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{{#Wiki_filter:. _ _ . _ __ __. ._. _ _ . _ | {{#Wiki_filter:. _ _ . _ __ __. ._. _ _ . _ | ||
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LO I | |||
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i t | |||
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e 1 | |||
1 | AN EVALUATION OF BORON PRECIPITATION DURING LONG-TERM COOLING | ||
; FOLLOWING A POSTULATED LOSS OF COOLANT ACCIDENT i | |||
AN EVALUATION OF BORON PRECIPITATION | |||
DURING LONG-TERM COOLING | |||
; FOLLOWING A POSTULATED LOSS OF COOLANT ACCIDENT | |||
i | |||
.i l | .i l | ||
l | l I | ||
'l 79120803[6 a | |||
I | |||
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g | g | ||
- ~ | - ~ | ||
I. Introduction l | I. Introduction l | ||
Reactor system circulation and boron concentration in the post-LOCA, long-term cooling environment have been analyzed for the potential of unacceptably high boric acid concentrations in the core region. Both large and small breaks of the reactor inlet and outlet pipes are con-sidered and the large break of a reactor vessel inlet pipe is shown to be the most limiting case. | Reactor system circulation and boron concentration in the post-LOCA, long-term cooling environment have been analyzed for the potential of unacceptably high boric acid concentrations in the core region. Both large and small breaks of the reactor inlet and outlet pipes are con-sidered and the large break of a reactor vessel inlet pipe is shown to be the most limiting case. | ||
Line 70: | Line 39: | ||
- the line routing takes it above the hot leg pipe. This decay heat line is, however, capable of being aligned (Mode 2) such that a connection from the LPI pump discharge to the decay heat line will route flow back-wards through this line into the hot leg. This will route dilute injection into the area above the core. The analysis description that follows describes hot leg injection by way of the auxiliary pressurizer spray. However, the hot leg injection results presented.are independent of source, e.g., auxiliary pressurizer spray or reverse flow through the decay heat line. | - the line routing takes it above the hot leg pipe. This decay heat line is, however, capable of being aligned (Mode 2) such that a connection from the LPI pump discharge to the decay heat line will route flow back-wards through this line into the hot leg. This will route dilute injection into the area above the core. The analysis description that follows describes hot leg injection by way of the auxiliary pressurizer spray. However, the hot leg injection results presented.are independent of source, e.g., auxiliary pressurizer spray or reverse flow through the decay heat line. | ||
1 | 1 | ||
* ^~ | * ^~ | ||
(~% | (~% | ||
,. ~ | ,. ~ | ||
Line 86: | Line 51: | ||
In the event that the decay heat line is not operational (failure of isolation valve to open), the alternate system to promote low boron concentration and to dilute the boron concentration is align-ment of the auxiliary pressurizer spray. The flow paths for this mode of operation (defined as " hot leg injection") are shown in Figure 6. | In the event that the decay heat line is not operational (failure of isolation valve to open), the alternate system to promote low boron concentration and to dilute the boron concentration is align-ment of the auxiliary pressurizer spray. The flow paths for this mode of operation (defined as " hot leg injection") are shown in Figure 6. | ||
Hot leg injection has little effect on circulation and concentration until the steaming rate, assuming evaporation only from the core, is equal to or less than the bot leg injection rate. As the injection rate approaches the steaming rate the hot leg injection acts to reduce the rate of core boron concentration by adding non-concentrated water. As the decay heat rate decreases with time., the hot leg injection becomes adequate to remove decay heat by sensible h::t removal. The core flow direction reverses, and the concentration of boron in the core becomes dilute with time. The concentration with time for " hot leg injectica" is shown in Figure 5, for an injection rate of 40 gpm. | Hot leg injection has little effect on circulation and concentration until the steaming rate, assuming evaporation only from the core, is equal to or less than the bot leg injection rate. As the injection rate approaches the steaming rate the hot leg injection acts to reduce the rate of core boron concentration by adding non-concentrated water. As the decay heat rate decreases with time., the hot leg injection becomes adequate to remove decay heat by sensible h::t removal. The core flow direction reverses, and the concentration of boron in the core becomes dilute with time. The concentration with time for " hot leg injectica" is shown in Figure 5, for an injection rate of 40 gpm. | ||
~ | ~ | ||
C \ | C \ | ||
Figure 7 shows the model used for calculating the concentration | Figure 7 shows the model used for calculating the concentration | ||
Line 98: | Line 58: | ||
) | ) | ||
C = Mass Solute Mass Solvent C= cCi+ft in in "tf out c | C = Mass Solute Mass Solvent C= cCi+ft in in "tf out c | ||
!o" + t1 dt - 1 dt (1) o e o e o where Ci is the concentration at t1 tl is time of vent valve opening or spray initiation Co is same reference concentration Equation 1 is used to calculate the concentration ratio after the natural circulation phase of the transient is terminated. | !o" + t1 dt - 1 dt (1) o e o e o where Ci is the concentration at t1 tl is time of vent valve opening or spray initiation Co is same reference concentration Equation 1 is used to calculate the concentration ratio after the natural circulation phase of the transient is terminated. | ||
The important assumptions used for this part of the transient are: | The important assumptions used for this part of the transient are: | ||
(1) Constant mixing r. ass, Mc = 30000 LBM (2) 40 gpm flow rate from pressurizer sprays (3) Constant LPI injection rate and concentration. | (1) Constant mixing r. ass, Mc = 30000 LBM (2) 40 gpm flow rate from pressurizer sprays (3) Constant LPI injection rate and concentration. | ||
(4) No' density gradients in calculation of forced circulation | (4) No' density gradients in calculation of forced circulation (5) 1000 BTU /LBM needed to produce steam (6) Maximum flow out break for letdown line case (7) K-factors based on full flow values - | ||
(5) 1000 BTU /LBM needed to produce steam (6) Maximum flow out break for letdown line case (7) K-factors based on full flow values - | |||
