B. A. R. C.-884

s°p

GOVERNMENT OF INDIA

ATOMIC ENERGY COMMISSION

FISStON PRODUCT RELEASE BEHAVIOUR AFTER REACTOR SHUTDOWNEXPERIENCE AT TARAPUR ATOMIC POWER STATION

by

S. V. Narasirahan. G. Venkateswaian and K. S. VenkateswarluChemistry Division

BHABHA ATOMIC RESEARCH CENTRE

BOMBAY, INDIA1977

B . A. R. C. -884

3°? GOVERNMENT OF INDIAo- ATOMIC ENERGY COMMISSION

FISSION PRODUCT RELEASE BEHAVIOUR A F T E R REACTOR SHUTDOWN:EXPERIENCE AT TARAPUR ATOMIC POWER STATION

by

S. V. Narau imhin , G. Venkateawaran and K. S. Venkate«w» irluChemietry- Division

BHABHA ATOMIC RESEARCH CENTREBOMBAY, INDIA

1976

INIS Subject Category < 831

p e e o r i p t c r s t

TARAHTR-1 HEACTCfi

TARAHJH-2 HBACTCR

BEACTQR SHUTDOWN

WATER

COOIAMTS

TRANSLOCATION

FISSION IRODOCTS

ICDIHE 131

ICDINE 132

ICDIHB 133

IODINE 1 3 4

ICDINE 135

CESIUM 1 3 4

CESIUM 1 3 7

FUEL ELEMENT CLUSTERS

ABSTRACT

A study on tbe fission product release behaviour after reactor

shutdown has been carried out at Tarapur Atomic Power Station. The

activity concentrations of Iodines, Caesium and Technitium in reactor

water have been measured. The release rates and release rate coefficients

have been computed. The nature of the variation of the release rate coeffi-

cients with decay constants of the Iodines has been used to find out the

mechanism of their release. In this connection an inter station compari-

Bion has been made between Gundremmingen BWR in West Germany and

TAPS BWR.

FISSION PRODUCT RELEASE BEHAVIOUR AFTER REACTOR SHUTDOWN:EXPERIENCE AT TARAPUR ATOMIC POWER STATION

by

S. V. Narasimhan, G. Venkateawaran and K. S. Venkateswarlu

1. INTRODUCTION

The production of solid and gaseous fission products in ceramic

oxide fuel elements has a wide range of effects, varying from radiological

hazard in the event of their release to the surroundings, to chemical and

physical effects in the fuel element itself. The normally impermeable

zircaloy Clad often develops defects during operation thereby leading to

a release of fission products into the coolant. The release of the refractory

and less volatile fission products is not the major contributor to high

reactor water activity levels. On the other hand it is the iodines, cesiums

and technitium activity levels in the coolant that cause a potential danger.

It is generally accepted^ ' that the mechanisms by which the volatile iodines

are released during operation are somewhat similar to that of noble gases

especially xenons. Besides the other factors that contribute to the fission

product release, the temperature gradient existing across the radial length

is a major one. On the other hand when fission product release rate

measurements are made when the reactor is under shut down conditions,

this temperature gradient no longer exists, thereby leading to a prediction

of the minimal release. But it is known from nuclear power plant experience

that there is a large increase in fission product release soon after the reacto?

power is either varied from the equilibrium value or is reduced to zero.

-2-

The incore and out-of-core wet sipping techniques used to identify leaky

fuel bundles also make use of the fact that there exists a definite release

of fission products to the surrounding cooling water used to remove the

decay heat. The question therefore arises as to whether the radial thermal

gradient of the pellet created by the decay heat is sufficient to cause release

under "cold" conditions. Based on a number of experiments carried out on

release of fission products from pellets without clad and fuel elements with

.intentional defects under simulated conditions of reactor operations,

sufficient data is available to enable prediction of models for fission

product release under reactor operating conditions. Such attempts were

rarely made for collecting data regarding fission product release after

(2)reactor shutdown. Recently Eickelpasch et. aU , have carried out a

similar set of experiments on fission product release after reactor shutdown.

