ML20150F281

Demonstration of Conformance of Prairie Island Units 1 & 2 to App K & 10CFR50.46 for Large Break Locas

ML20150F281
Person / Time
Site:	Prairie Island
Issue date:	05/31/1988
From:	WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
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ML20150F258	List: ML20150F254 ML20150F259 ML20150F265 ML20150F277 ML20150F281
References
NUDOCS 8807180212
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Text

.

..g DEMONSTRATION OF THE CONFORMANCE OF PRAIRIE ISLAND UNITS 1 AND 2.

TO APPENDIX K AND 10CFR50.46 FOR IARGE BREAK LOCAS Westinghouse Electric Corporation Nuclear Technology Systems Division .

Nuclear Safety Department Safeguards Engineering and Development May 1988 8807180212 880705 PDR ADOCK 05000282 P PDC -

-~

.. j I. Introduction L*

l L LThis document reports the results of an analysis that was performed to demonstrate that Prairie Island, Units 1 and 2, meet the requirements of Appendix K and 10CFR50.46 for Large Break

, Loss-of-Coolant-Accidents (LOCA) (Reference 1).

l l II. Method of Analysis l .The analysis was performed using the Westinghouse Large Break LOCA Best-Estimate Methodclogy (Reference 2). The Westinghouse Best-Estimate Methodology was developed consistent with guidelines set forth in the SECY-83-472 document (Reference 3). These guidelines provide for the use of realistic models and assumptions, with the exception of specific models and assumptions required by Appendix K. The technical basis for the use of this model is discussed in detail in Reference 2.

1 I

The Best Estimate Methodology is comprised of the ECOBRA/ TRAC and COCO computer codes (References 2 and 4, respectively). The HCOBRA/ TRAC code was used to generate the complete transient (blowdown through reflood) system hydraulics as well as the cladding thermal analysis. The COCO code was used to generate the containment pressure response to the mass and energy release from the break.

This containment pressure curve was used as an input to - e ECOBRA/ TRAC code.

The fuel parameters used as input for the LOCA analysis were generated using the Westinghouse fuel performance code (PAD 3.3)

(Reference 5). The fuel parameters input to the code were at beginning-of-life (maximum densification) values.

The analysis was performed using the four channel core model developed in Reference 2 for the 0.4 double-ended cold leg guillotine (DECLG) breaks. A break size coefficient (CD) of 0.4 was found to be

-.-----___---______-.J

. t most limiting as documented in Reference 2. These transients were considered to be terminated if the hot rod cladding temperature began to decline and the injected ECCS flows exceeded the break flow.

III. Results and Conclusions Table 1 shows the time sequence of events for the Large Break LOCA transients. Table 2 provides a brief summary of the important results of the LOCA analysis. Figures 1 through 8 show important transient results for the limiting 0.4 DECLG break (four channel core model). Note on these figures that the break occurs at time 0.0.

Figure 1 shows the core pressure during the transient. Figure 2 shows the vapor and liquid mass flowrate at the top of the hot assembly. Figures 3 and 4 show the collapsed liquid level in the downcomer and core hot assembly channel, respectively, indicating the refilling of the vessel. Figures 5 and 6 show the flow of ECCS water into the cold leg (accumulator and high head safety injection flow) with Figure 7 showing the flow of low head safety injection into the upper plenum (UPI flow). Figure 8 shows the resulting peak cladding temperature for the 0.4 DECLG break as a function of time for each of the five fuel rods modeled. Rod 1 is the hot rod in the hot assembly channel, Rod 2 is the hot assembly average rod, Rods 3 and 4 represent average assemblies in the center of the core and Rod 5 represents the lower power assemblies at the edge of the core. The safety injection (SI) system was assumed to be delivering to the RCS five seconds after the generation of a safety injection signal. This five second delay includes the time required for developing full flow from the SI pumps. No additional delay was required for diesel l

startup and sequencing since the analysis assumed reactor coolant pumps remain in operation in conjunction with no loss of offsite power. Sensitivity studies (Pe"erence 2) show that this assumption results in the worst peak clacd?ig temperature. Minimum safeguards f ECCS capability and operability has also been assumed.

