AE-131

<

LLJ Measurements of Hydrodynamic Instabilities,

Flow Oscillations and Burnout in a Natural

Circulation Loop

K. M. Becker, R. P. Mathisen, O. Eklind

and B. Norman

AKTIEBOLAGET ATOMENERG

STOCKHOLM, SWEDEN 1964

AE-131

MEASUREMENTS OF HYDRQDYNAMIC INSTABILITIES, FLOW

OSCILLATIONS AND BURNOUT IN A NATURAL CIRCULATION

LOOP

Kurt M. Becker, R« P. Mathisen. O. Eklind and B. Norman

Summary:

The hydrodynamic stability and the burnout conditions for flow

of boiling water have been studied in a natural circvtlation loop in the

pressure range from 10 to 70 atg. The test section was a round, duct

of 20 mm inner diameter and 4890 mm heated length.

The experimental results showed that within the ranges tested

the stability of the flow increases with increasing pressure, increas-

ing throttling before the test section, but decreases with increasing

inlet sub-cooling and increasing throttling after the test section.

The measured thresholds of instability compared well with the

analytical results by Jahnberg.

For an inlet sub-cooling temperature of about 2 C the measur-

ed burnout steam qualities were low by a factor of about 1.3 compared

to forced circulation data obtained with the same test section. At

higher sub-cooling temperatures the discrepancy between forced and

natural circulation'data increased, so that at A*, •, = 16 C, the na-

tural circulation data were low by a factor of about 2.5.

However, by applying inlet throttling of the flow the burnot

values approached and finally coincided with the forced circulation

data. '

Printed and Distributed in January 1964.

LIST OF CONTENTS

1.0

2 . 0

2 . 1

2 . 2

3 . 0

4 . 0

5 . 0

6 . 0

6 .1

6 . 2

6 . 3

6.4

6.5

6.6

7 . 0

Introduction

Apparatus

Test Section and Power Supply

Ins tr umentation

Experimental Procedures

Research Program and Range of Variables

Results of Preliminary Runs Without SteamSeparator

Results with Steam Separator

Effect of Pressure

Effect of Inlet Sub-cooling

Effect of Liquid Level

Effect of Inlet Throttling

Effect of Outlet Throttling

Measurements with Simultaneous Inlet andOutlet Throttling

Comparison with Analytical Results

Nomenclature

BibliographyTableFigures

Page

i

5

6

68

9

11

12

12

14

15

15

16

37

a 7

19

20

2122

- 3 -

1.0 Introduction

During recent years a research program concerning the flow

of steam water mixUires in vertical heated channels has been in

progress at the Heat Engineering Laboratory of AB Atomenergi in

Sweden. During the first phases of this program the steady forced

circulation flow was studied, and measurements of pressure drop,

void fractions, heat transfer coefficients and burnout have been

presented in a series of reports ( l , 2, 3, 4, 5, 6).

However, in the channels of a nuclear boiling reactor natural

circulation flow is encountered. For this case the driving head is

the difference in density of the steam water mixture inside the

channel and the water in the moderator which also acts as a down-

comer. In a system like this it has been observed by many investi-

gators that the flow may become unstable and that heavy hydrody-

namic oscillations may under certain conditions start to develop.

These oscillations have a great effect on the burnout conditions for

the channel, so that burnout values obtained in a natural circulation

system may only be a fraction of those which one would predict on

the basis of steady state measurer ents. Furthermore the oscilla-

tions influence the void volume in the channels and therefore also

the reactivity of the reactor.

It is therefore of major importance for the designer of boiling

reactors to be able to nredict the onset of flow instabilities in the

fuel elements, and also the nature of the flow and the burnout con-

ditions during oscillatory behaviour of the system. During the last

few years the results of a large amount of work, both, theoretical

and experimental, have appeared in published works concerning

this problem. Despite this, present knowledge in the field is not

sufficient for safe and accurate predictions of the hydrodynamic

stability of the flow in boiling water reactor systems.

It was therefore decided to include in our two phase flow research

program a study of the flow in verv leal heated channels during natural.

- 4 -

circulation. The method of attacking the problem has been to simu-

late the reactor fuel element by means of a test section which

is electrically heated. It is desirable to carry out full-scale experi-

ments, but such experiments would be very time-consuming and

expensive. In addition, it would be difficult to interprete or analyze

in terms of the basic flow variables, the results obtained in full-

scale test sections consisting of a large number of rods.

We therefore found it quite suitable to start the investigation

by studying the flow in channels of the most simple geometry, such

as round ducts with the purpose of determining the influence on sta-

bility and burnout of such basic parameters as static pressure, in-

let subcooling, surface heat flux, mass velocity, test section dia-

meter, heated length and inlet and outlet throttling. However, it is

planned later on to continue the investigation in annuli and rod

clusters.

The application of the results obtained in a simple geometry

to the design of fuel elements in nuclear reactors is of course quite

problematical. However, simultaneously with the present experi-

mental study, a theoretical analysis of the problem has also been

conducted, and the analytical results will be reported separately

by Jahnberg (7). Because of the simple geometry the present ex-

perimental results may prove to be very useful for testing the

accuracy of the theoretical model, which later on may be applied

to reactor computations.

One should also note that another important physical differen-

ce exists between a loop experiment and the conditions encountered

in a reactor. When the flow oscillates in the reactor, the steam

void fraction and the reactivity of the system become time depen-

dent. The change of reactivity influences the power which again in-

fluences the void fraction. In a loop experiment the above-mention-

ed coupling between void fraction and power is not present, nor is

the coupling between different channeLS.

- 5 -

The present report deals mainly with the measurements ob-

tained with a 20 mm inside diameter test section of 4980 mm heat-

ed length. Some preliminary measurements obtained with a 10 mm

inside diameter duct of the same length, and in a somewhat different

loop are also included.

2. 0 Apparatus

The flowsheet of the loop is shown in figure 1 and in figure 2

a photograph of the upper part of the apparatus is reproduced.

From the 4890 mm long electrically resistance heated test

section of 20 mm inner diameter the fluid flows through a riser of

36 mm inside diameter and into a steam separator. The details of

the separator are shown in figure 3. The steam water mixture was

discharged radially into the separator through 96 holes in the riser.