This report describes the experiments at Tarapur Atomic Power Station

(TAPS) and attempt*) to make an interstation comparison between

Gundremmingen BWR and TAPS BWR.

2. EXPERIMENTAL

2. 1 Brief description of TAPS

The Tarapur Atomic Power Station consists of two dual cycle boiling

water reactors <sach having a maximum output of 707 MWT/210 MWE. The

reactors use slightly enriched UO^ fuel (^2.4% U ) with light water as

coolant and moderator.

2.2 Reactor status during measurements

The shutdown activity concentration measurements were done during

- 3 -

the third refuelling outages of unit # 1 and unit # 2 TAPS in January 1975

and July 1975 respectively. Prior to shutdown, the unit ill 1 was operat-

ing at a power level of about 500 MWt and unit # 2 at about 585 MWt. In

both the cases power was reduced in a planned manner and in about 5 hours

time the reactors became subcritical. The zero time, i. e. the shutdown

time, was taken as the time at which power reduction started. Demir.erali-

sed (DM) water make up and feed/bleed techniques were employed to bring

down the system temperature. Hydro tests were carried out on the reactor

system (during the course of the present study) to locate leaks in the

primary system. Such tents would be normally carried out 20 to 30 bourn

after shutdown and last for about 4 to 5 hours,

2. 3 Sampling points and sampling techniques

During operation of the reactor and during shutdown barring the

hydrotesting periods, the reactor water was sampled before the filter in the

clean up system. During hydro testing the sampling was done from the

sampling point provided in the recirculation loop. Each time the sampling

was done the line was flushed for about 10 nits at a flew rate of about 1 tit/

min before collecting the sample.

Under operating conditions reactor water was sampled twice a day

while under shutdown conditions the sampling was done approximately once

in 3 hours upto 40 hours after Bhu'down and thereafter the frequency was

reduced to once in 6 hours. The experiments coul'd not be carried out beyond

90 hrs in the case of unit # 1 and 66 hra in the case of unit # 2 because of the

unknown dilution effects introduced by filling up of the reactor cavity with water.

-4-

2. 4 Sample analysis

Each sample was analysed to determine the activity concentration

of 1-131, 1-132, 1-133, 1-134, 1-135, Tc-99m, Cs-134 and Cs-137. *

The iodines were analysed by extraction with carbon tetrachloride and

subsequent silver iodide precipitation procedure. The Tc-99m was cr

precipitated with copper sulphide (> 95% carryover takes place) after

passing the water sample mixed with KT. carrier through a preconditioned

AgCl column to remove the iodines. The separated iodines and technitium

were counted at a known geometry on a 7. 5 cm x 7. 5 cm Nal(Tl) detector

coupled to a 512 channel analyser. The cesiums were estimated directly

from the. samples, by counting 50 ml reactor water samples on an approxi-

mately 12 cc active volume Ge(Li) detector coupled to a 1024 channel

analyser.

3. RESULTS AND DISCUSSION

3. 1 Calculation of activity concentration

The variation of the activity concentration of iodines, cesiums and

technitium are plotted in Figures 1, 2 and 3 respectively as a function j>f

time. The time at which maximum activity concentration has occurred was

practically constant for all nuclides (Fig. 4) except 1-134 in which case no

peaking could be seen. The peak to normal activity concentration ratio was

found to decrease with decreasing half life (Fig. 5). The variation of clean-

up flow rate with time is shown in Figs. & and 7.

The details concerning the calculation of fission product release rates

given in Appendix I. Plots of the release rates for different nuclides are

Some of the nuclear parameters of these isotopes are given in Table I.

- 5 -

shown in Figs. 8-10. The characteristic features noticeable from an exami-

nation of these graphs are

a) A peaking of the release rate soon after shutdown (within about

5 to 10 hours). The peaking effect in short lived nuciides was lees

pronounced than long lived ones. Moreover no peaking for short

lived nuciides was observable in the case of unit II.

b) A steep fall in release rate with time after the peaking was observed.