Summary: Reactor Inlet - Large Break The results of the calculations are shown in Figure 5. They show that the maximum concentration ratio for the letdown line case is 1.19 at 1 day; the maximum concentration ratio for the hot leg injection case is 11 at 60 days. The solubility curves show that a concentration ratio of 35:1 is needed before precipitation will occur. Thus, it has been shown that the proposed method for con-trolling concentration buildup in the long-term cooling phase of a LOCA is credible. This is particularly true when the conservatisms inherent in the analysis are considered. These conservatisms include: | Summary: Reactor Inlet - Large Break The results of the calculations are shown in Figure 5. They show that the maximum concentration ratio for the letdown line case is 1.19 at 1 day; the maximum concentration ratio for the hot leg injection case is 11 at 60 days. The solubility curves show that a concentration ratio of 35:1 is needed before precipitation will occur. Thus, it has been shown that the proposed method for con-trolling concentration buildup in the long-term cooling phase of a LOCA is credible. This is particularly true when the conservatisms inherent in the analysis are considered. These conservatisms include: | ||
l | l (1) No dilution of injection E 0 is considered 2 | ||
(1) No dilution of injection E 0 is considered 2 | |||
(2) Absorption of boric acid by concrete is neglected (3) Volatility of boric acid was neglected B. Pump Suction - Large Break For large breaks postulated at or in the pump suction line, the flow l 1 | (2) Absorption of boric acid by concrete is neglected (3) Volatility of boric acid was neglected B. Pump Suction - Large Break For large breaks postulated at or in the pump suction line, the flow l 1 | ||
paths are as shown on Figure 8. In this case the leak fluid must pass through the RC pump which is some 3 feet above the centerline of cold leg nozzle. This condition provides increased downcomer driving head for core flow which results in more core flow and a lower outlet quality and boron concentration when operating with LPI inj ection, | paths are as shown on Figure 8. In this case the leak fluid must pass through the RC pump which is some 3 feet above the centerline of cold leg nozzle. This condition provides increased downcomer driving head for core flow which results in more core flow and a lower outlet quality and boron concentration when operating with LPI inj ection, | ||
Line 116: | Line 69: | ||
Operations in the forced circulation mode will produce flow patterns l equivalent to that shown in Figure 9, with a near constant minimum flow rate of approximately 118 lb/sec, which is more than adequate to provide decay heat removal without evaporation within five days. | Operations in the forced circulation mode will produce flow patterns l equivalent to that shown in Figure 9, with a near constant minimum flow rate of approximately 118 lb/sec, which is more than adequate to provide decay heat removal without evaporation within five days. | ||
Switch over to this mode will provide a concentration ratio equal to or less than that shown in Figure 5. | Switch over to this mode will provide a concentration ratio equal to or less than that shown in Figure 5. | ||
In the event the decay heat line is not operational, the alternate l system, pressurizer spray, dilutes the boron concentration as ! | In the event the decay heat line is not operational, the alternate l system, pressurizer spray, dilutes the boron concentration as ! | ||
described iE"Section II.A. above. The hot leg injection flow paths , | described iE"Section II.A. above. The hot leg injection flow paths , | ||
Line 124: | Line 75: | ||
D. Reactor Outlet - Top of 180 Bend - Large Break In the case of a postulated large break at the top of the 180 bend, reactor outlet, the overall flow paths are as shown in Figure 12. | D. Reactor Outlet - Top of 180 Bend - Large Break In the case of a postulated large break at the top of the 180 bend, reactor outlet, the overall flow paths are as shown in Figure 12. | ||
With one LPI injection pump assumed operating, the injection flow will split approximately 50/50 between the ' core and steam generators until the steam generator stored heat is removed (approximately one day). During this period the flow paths within the vessel are approximately those of forced circulation. The corresponding core flow rates are equal to or greater than (approximately 200 lb/sec) those shown in Figure 2, because of increased drit ing head. | With one LPI injection pump assumed operating, the injection flow will split approximately 50/50 between the ' core and steam generators until the steam generator stored heat is removed (approximately one day). During this period the flow paths within the vessel are approximately those of forced circulation. The corresponding core flow rates are equal to or greater than (approximately 200 lb/sec) those shown in Figure 2, because of increased drit ing head. | ||
.- p | .- p the decay heat line with one LPI string (see Figure 13). The flow is E cough existing valves LP-1, LP-2, LP-3, LP-4 (for Units 1 and 2), | ||
the decay heat line with one LPI string (see Figure 13). The flow is E cough existing valves LP-1, LP-2, LP-3, LP-4 (for Units 1 and 2), | |||
LP-9, LP-12, LP-17 and into the reactor vessel through the core flood , | LP-9, LP-12, LP-17 and into the reactor vessel through the core flood , | ||
nozzle. I B. Mode 2 - Hot Leg Injection Through the Decay Heat Line i l | nozzle. I B. Mode 2 - Hot Leg Injection Through the Decay Heat Line i l | ||
Line 142: | Line 88: | ||
inside the reactor building which must be opened and closed during l the long-term cooling period to establish this flow path. Changes required are shown on Figure 3 and are: (1) change valve LP-45 to locked open, (2) add on an electric motor operator (EMO) to valve HP-340, and (3) add on EHO to valve HP-356. Valve HP-356 must remain open during normal operation to provide a continuous minimum makeup line flow to minimize thermal transients on the RC pipe nozzle. | inside the reactor building which must be opened and closed during l the long-term cooling period to establish this flow path. Changes required are shown on Figure 3 and are: (1) change valve LP-45 to locked open, (2) add on an electric motor operator (EMO) to valve HP-340, and (3) add on EHO to valve HP-356. Valve HP-356 must remain open during normal operation to provide a continuous minimum makeup line flow to minimize thermal transients on the RC pipe nozzle. | ||
This valve (HP-356) must be closed for Mode 3 to prevent the flow from diverting to the HPI line. Valve HP-340 must remain closed l during normal operation to prevent the continuous minimum makeup line l flow from diverting to'the pressurizer. The flow rate for this path l to the hot leg is controlled and limited to 40 GPM by the block orifice downstream of valve HP-340. | This valve (HP-356) must be closed for Mode 3 to prevent the flow from diverting to the HPI line. Valve HP-340 must remain closed l during normal operation to prevent the continuous minimum makeup line l flow from diverting to'the pressurizer. The flow rate for this path l to the hot leg is controlled and limited to 40 GPM by the block orifice downstream of valve HP-340. | ||
