ML17138A538

Rept Translated from German:Experimental Studies of Vent Clearing in Model Test Stand

ML17138A538
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Site:	Susquehanna
Issue date:	07/31/1975
From:	Werner PENNSYLVANIA POWER & LIGHT CO.
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ML17138A531	List: ML17138A530 ML17138A532 ML17138A533 ML17138A534 ML17138A536 ML17138A537 ML17138A538 ML17138A539 ML17138A540 ML17138A541 ML17138A542 ML17138A544 ML17138A545 ML17138A546 ML17138A547 ML17138A548 ML17138A549 ML18031A117 ML19284A738 ML19284A739 ML19284A747
References
KWU-R-521-3129, NUDOCS 7903150339
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PROPRIETARY INFORMATION This document has been made NON-PROPRIETARY by the deletion of that information which was classified as PROPRIETARY by KRAFTWERK UNION AG (KWU).

The PROPRIETARY.information deletions are so noted throughout the report where indicated by a)

Use of the term KRAFTWERK UNION AG PROPRIETARY INFORMATION.

b)

Use of blocked out areas by cross hatch bands in the report text and figures/tables, e.g.

iii) iv)

...." with a mass flow density of4%VKg/m2s...";

%% mm should be kept below ~K AMr. atm."

V/8 8/17/78

Kraftwerk Union R 521 partment Karlstein Jul 1975 Kaca ate Technical Report KWU/R 521-3129 File number R 521 - VR /Wr/Ho Author Warner Fountatateaattte

Title:

Experimental studies of vent clearing in the model test stand Key words (max.

12) to identify the report's content:

Pressure relief system, vent clearing, pipe pressure, bottom pressure, per-,

forated cross pipe, model test stand Pages of test:

Figures.

Circuit diagrams:

Diagr. /oscillogr.:

Tables:

Reference list:

Sunnnary Zn order to study the transposition of the knowledge obtained in the Mannheim large-scale test stand (GKM) concerning the reduction of loads in the suppression chamber of boiling-water reactors, parameter studies for the pressure relief system with perforated-pipe guenchers were performed in the condensation model test stand in Grosswelzheim.

The dependence of the bottom loads during vent clearing on the clearing pressure in the pipe was studied.

At a clearing pressure above about g har, the change of the positive pressure amplitude at the bottom with re~s ect to the change of the clearing pressure yielded, i%%%%1, a value which practically coincides with the results in GKM.

The pressure amplitudes at the bottom can he reproduced with an accuracy of L~

har (test series 2).

Parameter study during vent, clearing.

The relative sine of the water pool has proved meaningful for the pressure values at the bottan.

Because of the scale ratios of about 1

! 30 to 1 a 50, the absolute values measured in the test stand are not transposable to BWR plants.

s Werner Au or s signature Ex er Dr.

on s

ZT assr er

~Cess For information (cover sheet only) i Distribution list!,

lx KWU/GA 19 Erl lx

/PSW'22 Ffm Additional distribution according to appended list Transmission or duplication of this, document, exploitation or com-munication of its content not permitted unless expressly authorised.

Infringers liable to pay damages.

All rights,to the award of patents or registration of utility patents reserved; t

9-1

Distribution list (internal)

RZR 1

RS RS 1

RS 11 RS 11/GK7 RS 12/KKB RS 12/KKK RS 13/KW RS 13/KKP

'S 14/KKI RS 15 RS 2, RS 21 RS 21)

R 1

R 11 R ill R 11)

R 114 R 21)

R R 31 R 314 R )2 R 322 R 5 4'1o R 52 R 521 R 522 R 523 Irlo V 822/TA 2 x 2 x 2 X 2 x

) x 2 X

) x 5 x

l

)l

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NONLIABILITYCLAUSE This report is based on the current technical knowledge of KRAFTWERK TWERK UNION AG.

However the Federal Ninister for Research and Technol ogy, KRAFTWERK UNION AG and all persons acting in its behalf make no guarantee.

In particular, they are not liable for the correctn orrectness, accuracy and completeness of the data contained in this report nor for the observance of third-party rights.

