution evaluations discussert above, FTl also evaluated the impact of the HLl on the hot leg near the RV nozcles, the reactor vessel, and the reactor vesselinternals. -The evaluation includes:

- Steam-water interaction and or cold water-hot water interactions (water hammer),

- Stratified liquid flow in the hot leg pipe,

- Temperature rates of change for the RV and the RV internals,

- Operation within the pressure-temperature (P-T) limits, and

- Reverse flow in the core, t

The following paragraphs describe these evaluations in detall.

5.1 Water Hammer The injection of sump water, assumed cooled to 185 F by the operating decay heat

- cooler, into the reactor vessel hot leg is not expected to result in steam-water interactions (" water hammer"), because the HLI fluid is introduced into a water-to-water interface in the hot leg. The hot leg pipe will have a water level consistent with, but deeper than the water level in the cold leg pipe for the assumed CLPD break. The hot leg injection flow velocity is relatively low (less than about 0.25 ft/s) in the hot leg pipe and is expected to run along the bottom of the hot leg pipe under the saturated fluid in the pipe, gradually mixing with the hotter water in the hot leg pipe until the injection fluid reaches the upper plenum cylinder. This fluid injection into the hot leg is similar to the injection sites of the HPl into the RCS cold legs, and to the core flood line (CFL) nozzles on the reactor vessel. Direct contact of colder HLI water with steam and the resultant water hammer is not expected to occur.

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Framatome Tcchnologi;s, Inc.

i 51 5000519 06 l 5.2 The: mal Stratification i

The HLI flo.v velocity is relatively low (less than about 0.25 ft/sec) in the hot leg pipe and is expected to run along the bottom of the hot leg pipe under the saturated fluid in

{ the pipe, gradually mixing with the hotter water in the hot leg pipe until the injection fluid 3

reaches the upper plenum cylinder. At the reactor vessel, the injection fluid flows through the holes in the inner plenum cylinder and is expected to begin vigoro' mixing with the steam-water mixture in the plenum. The injection fluid begins at 185 F and is expected to rear., the saturation temperature for the pressuro in the reactor vessei (212 to 30S F).

Since the hot leg injection fluid is expected to flow under the saturated fluid in the hot leg pipe and reactor outlet nozzle, thermal stratification of the hot leg injection fluid between the DHDL nozzle and the reactor internals can occur. However, there is no significant pressure en the system (less then approximately 200 psia saturated) and the temperature difference between the HLI iluid and the RCS fluid is relatively small, between 72 and 242 F. Any stresses generated by this thermal stratification are expected to be insignificant for this LOCA event.

5.3 Rates Of Temnerature Chance As the core decay heat decreases with time, HLI fluiri 5 expected to eventually remove the core decay heat by reverse flow through the core with sensible heat removal (delta-T cooling). The suppression of core boiling is accompanied by a temperature reversal in the vessel wherein the colder (185 F) HLI water enters at the top of the core,- flows downward through the core removing heat by subcooled heat transfer, and exits the core at a higher temperature but below the boiling point. Since the decay heat will be slowly decreasing, the change in the decay heat removal process is expected to take place over a long period of time (davs) so that the changes in temperature in the 27 2

Frtmatoma Tcchnologi::s, Inc.

51 5000519-08 reactor vessel and the internals are slow and insignificant relative to the temperature changes in the reactor vessel and internals immediately post LBLOCA.

5A_L, essure-Temperature limits in the temperature pressure range where hot le0 injection is expected to operate, (saturated water in the range from 212 F to 305 F), the temperature and pressure conditions are well below the temperature pressure limits (Ref.11) for Crystal River Unit

3. No additional significant pressure nr thermal stresses are expected for these ,

operating conditions.

5.5 Reverse Flow In The Core The' eventual reversal of finw direction in the core will have no impact on the fuel assemblies or their support structures, because the downward flow velocity for flow rates in the range of 500 to 900 gpm is less than about 0.05 ft/s. This velocity is insignificant compared to the normal core velocity (about 15 ft/s) There wiil ossentially be no additional loads on the fuel assemblies above their own weight.

s 28

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l Frcmatome Tcchnologhs, Inc.

51 5000519 06

6. Summary of Results and Conclusions Evaluations of core boron conctntration have been performed for LBLOCAs and SBLOCAs. Hot leg injection by reverse flows of 500 gpm through the decay heat drop line is sufficient to exceed the gap bypass flow with the remaining flow offering a positive and rapid means for reducing the core boron concentration. The calculations supporting this flow rate consider both 1.2 and 1.0 times the ANS 1071 decay heat standard and conservative core mixing volumes (i.e. 790 and 1200 ft' for large and small LOCA, respectively). FTl has reviewed the required flow patterns and hydraulic resistance within the reactor vessel and concluded that there are no problems using HLI for boron concentration control provided it is initiated before the hot leg reaches the boron precipitation mixing limit as defined in Reference 10.

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29

Frcmatoma Tcchnologi:s, Inc.

515000u9-06 Appendix 1: Reactor Vessel HLI Flow Path pressure Losses Calculation of the pressure losst i mrough the several plate flow holes in the hot leg injection flow path is performed below.