IV. Single Failure Analysis The three modes listed above are necessary to satisfy the single failure criteria. Operations must be designed for a single failure in either the short-term or long-term cooling period but not a single failure in the short term and then another single failure in the Ivag-term period. | IV. Single Failure Analysis The three modes listed above are necessary to satisfy the single failure criteria. Operations must be designed for a single failure in either the short-term or long-term cooling period but not a single failure in the short term and then another single failure in the Ivag-term period. | ||
Since the operator may not be able to determine the location of the break, Mode 1 is attempted first (if both LPI strings are operable) to determine if the normal decay heat removal path can be established. It can be established if the break location is high enough in elevation so that the decay heat suction nozzle on the hot leg is sufficiently flooded to prevent gas or steam entrainment at the LPI pump flow rate. Even if there is no single failure during the attempt, success is not assured because of the possibility of gas or steam entrainment in the decay heat | Since the operator may not be able to determine the location of the break, Mode 1 is attempted first (if both LPI strings are operable) to determine if the normal decay heat removal path can be established. It can be established if the break location is high enough in elevation so that the decay heat suction nozzle on the hot leg is sufficiently flooded to prevent gas or steam entrainment at the LPI pump flow rate. Even if there is no single failure during the attempt, success is not assured because of the possibility of gas or steam entrainment in the decay heat | ||
Line 153: | Line 96: | ||
V. Operating Procedures for Long-Term Cooling The three operating modes which have been described for long-term cooling cannot presently be fully effected. The existing equipment is adequate to provide the necessary flow paths for Modes 1 and 2; however, dose calculations are not completed for areas of the Auxiliary Building in which manual valves must be operated. Operating Mode 3 cannot be implemented until electric motor operators are added to valves HP-340 and HP-356 which are located in the Reactor Building and valve LP-45 is modified to be locked open. | V. Operating Procedures for Long-Term Cooling The three operating modes which have been described for long-term cooling cannot presently be fully effected. The existing equipment is adequate to provide the necessary flow paths for Modes 1 and 2; however, dose calculations are not completed for areas of the Auxiliary Building in which manual valves must be operated. Operating Mode 3 cannot be implemented until electric motor operators are added to valves HP-340 and HP-356 which are located in the Reactor Building and valve LP-45 is modified to be locked open. | ||
The ECCS systems will be placed in one of the following three modes of operation (Mode 3 will only be possible after modifications) within one day of the accident. Injection flow to the RC System'should be maintained through two paths while attempting to place the system in one of the three operating modes. The two injection flow paths can be either the two LP injection lines or one LP injection line combined with one HPI string (LPI pump acting as a booster pump for the EPI pump). | The ECCS systems will be placed in one of the following three modes of operation (Mode 3 will only be possible after modifications) within one day of the accident. Injection flow to the RC System'should be maintained through two paths while attempting to place the system in one of the three operating modes. The two injection flow paths can be either the two LP injection lines or one LP injection line combined with one HPI string (LPI pump acting as a booster pump for the EPI pump). | ||
e ( | e ( | ||
Line 166: | Line 108: | ||
( If two LPI pumps are operable, use String A to inject through LPI line to reactor vessel. Use String B's full flow through the cross connect (valve LP-68) to decay heat line and into the hot leg. Close String B LPI line EMO valves LP-18 and LP-14. | ( If two LPI pumps are operable, use String A to inject through LPI line to reactor vessel. Use String B's full flow through the cross connect (valve LP-68) to decay heat line and into the hot leg. Close String B LPI line EMO valves LP-18 and LP-14. | ||
(2) If only one LPI pump is operable, split the flow between one LPI line to the reactor vessel and the cross connect path to the hot leg. The flow split is accomplished by throttling the LPI line EMO control valve (LP-18) and manual valve LP-68 in the cross connect. Flow split indication is confirmed by LPI pump discharge pressure indication remaining the same (same as for 3000 GPM LPI line injection flow rate) and the LPI line flow l rate indicator at approximately 1500 GPM. | (2) If only one LPI pump is operable, split the flow between one LPI line to the reactor vessel and the cross connect path to the hot leg. The flow split is accomplished by throttling the LPI line EMO control valve (LP-18) and manual valve LP-68 in the cross connect. Flow split indication is confirmed by LPI pump discharge pressure indication remaining the same (same as for 3000 GPM LPI line injection flow rate) and the LPI line flow l rate indicator at approximately 1500 GPM. | ||
: d. If Mode 2 is successful, injection flow to the reactor vessel is | : d. If Mode 2 is successful, injection flow to the reactor vessel is through two injection flow paths and dilute injection is reaching the area above the core (if the break is a cold leg break). | ||
through two injection flow paths and dilute injection is reaching the area above the core (if the break is a cold leg break). | |||
Oconee Unit 3 | Oconee Unit 3 | ||
: a. Step a, for Oconee Units 1, 2 above,.is applicable. | : a. Step a, for Oconee Units 1, 2 above,.is applicable. | ||
Line 174: | Line 114: | ||
: c. Line up cross connect (valve IP-96) flow path from LPI String B to HPI System letdown line. Complete the flow path up to the return cross connect (valve BP-363) to the LPI System. In the HPI System | : c. Line up cross connect (valve IP-96) flow path from LPI String B to HPI System letdown line. Complete the flow path up to the return cross connect (valve BP-363) to the LPI System. In the HPI System | ||
: letdown line, isolate the filters and demineralizers and open the bypasses around them. Close the inlet valve to the letdown storage tank. | : letdown line, isolate the filters and demineralizers and open the bypasses around them. Close the inlet valve to the letdown storage tank. | ||
n s~ | n s~ | ||
s .: | |||
: d. LPI pump P1A must not be operating and its suction EMO valves LP-5 and LP-6 nnst be closed. The building spray pump assSciated with LPI String A must be shut off and the sump EMO outlet valve LP-19 must-be closed. Open manual valve HP-363 in return cross connect-to LPI System. Open EMO valve LP-3 in decay heat drop line. | : d. LPI pump P1A must not be operating and its suction EMO valves LP-5 and LP-6 nnst be closed. The building spray pump assSciated with LPI String A must be shut off and the sump EMO outlet valve LP-19 must-be closed. Open manual valve HP-363 in return cross connect-to LPI System. Open EMO valve LP-3 in decay heat drop line. | ||