This reservation doe does not apply insofar as the report is delivered in fulfillment of contractual obligations, nor with respect to licensining authorities or the experts appointed by them.

DRAFTWERK UNION AG reserves all rights to the technical infor-mation contained in this report, particularly the right to apply for patents.

Further dissemination of this report and of the knowledge con-tained therein rerequires the written approval of KR~WERK UNION AGi moreover, this report is communicated under the assumption that it will be handled confidentially.

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TABLE OF CONTENTS

.1.

Introduction 2.

Condensation model test stand 2.1. 1 Basic set-up 2.1. 2 Steam-boiler connection 2.1.3 Adjustment of steam flow rate / valve opening time

2. 2 Instrumentation 2.2.1 Instrumentation of the steam su 1

pp y 2.2.2 Determination of steam flow rate 2.2.3 pressure transducers in the test stand 2.2,4 Temperature transducers in the test stand 2.2.5 bisplacement transducers on the diaphragm valve 2.2.6 Integral load on the test stand 3 ~

3.1 3.1.1 3.1.2 3.lo3 3.1+4 3.2 3.2.1 3 2.2 3.2.3 3.2.4 Vent clearing tests in the model test stand Test aeries 1

Influence of tank geometry on the bottom pressure Test goal Special 'test set-up Test execution Teat results Test series 2

Investigation of parameters during vent clearing Test goal Special test aet-up Test execution Test results 4.

Summary of results A~~ndix, Tables Figures References

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I IST OF TABLZS Tab. l Tab.

2 Tab.

3 Tab.

4 Tab.

5 Tab.

6 Tab.

7 Tab.

8 test facility list of vent clearin tes g

ts in the condensation model t

Test series l - characteristics of v i arrangements var ous test Test series l - compilation of test, data and results

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Test series 2 - compilation of transposition parameters Test series 2 - test data and maximum pressure values Test series 2 - m boundary surfaces ean speed of the water-air phase 1

vi i Test aeries 2 - assi s corder I (temperatures) signment of measurement points for Visic Test series 2 - assi gnment of measurement points for s corder II (pressures and displacements) 9"5

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1 LIST OF FIGURES Pigure 1:

Figure 2:

Figure 3:

Figure 4:

Figure 5:

Figure 6:

Figure 7:

Figure 8:

Figure 9,:

Figure 10:

Figure lls Figure 12:

Figure 13:

Figure 14:

Figure 15:

Pigure 16>

Figure 17:

Figure 18:

Figure 19:

Figure 20<

Condensation model test stand High-pressure steam-connection instrumentation Flow rate of saturated water vapor through throttle nozzles of different diameter as a function of the, initial pressure for supercritical pressure ratio Mass -flow density of saturated water vapor fl thro g utah throttle nozzles, with respect to the area r

owing A>> ~~~% m2 (perforated cross pipe 2)

Termination geometry, perforated cross pipe Test series 1:

Instrumentation Test series 1:

Influence of tank geometry on bottom pressures Test series 1:

Influence of tank geometry on, bottom pressures Influence of preheating of the blowdown pipe on the bottom pressures during vent clearing Test series ls Visicorder strip for test 212 Test series lc Copy of Visicorder strip for test 215 Test series 1:

Copy of Visicorder strip for test 235 Test series 2:

Test set-up and arrangement of measurement points Test series 2a Test sat-up and data Test series 2:

Vent clearing pressure as a function of the pressure before Qe throttle nozzle Test series 2:

Vent clearing pressure as a function of mass flow density Test series 2c Maximum bottom pressure as a function of vent clearing pressure Test series 2:

Mean speed of the water-air phase boundary surface as a function of vent clearing pressure Test series 2:

Speed of the water>>air phase boundary surface Test series 2:

Mean speed of the water-air phase boundary surface at time ht after beginning of valve.

opening as a function of vent clearing pressure 9-6

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Figure 2l:

Figure 22:

Figure 23:

Figure 24:

Figure 25:

Test series 2:

Mean speed of the water-air h

ary surface for various vent clearing pressures LPDE as a function of the time bv after beginning of valve opening no.

335 Test series 2:

Copy of Visicorder strip f t

or est no.