No additional penalties were required for upper plenum injection since the Westinghouse Large Break LOCA Best-Estimate Methodology models the RHR flow to be injected into the upper plenum. This analysis result is below the 22000 F Acceptance Criteria limit established by Appendix K of 10CFR50.46 (Reference 1).

e 1

REFERENCES

( ,

l f 1. "Acceptance Criteria for Emergency _ Core Cooling Systems for Light Water Cooled Nuclear Fower Reactors: 10CFR50.46 and Appendix K of 10CFR50.46," Federal Recister, Vol. 39, No. 3, January 4, 1974.

I 2. Dederer, S. I., et al. , Westinchouse Larce-Break LOCA Best-Estimate Methodoloov, Volumes 1 and 2, WCAP-10924-P, (Proprietary Version), April, 1988.

3. NRC Staff Report, "Emergency Core Cooling System Analysis Methods," USNRC-SECY-83-472, November, 1983.

4. Bordelon, F. M., and E. T. Murphy, Containment Pressure Analysis Code (COCO), WCAP-8327 (Proprietary Version), WCAP-8326 (Non-Proprietary Version) , June, 1974.

5. Westinchouse Revised PAD Code Thermal Safety Model, WCAP-8720, Addendum 2 (Proprietary), and'w CAP-8785 (Non-Proprietary).

c t

e ,

t

. TABLE 1 LARGE BREAK TIME SEQUENCE OF EVENTS l

l Four Channel l Core EVENT 0.4 DECLG (seconds)

Start 0.0 Reactor Trip Signal 0.1 Safety Injection (S.I.) 2.0 Signal High Head S.I. Begins 7.0 Blowdown PCT Occurs 7.8 Accumulator Injection 10.0 Low Head S.I. Begins 21.0 End of Bypass 24.2 Bottom of Core Recovery 32.8 Hot Rod Burst 33.8 Hot Assembly Average 42.9 Rod Burst Accumulator Water Empty 45.7 Accumulator Nitrogen 70.0 Injection Ends Reflood PCT Occurs 107.9

)

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• .t

,, TABLE 2 LARGE BREAK RESULTS 1

Four Channel Core EVENT 0.4 DECLG (seconds) s F9ak Cladding Temp., OF 2060.

Peak Clad Temp. 7.0 Location, ft.

l Local Zr/ Water Reaction 1.26 (max),%

l

! Local Zr/ Water Reaction 8.0 l Location ft.

Total Zr/ Water Reaction, % <0.3 l

Hot Rod Burst Time, sec. 33.81 Hot Rod Burst Location, ft. 4.60 Hot Assembly Burst 42.9 Time, sec.

1 1

Hot Assembly Burst 8.00 l

Location, ft.

Hot Assembly % Blockage 35.33 Calculation Input Values:

NSSS Power, Mwt, 102% of 1650.

Peak Linear Power, kw/ft, 102% of 15.789 Peaking Factor (At Design Rating) 2.50 l Accumulator Water Volume 1270.

(Cubic ft. per tank, nominal)

Accumulator Pressure, psia 754.7 Number of Safety Injection Pumps 3 (Operating (1 RHR + 2 HHSI)

Steam Generator Tubes Plugged 10%

I

. . r .

PRESSURE (PSIA)

CHANNEL 10. NODE 7 TOP OF CORE

.25E C4-

.225E 04- k

.2E 04-c

{.175E*04-

. u .15E 04-g .125E 04-w E .lE*04-750.-

500.-

250.

75. 100. 125. 150. 175. 200.

-25. O. 25. 50.

TIME ISECONDS) . _ .

Figure 1:

Core Pressure (Four Channel Core Model)

(0.4 DECI4)

1 1

LIQUID, VAPOR, AND ENTRAINED MASS FLOW TOP OF CORE - CHANNEL 12. NODE 7 (HOT ASSEMBLY) 1-LIQUID FLOW, 2-VAPOR FLOW, 3-ENTRAINED LIQUID FLOW 20.