The activity concentrations of reactor water soon after the hydrotest

was considerably higher than that observed just before the hydrotest. This

was true especially'in the case of unit II. Though an exactly identical behaviour

was not noticed in the case of unit 1, a shallow region was obtained as evidenced

by the graphs. During the hydrotests, lack of circulation of reactor water and

the absence of the clean up system cause a considerable build up of activity

concentration in the core. This leads.to a prediction of sudden/apparent jump

in the release rates of the nuciides concerned. But this is contradictory to the

general belief that the release rate should monotonously decrease with time

after shutdown paaking,

3.2 Calculation of release rate coefficient (ri )̂

Th* reUase rate coefficient or the fractional reUase rat* is defined as

r i • * *i t ^ t where

% | • ralaas* rat* of 1 th nuclide at tima t

\ t * Fual Inventory of leaky bundles at that time t for th* 1 th nuclide

r, t i* an indue of th* mechanism of r*l«as* of fission products from the fuel

alamsnts,

3.3 Calculation qf ftzal inventory (I. t)

Sine* th* exact energy output of each fuel bundle with time is net available,,

- 6 -

attemptB were not made to compute the fuel inventory at shutdown time for

longlived nuclides such as 1 3 4Cs and 1 3 7 Cs. Moreover the 1 3 4Ca being an

activation product of 1 3 3 Cs, which is a daughter of i 3 3 Xe, inventory cal-

culations require an exact knowledge of flux as a function of fuel cycle time.

This data also could nut be obtained at the time of compilation of this paper.

Since technitium isotopes are volatile under highly oxidising conditions,

T c99m behaviour cannot be similar to that of iodines. Among different isotopes

of Tc, since Tc only has been measured its mechanism of release after

shutdown could not be predicted. The reactors were continuously operating at

a power Level of 500 MWT for about 40 days prior to shutdown. As a result of

this, it'is assumed that all the iodines and tellurium nuclides have reached

equilibrium activity levels given by equation (1)

JTyi = NiA i (1)

where yj = Cumulative fission yield oi i t h isotope

F = Number of fissions per second

Nj[ = Number of atoms of i"1 isotope

A j = Decay constant

Therefore the activity, A^o, of any isotope at shutdown time is obtained from

expression (2)

A i o = FY i (2)

Further the activity of indicator isotopes at different times after shutdown were

computed using the following equation (3)

(3)

where subscript k stands for precursor and subscript j stands for the indicator

- 7 -

i a c ' ^ p " r ' • ii_- ' : . . • . ' : . ' • ; • o.-- '•' '•'' : . ; u i f ; ' : d 'i*±u>.-r l i y . t d i o E v h i c h c o n t r i b u t e

t o w . : . . ! : • ! : : . - . - •: ..-• - h , . : c i o G ' . i c , . - ' • > r ; : > . o ' - . •:• "•• •"•.:- - " ^ m p u t e d u s i n g

I, f ; A,(I) v. .-_"'.. (4 )

N T

where ?<,, ~ Numbev <ji •"''h -tive fuol pins present in the core an estimate of

whic.'i in obtained from B\pr,'Lri>'' r esu l t s . It is assumed that each

leaky fni?' VjndUj '.or.ta.infc ;;ot -nore than one ie^ky fuel pin. Even

if this assumption is conservative, only the absolute value of release

rate coefficient will change for the indicator isotopes, but not the

ni^chpniani of s:c\p.nsf which is discugsed later.

Nrp - Tol^J m i m b e " •. • ' u i ! -.'nm

- 1VZ2A (at TV,/•••: f:..-. t a r h imii.)

As an example 1 able H gi'-'c :; the inventory of indicator isotopes in unit-I as a

function of time after shutdown.

The plot of release rate coefficient as a function of time is given in

Figs. (11-12).