; e. The flow path is now complete. The flow rate indicator in the HPI System letdown line indicates the flow rate in this path from LPI String B to EPI System letdown line to LPI String A suction to decay heat line and backwards through this line to the hot leg. | ; e. The flow path is now complete. The flow rate indicator in the HPI System letdown line indicates the flow rate in this path from LPI String B to EPI System letdown line to LPI String A suction to decay heat line and backwards through this line to the hot leg. | ||
Line 188: | Line 122: | ||
2 | 2 | ||
: b. .Close main pressurizer spray line EMO valve RC-1 or RC-3 or both. | : b. .Close main pressurizer spray line EMO valve RC-1 or RC-3 or both. | ||
* c. Open auxiliary spray line EMO valve HP-340. Open manual valve HP-355 | * c. Open auxiliary spray line EMO valve HP-340. Open manual valve HP-355 | ||
; in Auxiliary Building. C1cse EMO valve HP-356 to force flow to the auxiliary spray line, | ; in Auxiliary Building. C1cse EMO valve HP-356 to force flow to the auxiliary spray line, | ||
Line 195: | Line 128: | ||
Injection flow to the reactor vessel should be maintained through l | Injection flow to the reactor vessel should be maintained through l | ||
two paths per Item a of Mode 2. Auxiliary spray line flow rate is indicated by the flow measurement upstream of manual valve HP-355 (normal makeup line flow indication). | two paths per Item a of Mode 2. Auxiliary spray line flow rate is indicated by the flow measurement upstream of manual valve HP-355 (normal makeup line flow indication). | ||
VI. Summary of Results | VI. Summary of Results The reconsnended operating procedures for Oc'onee 1, 2, and 3 to minimize boron concentration following a LOCA are, in order of preference: | ||
i A. Always maintain a minimum of 3000 GPM LPI injection into the down-comer. This provides for a natural circulation flow path within the reactor vessel and the maximum concentration buildup is C/Co = | |||
The reconsnended operating procedures for Oc'onee 1, 2, and 3 to minimize boron concentration following a LOCA are, in order of preference: | |||
i A. Always maintain a minimum of 3000 GPM LPI injection into the down- | |||
comer. This provides for a natural circulation flow path within the reactor vessel and the maximum concentration buildup is C/Co = | |||
1.19 for the first 24 hours after a LOCA. (Co is initial concentration | 1.19 for the first 24 hours after a LOCA. (Co is initial concentration | ||
- 2200 ppm boron solution.) | - 2200 ppm boron solution.) | ||
Line 210: | Line 139: | ||
- r l- ~ -- . . . , . . , , . . , , ,, .,,.w., | - r l- ~ -- . . . , . . , , . . , , ,, .,,.w., | ||
n e | n e C. Should Step B not be successful, the decay heat line is aligned for a reverse flow of 40 gpm minimum within 24 hours af ter the LOCA. | ||
This is called hot leg injection and limits the concentration ratio to 11.0 at 60 days (Figure 5). If larger reverse flow rates are available through the decay heat line, the concentration ratio will be held to a smaller value 1.9 at 7 days (140 gpm hot leg injection Figure 5). | |||
C. Should Step B not be successful, the decay heat line is aligned for a reverse flow of 40 gpm minimum within 24 hours af ter the LOCA. | |||
This is called hot leg injection and limits the concentration ratio to 11.0 at 60 days (Figure 5). If larger reverse flow rates are | |||
available through the decay heat line, the concentration ratio will be held to a smaller value 1.9 at 7 days (140 gpm hot leg injection | |||
Figure 5). | |||
D. In the event that the decay heat line is not operational (single failure), the auxiliary pressurizer spray ficw is aligned to provide 40 gpm minimum flow within 24 hours after the LOCA. | D. In the event that the decay heat line is not operational (single failure), the auxiliary pressurizer spray ficw is aligned to provide 40 gpm minimum flow within 24 hours after the LOCA. | ||
This mode is also called hot leg injection and produces the same results as discussed in C above. (C/Co=11.0 60 days) | This mode is also called hot leg injection and produces the same results as discussed in C above. (C/Co=11.0 60 days) l I | ||
l I | |||
l 1 | l 1 | ||
n . | n . | ||
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.3 7 | .3 7 | ||
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4 | 4 LOW QUALITY- | ||
LOW QUALITY- | |||
/ STEAM-WATER | / STEAM-WATER | ||
===} | ===} | ||
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' a (y) _ yr l<- INJECTION e STER 1 i M | ' a (y) _ yr l<- INJECTION e STER 1 i M | ||
* 1 - . .. - J* o * '' | * 1 - . .. - J* o * '' | ||
Line 270: | Line 168: | ||
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Line 286: | Line 177: | ||
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_o cf * ' e [! , | _o cf * ' e [! , | ||
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FIGURE 1. < | |||
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'. FLOW PATHS-REACTOR-INLET-LARGE BREAK- | '. FLOW PATHS-REACTOR-INLET-LARGE BREAK- | ||
" NATURAL ~ CIRCULATION"'. , | " NATURAL ~ CIRCULATION"'. , | ||
D,, | D,, | ||
,D Ly oji ; | |||
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Ly oji ; | |||
oo ol' 1 A,L'uo. | oo ol' 1 A,L'uo. | ||
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t 0 | t 0 | ||
0 T N 1 E O L I N T I A L | 0 T N 1 E O L I N T I A L | ||
R U O C T R _ | R U O C T R _ | ||
C I A C 2 E R L s E A r R E R u U M U o G I T . H I T A F N , | C I A C 2 E R L s E A r R E R u U M U o G I T . H I T A F N , | ||
S e V K m A l WE i O R L B F | S e V K m A l WE i O R L B F | ||
Line 376: | Line 218: | ||
R R O A _ | R R O A _ | ||
C L 0 | C L 0 | ||
1 | 1 1 | ||
0 0 0 0 0 1 - | |||
0 0 1 | |||
0 1 - | 0 1 - | ||
1a 9 . , . - | 1a 9 . , . - | ||
Line 413: | Line 231: | ||
I K T A E | I K T A E | ||
S R V B s 3 N E N r O G O u E I R I o R T A T H U A L A G R - L I T T U F N E C j e m | S R V B s 3 N E N r O G O u E I R I o R T A T H U A L A G R - L I T T U F N E C j e m | ||
E i C LR t I T N I C O | E i C LR t I T N I C O | ||
C RO AL . | C RO AL . | ||
N T R O C U R A T O E A B R N 0 | N T R O C U R A T O E A B R N 0 | ||
1 | 1 1 | ||
0 . | |||
0 1 0 1 1 | 0 1 0 1 1 | ||
i t | i t | ||
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: i, O h. n .[ ' I' | : i, O h. n .[ ' I' I | ||
I ._ ra l+- INJECTION | |||
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Line 460: | Line 253: | ||
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TO SUMP - | TO SUMP - | ||
A A O | A A O | ||
.I ti , | .I ti , | ||
-! !i c | -! !i c | ||
) | ) | ||
I -.h. | I -.h. | ||
e . | e . | ||
N , | N , | ||
5 | 5 | ||
- -:y t p | - -:y t p | ||
-I | -I | ||
; p 'ha, .. ! | ; p 'ha, .. ! | ||
u' ! =-L u i i .-! .i!!- ! I F i i rpj | u' ! =-L u i i .-! .i!!- ! I F i i rpj | ||
~ | ~ | ||
,% a 7 t.g# /. , | ,% a 7 t.g# /. , | ||
I | I | ||
,x V 'A. w e v ,. ' | ,x V 'A. w e v ,. ' | ||
: a. - . | : a. - . | ||