342 Test aeries 2s Copy of Visicorder strip for t t or es no.

345 Test series 2:

Copy of Visicorder strip f t t

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or est

.no.

346 Test series 2:

Copy of Visicorder strip f t t

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or es 9~7

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). Introduction Pressure oscillations vhich occur in a vater pool vhen pipes pa y

lied with vater are cleared generate noticeable rtiall fi loads on the bottom and lateral v ll i th a

s n

e vater space of the suppression chambers of boiling~ater reactors.

These loads arise from oscillations of the air flushed over into the vater space vhen the safety/relief valves are actuated.

In order to reduce the loads on the relevant structural components,

'I pipe termination geometries vere developed'nd tested in the test stand of the Mannheim Central Pover Station (GEM).

Disadvantages of this large-scale test stand are the low pressure of the available steam (~bar) and the unalterability of the tank geometry (earlier condensate hank).

In order to obtain more exact knowledge concerning the deter-minative parameters for the analyses of the transposition from the GKM test t s and to the reactor, the condensation model test stand located inin the Grosswelsheim nuclear-power experimental facilit vas y

connected to the high-pressure steam boiler of the test facilit.

The set-up and operation of the test stand are described in /1/.

With this set>>up it vas possible to include the entire pressure range of interest, starting from the initial pressure, and its influence on the pressure build-up in the blovdown pipe and the loads on the bottom of the vater pool.

These relationships vere 9-8

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investigated primarily in the second test series.

Additional tests nerved to prepare for large-scale tests in the GKH.

Among other things, these vere to clarify the influence of different dimensions of the water pool. It should be noted that because I

of the too sharply differing ratios of the quantities involved, the test results are not transposable as absolute values to the plant.

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2.

Condensation model test stand 2.1.1 Basic set-up

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The set-up and dimensions Figure 1.

The model tank high, Qgg m vide and 4~9 frame.

of the test stand are shown in consists of a rectangular tank+

m m deep, vhich is supported by a steel The tank is provided with glass discs on to a height of~9 m in order to be able vent clearing and condensation processes I

l the front and back up to also observe'hei optimally.

For safety reasons, the test stand is placed in a sheet-metal trough vhich can hold the water content of the tank if the glass discs should possibly break.

Furthermore, the sheet-metal trough is shielded by movable positioning walls made of PLexiglas in order to protect persons.and instruments from the outflowing hot vater in the event of a glass break.

2.1.2 Steam.-boiler connection

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The high-pressure boiler of the experimental facility vas used as the steam generator.

The steam output is 40 Ng/h, maximum pressure 165 bar and max,.. superheated-steam temperature

.520'C.

Figure 2 shovs the connection of the model test stand to the high-pressure boiler.

Before beginning the test, the boiler is run up to the steam output and temperature desired Later in the test.

The generated steam is conducted fran the main-steam line 9-10

via an exhaust-steam line into the n o e condenser.

The condenser is capable of absorb'orbing the entire output of th b i e

o ler.

t'e ores<<

sure in the n the condensation system (32 bar) is kept constant During vent clearin and g

condensation tests, a pneumatically operated i

qu ck-opening valve is opened in the connection line to the boiler er and two parallel-connect d

1 e

va, ves in the connection to the exhaust-steam header are closed.

At the end of the test, the valves are actuated in the opposite direction.

These switchin o e ng opexations cause large changes in the flow rate in the condenser enser and thus large pressure oscilla-tions which canno annot be compensated so quickly by the automatic pressure control.

Zn orde rder to prevent a response of the'afety valves of the condenser thee steam flow rate therefore had to be limited to about 25 Ng/h in the tests.

ht hi he g er pressures, the setting of th d

e es red steam pressure at the uick quickmpening valve of the test st nd i s

s a s effected directly at, the main-steam outlet.

Then it, is necessary to allow for an overpressure covering the i in 1

p p g

osses.

For =required steam pressures of <30 bar the

, the steam is throttled from higher boiler-pressure b

means Y

of a manually operated valve in the connection line to the test stand.

The desired steam condition en on, generally saturated steam, is ensured by monitoring the steam temperature X

rd e.

o er to avoid wet steam with certaint

, the y,

e tests were always performed with minimally superheated steam.