Some of the characteristic features observable from the je plots are,

a) The behaviour of re lease rate coefficient with time is once again

similar to that ol the concentration or release rate profile.

b) The maximum increase of release rate coefficient from the normal

operating value is the greatest for ^ 1 and it decreases as a function of

half life. Table III shows these treads.

c) 1 to 3 days after shutdown, the release rate coefficient value reaches

the value during operation, eventhough the temperature of the fuel i s quite

different.

-8 -

It was noted earlier that the concentration jumps observed during peak-

ing for the different radionuclides between the two units are remarkably different.

So i« the case with the release rate coefficient jump. Thus the magnitude of these

numbers are characteristic of the system, though their trends predict the operat-

ing mechanism of fission product release after shutdown.

c).Similarly the abnormal fluctuations in release rates and release rate

coefficients during 5 to 15 hours after shutdown are due tp the unexpected non-

steady cleanup flow rates. Though the clean up flow rate values as observed

in Figs. 6 & 7 have been substituted in the calculations, there could be a "phase

shift". Suppose a sample is collected at say 10 hrs after shutdown and the

clean up flow rate has been observed to change continuously from say 9. 75 hra

to 10.25 hrs. In such a case the magnitude of the clean up constant substituted

in calculation will definitely affect the release rate values. It was found difficult

to overcome this arbitration.

Plots of log release rate coefficient vs the log of decay constants were

made in order to predict the mechanism of release of fission products (Fig.

Nos. 13-16). The fractional release rate (or the release rate coefficient) of

fission products show A dependence characteristic of the operating mechanism

of release. This logic was utilised in supporting the following model for predict-

ion of the mechanism of release during shutdown.

When the system is under steady state during operation, the diffusion

model of release of fi»»ion products to coolant is given by

The equilibrium activity which causes diffusion type of release is given by (z).

Dividing eqn. (5) by Fyi and take ing log, eqn. (6) is obtained.

- 9 -

x, . .log —iii— = log k_ + 0. 5 log A*' (6)

Fy. D

At predicted by equation (6), a slope of about +0. 5 is expected when the

system is under operation for diffusion type of release. Figs. (13-15) con-

firm thin. It should be noted that the reactor achieved subcriticality about

5 hours after the 'serotime' referred to In the text earlier. The constant

decrease in fission rate during the shutdown will affect equation (6) to a

certain extent and that it is not unreasonable to uxpect that the effect will be

felt considerably on short lived nuclieds (especially 1-134).

The release rate of any fit sion product long-time after a shutdown

will be proportional to the total inventory p-esent inside the fuel element and

ilia ia known at* equilibrium type of re lea to under shutdown conditions.

lag *i, t . - lOg k + 0. 0 log A ,^ . t E

(8)

It can be seen from plots (14-16) that the slopes approach zero. The plots

(13 15) do not conform to either of the two mechanisms. In the region of

the time span, namely 2 to 10 hrs after zero time, there is a dramatic change

in the release mechanism, whereby relatively short lived nuclides continue to

follow diffusion mechanism (with a slope in the region of + 0, 5), while the others

the follow the so-called "Diffusion-Equilibrium" mechanism (with a slope in the

region of -0. 5), This explains why the variation of release rate coefficient of

I with time does not show any maximum in both the units. The slopes

obtained In this atudy and that obtained by Eickelpasch et &l' ' are tabulated in

-10-

table IV for comparison. The agreement is found to be a good indication in

a general way of the comparatively similar behaviour of the fuel loada in

KRB and TAPS at the time of planned refuelling shutdown*.

1. CONCLUSIONS

The above study reveals that,

a) All the fission products studied show activity concentration peaking,

release rate and release rate coefficient spikes soon after the reactor .

shutdown.

b) The longest lived nuclide shows the highest spike , The magnitude

of the spike for the same nucleus was found to be system dependent

namely number and size of fuel defects.

c) The time of occurrence of the peaking for all nuclides except 1-134

was found to be nearly same.

d) The release rate mechanism of iodines drastically changes immediately

after shutdown. All the iodines comply to a diffusion mechanism of

release during operation. However immediately after shutdown the

short-lived iodines follow a diffusion process of release, while the

long lived iodines follow the socalled diffusion-equilibrium process of

release. After about 10 hours from the shutdown time all the isotopes

tend to follow an equilibrium type of release process.

e) The mechanisms predicted for iodine release from these experiments

are in good agreement with what has been observed in Gundremmingen

Nuclear Power Plant in West Germany.