v. | v. | ||
s FIGURE 4 | s FIGURE 4 | ||
~ | ~ | ||
FLOW PATHS-REACTOR INLET-L'ARGE BREAK- .i | FLOW PATHS-REACTOR INLET-L'ARGE BREAK- .i | ||
~ | ~ | ||
" FORCED CIRCULATION" | " FORCED CIRCULATION" | ||
'WY t "~ | 'WY t "~ | ||
D"}D oa o D | D"}D oa o D | ||
f 51 ${ | f 51 ${ | ||
n . | n . | ||
+ | + | ||
FIGURE 5 BORON CONCENTRATION VS TIME , | FIGURE 5 BORON CONCENTRATION VS TIME , | ||
1000 1 | 1000 1 | ||
o b | o b | ||
g 100 | g 100 | ||
'n | 'n 8 | ||
8 | |||
'n 2 | 'n 2 | ||
c | c o | ||
o E | |||
o | -3 [ Hot Leg Injection 40 GPM 10 | ||
E | |||
-3 [ Hot Leg Injection 40 GPM | |||
10 | |||
. Natural Circulation | . Natural Circulation | ||
. Forced Circulation - | . Forced Circulation - | ||
Hot Leg Inj ection-3000 GPt ' 140 GPM | Hot Leg Inj ection-3000 GPt ' 140 GPM | ||
, % Forced Circulation-500 GPM 1 - - - . - | |||
, % Forced Circulation-500 | |||
GPM 1 - - - . - | |||
1 10 100 1000 10,000 100,000 | 1 10 100 1000 10,000 100,000 | ||
, Time, Hours | , Time, Hours | ||
. . . . - - _ ~ .. | . . . . - - _ ~ .. | ||
INJECTION 4 | |||
INJECTION | Y .__. _ . . | ||
C>^ - Q. ~i- . | C>^ - Q. ~i- . | ||
! j '/ i - - | ! j '/ i - - | ||
l j_ \ , -> | l j_ \ , -> | ||
. b,-- | . b,-- | ||
/ | / | ||
n | n | ||
' U'' t li k V !.i-r 5 <- INJECTION | ' U'' t li k V !.i-r 5 <- INJECTION L. V j. | ||
_j y-- _ _ - - l ':' | |||
L. V j. | |||
_j | |||
y-- _ _ - - l ':' | |||
,\ | ,\ | ||
)%.ggggg | )%.ggggg | ||
~~ ! s _q N m-- - - ~ {4 - u , | ~~ ! s _q N m-- - - ~ {4 - u , | ||
i \ / | i \ / | ||
!\ '.. | !\ '.. | ||
I. | I. | ||
! N J. , | ! N J. , | ||
L' L | L' L | ||
'k g | 'k g | ||
-i | -i | ||
/ | / | ||
/ - | / - | ||
-l, I | -l, I | ||
Y | Y | ||
/ | / | ||
l y qN | l y qN | ||
, ~ | , ~ | ||
~ c; < | ~ c; < | ||
-; / : i j/ _- . | |||
-; / : i | |||
j/ _- . | |||
--* ~ ' | --* ~ ' | ||
I | I | ||
. ., 4 - -. . | . ., 4 - -. . | ||
it\, | it\, | ||
id,l: : tillliit!'e' _ | id,l: : tillliit!'e' _ | ||
s < | s < | ||
's s ,-- | |||
's | |||
s ,-- | |||
':y _ | ':y _ | ||
_ ;_-;,,;} ^ | _ ;_-;,,;} ^ | ||
Line 656: | Line 348: | ||
~ | ~ | ||
FLOW PATHS-REACTOR' INLET-LARGE BREAK | FLOW PATHS-REACTOR' INLET-LARGE BREAK | ||
'" HOT LEG; INJECTION'" g | '" HOT LEG; INJECTION'" g u j | ||
u j | |||
"'g_g | "'g_g | ||
*T'I 'r'T 'F 7 S- 7 | *T'I 'r'T 'F 7 S- 7 | ||
* y"y"y' t- ? - | * y"y"y' t- ? - | ||
* f | * f | ||
1 FIGURE 7 MODEL USED FOR CALCULATING CONCENTRATION AFTER NATURAL CIRCULATION PHASE Ws i | |||
l, i | |||
e Wout,C Mc,C 3 | |||
1 | |||
FIGURE 7 MODEL USED FOR CALCULATING CONCENTRATION AFTER NATURAL CIRCULATION PHASE Ws i | |||
l, | |||
i | |||
e Wout,C | |||
Mc,C 3 | |||
~ | ~ | ||
i Concentrating Win,Cin Region | i Concentrating Win,Cin Region l | ||
l | |||
l 1 | l 1 | ||
I , | I , | ||
\ | \ | ||
. I | . I | ||
.I O | .I O | ||
e | e i | ||
y -,--,--,.,-,y,.,- e , v.-.mw. . , , a--- - . - ,we--y - | |||
e-- m- -- y * - | e-- m- -- y * - | ||
P' s .% | P' s .% | ||
-3 , | -3 , | ||
d \ | d \ | ||
5 7- . . . | |||
5 | |||
7- . . . | |||
; ~Q ! i PUMP | ; ~Q ! i PUMP | ||
, /', t | , /', t | ||
' _j , ~M. , N . | ' _j , ~M. , N . | ||
7-r )! | |||
7- | |||
r )! | |||
_.u - -AL | _.u - -AL | ||
; 3 -w y | ; 3 -w y | ||
w- _/ U l ~~' v/>o 4o o | w- _/ U l ~~' v/>o 4o o | ||
n a-1w c | n a-1w c | ||
eo o | eo o | ||
v/p;'\u S -INJECTION f o % | v/p;'\u S -INJECTION f o % | ||
N / | N / | ||
M | M i | ||
1.9 | |||
!? p/ i NJ:. | !? p/ i NJ:. | ||
c l l 4 , | c l l 4 , | ||
. . . . _ _ . I ,. \ | . . . . _ _ . I ,. \ | ||
, i | , i | ||
_/ A | _/ A | ||
-~ | -~ | ||
Line 765: | Line 394: | ||
~?\ /~ | ~?\ /~ | ||
N , | N , | ||
: \- : . | : \- : . | ||
! s s ~s | ! s s ~s | ||
.: ~ | .: ~ | ||
E : | |||
*t l | |||
*t | |||
l | |||
. ': [ | . ': [ | ||
N 1 : | N 1 : | ||
I \ '- | I \ '- | ||
/ \ + | / \ + | ||
1 | 1 | ||
Line 790: | Line 407: | ||
5j f ,. | 5j f ,. | ||
, J/: | , J/: | ||
,>c , | ,>c , | ||
e t | e t | ||
Line 798: | Line 413: | ||
!,,i- l 4ti!lI6 I i ! iM i r | !,,i- l 4ti!lI6 I i ! iM i r | ||
./ | ./ | ||
d %~~ | d %~~ | ||
w g f d | w g f d | ||
?, O ~-- _ | ?, O ~-- _ | ||
fu y | fu y | ||
9 | 9 | ||
':: 2 ;;_ 7 " - | ':: 2 ;;_ 7 " - | ||
FIGURE:8 FLOW--PATHS-PUMP SUCTION-LARGE-BR_EAK | FIGURE:8 FLOW--PATHS-PUMP SUCTION-LARGE-BR_EAK | ||
'" NATURAL 2 CIRCULATION"- : | '" NATURAL 2 CIRCULATION"- : | ||
A - | A - | ||
0{ O0 | 0{ O0 4 | ||
4 | |||
-- w | -- w | ||
- n s | - n s | ||
. g | . g | ||
,.- s | ,.- s | ||
~. . J , ! !; !! l.L_. | ~. . J , ! !; !! l.L_. | ||
^ | ^ | ||
l ' .' ~ a PUMP I \ l' t -- ., nZE+ INJECTION -- ~ | l ' .' ~ a PUMP I \ l' t -- ., nZE+ INJECTION -- ~ | ||
/ | / | ||
i | i | ||
,- -m_-.. . lt | ,- -m_-.. . lt G _ _ _ __., _ | ||
G _ _ _ __., _ | |||
., .' w - - | ., .' w - - | ||
c | c | ||
-_ ~- | -_ ~- | ||
Line 851: | Line 440: | ||
() _ | () _ | ||
< v. | < v. | ||
i, O.r.J y | |||
i, | |||
O.r.J y | |||
~% | ~% | ||
I ~. i"y : .- | I ~. i"y : .- | ||
t | t Ns_ N - | ||
Ns_ N - | |||
BREAK y - | BREAK y - | ||
; i .x I | ; i .x I | ||
/i- | /i-e' s | ||
e' | |||
s | |||
/ | / | ||
/ 1 TO SUMP I ' | / 1 TO SUMP I ' | ||
-j \ , | -j \ , | ||
s E. | s E. | ||
y 4 & -i | y 4 & -i | ||
~ | ~ | ||
.) \ , | .) \ , | ||
s | s | ||
/ .- | / .- | ||
: v. , | : v. , | ||
s, , | s, , | ||
.. i t r--- , i | |||
.. i t | |||
r--- , i | |||
..i.-- - | ..i.-- - | ||
I 1, '2 | |||
.. i,d.__III!lIIIeIIi,br$ | .. i,d.__III!lIIIeIIi,br$ | ||
'' % L h.: " , ; | '' % L h.: " , ; | ||
3 U '~~ _ '' V ' | 3 U '~~ _ '' V ' | ||
~ | ~ | ||
N.- =w ' *1 1 | N.- =w ' *1 1 | ||
FIGURE 9 j FLOW PATHS-PUMP SUCTION-LARGE~ BREAK | FIGURE 9 j FLOW PATHS-PUMP SUCTION-LARGE~ BREAK | ||
" FORCED CIRCULATION" T } | |||
" FORCED CIRCULATION" | |||
T } | |||
D"*]D o o Ju o | D"*]D o o Ju o | ||
]D Ju.Jl. | ]D Ju.Jl. | ||
llr h t | |||
llr h | |||
t | |||
'9% | '9% | ||
e | e | ||
: INJECTION '..,. | : INJECTION '..,. | ||
1 | 1 | ||
,.. im ; ,- | ,.. im ; ,- | ||
s . .- p g p. | s . .- p g p. | ||
i ;,,,s e. : | i ;,,,s e. : | ||
i.7 | i.7 | ||
: i. s , | : i. s , | ||
, .s , | , .s , | ||
\; \ | \; \ | ||
- .~ m m - | - .~ m m - | ||
;I i. 's. ,/ _t' N | ;I i. 's. ,/ _t' N | ||
*vo C, t ._e;x) = J; <- INJECTION | *vo C, t ._e;x) = J; <- INJECTION | ||
\j | \j | ||
:.k 4 | :.k 4 | ||
xs . | xs . | ||
_..... .. >!v. | _..... .. >!v. | ||
mcq t% . .t | mcq t% . .t | ||
. 'c. . - | . 'c. . - | ||
t | t A | ||
A | |||
=- | =- | ||
3 I | 3 I | ||
\ 7,. U l | \ 7,. U l | ||
^ e x :_ _._ s S | ^ e x :_ _._ s S f, , | ||
;r -- | ;r -- | ||
x BR.- . ,,:*.M. \ | |||
x | |||
BR.- . ,,:*.M. \ | |||
/r | /r | ||
-t. 'N, ,- | -t. 'N, ,- | ||
Line 991: | Line 504: | ||
'i i \ / | 'i i \ / | ||
-i , | -i , | ||
r a | |||
f | |||
r | |||
a | |||
! s _ | ! s _ | ||
1 , 's i i e s .' | 1 , 's i i e s .' | ||
. _! / ?i I / | . _! / ?i I / | ||
~; / | ~; / | ||
l/ s- | l/ s-u_.__w.- , | ||
u_.__w.- | |||
i' i-. -r.q _s Y. s(.:,T.r.. | i' i-. -r.q _s Y. s(.:,T.r.. | ||
i 7 | i 7 | ||
..s._. | ..s._. | ||
,. '"% v,w -v | ,. '"% v,w -v | ||
? ./ | ? ./ | ||
'~,*- | '~,*- | ||
. ./ | . ./ | ||
y e," | |||
q....._g, , | q....._g, , | ||