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2.1.3 Adjustment of steam flow rate g ya1ve opening time

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An exchangeable throttle nozzle was placed after the valve in order to set particular steam flow rates for different steam pressures before the valve.

When the valve is opened, there results a flow rate which corresponds to the critical pressure drop across the valve at the beginning of the opening phase and

. to the critical pressure ratio across the quencher later.

The full initial'ressure across the quencher corresponding to the full flow rate is reached in a shorter time'han the valve

'I opening time.

By measuring the pressure build-up before the

throttle, a "fictitious valve-opening time" can be determined.

Only for an initial fraction of the valve opening time does the increase of the flow rate not correspond to the flow rate through a valve operating in the critical pressure ratio.

See Figure 20 for a clarification of this relation.

'cnirlBf<nunqszf! I 80

l. Steam flow, rate at valve opening (idealized)

Yalve opening time 9-12

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2. Steam flov rate through throttle nozzle connected further on (idealized}

fictitious The valve opening time affects the quantities being measured.

As mentioned before, the steam is supplied through a "quick-opening membrane valve".

The air connections for the pneumatic drive vere substantially enlarged in comparison to the normal design in order to make possible shorter opening and closing times.

The valve opening time @as controlled by providing the preceding electromagnet control valve with a manual control valve with which the air, flcwing from the membrane valve was regulated.

Zt was thereby possible to vary the valve opening time in the range of about 150 - 900 ms.

2.2 Instrumentation An extensive outfitting of the test, stand vith measurement trans-ducezs provided for a careful recording of static and dynamic pressuzes, temperatures, loads and steam floe rates.

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Nost of the instrumentation was the same in all the tests described inin this report.

Deviations from the basic equipment are mentioned in the individual test series.

2.2.1 Xnstrumentation of the steam sup~le

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To ad)ust the desired steam condition umb

ons, a n er of measurement transducers for ress p essure and temperature were installed in the supply line between the main-steam lin d th ne an the test stand (see Figure 2, measuring points P

, FP07-01 FT07-01

.).

Between the quick-opening valve and test tank ddi i

, a t onal measuring points were arranged in order to check the steam condition along the pipe.

Especially important was the hi hl t i

e g

y transient pressure and temperature variation during the valve opening open ng.

I 2.2.2 Determination of steam flow rate

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Zn, order to de o determine the amount of steam introduced into the test facilit we s

y, u ed 3 methods which were differently well suited for different boundary conditions.

a)

A measurin orifice g

was installed in the connection between the main-steam line and quickmpening valve.

The differential pres-sure occurring there was measured by a Barton cell.

Ths mea-surement signal could be read off on a directly indicating instrument.

Here we m we measured the steam flow which flowed before the beginnin of g

the test in the exhaust-steam header and then the amount that flowed during the test t th bl o

e ow-out geometry.

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The steam flow rate in the steady-state can be determined quite exactly in long-term tests (condensation tests}

by this measure-ment.

This method is not suitable for vent clearing tests in which only the first few seconds of the test are of interest.

But during this time the alternate closing and opening of the valves in the connection lines to the exhaust-steam header and to the test tank cause intense pressure fluctuations in the pipe.

Of course, no reasonable measurement of the differential pressure across the orifice is then possible.

b)

The second method to determine the flow rate is made possible by the throttle nossle between the quick-opening valve and the test tank.

Since ce there is a supercritical pressure ratio across this nosrle under almost all existing conditions, the speed of sound is reached in the narrowest, cross-section.

Together with the nosrle cross-section and the pressure before the noszle, the flow h

rate can be indicated exactly at any arbitrary time.

Therefore, this method is especially well suited for recording the increasing steam flow rate through the opening valve during vent clearing tests.

An inspection and calibration of the measurement values is possible with the method described under c).

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Zn this regard, see also the dependence of the steam flow rate I

on the initial pressure for various throttle diameters as illuy-trated in Figures 3 and 4.

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c}

The most exact method for determi i th i n ng e

ntegral value oi the supplied steam is to measure the water 1

i th eve n

e test tank.