5. ACKNOWLEDGEMENTS

The authors would like to gratefully acknowledge the cooperation and

-11-

facilitiea given by Tarapur Atomic Power Station authorities and personnel

in general and by Shri V. V, Kothare, Chief Superintendent, Shri K. Nanjundeswaran,

Technical Services Superintendent and Shri T, B. Nandwani, Chemical Engineer

in particular for successfully carrying out this work. The authors would like to

thank Dr. M. D. Karkhanavala, Head, Chemistry Division for his keen interest In

the work.

REFERENCES

1. A comparison of fission product release studies in loops and the VBWR,F. J. Brutschy, AECL 1265 (1961).

2. Fission product release after reactor shutdown, N, Eickelpasch andR. Hock, IAEA-SM-178/19 (1974).

3. Compilation of fission product yields, Vallecitoa Nuclear Center-1972,M.E. Meek and B.F. Rider, NEDO-12154 (1972).

-12-

TAELEI

Relevant nuclear parameters of the Indicator Nuclide

Nuclide Precursor(Kev)

1-131

1-132

1-133

1-134

1-135

8. 041 d

2.285 h

20. 800 h

52. 600 m

6. 585 h

Tc-99m 6. 020 h

Cft-134 2.060 y

Ci-137 30.100 y

9. 977 E-7 2. 84 364

8.426E-5 4.22 670

9.257E-5 6.77 530

2.196 E-4 7.60 860

2.924E-5 6.48 1260

3.198E-5 5.39 140

1.067E-8 - 800

7.302E-10 6,26 662

Te-131

Te-132

Te-133m

Te-134

Te-135

Mo-99

Cs-133Xe-133Xe-137

25.00m

78. OOOh

55.4 m

42. 00 m

0. 5 m

66. 02 h

Stable

3.84 m

2.54

4.18

3.03

6.06

4.02

6.13

6.776.776.13

• Calculated comulatlve yields in % Ref. (3)+ M?e» prominent "f energy of the indicator nuclide

TABLE II

Inventory (curies) of indicator isotopes present in leaky bundles as a function of time after shutdown

Time 0 1.5 5.5 9.5 12.5 15.5 29.5 42.5 55.5(hrs)

1-131 7.81E4 7.78E4 7.67E4 7. 56E 4 7.48E 4 7. 40E 1 7.04E 4 6.7,'it 6.42E4

1-132 1.16E5 1.15E5 1.12E 5 1.08E 5 1.05E 5 1.02iS 5 9.03E 4 8.05*3 1 7.17E 4 I

1-133 1.86E5 1.78E5 1.56E 5 1.36E5 1.23E 5 1. 12E 5 7.00E 4 t . i ' . S l i . 94E 4

1-134 2 .09E5 1 .22E5 8 .99E3 4.53E 2 . . . -

1-135 1.76E5 1.51E5 9.89E 4 6.49E 4 4.74E 4 3.45E 4 7.91E3

-14-

TABLE in

Peak relative release rate coefficient variation as a functionof half life

Nuclide t 1 / 2 Unit I Unit II

1-131

1-132

1-133

1-134

1-135

Peak relative release) a Release rate coefficient at its maximum

8.

2.

21.

6.

05 d

28 h

0 h

52 m

7 h

87.

5.

13.

-

7.