The diameter of the holes was 8. 2 mm. From the top of the steam

separator the steam flowed to an aircooled condenser, with a capa-

city of 300 kW, a.nd the condensate returned to the bottom of the

steam separator where it mixed w _th the rest of the water. From

the separator the water flowed through a 51 mm inner diameter

downcomer, passed a preheater and a cooler for adjusting the in-

let temperature, before returning to the inlet of the test section.

The downcomer was also supplied with a throttle valve and between

the preheater and the test section a venturimeter was mounted for

measuring the flow rate.

The loop was designed for an operating pressure of 65 atg

and constructed of stainless steel.

For further details of the loop and its exact dimensions we

refer to a previous report (&).

Initially the loop was constructed without a steam separator

in accordance with the flowsheet i i figure 4. Some measurements

- 6 -

obtained with the loop without separator are also included in the

present report.

2.1 Test section_andjDowe£ jsupply

The test section consisted of a 20 mm inner diameter stain-

less steel duct of 4980 mm heated length. Three copper cylinders,

32 mm outside diameter and 25 mm long were brazed on the test

section at three points, one in the center and one at each end. The

copper electrodes, supplying the power to the test section, were

clamped round the copper cylinders. The power was supplied from

a direct current generator. The maximum available current was

6000 amps, and voltages ranging from 0 to 140 volts could be ob-

tained. The two end electrodes were connected to one pole of the

generator, and the central electrode to the other pole. This arrange-

ment made it unnecessary to insulate the test section from the rest

of the loop in order to prevent loss of electric power to the other

parts of the loop.

The pressure taps, consisting of 4 mm inner diameter stain-

less steel tubes, were welded round \,. 0 mm diameter holes on the

test section, just below the lower electrode and just above the upper

electrode.

2,2 Instrumentation

The following quantities were measured.

1. Static pressure

2. Pressure drop over test section

3. Inlet and outlet water temperatures

4. Power input

5. .Mass fliow rate - .

6. Liquid level in the steam separator

7. Wall temperatures at 16 axial positions of the test section

8. Pressure drop over the throttle valve

— i —

The static pressure in the loop was measured with a precision

calibrated manometer connected to the inlet of the test section.

The pressure drops over the test section and the throttle

valve were obtained by means of D.P. cells.

The fluid temperature measurements were accomplished by-

means of copper constantan thermocouples mounted in wells

100 mm deep and with a 3 mm inside diameter. A precision

Cambridge potentiometer was used for measuring the voltages.

The wall temperatures were also measured by means of copper

constantan thermocouples connected to the potentiometer.

The liquid level in the steam separator was measured by

means of a D.P. cell, and is in the present report given as the

height above the lower electrode, where the heating of the test

section starts.

The power was obtained by measuring the voltage over and

the current through the test section. The voltage was measured with

a Goerz precision voltmeter of 4/4 per cent rated accuracy, and

the current was obtained by measuring the voltage over a calibrated

shunt. For the latter measurement a millivoltmeter with a rated

accuracy of l/4 per cent was used.

The mass velocity was measured with a calibrated venturi-

meter. The venturimeter pressure drop was obtained with a D.P.

cell. The accuracy of the flow measurement is estimfe-ted at 2 per

cent.

The flow oscillations were observed by studying the time

variations of the mass velocity. The output of the D.P. cell was

coupled to an oscillograph where traces of the oscillations were

obtained. Observations of the oscillations were also possible by

studying the pressure drop över the test section.

Further, two burnout detectors were installed in order to

prevent the test section from being damaged by overheating when

burnout conditions were reached.

3.0 Experimental Procedures

Before starting ä run the loop was completely filled with de-

salinated water, and all ducts connecting instruments to the loop

were degassed.

* Then a small amount of power was supplied to the test

section. As the temperature of the water increased, the surplus

water due to thermal expansion was discharged from the loop

through a cooler and to the laboratory drain, so that the desired

operating pressure was obtained. The power to the test section was

slowly increased, and as steam started to be generated the dis-

charge rate from the loop increased and a water surface in the

loop was formed. This procedure continued until the water surface

had reached the desired level in the steam separator. Then the

first readings of the instruments were taken. After noting the ob-

servations the power was slightly increased, the liquid level adjust-

ed by discharging more fluid and after about 15 minutes thermal

equilibrium was obtained so that a new set of readings could be tak-

en. This procedure continued until the burnout detector shut off the

power, indicating that burnout conditions had been reached in the

test section

As the power increased and the void fraction in the test sec-

tion and the riser increased, the driving head, which is equal to the

difference in weight between the fluid in the downcorner ana the test

section-including the riser, also increased. This caused the flow

rate to increase. However, one generally reached a point where the

additional driving head due to increased power was not sufficient-to

compensate for the increased friction aid acceleration pressure

drops in the test section. Then the mass flow rate started to de-

- 9 -

crease when the power was further increased. Ultimately the pow-

er reached a value where the flow became unstable and started to

oscillate. Three cases are actually possible.

I* Diverging oscillations causir-? burnout

2. Stable oscillations

3. Burnout without oscillations.

For the second case, the amplitude of the oscillations in-

creases, if one continues to increase the power, and burnout will

finally be obtained.

For the third case the flow is completely stable until burnout

is obtained, and one would expect the burnout values to be identical

with values obtained during steady state forced circulation.

During the present study all three cases have been encountered.

4. 0 Research Program and Ran g e of Variables

The main part of the present, report deals with measurements

obtained with a 20 mm inner diameter test section of 4980 mm heat-

ed length. An examination of the problem revealed that for a fixed

geometry of the loop and the test section the following parameters

may influence the threshold of instability.

1. System pressure

2. Inlet sub-cooling

3. Liquid level in the steam separator.

The critical power may therefore be defined by the func-

tion.

=f(p, £s tgub , H) (1)

The mass velocity, m/F, and the steam quality x are not

included since thes t parameters a~>; determined when the parame-

ters in eq. 1 are fixed. In addition to the parameters in equation 1

- 10 -

it was decided also to study the effects of changing the geometry of

the loop. The geometrical changes employed were throttling of the

flow before or after the test section.

The performance of the loop permitted the static pressure to

be varied between 10 and 70 atg, the inlet sub-cooling between 2

and 16 C and the liquid level between 563 5 and 593 5 mm above

the reference level.

Throttling of the flow before the test section was achieved by

means of the throttle valve in the downcomer: 5 positions of this

valve were employed.

Throttling of the flow after the test section was obtained by

reducing the number of 8 mm holes in the riser exit. 2, 3, 4 and

96 holes were used. In addition, a few runs were made with both

inlet and outlet throttling.