Zn condensation tests with ttemperature increases of about, 20 C

to about 90 C

90 C, the water level rose by 200 to 250 mm.

Thus the measurement error is no larger than +1%.

Zn long-term tests with constant steam mass flow, method c) can be used to check the ac e accuracy of the first two methods, which are affected b

a la y

arger error because of their underlying principle.

2.2.3 Pressur e transducers in the test stand

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A number of pressure transducers are mounted th bo on e

ttom and on one side of the tank in order to record the pressure waves emanating from the i te p pe ezmination geometry.

Zn order to avoid effects caused by deformations of the tank th b

e ottom pressure tzansducers were inserted into a rigid guide sunk into the bottom of the tank.

In order to be be >able to continue comparison studies begun earlier concerning the suitabilit o

y of different types of pressure trans-ducers /l~ trransducers having rear and external diaphragms and pieso-electric transducers were used.

The lateral pressure transducers could be used at various heights on the side wall inn order to make possible an adaptation to the particular test geometry.

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y I'n order to be able to check whether and to what extent tank oscillations are superimposed on the recorded pressure amplitudes, in most of the tests an additional pressure traniducer, diaphragm transducer vas mounted down from the ceiling of the hall vithout any connection to the test tank.

The data transmitter was placed freely in the vater space.

The measurement values vere recorded by a light-beam oscillograph

<Visicorder}.

The feed of the recording paper vas variable vithin broad limits.

For most of the vent clearing tests, t'e recording vas made at a paper speed of 1 m/s.

The basic configuration of the measurement chain is sketched belov.

Diaphragm transducer Monbronauf nohaor Aufnohaor Trhyor fr oquons NoarorotRrkor AnpaoounS Yiofcorder Piesoelectric transducer Pioso Aufnahaor I

Ilufnohao

~ VorvorotÃrkor, L.~

Hochvoratorkor AnpaaounS Yio accorder KEY:

1. Transducer

2. Carrier-frequency measuring amplifier

3. Matching

4. Preamplifier

5. Post-amplifier 9"17

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2.2.4 temperature transducers in the test stand

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Xn anal to the ogy pressure measurement points, thermocouple elements (NiCr-Ni) were built into the test tank for temperature measurement.

During the vent clearing tests, which last only a few seconds, they were used primarily only to check the water temperatures before beginning the test.

2.2.5 Dis lacement p

transducers on the diaphragm valve

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For an exact measurement of the valve opening time, an inductive<<

type displacement transducer was mounted parallel to the valve spindle.

This recorded not only the end points of the valve travel but also the behavior during the opening displacement.

2.2.6 Inteqral load on the test stand The test tank w ank was mounted at its four support points on load

,.cells (piesoelectric measurement principle) which in turn sat on the substructure.

The sum signal from these transducers cor-.

responded to the total load on the test tank due to the pressure pulsations occurring in the water spacy during vent clearing.

Beginning in test 275, the load cells were removed and the tank bottom was propped additionally in order to reduce its suscep-tibilityto oscillation.

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Vent clearin tests in the model test stand The tests performed from Hay 1973 to january.1974 on the clearing of water-filled pipes are listed in Table 1, Sheets 1-4.

This list provides the test date, assignment to a particular test series and valve opening time.

In this Table, the indicated mass flow density mA always relates to the outlet cross-section of the termination geometry of the blowdown pipe.

A geometric configura-tion (a,perforated cross pipe) with two different outlet areas was used exclusively for the testa covered in this Report, (see Figure 5).

The individual outlet opening was always a hole having a diameter of A~mm, corresnondinq to the stipulated reactor design.

3.1 Test series 1

Influence of tank geometry on the bottom pressure during vent clearing.

3.1.1 Test goal

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Observations in earlier,tests revealed an influence of thedimen-sions of the water pool on the measured bottom pressures.

In the following posts, this influence was to be examined more exactly in order to make certain about the transposition of the values measured in the GKM test stand to. reactor conditions.

In these

tests, the pipe between the valve and model tank was heated.

3.1.2 Special test set-up

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The set-up corresponds essentially to the general description in 9-19

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Item 2.

The measurement set-up is illustrated in Figure 6.

The perforated cross pipe 1 vith A

~ 4~3 cm was used as blow-out geometry.