8

50

60

40

29.3

1.06

4.65

-

2.86

rate coefficient ) Release rate coefficient at Normal operation

-15-

TABLE IV

A comparison of slopes obtained for log release rat*coefficient va log A plots

Time (hre)

0

0. 5

5.0

5.5

9.5

Jl. 0

12. 5

15.5

2.'. 0

29.5

43.5

52.15

54.0

Slope (TAPS)Un'it-1 Unit-2

0.54

•0.59; +0.60

- 0.63; +0. 50

-0.24

-0.20

-0.08

0.60

-0.54; +0.64

-0. 60; +0. 64

-0. 19

-0.21

-0.13

0.05

Slope(G and remmingen)

+0. 45 to +0. 5°

-0.52; +0.57

-0.37 to -0.52

-0.?

-0.36 to -0.55

-0.11

-0. 09 to -0. 39

-16-

Appendix-I

Calculation of fission product release rates

Release of fission productsfrom the fuel (x.:

Definition of terms:

x. j. = Release rate of i isotope from fuel to the coolant at any timetin(Ci/a).

m. t = concentration expressed in Ci/1 of i tn isotope at any time t.

"7 . . = purification constant of i isotope tit any time t, defined as theratio

[D. M. inlet cone. - D. M. outlet cone. ID. M. inlet cone. I

•*• 1 in most cases.

(for a small time interval, ft *7. . can be assumed to be a constant)

t. = purification flow (in IH/s)

V s system volume (in lit)

t = time (in sec)

\ . = decay constant of i th species (s~ ')

At any time the change in the activity concentration of i*n isotope is

-17-

jriven by equation (1).

dm x .

dt V i, t i "

- ms J A . +V \.|>

When the reactor is under steady operation it may possibly be assumed

that there is no development of new fuel defects or »'•' hange in the fuel

pellet structure leading to an fibnormal release of fission products. Under

surh conditions the xj j. can be treated to be !,-<*ependent of time. Since for

the present P . . is also assumed to independent of time, equation (2) can be

reduced as follows :

V d mx-mV(A+

= dt

Upon integration under the condition at t = O ; m * xnQ

x = ( n . - m o . - » ^ P ) ' ) v ( X , M (J)

If m = O, then

P)

when t » A + ̂

V(A i+p i) (5)

Thus the expression (5) can be utilised for the calculation of releaae rates

under steady operating conditions.

On the contrary the release rate of i t n isotope varies as a function

of time when there is a power fluctuation and also during shutdown cooling

-18-

of fuel elements. Thus the assumption that x> t is independent of time is

no longer valid a-d as such the functional dependence of x- t on t is not

predictable. In order to effect the calculation of xj t equation (2) is

rearranged

Vdm,x i t = • - h l - + Vm i / t (A i + h) (*>

*• * dtdmi *.

The graphical plots of m; ¥ vs time were Bmoothened from which *x ' t dt

were calculated. These values and other constants were substituted in

equation (6) to get X{ t as a function of time. A plot of clean-up flow rate

vs time is shown in Figs. 6 b 7 from which ft. . were computed and used

in equation (6).

«'#•.'

140 100 60 20 (JlTIME BEFORE SHUT-

DOWN (HOURS)

10 20 30 40 50TIME AFTER SHUTDOWN (HOURS)

70 80 90

Fig. 1 VARIATION OF ACTIVITY CONCENTRATION OF IODINES WITH TWE

10

e -2v 10

Ia:i—

I

io4

Cs-134

Tc99 m

UNIT # I TAPS

140 100 60 20 IITIME BEFORE SHUT- -

DOWN (HOURS)

Cs-137

HYDRO TESTING

10 20 30 40 50 60

TIME AFTER SHUTDOWN (HOURS)

70 801O2

90

Fig. 2 VARIATION OF ACTIVITY CONCENTRATION CESIUMS AND TECHNTTIUM WITH TIME

Irf

o

u

-210

1-134

1-1321-135

1-133

1-131

UNIT # 2 TAPS

75TIME BEFORE-

SHUTDOWN(HOURS)

10 20 30 40 50 60 70 80

TIME AFTER SHUTDOWN (HOURS)

90 100

Fig. 3 VARIATION OF ACTIVITY CONCENTRATION OF IODINES WITH TIME

•2

•1

•0

" 1

•

'. *

- PiMuf l .