1.1 Identification of Flow Holes 1

a) Plenum Cylinder Flow Holes (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 q

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'=1.1775 ft'. Use 1.18 ft 2-b) Upper Core Plate Flow Holes (Reference 5 )

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

8-3 inch dia ho;es: 8*0.785*(3.0 in)'/144 in'/Ft'= 0.392 ft' 2

8-2 inch dia holes: 8*0.785*(2.0 in)2/144 in'/Ft'= 0.174 ft B-4 inch dia holes: 8*0.785*(4.0 ir;f/144 in'/Ft = 0.70 ft2 2

1.266 ft' 30 l

s Framatom) Tcchnologt:s, Inc.

51-5000519 06 c) Former Plate Flow Holes (Reference 6) .

The former plates have 80-1,312 in dia flow holes.

The flow area per former phte is:

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

There are:

8-3 in dia holes- 8* 785*(3 in)'/144 in'/ft'= 0.392 ft' 8 2.5 in dia holes---8*.785*(2.5 in)'/144 in'/ft'= 0.273 ft' 8 2.0 in dia holes--8*.785*(2.0 in)'/144 in'/ft'= 0.174 ft' 8-6.0 in dia holes- 8*.785*(6.0 in)'/144 in'/ft* = 1,57 ft' 8

8-3.5 in dia holes-8* 785*(3.5 in)'/144 in'/ft = 0.534 ft 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)'/144 in'/ft'= 1.090 ft' Total-- i 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-- - -- - -- -

---3.75 ft' -

Outlet holes in lower core plate-- --4.30 ft2 1.2 Calculation of Velocities in the Flow Holes velocity = flow / area / density Flow = 500 gpm Density of water at 185 F=1/0.01654 ft'/lbm=60.46 lbm/ft' Mass flow =500 g/ min *60.46 lbm/ft'/7.48 gal /ft'/60 sec/ min =67.4 lbm/sec a)- velocity in plenum cylinder flow holes =

67.4 lbrn/sec/1.18 ft2/60.46 lbm/ft' 0.945 ft/sec 31

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

s Frcmatome Tcchnolog!cs, Inc. 51 5000519 06 l b) velocity in upper core plate flow holes =

67.4 lbm/sec/1.26 ft2/60.46 lbm/ft'=0.88 ft/see c) velocity In former plate flow holes; 67.4 lbm/sec/0.75 ft2/60.46 lbm/ft'=1.49 ft/sec d) velocity in lower core plate flow holes; 67.4 lbm/sec/4.30 ft2/60.46 lbm/ft'=0.26 ft/sec 1.3 Calculation of pressure drops in the several flow holes:

delta p= DP = k* rho *v'/144/2g-l k = it, 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) l rho is water +nsity = taken as 60.46 lbm/ft' as above. This value of density is used for cons. atism (higher DP) of the pressure losses in hot leg injection flow path.

( g= gravita!!onal constant =32.2 ft/sec/sec l

l a)- DP plenum cylinder flow holes =

1.5*60.46 lbm/ft'*(0.945 ft/sec)'/(144 in'/ft2*2*32.2 ft/sec')=0.00873 psi b) DP upper core plate:

1.5*60.46 lbm/ft'*(0.88 ft/seci'/(144 in'/ft 2*2*32.2 ft/sec')=0.00757 psi I

c) DP former plates:

8 plates *1.5*60.46 lbm/ft'*(1.49 ft/sec)'/(144 in'/ft'*2*32.2 ft/sec r) n0.174 psi d) DP lower core plate:

1.5*60.46 lbm/ft'*(.026 ft/sec) /(144 in'/ft'*2*32.2 ft/sec')=0.0000066 psi 32

U.S. Nuclear Regulatory Commission Attachment E 3F0298 07 Page1 of1 ATTACitMENT E ACRONYMS AND ABBREVIATIONS i

APS . . . . . . . Auxiliary Pressurizer Spray B&W . . . . . . . Babcock and Wilcox BWST , . . . . . Borated Water Storage Tank CFT . . . . . . . Core Flood Tank CR 3 . . . . . . . Crystal River Unit 3 DL RB Sump . . Drop Line to Reactor Building Sump (mitigation method)

ECCS ... . . Emergency Core Cooling System FPC . . . . . . . Florida Power Corporation FTl . . . . . . . . Framatome Technologies incorporated gpm . . . . . . . gallons per minute llLI-RF . . . . Ilot leg injection via Reverse Flow (mitigation method)

IIPI . . . . . . . . liigh Pressure Injection system LAR . . . . . . License Amendment Request LBLOCA . . . . Large Break LOCA LOCA . . . . . . Loss of Coolant Accident LPI . . . . . . . , Low Pressur,, Injection system NRC , . . . . . U.S. Nuclear Regulatory Commission ppm . . . . , . , parts per million RB . . . . . . . Reactor Building RCS . . . . . . . Reactor Coolant System RV . . . . . . . . Reactor Vessel c

RVVV . . . . . . Reactor Vessel Vent Valve SBLOCA . . . . Small Break LOCA TSC_ . . . . ._._. Technical Support Center

_