FIGURE 10 FLOW PATHS-PUMP SUCTION-LARGE BREAK | FIGURE 10 FLOW PATHS-PUMP SUCTION-LARGE BREAK | ||
" HOT LEG IN'JECTION" D""D *]D'T)[$ | " HOT LEG IN'JECTION" D""D *]D'T)[$ | ||
ou -e Ju 2..\.ir"d o | ou -e Ju 2..\.ir"d o | ||
,- . . .p | ,- . . .p | ||
.. s. L | .. s. L | ||
; i . t i- | ; i . t i- | ||
-- l' ' | -- l' ' | ||
PU:P | PU:P | ||
- _. y/ L l ~ | - _. y/ L l ~ | ||
1-t,._' g G , = | 1-t,._' g G , = | ||
(. j i | |||
(. j | is_/ | ||
SRE ,K ! ;(> U Lf 7,' | SRE ,K ! ;(> U Lf 7,' | ||
* INJECTION j | * INJECTION j f, . .,c -~. - | ||
f, . .,c -~. - | |||
\ ._ | \ ._ | ||
p -_. . - - | p -_. . - - | ||
out ! *,e" J | out ! *,e" J | ||
-~~.-~~.c~. t | -~~.-~~.c~. t | ||
~ | ~ | ||
(I 1(;-.--- _. . | (I 1(;-.--- _. . | ||
. J' g _ :g. , | . J' g _ :g. , | ||
. ./ | . ./ | ||
x | x | ||
. .- _ ir . . . . . . . . . . , . . .... , | . .- _ ir . . . . . . . . . . , . . .... , | ||
i N ' | i N ' | ||
r | r | ||
_I. | _I. | ||
z- | z- | ||
/ | / | ||
/ A _ V' | / A _ V' | ||
Line 1,102: | Line 554: | ||
.l ': | .l ': | ||
-l | -l | ||
. f< n. . , | . f< n. . , | ||
\ | \ | ||
. , , t ,. | . , , t ,. | ||
_. _ e. . | _. _ e. . | ||
e1 | e1 | ||
-t | -t | ||
. i 2 | . i 2 | ||
t _1 MiFlir.iiD'i!i1.: | t _1 MiFlir.iiD'i!i1.: | ||
: n. - 1 , i. ,,/- | : n. - 1 , i. ,,/- | ||
pw s>v | pw s>v | ||
: v. % | : v. % | ||
....:. ~ n . | ....:. ~ n . | ||
w *' | w *' | ||
FIGURE 11- | FIGURE 11- | ||
~ FLOW PATHS . | ~ FLOW PATHS . | ||
. REACTOR OUTLE'T .LARGE BREAK | . REACTOR OUTLE'T .LARGE BREAK | ||
- " FORCED: CIRCUL ATION" eg | - " FORCED: CIRCUL ATION" eg | ||
'- U - | '- U - | ||
.J L , | .J L , | ||
. i.f ^ | . i.f ^ | ||
,- .. , c | ,- .. , c FIGURE 12 - | ||
FIGURE 12 - | |||
HOT LEG BREAK TOP OF 180 BEND BREAK fl 7 | HOT LEG BREAK TOP OF 180 BEND BREAK fl 7 | ||
/- ; | /- ; | ||
/ \ | / \ | ||
[ ^ [ \ | [ ^ [ \ | ||
- = _ | - = _ | ||
N I | |||
N | |||
I | |||
t j ,8'-O" 7{"ygP\lNJECTION | t j ,8'-O" 7{"ygP\lNJECTION | ||
' I I i 79'-8 1/2 | ' I I i 79'-8 1/2 | ||
)~ | )~ | ||
y= v ' | y= v ' | ||
'M - ; __ __ _ . | 'M - ; __ __ _ . | ||
I= | I= | ||
31'-0" 24'-0" n | 31'-0" 24'-0" n | ||
Line 1,179: | Line 593: | ||
! ( | ! ( | ||
XUW/j:W## TH///g'6%'// | XUW/j:W## TH///g'6%'// | ||
e L gf9 , , -4_a _e.-.-evae- | e L gf9 , , -4_a _e.-.-evae- | ||
~ .s =e.n- . | ~ .s =e.n- . | ||
e3 y---<---.w-e-- . we.es em | e3 y---<---.w-e-- . we.es em | ||
-+---- _ m ee_==+Ae- | -+---- _ m ee_==+Ae- | ||
i e, t II | i e, t II | ||
,I | ,I th | ||
th | |||
:-@Il@i | :-@Il@i | ||
[.} | [.} | ||
l . t | l . t | ||
. 9,-I 7, I | . 9,-I 7, I I v = = | ||
I v = = | |||
g | g | ||
! a P > 1O 7' W w | ! a P > 1O 7' W w i I - | ||
I a > | |||
i I | |||
I | |||
a > | |||
I D- et;*, e r ; - | I D- et;*, e r ; - | ||
2 x :> { | 2 x :> { | ||
Line 1,218: | Line 613: | ||
" I---x ! * | " I---x ! * | ||
,l, m s | ,l, m s | ||
% j- fg; l | % j- fg; l I | ||
I | |||
+1 .._ . | +1 .._ . | ||
b I | b I i, | ||
i | |||
'I | 'I | ||
--s ! z o- I" --A-N- l-t ** X, _g O | --s ! z o- I" --A-N- l-t ** X, _g O | ||
,,t ! | ,,t ! | ||
-- N aIEE! i 3 - | -- N aIEE! i 3 - | ||
l-6 | l-6 r - --- --- | ||
r - --- | |||
e , | e , | ||
i -ko++ ' | i -ko++ ' | ||
n -] s' . . - | n -] s' . . - | ||
e! 1 1 | e! 1 1 | ||
,t | ,t | ||
~' | ~' | ||
{y T | {y T | ||
.i!* e-I! I 5 | .i!* e-I! I 5 | ||
E;E | E;E 1,i- - | ||
1,i- - | |||
58 r r i!! | 58 r r i!! | ||
l5.a-i i J | l5.a-i i J | ||
;lk | ;lk | ||
. II | . II s | ||
s | |||
g Hs E:,s 1:e | g Hs E:,s 1:e | ||
!! ,O D e- 6) f l 6; '" | !! ,O D e- 6) f l 6; '" | ||
e q | e q | ||
-'- _A___________..___.__All .. II + | -'- _A___________..___.__All .. II + | ||
Line 1,279: | Line 644: | ||
. r L} | . r L} | ||
rIt , | rIt , | ||
T .s. 1 | T .s. 1 | ||
,g e | ,g e | ||
i 9 | |||
i | emme | ||
= .w - | = .w - | ||
*.,=-,sa . me +-w-. e_. .m-.m .. ........-..,%. | *.,=-,sa . me +-w-. e_. .m-.m .. ........-..,%. | ||
_ _ _ _ _ _ -- --}} | _ _ _ _ _ _ -- --}} |
Latest revision as of 20:06, 21 February 2020
ML19312C085 | |
Person / Time | |
---|---|
Site: | Oconee ![]() |
Issue date: | 04/16/1975 |
From: | DUKE POWER CO. |
To: | |
Shared Package | |
ML19312C084 | List: |
References | |
NUDOCS 7912030385 | |
Download: ML19312C085 (22) | |
Text
. _ _ . _ __ __. ._. _ _ . _
_ ;~ p..
LO I
i i
i t
1 1
e 1
AN EVALUATION OF BORON PRECIPITATION DURING LONG-TERM COOLING
- FOLLOWING A POSTULATED LOSS OF COOLANT ACCIDENT i
.i l
l I
'l 79120803[6 a
g
- ~
I. Introduction l
Reactor system circulation and boron concentration in the post-LOCA, long-term cooling environment have been analyzed for the potential of unacceptably high boric acid concentrations in the core region. Both large and small breaks of the reactor inlet and outlet pipes are con-sidered and the large break of a reactor vessel inlet pipe is shown to be the most limiting case.
The analysis indicates that natural circulation within the reactor vessel, where the flow path is downcomer-core-upper head-vent valves downcomer , provides adequate circulation to prevent rapid increases in solute concentrations, including the limiting case. The resulting slow concentration buildup indicates that a time period in excess of 30 days is available for alignment and operation of alternate flow paths. If both Low Pressure Injection (LPI) strings are operable, then the pro-cedure, one day af ter the postulated LOCA, is to establish suction on the reactor vessel outlet pipe (hot leg) through the decay heat line with one LPI string. This will force flow from the LPI string through the core. This procedure, (Mode 1), will limit concentration buildup to a factor of two or less.
In the event the decay heat line is not available, the procedure (Mode 3) is to open the auxil,iary spray to the pressurizer. This will act as hot leg injection by routing dilute injection to the area above the core. The flow path will be through the auxiliary spray line into the pressurizer, out of the pressurizer through the surge line, into the hot leg and then into the reactor vessel. This flow path will act first as a dilutant for care water and then, reversing the direction of core flow, providing long-term sensible heat removal. The concentration buildup rate decreases as auxiliary pressurizer spray becomes effective and the concentration gradually decreases as sensible heat removal proceeds. The minimum auxiliary spray capacity is 40 gpm. This auxiliary spray rate, if required, will limit concentrat on buildup to C/Co=ll.
The decay heat line may not permit circulation of saturated water because
- the line routing takes it above the hot leg pipe. This decay heat line is, however, capable of being aligned (Mode 2) such that a connection from the LPI pump discharge to the decay heat line will route flow back-wards through this line into the hot leg. This will route dilute injection into the area above the core. The analysis description that follows describes hot leg injection by way of the auxiliary pressurizer spray. However, the hot leg injection results presented.are independent of source, e.g., auxiliary pressurizer spray or reverse flow through the decay heat line.