•

134

•V)

O

J

• UNIT* UNIT

i

1 TAPS2 TAPS

m

w- <

M •

1

« K

O)

i IT

(VI *

1 1. . . .-10 -9 -8 -7 -6 -5

LOO A-4 -3 -2

Fig. 4 PLOT OF LOG PEAK TIME vs LOG X

I

§

2-5

20

15100500

-

-

-137

MO

, . I.-10 -9

-134

V)O

, I-8

. |-7

. -UNIT 1x-UN(T 2

•

31

«

•1-1

33

t . I-6 -5

TAPSTAPS

fifei .* -3 -26

L08 A

Fig. 5 PLOT OF LOG PEAK TO NORMAL ACTIVITY RATIO vs LOG X

Ipmooo

r o * • o>o o oo o oCDoo

ooo

5o

m

CD

o a

s "

^ O

f

c

-n5̂j

X

—f

1m

>Tl-1mXI

0)Xc—̂o1Xo

roo

U )

o

o

o

0)

§

HYDRO

*

•n

I

o•n

om>

-Tl

m

00 .o

IDO

1

10°

103

1-134

1-1321-1351-133

1-131

UNIT*? TAPS

HYDRO TESTING

i40TIME BEFORE SHUT-

DOWN (HOURS)

10 20 30 40 50 60TIME AFTER SHUTDOWN (HOURS)

Fig. 8 VARIATION OF RELEASE RATE OF IODINES WITH TIME

70 80 90

id3

o

UJ

a:

io6

UNIT # 1 TAPS

HYDRO TESTING

99m

Cs-

140 100 60 20 l 10 ZO 30 40 50 60TIME BEFORE SHUT-

DOWN (HOURS)

70 80 90

- TIME AFTER SHUTDOWN (HOURS)

Fig. 9 VARIATION OF RELEASE RATE OF CESIUMS AND TECHNETIUM WITH TIME

10

. M34

- 1-132

oz

I- M33

1b4

UNIT* 2 TAPS

1-135

- 1-131

M 3 3

HYDRO TESTING

140 100 60 20 I

TIME BEFORE SHUT-DOWN (HOURS)

10 20 30 40 50 60

TIME AFTER SHUTDOWN (HOURS)

70 80 90

Fig. 10 VARIATION OF RELEASE RATE OF IODINES WITH TIME

io5r

166

To8

fo9

1-134

1-132

I-tS

1-133

1-131

UNIT • # 1 TAPS

1-133

HYDRO TESTING

140 100 60 20 (i 10 20 30 40 50 60 70 80 90TIME BEFORE SHUT t\+— TIME AFTER SHUTDOWN (HOURS)

DOWN (HOURS)Fig 11 VARIATION OF RELEASE RAIL COEFFICIENT OF IODINES WITH TIME

io6

- M34

u)

1 M

M3I

1-136

M33

1 0 8 - M 3 1

UNIT * g TAPS

HV0ROTE8TW

140 100 60 toTIME BEFORE SHUT-

DOWN (HOURS)

10 20 30 40 50 80

TIME AFTER SHUTDOWN (HOURS) i

Fig. 12 VARIATION OF RELEASE RATE COEFFICIENT OF IODINES Wffft TME

UNIT # 1 TAPS

106 LOG X (sec1)

Fig. 13 PLOT OF LOG RELEASE RATE COEFFICIENT vs LOG X1b5

104

LOG X (Sec1)Fig. 14 PLOT OF LOG RELEASE RATE COEFFICIENT vs LOG X

RELEASE RATE COEFFICIENT (Sec 1 )

O, O,

RELEASE RATE COEFFICIENT (Sec 1 !

10-6

1-131

UNIT # t TAPS

M33 M35 M32 1-134

106 105 L o 6 A (S .c 1 ) *

* f a 16 PLOT OF LOG RELEASE RATE COEFFICIENT vs LOO X