ML20050C895

Natural Circulation Boron Mixing & Cooldown, Test Rept

ML20050C895
Person / Time
Site:	North Anna
Issue date:	04/05/1982
From:	Dunesia Clark, James Smith VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20050C894	List: ML20050C892 ML20050C895
References
NUDOCS 8204090441
Download: ML20050C895 (5)

Text

-

VIRGINIA EECIRIC AND POWER OCEPANY NOKIH ANNA POLTR STATION UNIT 2 NATURAL CIRCULATION BORON MIXING AND C001DOLW TEST REPORE i

Prepared by: / // p / _

' D. E. Clark ~

' N/st-Approved by: b ' J . ~ P .' Teith

/ Reactor Engineering Supervisoi i 8204090441 820405 PDR ADOCK 05000339 P PDR s

NAIURAL CIRCU1ATION BORON MIXING AND 000LDOWN TEST 2-ST-34 North Anna Unit 2 successfully completed the Natural Circulation Boron Mixing and Cooldown Test, 2-ST-34, on March 7, 1982. This test was perfomed using decay heat and was similar to the Sequoyah Nuclear Plant Test #9B, Boron Mixing and Cooldown. The objectives of this test were to verify boron mixing and the ability to cooldown the reactor coolant systs while in a natural circulation condition. This test was initiated following an orderly shutdown from 1007. for the first refueling outage.

Test Results Boration Following the shutdown reactor coolant system stability was obtained and then the reactor coolant pmps were tripped. Stable natural circulation developed in approximately 15 minutes with a AT of approximately 20*F.

Boration was initiated at a rate of approximately 22 gpm of 127. boric acid.

h reactor coolant system boron concentration was monitored fra the loop A cold leg and the loop B hot leg at 20 minute intervals. The boration was teminated after 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, appmximately 1400 gal, of 127. boric acid were added. Both loops showed the same rate of increase in baron concentration. h A cold leg concentration lagged behind the loop B hot leg concentration because of the heavy boration rate and a difference in s uple delay time. The heavy boration rate caused the boron concentration to increase rapidly. The difference in sample delay time is caused by the additional A loop coolant transit time frm hot leg to cold leg and the additional sample line length to the A cold leg cmpared to the sacple line length a the B hot leg. Both loops stabilized at a concentration of approximately 642 ppm approximately 50 minutes after boration was teminated.

h pressurizer boron concentration increase was controlled by tuming on additional pressurizer heaters and diverting same of the charging flow to pressurizer auxiliary spray. By the end of the test pressurizer boron concentration was 1200 ppm. Ad'itional d boron was added to the reactor coolant systs at a slower rate during the cooldown phase. The concentration of both loops reained equal during this phase and increased frm 642 ppm to 770 ppn. (See Figure 1)

Cooldown h cooldown was initiated at approximately 0400 and was terminated at approximately 0615. Wide range T h at ranged fr a approximately 555 F to approximately 475 oF, an 85 oF decrease. Wide range Tcold ranged frm approximately 534 0F to approximately 449 oF, an 85 0F decrease. The overall cooldown rate, was -39.7 T/hr. The maximn cooldown rate, which had a duration of approximately 35 minutes, was -65.4 0F/hr. (See Figure 2)

The hottest core exit thermocouple for each quadrant was monitored throughout the test. The cooldown was unifom radially across the core with approximately the same rate for each quadrant. h cooldown rate for Quadrant 1 was -39.6O F/hr, for Quadrant 2 was -39.4 OF/hr, for Quadrant 3 was -39.5 0 F/hr, and for Quadrant 4 was -39.4 0F/hr.

Conclusion h reactor coolant syst s was in a stable condition throughout the test. Natural circulation flow developed smoothly after tripping the reactor coolant punps. Reactor coolant syst e pressure was easily controlled with pressurizer heaters and auxiliary spray. The ability to mifomly borate the reactor coolant systs was dmonstrated. The boron concentration of two loops increased fra 42 ppm up to 770 ppm. h ability to unifomly cooldown the reactor coolant systs was deonstrated.

h core exit thermocouples showed no evidence of a radial tilt. h acceptance criteria of the test was met.

'=- - ,, , ,_

9 9

e O

@1m e I 0 7

2 N

O t 0 I I T o 4 A

L T h 2 U

C R

I C

L 0 A I 1

R 2 U

T A

EN 4 DG3 TN-

.IT RS 0 SU - 8 8

VD2 1

)

S E

8 0I 5U 1N I

(M d

E

- l H o 0 T

c

• I T 2 1

0 i 9 0

i 6

^

0 I

3 f

F -

1 O

0 0 0 0 0 0 5 3 1 9 7 5 5 5 5 4 4 4

[ ,

, i I  !

l l 4

e w mf( N D

0

>7

- 2 0

4 2

0 1

.2 4

3 T 0 S ,6 1

2 s N DO TH SA vL U

C _

mR 0 nC I

9 G 5

a. E L

1 )

S E

mLM M

I D T aU cI L

O I

N I

C mR O

t A

M

(

e E P 0 E mD aR O

D 2

1 TD om B

I U

N 0

G E

I r

7 M b B 3 P

O '

O L

e h

5 0 5 5 0 5 0 5 0 5 0 2

8 5

7 6L5 7 2 5 4

7 3

h8 0

3 2

2 5

1 7

l t