In order to reduce the number of runs, the effect of inlet sub-

cooling, liquid level and throttling were only studied at a pressure

of 50 atg. The total research program consisted then of 30 runs.

Some preliminary runs obtained before the steam separator

was installed are also included in the present report. These runs

comprised measurements with a section of 10 mm inner diameter

of 4980 mm heated length.

For the runs without steam separator it was difficult to keep

the water level constant during a complete test. As the power was

increased and more cooling capacity was required, the liquid level

in the cooler moved downwards. Further it was very difficult to

operate at low sub-cooling temperatures, so that the measurements

were performed in the sub-cooling temperature range from about

80 to 250 °C.

- 11 -

5. 0 Results of Preliminary Runs Without Steam Separator

In figures 5 and 6 the measured mass velocities are plotted

versus the surface heat flux. The figures cover data between 10

and 60 atg obtained with a 10 mm tube, and the inlet temperatures

were 20 and 100 C respectively for the two sets of data given in

the figures. One should note that the inlet temperature and not the

inlet sub-cooling is constant so that the sub-cooling varies with the

pressure.

The end point on each curve represents the last measurement

of the series. A further increase of the power caused the burnout

detector to react, indicating that burnout conditions had been ob-

tained in the test section. For all the runs shown in figures 5 and

6 the flow was stable until the last power increase. Then diverging

oscillations with a frequency of about l /4 sec" developed and

after a period varying between 10 and 45 seconds the burnout de-

tector reacted. The oscillations were observed as fluctuations on

the mass flow rate, the inlet temperature and the test section

pressure drop measurements.

The figures reveal that the stability of the loop increases with

the pressure. Concerning the effect of inlet sub-cooling a compa-

rison of the data in figures 5 and 6 indicate that the critical power

increases as the inlet sub-cooling increases. This, however,

should not lead to any general conclusion that the stability of the

flow increases as the inlet sub-cooling increases. One should note

that in the present case where the inlet temperatures for the two

"sets of data are 20 and 100 C respectively, a substantial part of

the power is used for heating the water up to the saturation temp-

erature. A more correct measure of the effect of inlet sub-cooling

on the stability is obtained by considering the exit steam qualities

which are plotted in figure 7 versus the static pressure. One ob- .

serves that the exit steam quality at the onset of ixwtability increas-

es with both the pressure and the inlet temperature, indicating that

the flow becomes more stable at higher pressures and at lower in-

- 12 -

let sub-coolings. Actually, one might expect the flow to become

completely stable when the pressure approaches the critical pressu-

re since no flow oscillations of the kind studied in the present work

can exist at the critical pressure.

6. 0 Results with Steam Separator

The main and most important part of the present study dealt

with measurements obtained when the steam separator was mount-

ed in the1 loop. The performance of the loop was now much better,

compared with the earlier case, as it was easier to control the

pressure and the inlet temperature, and the data obtained under

these conditions were therefore more accurate and possessed an

excellent reproducibility.

The effects of pressure, inlet sub-cooling, liquid level, in-

let throttling and outlet throttling were studied separately. In the

following paragraphs the measurements dealing with each of these

variables will be discussed.

6.1 Effect of pressure

The effect of pressure was studied for the case where the in-

let sub-cooling was approximately 2 C, and where the liquid sur-

face was 5835 mm above the reference level. The reults are shown

in figure 8, where the measured mass velocities are plotted versus

the surface heat flux. The power density,or the power per litre test

section, is also indicated along the horizontal axis, since perhaps

this parameter is of greater significance for the stability than the

surface heat flux. Curves representing the threshold of instability

and the burnout values are also given. Concerning the measurement

of mass velocity after the onset of instability, there may be slight

errors in the measured values, due to the effects of fluid accellera-

tion on the venturimeter readings. Only dotted curves are therefore

shown in the oscillating flow regime.

13 -

One observes that as the pressure increases the threshold

of instability increases and approaches the burnout curve with

which it coincides at approximately 65 atg. For higher pressures

burnout is obtained directly without the,,flow passing through the

oscillating regime.

The flow oscillations were studied by recording the output from

the venturimeter and its D.P. cell. Figures 9 and 10 show traces

obtained at different pressures just before burnout. Although the

absolute values may possess serious errors, the figures show

that as the pressure increases the amplitude of the oscillations

becomes smaller, indicating less violent oscillations and more

stable flow.

Figure 11 shows the frequencies of the oscillations discuss-

ed in the previous diagrams. A slight increase in frequency from

0. 55 sec t(

10 to 50 atg.

-1 -10. 55 sec to 0. 62 sec is found as the pressure increases from

Figure 12 shows traces of mass velocity oscillations obtain-

ed at a pressure of 20 atg. As the heat flux increases and burnout

conditions are approached, the amplitude of the oscillations in-

creases while the frequency remains almost constant.

Reverting to figure 8, one observes that the burnout heat flux

has a maximum value at a pressure of 65 atg. This is in agreement

with the available information for steady state forced convection

burnout where the maximum heat flux occurs at a pressure between

40 and 7 5 atg (9).

In order to compare the measured burnout values with forced cir-

culation burnout conditions, the test section was, on completion of

the measurements, mounted in a forced circulation loop. This loop

had a pump with a pressure head of 8 atg. It was therefore possible

to apply heavy throttling of the flow before the test section, securing

- 14 -

stable operation of the loop. Unfortunately the forced circulation

loop had only a maximum operating pressure of 40 atg, so that the

comparison could only be established up to this pressure»

The comparison in question is given in figure 13 in terms of

the burnout steam qualities and the data are summarized in table

I on page 21. One should note that the forced circulation data were

obtained by extrapolating from the measurements to the same heat

fluxes as the natural circulation data. The comparison reveals that

the forced circulation data are higher by a factor of about 1.3 . This

seems to be the case even at the highest pressures where no flow

oscillations were observed. No satisfactory explanation has been

found for this discrepancy.

However, this could be attributed to the fact that the ampli-

fication of the signals from the flow measuring device has not been

adequate to indicate minor oscillations in the natural circulation

flow at high pressures.