G 15.

d r 10.

5

~

5.- f a L .-

d e' .

", d . w.-. AnJ%

yF g f

. r -5.- "

t g! '

-10. I

\

-15.

-20 25.

O. 25. 50, 75. 100. 125. 150. 175. 200.

1IME (SECONDS 1 Figure 2: Core Flow at Top of Hot Assembly (Four Channel Core Model)

(0.4 DECI4)

___________-______-_-__________________________________________J

LIQUID LEVEL DOWNCOMER LIQUID LEVEL CHANNELS 2 3.7.8 14.15 22.23 29.30.37.38.43.44 i i

50.-

t 25.' BOTTOM OF COLD LEG ELEVATION

/

d 20. .

, 5 a

, e 9 15.< h 8

i

10. I 1

l I

l

-25. O. 25. 50, 75, 100, 125. 150. 175. 200.

TIME ISECONDS)

Figure 3: Downconer Collapsed Liquid I4 vel (Four Channel Core Model)

(0.4 DECI4)

.a

, LIQUID LEVEL CORE LIQUID LEVEL CHANNEL 12. (HOT ASSEMBLY) 12.- -

i

_ 10.-

[

d 8.-

5>

g 6.-

8 3 4.-

2.-

N ) 0

. C L isi g-,25 . O. 25. 50. 75. 100. 125. 150. 175. 200.

TIME (SECONDS) ,

I Figure 4: Collapsed Liquid Level in Hot Assembly (Four Channel Core Model) (0.4 DECIA)

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _a

?v TOTAL FLOW ACCUMULATOR TO INTACT COLD LEG

' COMPONENT 10, CELL 3

.5E 04-G .25E+04-U s

5 2E*04 d

=

3 w

15E+04-w

$ .lE+04 O

• 500.

D.

k

-500 25.

O. 25. 50. 75. 100. 125. 150. 175. 200.

TIME ISECONDS) i Figure 5: Accumulator Mixture F1 W (Four Channel Core Model) ,

(0.4 DECLG) i

<- . _ _ -. - , - . - --..,.,n. .---._,,,-,.--.-.------.-,,n..- .

._-_---..---.,a. - ,

4

.~

TOTAL FLOW HHSI TO INTACT COLD LEG C0t1PONENT 6. CELL 5 200.-

- 150.<

d g 100, 5

50.

b y O. i-4 0 -50.

E

-100.

-150.

-200 25.

O. 25. 50. 75. 100. 125. 150. 175. 200.

TIME (SECOND5) .~

Figure 6: HHSI Flow to Intact Cold It g (Four Channel Core Model)

(0.4 DECIA) n

TOTAL FLDW RHR FLOW UPPER PLENUn COMPONENT 24. CELL 2 500.

S 250.

R g g:- __

d 200.

E d

g 150.-

E

- 100.

50.

t 3 25. -

O. 25. 50. 75. 100. 125 150. 375 200.

! TIME (SECONDS) l l

Figure 7: 281IR Flow te IPpper Timma (Four Charanel Core Model)

(0.4 DECIs)

v. , ,,

4 CLADDING TEMPERATURE AT 6.25 FT ROD 1 -HOT ROD- CH 12. ROD 2 -HOT ASSEMBLY -CH 12 3-AVG ROD-CH 11, ROD 4-AVG ROD- CH 10, ROD 5-L.P. ROD -CH

.22E 04-

.18E 04 S .16E+04-a

].14E+04-n:

l {.12E+04-

.IE+04- -- 3 W B00.

600.

in 400.

.__ r 200

-2 5. O. 25. 50. 75. 100. 125. 150. 175. 200.

TIME (SECONDS) .

Figure 8: Cladding Temperature (Four Channel Core Model)

(0.4 DMCI41) l 1

f l

, - - - . . . - -. , _ . _