1
- ^~
(~%
,. ~
II. Discussion of Analysis 1
A. Reactor Inlet - Large Break
]
The reactor vessel internal natural circulatior. flow paths are shown in Figure 1. In this circulation mode, the driving head for the core flow is provided by downcomer fluid. The downcomer head is sufficient to promote significant core flow and to provide an adequate pressure differential to open the vent valves.
The core flow rate as a function of time is shown in Figure 2. This flow rate from the core and through the vent valves is assumed to mix with the injection flow (3000 gpm) and exit from the vessel through the inlet break. For concentration calculations, however, the concentration entering the core is conservatively assumed to be equal to that leaving the core at a given time step. (In effect, no boron is assumed to leave the vessel through the break.) The resulting concentration ratio of boron as a function of time is shown in Figure 3. The resultant natural circulation flow is such that very low quality mixture is produced which produces relatively low concentrating rates. The rate of concentration is such that alignment of an alternate flow path is not required for a time period in excess of one month.
However, in order to provide measurable assurance that boron con-centration is minimized, alignment of the decay heat line is performed within one day af ter the postulated LOCA. The flow path in the reactor vessel in this flow mode called " forced circulation,"
is shown in Figure 4. The minimum core flow in this " forced circu-lation" mode, assuming no density gradient in the core is approxi-mately 118 lb/sec, whichis more than adequate to provide decay heat removal without evaporation within five days. Figure 5 shows the boron concentration change and peak value following alignment of the decay heat line after one day of natural circuation operation.
In the event that the decay heat line is not operational (failure of isolation valve to open), the alternate system to promote low boron concentration and to dilute the boron concentration is align-ment of the auxiliary pressurizer spray. The flow paths for this mode of operation (defined as " hot leg injection") are shown in Figure 6.
Hot leg injection has little effect on circulation and concentration until the steaming rate, assuming evaporation only from the core, is equal to or less than the bot leg injection rate. As the injection rate approaches the steaming rate the hot leg injection acts to reduce the rate of core boron concentration by adding non-concentrated water. As the decay heat rate decreases with time., the hot leg injection becomes adequate to remove decay heat by sensible h::t removal. The core flow direction reverses, and the concentration of boron in the core becomes dilute with time. The concentration with time for " hot leg injectica" is shown in Figure 5, for an injection rate of 40 gpm.
~
C \
Figure 7 shows the model used for calculating the concentration
)
after the decay heat letdown is opened or after the pressurizer l spray injection is initiated. The concentration, C,' is given by
)
C = Mass Solute Mass Solvent C= cCi+ft in in "tf out c
!o" + t1 dt - 1 dt (1) o e o e o where Ci is the concentration at t1 tl is time of vent valve opening or spray initiation Co is same reference concentration Equation 1 is used to calculate the concentration ratio after the natural circulation phase of the transient is terminated.
The important assumptions used for this part of the transient are:
(1) Constant mixing r. ass, Mc = 30000 LBM (2) 40 gpm flow rate from pressurizer sprays (3) Constant LPI injection rate and concentration.
(4) No' density gradients in calculation of forced circulation (5) 1000 BTU /LBM needed to produce steam (6) Maximum flow out break for letdown line case (7) K-factors based on full flow values -
Summary: Reactor Inlet - Large Break The results of the calculations are shown in Figure 5. They show that the maximum concentration ratio for the letdown line case is 1.19 at 1 day; the maximum concentration ratio for the hot leg injection case is 11 at 60 days. The solubility curves show that a concentration ratio of 35:1 is needed before precipitation will occur. Thus, it has been shown that the proposed method for con-trolling concentration buildup in the long-term cooling phase of a LOCA is credible. This is particularly true when the conservatisms inherent in the analysis are considered. These conservatisms include:
l (1) No dilution of injection E 0 is considered 2
(2) Absorption of boric acid by concrete is neglected (3) Volatility of boric acid was neglected B. Pump Suction - Large Break For large breaks postulated at or in the pump suction line, the flow l 1
paths are as shown on Figure 8. In this case the leak fluid must pass through the RC pump which is some 3 feet above the centerline of cold leg nozzle. This condition provides increased downcomer driving head for core flow which results in more core flow and a lower outlet quality and boron concentration when operating with LPI inj ection,
" Natural Circulation mode." In this case, the core flow versus time will be equal to or greater than that shown in Figure 3.
Operations in the forced circulation mode will produce flow patterns l equivalent to that shown in Figure 9, with a near constant minimum flow rate of approximately 118 lb/sec, which is more than adequate to provide decay heat removal without evaporation within five days.
Switch over to this mode will provide a concentration ratio equal to or less than that shown in Figure 5.
In the event the decay heat line is not operational, the alternate l system, pressurizer spray, dilutes the boron concentration as !
described iE"Section II.A. above. The hot leg injection flow paths ,
are shown in Figure 10, and the concentration ratio versus time is I equal to or less than that shown in Figure 5. !
C. Reactor Outlet - Large Break in the case of a postulated large break, the flow paths are as shown in Figure 11. Any parallel alignment such as opening the decay heat line, or hot leg injection, will produce little or no effect. This case corresponds to the forced circulation cold leg break with the decay heat line open, except that all injection water flows through the core. The minimum core flow with one LPI pump operating is expected to be 3000 gpm (416 lb/sec) which will prevent boiling and concentration within approximately 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />. The resulting concen-tration ratio, then will be significantly less than that shown in Figure 5.
D. Reactor Outlet - Top of 180 Bend - Large Break In the case of a postulated large break at the top of the 180 bend, reactor outlet, the overall flow paths are as shown in Figure 12.
With one LPI injection pump assumed operating, the injection flow will split approximately 50/50 between the ' core and steam generators until the steam generator stored heat is removed (approximately one day). During this period the flow paths within the vessel are approximately those of forced circulation. The corresponding core flow rates are equal to or greater than (approximately 200 lb/sec) those shown in Figure 2, because of increased drit ing head.
.- p the decay heat line with one LPI string (see Figure 13). The flow is E cough existing valves LP-1, LP-2, LP-3, LP-4 (for Units 1 and 2),
LP-9, LP-12, LP-17 and into the reactor vessel through the core flood ,
nozzle. I B. Mode 2 - Hot Leg Injection Through the Decay Heat Line i l
This flow path uses a connection from the LPI pump discharge to the l decay heat line to route flow backwards through the decay heat line and into the hot leg.
The flow path will be different for Oconee Units 1 and 2 and Unit 3.
Oconee Units 1 and 2 have a cross connect (8" line) from LPI String B (upstream of the LPI cooler) to the decay heat line. Flow path is through the cross connect (valve LP-68) into the decay heat line and backwards in the decay heat line through valves IP-3,12-2 and LP-1 to reach the hot leg. Oconee Unit 3 does not have this cross connect to the decay heat line. For Unit 3, cross connects to the letdown line of the HPI System will be used. The cross connect from LPI String B cooler outlet is a 2" line connecting the HPI System letdown line downstream of the letdown control valve and upstream of the demineralizers.
A return cross connect leaves the HPI System letdown line downstream of the purification demineralizers but upstream of the letdown storage tank and connects into the LPI System downstream of the valve IP-4 in the decay heat line. The normal functiorof these cross connects to the HPI System is to obtain purification flow during cold shutdown af ter the HPI System is shut down. When using this path during long-term cooling, the filters and demineralizers in the HPI System would be bypassed. Units 1 and 2 will be able to achieve, as a minimum, several hundred GPM into the hot leg with only one LPI pump operational and a large majority of the pump flow split between the two LPI lines.
Unit 3 will be able to achieve a flow rate greater than the 40 GPM minimum into the hot leg.