6. 2 Effect of Inlet Sub-cooling

The effect of inlet sub-cooling was studied at a pressure of 50

atg and a liquid level, H, of 5835 mm in the steam separator. The

mass velocity versus heat flux curves are given in figure 14, and in

figure 15 the heat fluxes at the onset of oscillations and at burnout

are plotted versus the inlet sub-cooling. It is observed that the sta-

bility of the flow is strongly reduced as the inlet sub-cooling in-

creases. At 16 °C inlet'sub-cooling a critical heat flux of 24 W/cm

was obtained compared with 73 W/cm at 2 C sub-cooling.

However, at very large sub-cooling temperatures it is possible,

as discussed in section 5. 0, that the critical power will start to in-

crease with a further increase of the inlet sub-cooling, since a re-

latively large portion of the power is then used for just heating the

water up to the saturation temperature. This behaviour is demonstrat-

- 1 5 -•

ed in figure 16, where the critical power density at a pressure of

50 atg is plotted versus the inlet sub-cooling. In the figure are al-

so included the data obtained at 164 C and 244 C inlet sub-cooling

with the 10 mm diameter test section before the steam separator

was installed. A very large increase of the critical power density

is observed at the highest sub-coolings, so that the valu^ obtained

at 244 C inlet sub-cooling, is actually higher than the value

corresponding to 2 C sub-cooling.

Our loop is now being modified with the purpose of being

able to study the flow in the whole range of sub-cooling tempera-

tures.

6 . 3

The effect of the liquid level in the steam, separator was

studied for the case of 2. 0 °C inlet sub-cooling and 50 atg pressu-

re. The maximum possible variation was 3 00 mm, and since this

value is small compared with the length of the test section with

the riser, only small variations of the measured critical and burn-

out heat fluxes may be expected. The conclusions reached should

therefore be treated with caution.

The measured mass velocities versus surfase heat flux are

shown in figure 17. One observes that the burnout heat flux increas-

es slightly with increasing liquid level, while the critical heat flux

remains constant. The corresponding steam qualities, however,

which are indicated in figure 18, decrease with increasing liquid

level, suggesting that the loop stability decreases.with increasing

liquid level.

lnlelThe effect of throttling before the. test section was studied for

the cases of 50 atg pressure, 583 5 mm liquid level and — 2, 0 C

and ~ 11,0 C respectively inlet sub-cooling. The measured mass

- 16 -

velocities are given in figures 19 and 20. The throttling of the flow

through the throttle valve is indicated by means of the | j-values de-

fined by the equation

where v is the velocity of saturated water through the test section.

One observes that as the throttling increases, the stability of

the loop also increases and one reaches a point where the flow is so

stable that burnout is obtained directly without preceding flow

oscillations. With regard to the burnout heat fluxes, these also in-

crease with increasing inlet throttling until they reach a maximum

whereafter they decrease with further throttling due to the high

steam qualities which are now encountered in the test section»

This is more clearly demonstrated in figure 21, where the

burnout steam qualities are plotted versus the inlet throttling. The

corresponding values for forced circulation are also indicated in

the figure. The forced circulation points were obtained by extra-

polation to 50 atg fromthe measured values, which were obtained

between 10 and 40 atg. As the pressure drop over the throttle valve

increases, the measured burnout steam qualities rapidly approach

the values for forced circulation, indicating the absence of flow

instabilities.

k'- - JFIf Lcl °A.P^I0! Throttling

The outlet throttling was varied by changing the number of 8

mm holes at the end of the riser. For all the measurements in the

previous paragraphs 96 hole's were used corresponding to a value

of 16.15 of the ratio F /F , where F is the cross sectional area

of the test section and F is the area of the riser outlet. The flowo

was throttled by reducing the number of holes to 2, 3 and 4 corre-

sponding to area ratios of 0.328, 0.492 and 0.656. For these runso

the pressure was fixed at 50 atg, the inlet sub-cooling at « 2 C andthe liquid level at 583 5 mm.

- 17 -

The results arc shown in figure 22. As the outlet throttling of the

flow increases, the critical and the burnout heat fluxes decrease

sharply, indicating that outlet throttling renders the flow more

unstable. The burnout steam qualities, which are also indicated,

first approach the forced circulation value of 0. 80, but the value

for the highest throttling is only 0.48. No satisfactory explanation

has been found for this fact.

6. 6Measurement^ ^i£h ^ m u - l t a ^ o u s Inlet

Finally one test series was obtained using a riser with three

8 mm holes and varying the inlet throttling. This test series was

performed at a pressure of 50 atg, 2 C inlet sub-cooling and a

liquid level of 583 5 mm. The results are shown in figure 23. One

observes that the burnout heat flux first increases, reaches a maxi-

mum value and thereafter decreases with the inlet throttling. Further,

it is seen that the flow becomes more stable as the inlet throttling in-

creases and reaches a condition where burnout is obtained directly

without preceding flow oscillations.

The burnout steam qualities for the runs in figure 23 varied

between 0. 82 and 0. 93, which is well above the forced circulation

value of 0. 80. This inconsistency is probably due to an error in the

mass flow rate measurements at burno\it.

7.0 Comparison with Analytical Results

Simultaneously with the measurements described in the present

report, an analytical study of the problem was undertaken by Jahnberg

(7) with the aim of developing a model which later could be used for

predictions of reactor stability. The first phase of that study consist-

ed of developing a model describing the flow during steady state. Du-

ring the second phase small perturbations were added to the steady

flow, and a model for predicting when the perturbations would grow

or decay was established. The details of the analysis are given in

the reference mentioned above.

Figures 24 and 25 show a comparison between the predict-

ed and the measured mass velocities for the case of 2 C inlet sub-

cooling and no throttling. In the pressure range from 20 to 50 atg

the agreement between 'theoretical and measured mass velocities is

rather good, the discrepancy being a maximum of 10 per cent and on

the average only 3 - 4 per cent. For 10 atg the theoretical values

are about 15 per cent higher than those measured, but at 7 0 atg the

theoretical are about 15 per cent lower. The measured and the pre-

dicted thresholds of instability are also indicated in the figure. One

should note that for the case of 70 atg burnout was obtained without

observing any oscillations. In this case the analysis predicts stable

flow up to a steam quality of 1.0.

The thresholds of instability are more clearly demonstrated

in figure 25, where the surface heat fluxes at the onset of oscillations

are plotted versus the pressure. The measured values compare

excellently with the predictions, the difference between the two sets

of values being always less than 10 r>er cent.

The data obtained at 50 atg inlet sub-cooling temperatures of

7, 11 and 16 C were also analyzed by Jahnberg. Figure 26 shows

the predicted and the measured stability limits. The agreement

between experimental and analytical results is excellent also for these

cases.

As regards the cases with inlet or .otttlet throttling, these are

now being analyzed and the results will be given in a later report.

Nomenclature

- 19 -

Symbol Definition Units

d

F

Fo

f

H

L

m / F

P

A P

Q

q / A

(q/A)CR

(q/A)BO

t

A t sub

V

V

X

XCR

XBO

P

Diameter

Cross section of heated duct

Outlet a r ea of r i s e r

Frequency

Liquid level

Heated length

Mass velocity

Pressure

Pressure drop over test section

Pressure drop over throttlevalve

Power input

Surface heat flux

Critical surface heat flux

Burnout heat flux

Temperature

Inlet sub-cooling

Volume of test section

Fluid velocity

Steam quality

Critical steam quality

Burnout steam quality

. Density

Resistance factor for throttle

m2m

2in

i

~isecm

i n

kg/ m" sec

atg

mm HO

mm H...0

kW

W/cm2

W/cm2

W/cm2

°C

°c3m

m/sec

Dimensionless

Dimensionless

Dimensionless

kg/m

Dimcnsionles svalve

- 20 -

Bibliography

1. KM Becker, G Hernborg and M BodeAn Experimental Study of Pressure Gradients for Flow ofBoiling Water in a Vertical Round Duct (Part 4, 2, 3 and 4),Reports AE-69, AE-70, AE-85 and AE-86, AktiebolagetAtomenergi, Stockholm, Sweden.

2. S Z Rouhani and K M BeckerMeasurements of Void Fractions for Flow of Boiling HeavyWater in a Vertical Round Duct, Report AE-108, Aktiebola-get Atomenergi, Studs vik, Sweden.

3. KM Becker et al. , IMeasurements of Burnout Conditions for Flow of Boiling Waterin Vertical Round Ducts (Part 1 and 2), Reports AE-87 andAE-114, Aktiebolaget Atomenergi, Studsvik, Sweden.

4. KM Becker and P PerssonAn Analysis of Burnout Conditions for Flow of Boiling Waterin Vertical Round Ducts, Report AE-113, Aktiebolaget Atom-energi, Studsvik, Sweden.

5. KM Becker and G HernborgMeasurements of Burnout Conditions for Flow of Boiling Waterin a Vertical Annulus, Trans. ASME Paper 63-HT-25

6. KM BeckerBurnout Conditions for Flow of Boiling Water in Vertical RodClusters, AICHE Journal, March 1963

7. S JahnbergA One -dimensional Model for Calculation of Non-Steady Two-Phase Flow, Paper presented at EAES-Symposium, StudsvikOctober 1-962.

8. R P Mathisen, G Hernborg and L ValkingNatural Circulation Experiment. Description of the Loop andits Behaviour, Including Some Test Results, Report R4-172/RPL.-641, Aktiebolaget Atomenergi, Studsvik, Sweden.

9. • J G CollierHeat Transfer and Fluid Dynamic Research as Applied to FogCooled Power Reactors, Report AECL.-1631, June 1962.

- 21 -

Table I. Burnout Data

Natural Circulation

p

g/cm

20

30

40

50

60

70

20

30

40

' sub

°C

4 . 1

3 . 2

2 . 8

2 . 1

2 . 2

2 . 4

70

70

115

m/F

kg/m s

500

563

630

732

805

900

q/A

W/cm2

51.5

58.8

67.0

75.7

80.5

79.0

Forced Circulation

310

350

350

51.5

58.8

67,0

XBO

%

52.6

56.2

60.0

60.9

61.4

51.7

0.70

0.75

0, 80

AIR COOLED CONDENCER

LEGENDH- RISER HEIGHTI-INDICATORP-PRESSURER-RECORDERT-TEMPERATURE

STEAM SEPARATOR

LIQUID SURFACE

H

LOWER ELECTRODEi

VENTURIMETER htffi-H1 2 3 A S « 7 • I t t f l Q

DIFFERENCE PRESSURE GAUGE

FIG 1 NATURAL CIRCULATION LOOP

Fig. 2. Upper part of natural circulation loop.

TO CONDENSER

SO

LIQUIDSURFACE

CONDENSATE FROM

CONDENSER ~~*"

TO INLET OFTEST SECTION

FROM TEST SECTION

Fig. 3, Steam separator.

TO DRAIN

• ELECTRODE

• INLET TEMPERATURE' THERMOCOUPLE

TURBINEMETER ORVENTURIMETER

M ) MANOMETER

Fig. 4. Flow diagram for loopwithout steam separator,

800

600

400

X

+oo

vo

10152030405060

"-THRESHOLD OF INSTABILITYAND BURNOUT

INLET TEMPERATURE, t,,, = 20*CINNER DIAMETER, d = 10 mmHEATED LENGTH, L=4890

10 20 30 40 50 , . , , 60SURFACE HEAT FLUX, q|A( W|cm*

Fig. 5. Measured mass velocities.

INLET TEMPERATURE, tto =100 CINNER DIAMETER,d*10mmHEATED LENGTH, t"4890

THRESHOLD OF INSTABILITYAND BURNOUT

30 40 50 , . , 60SURFACE HEAT FLUX, qJA,W|cma

Fig. 6. Measured mass velocities.

INNER DIAMETER,d=10mmHEATED LENGTH, L=A890

20 30 40 50 60 70PRESSURE, p, kg|cm2

Fig. 7. Exit steam quality at onset of oscillations.

1500

o>

1000

K-

8

Ulen

500

ONSET OF INSTABILITY

M 0o 20A 30

>aoO50vSO•7 0

60 70 80SURFACE HEAT FLUX, WJcm2

20 60 100 120 140 160POWER DENSITY, OJV,kW/liter

Fig. 8. Effect of pressure.

*|F-= P=10atg<|/A=12

P=20otgqJA= 51. S wjem1

10TIME, T, see.

Fig. 9. Traces of oscillations.

wjcm1

"q(A=75.7

10TIME, T, s«c.

Fig. 10. Traces of oscillations.

0.7

0.6

"oUl

o

§ 0.4oUJDCU.

0.3

0.1

0

r—

i

_ —

r— —,

10 20 30 40 50 60

PRESSURE, p, kgjcm2

Fig. 11. Measured frequencies.

mJF

P=20otg

q|A=16.5 w|cm2

at =2.6«C

s = 3.3 »C

BURNOUT

q(A=51.5 w|cmJ

a t = 3 . 5 "C

10TIME, T, sec.