C. Mode 3 - Open Auxiliary Spray Line to Pressurizer This flow path uses an HPI pump taking suction from an operating LPI string through cross connect valves LP-15 or LP-16. The flow path to the hot leg will be through the auxiliary pressurizer spray line which is through valves HP-355, HP-340 and LP-45. Changes are required to make this a workable flow path as there are manually operated valves
[
inside the reactor building which must be opened and closed during l the long-term cooling period to establish this flow path. Changes required are shown on Figure 3 and are: (1) change valve LP-45 to locked open, (2) add on an electric motor operator (EMO) to valve HP-340, and (3) add on EHO to valve HP-356. Valve HP-356 must remain open during normal operation to provide a continuous minimum makeup line flow to minimize thermal transients on the RC pipe nozzle.
This valve (HP-356) must be closed for Mode 3 to prevent the flow from diverting to the HPI line. Valve HP-340 must remain closed l during normal operation to prevent the continuous minimum makeup line l flow from diverting to'the pressurizer. The flow rate for this path l to the hot leg is controlled and limited to 40 GPM by the block orifice downstream of valve HP-340.
IV. Single Failure Analysis The three modes listed above are necessary to satisfy the single failure criteria. Operations must be designed for a single failure in either the short-term or long-term cooling period but not a single failure in the short term and then another single failure in the Ivag-term period.
Since the operator may not be able to determine the location of the break, Mode 1 is attempted first (if both LPI strings are operable) to determine if the normal decay heat removal path can be established. It can be established if the break location is high enough in elevation so that the decay heat suction nozzle on the hot leg is sufficiently flooded to prevent gas or steam entrainment at the LPI pump flow rate. Even if there is no single failure during the attempt, success is not assured because of the possibility of gas or steam entrainment in the decay heat
, suction nozzle. If Mode 1 fails because LPI pump flow is erratic or loses prime, then Mode 2 is attempted. Success or failure of Mode 2 will be indicated by flow indicators. On Oconee Units 1 and 2, opening of the last valve to establish reverse flow in the decay heat line will cause the LPI string flow to decrease. On Oconee Unit 3, a flow indicator in the letdown line of the HPI System will indicate the reverse flow rate in the decay heat line. If Mode 2 fails due to single failure, then Mode 3 is performed. The above was for a single failure in the long term.
The single failure could occur in the short term with the single failure being such that only one LPI string is operable. Mode 1 then cannot be attempted because prime could be lost on the only LPI pump operating. So, Mode 2 would then be performed.
All valves located within the reactor building, that must be operated in any of the three modes will be electric motor operated and located outside the secondary shield wall. All of the existing valve EM3's are qualified for the LOCA environment and all EM0's to be added will i be qualified EM0's. If power is not available to any of the EM0's required to implement any of the three modes, electrical jumper cables will be used to connect power to the EMO controller.
V. Operating Procedures for Long-Term Cooling The three operating modes which have been described for long-term cooling cannot presently be fully effected. The existing equipment is adequate to provide the necessary flow paths for Modes 1 and 2; however, dose calculations are not completed for areas of the Auxiliary Building in which manual valves must be operated. Operating Mode 3 cannot be implemented until electric motor operators are added to valves HP-340 and HP-356 which are located in the Reactor Building and valve LP-45 is modified to be locked open.
The ECCS systems will be placed in one of the following three modes of operation (Mode 3 will only be possible after modifications) within one day of the accident. Injection flow to the RC System'should be maintained through two paths while attempting to place the system in one of the three operating modes. The two injection flow paths can be either the two LP injection lines or one LP injection line combined with one HPI string (LPI pump acting as a booster pump for the EPI pump).
e (
- u.
Mode 2 - Route Flow Backwards Through the Decay Heat Line Into the Hot Leg Oconee Units 1 and 2
- a. If Mode 1 is not successful, maintain injection flow to reactor vessel through two injection flow paths by any of the following:
(1) Two LPI strings (2) One LPI pump operating with LPI pump discharge header open (valves LP-9 and LP-10 open) and the flow split between the two injection lines by the control valves.
(3) One LPI string in series with one HPI string.
,1)
( If two LPI pumps are operable, use String A to inject through LPI line to reactor vessel. Use String B's full flow through the cross connect (valve LP-68) to decay heat line and into the hot leg. Close String B LPI line EMO valves LP-18 and LP-14.
(2) If only one LPI pump is operable, split the flow between one LPI line to the reactor vessel and the cross connect path to the hot leg. The flow split is accomplished by throttling the LPI line EMO control valve (LP-18) and manual valve LP-68 in the cross connect. Flow split indication is confirmed by LPI pump discharge pressure indication remaining the same (same as for 3000 GPM LPI line injection flow rate) and the LPI line flow l rate indicator at approximately 1500 GPM.
- d. If Mode 2 is successful, injection flow to the reactor vessel is through two injection flow paths and dilute injection is reaching the area above the core (if the break is a cold leg break).
Oconee Unit 3
- a. Step a, for Oconee Units 1, 2 above,.is applicable.
- c. Line up cross connect (valve IP-96) flow path from LPI String B to HPI System letdown line. Complete the flow path up to the return cross connect (valve BP-363) to the LPI System. In the HPI System
- letdown line, isolate the filters and demineralizers and open the bypasses around them. Close the inlet valve to the letdown storage tank.
n s~
s .:
- d. LPI pump P1A must not be operating and its suction EMO valves LP-5 and LP-6 nnst be closed. The building spray pump assSciated with LPI String A must be shut off and the sump EMO outlet valve LP-19 must-be closed. Open manual valve HP-363 in return cross connect-to LPI System. Open EMO valve LP-3 in decay heat drop line.
- e. The flow path is now complete. The flow rate indicator in the HPI System letdown line indicates the flow rate in this path from LPI String B to EPI System letdown line to LPI String A suction to decay heat line and backwards through this line to the hot leg.
1 Mode 3 - Open Auxiliary Spray Line to Pressurizer i a. This operating mode will be used if Mode 2 is not successful.
2
- b. .Close main pressurizer spray line EMO valve RC-1 or RC-3 or both.
- c. Open auxiliary spray line EMO valve HP-340. Open manual valve HP-355
- in Auxiliary Building. C1cse EMO valve HP-356 to force flow to the auxiliary spray line,
- d. Start any one of the three HPI pumps taking suction from an operating LPI string through the cross connect.
- e. HP injection can be stopped by closing injection valves HP-26, HP-27, and HP-120 or HP injection flow can be maintained in parallel with the auxiliary spray flow by controlling valve HP-26 or HP-120.
Injection flow to the reactor vessel should be maintained through l
two paths per Item a of Mode 2. Auxiliary spray line flow rate is indicated by the flow measurement upstream of manual valve HP-355 (normal makeup line flow indication).
VI. Summary of Results The reconsnended operating procedures for Oc'onee 1, 2, and 3 to minimize boron concentration following a LOCA are, in order of preference:
i A. Always maintain a minimum of 3000 GPM LPI injection into the down-comer. This provides for a natural circulation flow path within the reactor vessel and the maximum concentration buildup is C/Co =
1.19 for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after a LOCA. (Co is initial concentration
- 2200 ppm boron solution.)
l B. Align decay beat line in a low flow mode within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after-
, the LOCA (see Step e of Mode 1 in Section V) which provides a j minimum core flow of 500 gpm. This is called a force circulation mode and if' successful will provide a maximum concentration ratio of 1.3 as shown in Figure-5.
l In addition, if this operating mode is successful and operation proceeds I
to the normal decay heat system flow rate, the forced core flow is 3000 gpm =in4== resulting in even lower concentration ratios (< 1.19) _
as shown in Figure 5.
- r l- ~ -- . . . , . . , , . . , , ,, .,,.w.,
n e C. Should Step B not be successful, the decay heat line is aligned for a reverse flow of 40 gpm minimum within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> af ter the LOCA.
This is called hot leg injection and limits the concentration ratio to 11.0 at 60 days (Figure 5). If larger reverse flow rates are available through the decay heat line, the concentration ratio will be held to a smaller value 1.9 at 7 days (140 gpm hot leg injection Figure 5).
D. In the event that the decay heat line is not operational (single failure), the auxiliary pressurizer spray ficw is aligned to provide 40 gpm minimum flow within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the LOCA.
This mode is also called hot leg injection and produces the same results as discussed in C above. (C/Co=11.0 60 days) l I
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