Fig. I 2. Traces of oscillations.

1.0

S

w0.5tft

o

ffio NATURAL CIRCULATIONCqJA TO BE TAKEN

FROM FIGURE 8).o FORCED CIRCULATION (THE q/A-VALUES ARE

EQUAL TO THE CORRESPONDING NATURALCIRCULATION VALUES). , .

10 20 30 40 50 60 70 80PRESSURES, kgjcm2

Fig. 13. Comparison between naural and forcedcirculation burnout data.

1500

u.•e

1000

ooUJ

500

•

• I,11

•

1 ONSET OF IN

o 2.1 S 0.3v 7.2 ± 0.2o 11.0 S0.2A 16.0 ±0.2

^

\STABILITY^

I4-5035 mmt = 50 otg

nu. _ -

- « . A

•

C

7.2 *C

•

•

**^*^. IBURNOU1

10 20 30 40 50 60 70 60SURFACE HEAT FLUX, W cm2

» • 1 i i .. —«—

20 60 eo 100 120 UO 160POWER DENSITY, o|v,kW/tit«r

Fig. 14. Effect of inlet subcooling.

100

"g 80

6 0

20

I

1

V

P != 50 atg* 5S3S mm _,.

. —

ONSET OF INSTABILITY

|

BURNOUT

~ ~ - — — •

u

I

i

>>•—

1 — - - .

I* 6 8 10 12 14 IS 18INLET SUBCOOLJNG TEMPERATURE,

Fig. 15. Effect of inlet subcooling on critical and burnoutheat fluxes.

20°C

200

1150

100

p= 50 otg

50

\

e 20 mm ID, WITH STEAM SEPARATOR .

A 10 mm ID.WITHOUT STEAM SEPARATOR.

50 100 150 200INLET SUBCOOUNG TEMPERATURE, At J u b , °C,

Fig. 16. Effect of inlet subcooling on critical power density.

250

1500

2.0 i 0.31.9 ±0.32.1+0.32.0+0.3

60 70 , 80SURFACE HEAT FLUX, W cm*

80 100 120 140 160POWER OENSITY, Q/V, kwflitar

Fig. 17. Effect of liquid level.

0.7

tz<os:<UJ

0.6

0.5

ONSET OF INSTABILITY

5600 5700 5800 5900 6000LIQUID LEVEL, H,mm

Fig. 18. Effect of liquid level on critical and burnoutsteam qualities.

1506

»00

tu

into

500

2.1 +0.3X 2.0 +0.3

2.2 +<U2.4 iOA

FULLY OPEN VALVE0.27 ± 0.031.68 + 0.084.30 ±

*o SO SO 70 SOSURFACE HEAT FLUX, Wjcm*

20 • 0 190 120 UO ISOPOWER 0EM5ITY, ofv, Waite

Fig. 19. Effect of inlet throttling.

1500

- i .

»00

oo

inV)

500

11 i 0.211 i 0.2

o 11 i 0.2X 1 1 + 0.2

11 t 0.2

FULLY OPEN VALVE0.61 t 0.061.38 t 0.073.2' i 0.2

60 70 80SURFACE HEAT FLUX, Wjcm2

20 80 100 120 140 160POWER DENSITY, QJV, kW/liter

Fig. 20. Effect of inlet throttling.

1.0p*50 atgH= 5835 mm

— t r

a

iUi

COI-oz

CD

0.5- -o- - NATURAL CIRCULATION, * t s l l h - 2 °C , \ , ̂ _B

- . ^ . - N A T U R A L CIRCULATION, * t ^ M f C J i 5 < ^ < 7 8

FORCED CIRCULATION (THE qJA-VALUES AREEQUAL TO THE CORRESPONDING NATURALCIRCULATION VALUES).

500 1000 1500PRESSURE DROP OVER THROTTLE VALVE FOR NATURAL CIRCULATION,

Fig. 21. Effect of inlet throttling on burnout.

2000a Pj , mm H2OJ

1503

o 2.1 ±0.3»3.1 10.4o 3.0 i 0.6

3.2 t OX

60 70 , «05USF/CE KEAT FLUX, Wjcms

120 HO ISOPOWER DENSITY, ojv, kW/Ut«r

Fig. 22. Effect of outlet throttling.

1500 :

t/i

Xen

LL.

• c

100 Q

ooUJ

ent/)

500

H ~ BÖJS rnrnp~ 50 atg suh

o 3.0 i 0.63.1 i 0.5

o 3-.4 i 0.44.2 i 0.84.5 t 0.5

FULLY OPEN VALVE1.32 i 0.186.7 i 0.3

16.1 t O.S52.8

ONSET OF INSTABILITY

BURNOUT

SURFACE HEAT FLUX. W cm

20 40 60 80 100

FIG. 23.

120 MO 160POWER DENSITY, QJV, kW/liter

EFFECT OF INLET AND OUTLET THROTTLING.

1500

i.PREDICTED

-MEASURED

\

\

p—10 o

-ONSET OF INSTABILITY

I I

50 SURFACE HEAT FLUX,

p»30otg

»ONSET OF INSTABILITY

SO SLKFACS HEAT F L U X , q|A W | c m s

Fig. 24. Comparison between analytical andexperimental results.

XX»

rPREDICTED-

\

-MSASURED

X -jONSCT OF 11

X

p»40otg

STABILITY

SURFACE HEAT FlUX, q|A,

^MEASURED

PREDICTED— " * * v

ON! 6T OF INSTABII

60 SURFACE HEAT FLUX, ijJA.Wjcm2

«0 SURFACE HEAT FLUX.qjA.Wjen?

Fig. 25. Comparison between analytical andexperimental results.

100

CMM

Q

3 60u.

5tu

DC

3

BURNOUT WITHOUT OSCILLATIONS.

o PRESENT MEASUREMENTSA ANALYTICAL RESULTS

<o

§ o10 20 30 50 60 70 .80

PRESSURE, p, kgjcrr/

Fig. 26, Comparison between experimental and analyticalresults.

CM

o•"5-100

-_ 80X *

_iu.5 60

UJ

UJu

ocw

0 2 0

CR

IT

0

p= 50 atg

H= 5835 mm

t

) EXPERIMENTAL RESULTS

» MINHLlf t f^A l

t

. RESULTS

~^- , _^

t

t

-

-

3 2 L, 5 8 10 12 U 16 18 20INLET SUBCOOLING TEMPERATURE, ats u b ,°C

Fig. 27. Comparison between experimental and analytical results.

LIST OF PUBLISHED AE-REPORTS

1—60. (See the back cover earlier reports.)61. Comparative and absolute measurements of 11 inorganic constituents of

38 human tooth samples with gamma-ray spectrometry. By K. Samsahland R. Söremark. 19 p. 1961. Sw. cr. 6:—.

62. A Monte Carlo sampling technique for multi-phonon processes. By ThureHögberg. 10 p. 1961. Sw. cr. 6:—.

63. Numerical integration of the transport equation for infinite homogeneousmedia. By Rune Håkansson. 1962. IS p. Sw. cr. 6:—.

64. Modified Sucksmith balances for ferromagnetic and paramagnetic mea-surements. By N. Lundquist and H. P. Myers. 1962. 9 p. Sw. cr. 6:—.

65. Irradiation effects in strain aged pressure vessel steel. By M. Grounesand H. P. Myers. 1962. 8 p. Sw. cr. 6:—.

66. Critical and exponential experiments on 19-rod clusters (R3-fuel) in heavywater. By R. Persson, C-E. Wikdahl and Z. Zadworski. 1962. 34 p. Sw. cr.

67. On the calibration and accuracy of the Guinier camera for the deter-mination of interplanar spacings. By M. Möller. 1962. 21 p. Sw. cr. 6:—.

68. Quantitative determination of pole figures with a texture goniometer bythe reflection method. By M. Möller. 1962. 16 p. Sw. cr. 6:—.

69. An experimental study of pressure gradients for flow of boiling water ina vertical round duct. Part I. By K. M. Becker, G. Hernborg and M.Bode. 1962. 46 p. Sw. cr. 6:—.

70. An experimental study of pressure gradients for flow of boiling water ina vertical round duct. Part I I . By K. M. Becker, G. Hernborg and M.Bode. 1962. 32 p. Sw. cr. 6r—.

71. The space-, time- and energy-distribution of neutrons from a pulsedplane source. By A. Claesson. 1962. 16 p. Sw. cr. 6:—.

72. One-group perturbation theory applied to substitution measurementswith void. By R. Persson. 1962. 21 p. Sw. cr. 6:—.

73. Conversion factors. By A. Amberntson and S-E. Larsson. 1962. 15 p. Sw.cr. 10:—.

74. Burnout conditions for flow of boiling water in vertical rod clusters.K M B k 1962 44 S

Burnout conditions for flow of boiling wBy Kurt M. Becker. 1962. 44 p. Sw. cr. 6:—.

75. Two-group current-equivalent parameters for control rod cells. Autocodeprogramme CRCC. By O. Norinder and K. Nyman. 1962. 18 p. Sw. cr.6;—.

76. On the electronic structure of MnB. By N . Lundquist. 1962. 16 p. Sw. cr.6:—.

77. The resonance absorption of uranium metal and oxide. By E. Hellstrandand G. Lundgren. 1962. 17 p. Sw. cr. 6:—.

78. Half-life measurements of »He, »N , »O, »F, »Al , "Se™ and "»Ag. By J.Konijn and S. Malmskog. 1962. 34 p. Sw. cr. 6:—.

79. Progress report for period ending December 1961. Department for Reac-tor Physics. 1962. 53 p. Sw. cr 6:—.

80. Investigation of the 800 keV peak in the gamma spectrum of SwedishLaplanders. By I. D . Andersson, I. Nilsson and K. Eckerstig. 1962. 8 p.Sw. cr. 6,:—.

81. The resonance integral of niobium. By E. Hellstrand and G. Lundgren.1962. 14 p. Sw. cr. 6:—.

82. Some chemical group separations of radioactive trace elements. By K.Samsahl. 1962. 18 p. Sw. cr. 6:—.

83. Void measurement by the [y, n) reactions. By S. Z. Rouhani. 1962. 17 p.Sw. cr. 6,i—.

84. Investigation of the pulse height distribution of boron frifluoride pro-portional counters. By I. O. Andersson and S. Malmskog. 1962. 16 p.Sw. cr. 6,:—.

85. An experimental study of pressure gradients for flow of boiling waterin vertical round ducts. (Part 31. By K. M. Becker, G. Hernborg and M.Bode. 1962. 29 p. Sw. cr. 6r—.

86. An experimental study of pressure gradients for flow of boiling waterin vertical round ducts. (Part 4). By K. M. Becker, G. Hernborg and M.Bode. 1962. 19 p. Sw. cr 6:—.

87. Measurements of burnout conditions for flow of boiling water in verticalround ducts. By K. M. Becker. 1962. 38 p. Sw. cr. 6:—.

88. Cross sections for neutron inelastic scattering and (n, 2n) processes. ByM. Leimdörfer, E. Bock and L. Arkeryd. 1962. 225 p. Sw. cr. 10:—.

89. On the solution of the neutron transport equation. By S. Depken. 1962.43 p. Sw. cr. 6:—.

90. Swedish studies on irradiation effects in structural materials. By M.Grounes and H. P. Myers. 1962. 11 p. Sw. cr. 6:—.

91. The energy variation of the sensitivity of a polyethylene moderated BFjproportional counter. By R. Fräki, M. Leimdörfer and S. Malmskog. 1962.12. Sw. cr. 6 r - .

92. The backscaftering of gamma radiation from plane concrete walls. ByM. Leimdörfer. 1962. 20 p. Sw. cr. 6:—.

93. The backscattering of gamma radiation from spherical concrete walls.By M. Leimdörfer. 1962. 16 p. Sw. cr. 6s—.

94. Multiple scattering of gamma radiation in a spherical concrete wallroom. By m. Leimdörfer. 1962. 18 p. Sw. cr. 6:—.

95. The paramagnetism of Mn dissolved in a a n d B brasses. By H. P. Myers

and R. Westin. 1962. 13 p. Sw. cr. 6:—. ^

96. Isomorphic substitutions of calcium by strontium tn calcium hydroxy-apatile. By H. Chrisfensen. 1962. 9 p. Sw. cr. 6:—.

97. A fast lime-to-pulse height converter. By O. Aspelund. 1962. 21 p. Sw. cr.6:—.

98. Neutron streaming in D2O pipes. By J. Braun and K. Randen. 196241 p. Sw. cr. 6:—.

99. The effective resonance integral of thorium oxide rods. By J. Weitman.1962. 41 p. Sw. cr. 6:—.

1C0. Measurements of burnout conditions for flow of boiling water in verticalannuli. By K. M. Becker and G. Hernborg. 1962. 41 p. Sw. cr. 6:—.

101. Solid angle computations for a circular radiator and a circular detector.By J. Konijn and B. Tollander. 1963. 6 p. Sw. cr. 8:—.

102. A selective neutron detector in the keV region utilizing the "F(n, y)MFreaction. By J. Konijn. 1963. 21 p. Sw. cr. 8:—.

103. Anion-exehange studies of radioactive trace elements in sulphuric acidsolutions. By K. Samsahl. 1963. 12 p. Sw. cr. 8:—.

104. Problems in pressure vessel design and manufacture. By O. Hellströmand R. Nilson. 1963. 44 p. Sw. cr. 8:—.

105. Flame photometric determination of lithium contents down to 10-3 ppmin water samples. By G. Jönsson. 1963. 9 p. Sw. er. 8:—.

1C6. Measurements of void fractions for flow of boiling heavy water in avertical round duct. By S. Z. Rouhani and K. M. Becker. 1963. 2nd rev.ed. 32 p. Sw. cr. 8:—.

1C7. Measurements of convective heat transfer from a horizontal cylinderrotating in a pool of water. K. M. Becker. 1963. 20 p. Sw. cr. 8:—.

108. Two-group analysis of xenon stability in slab geometry by modal expan-sion. O. Norinder. 1963. 50 p. Sw. cr. 8:—.

109. The properties of CaSOjMn thermoluminescence dosimeters. B. Bjärn-gard. 1963. 27 p. Sw. cr. 8:—.

110. Semianalytical and seminumerical calculations of optimum materialdistributions. By C. I. G. Andersson. 1963. 26 p. Sw. cr. 8:—.

111. The paramagnetism of small amounts of Mn dissolved in Cu-AI andCu-Ge alloys. By H. P. Myers and R. Westin. 1963. 7 p. Sw. er. 8:—.

112. Determination of the absolute disintegration rate of Cs137-sources by thetracer method. S. Hellström and D. Brune. 1963. 17 p. Sw. cr. 8 r - .

113. An analysis of burnout conditions for flow of boiling water in verticalround ducts. By K. M. Becker and P. Persson. 1963. 28 p. Sw. cr 8:—.

114. Measurements of burnout conditions for flow of boiling water in verticalround ducts (Part 2). By K. M. Becker, et al . 1963. 29 p. Sw. cr. 8:—.

115. Cross section measurements of the ssNifn, p)s!Co and MSi{n, a)26Mg reac-tions in the energy range 2.2 to 3.8 MeV. By J. Konijn and A. Lauber1963. 30 p. Sw. cr. 8:—.

116. Calculations of total and differential solid angles for a proton recoilsolid state detector. By J. Konijn, A. Lauber and B. Tollander. 1963. 31 p.Sw. cr. 8:—.

117. Neutron cross sections for aluminium. By L. Forsberg. 1963. 32 p.Sw. cr. 8:—.

118. Measurements of small exposures of gamma radiation with CaSOcMnradiothermoluminescence. By B. Bjärngard. 1963. 18 p. Sw. cr. 8:—.

119. Measurement of gamma radioactivity in a group of control subjects fromthe Stockholm area during 1959—1963. By I. P Andersson, I. Nilssonand Eckerstig. 1963. 19 p. Sw. cr. 8:—.

120. The thermox process. By O. Tjälldin. 1963. 38 p. Sw. cr. 8:—.

121. The transistor as low level switch. By A. Lydén. 1963. 47 p. Sw. cr. 8:—.

122. The planning of a small pilot plant for development work on aqueousreprocessing of nuclear fuels. By T. U. Sjöborg, E. Haeffner and Hult-gren. 1963. 20 p. Sw. cr. 8:—.

123. The neutron spectrum in a uranium tube. By E. Johansson, E. Jonsson,M. Lindberg and J. Mednis. 1963. 36 p. Sw. cr. 8:—.

124. Simultaneous determination of 30 trace elements in cancerous and non-cancerous human tissue samples with gamma-ray spectrometry. K. Sam-sahl, D. Brune and P. O. Wester. 1963. 23 p. Sw. cr. 8:—.

125. Measurement of the slowing-down and thermalization time of neutronsin water. By E. Möller and N. G. Sjöstrand. 1963. 42 p. Sw. cr. 8:—.

126. Report on the personnel dosimetry at AB Atomenergi during 1962. ByK-A. Edvardsson and S. Hagsgärd. 1963. 12 p. Sw. cr. 8:—.

127. A gas target with a tritium gas handling system. By B. Holmqvist andT. Wiedling. 1963. 12 p. Sw. cr. 8 : - .

128. Optimization in activation analysis by means of epithermal Neutrons.Determination of molybdenum in steel. By D. Brune and K. Jirlow. 1963.11 p. Sw. cr. 8:—.

129. The Pi-approximation for the distribution of neutrons from a pulsedsource in hydrogen. By A. Claesson. 1963. 18 p. Sw. cr. 8:—.

130. Dislocation arrangements in deformed and neutron irradiated zirconiumand zircaloy-2. By R. B. Roy. 1963. 18 p. Sw. cr. 8:—.

131. Measurements of hydrodynamic instabilities, flow oscillations and bur-nout in a natural circulation loop. By K. M. Becker, R. P. Mathisen, O.Eklind and B. Norman. 1964. 21 p. Sw. cr. 8:—.

Förteckning över publicerade AES-rapporter

1. Analys medelst gamma-spektrometri. Av D. Brune. 1961. 10 s. Kr 6:—.

2. Besträlningsförändringar och neutronatmosfär i reaktortrycklankar —några synpunkter. Av M. Grounes. 1962. 33 s. Kr 6:—.

3. Studium av sträckgränsen ! mjukt stål. G. Östberg, R. Attermo. 1963.17 s.Kr 6:—.

4. Teknisk upphandling inom reakloromrädet. Erik Jonson. 1963.64 s. Kr. 8.—.

Additional copies available at the library of AB Atomenergi, Studsvik, Nykö-ping, Sweden. Transport microcards of the reports are obtainable throughthe International Documentation Center, Tumba, Sweden.

EOS-tryckerierna, Stockholm 1964