Pi heatin The specific surface area of the pipe betveen the valve and out-let geometry relative to the reactor is larger by a factor of 10 to 12 in the model test stand than in the reactor.

Zn order to reduce the associated substantially higher condensation rate in the mode e model test stand, an electrical heater vas installed along the ma)or portion of this pipe.

Zt consists of a total of 5 heater bands of 1070 vatts each.

They are divided into 3 groups of 2 or 1 heater band each, and each group is controlled by its own thermostat.

The associated temperature sensors vere installed betveen the pipe surface and heater band.

For an ad)usted nominal temperature of 200 C, the temperature of the pipe surface is kept, constant to vithin approximately +5 C.

Larger deviations vere found at the ends of the heated section and at a fev unheated flanges.

Here the temperature before beginning the tests vas about 100- C.

Restriction of the water s ace The tank's influence vas investigated by arranging a circular sheetwetal

)acket from the bottom up to the vater surface con-centrically around the blow-out geometry or using the model tank

=

vithout any restriction.

Since the pipe heyting ended about 1 m 9-20

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above the water surface, an aappreciable heating of the vater and increase of the water-va or

- apor partial pressure vas avoided.

The transposition parameter betveen the mod 1 t e

est stand and GKM or the reactor was assumed to be thee ratio of the water surface area to the cross-sectional area of the air bubble, assumed spherical, correspondin to po g

o the amount of air enclosed in the pipe.

In one case the GKH conditions were to be simulated in this vay in the model test stand.

In the model test stand, the preheating of the i to p pe to 120 C on the average must be allowed for vhen determining the air volume.

Th f

e e fective air volume is reduced correspondingly.

3.1.3 Test execution

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Vent clearining tests vere performed with 4 different dimensions of the vater space.

The ratios described above bettween the air volume and vate water surface area are shown i Tabl n

e 4.

The last two columns indicate which vater surface 'area or vhich suppres-sion-chamber sect~o tion in the reactor corresponds,to the particular'xperimental set-up.

The tests vere e

p rformed with a mass flow density of 4~+ kg/m s and, in a few cases, also vith M% /

kg m s.

The setting vas done by the'nitial res pressure across the throttle nozzle g~ kg/cm

\\

[gauge) at i~~

W~ kg/m s).

The submergence vas +Q mm and the 2

distance from the bottom vas ~~'m.

Chosen as the representative bottom pressure was thee measuring point P>4 (piezoelectric trans-.

ducer) which vas located e

precisely under the quencher

<<nd which 9"21

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,always indicated the highest values.

In the eccentric arrangement of the quencher, the shortest distance to the tank wall was 0'3 Dtm 3.1.4 Test results

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i All the essential test data are compiled in Table Figure 7

shows the bottom pressure as a function'f the valve opening time.

The various curves make clear the influence of the tank

• dimensions.

This trend becomes still more clear from Figure 8 where the bottom pressure was plotted for various valve opening times as a function of the free water-surface-area or the ratio of air/

bubble cross-sectional-area to water-space cross-sectional area.

For the unrestricted water apace, it seemed appropriate here to use the cross-sectional area of an inscribed circle.

Zf we compare the bottom pressures for A/A

~ i~$ (GKH ratio) to those for A+A

~ g~~ then we find a reduction of about L+ for the positive pressures and an even somewhat larger I

I reduction for the negative values.

The question as to which A+A ratio should be used for BWR cannot be answered here.

The entire water surface area in KXB is approximately <~$ m.

The cross-sectional area of the air bubble ex'pelled frcNL one quencher is approximately I@5 m.

Figures 10, ll and 12 represent copies of the Visicorder traces with which the pressure values were obtained for three different 9-22

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test set-ups.

Except for the water space, the boundary condi>>

tions were the, same in all three tests.

The influence of the i e re p pe preheating is clearly shown in Figure 9.

Tests which were performed during the last series to examine the double pipe with thee unheated pipe are compared here with similar tests with a heated i p pe.

Although no transposition factor can be read off here either, the influence of th i

e p pe heating and of a more or less marked condensation can be seen 3.2 Test series 2

Investigation of parameters during vent clearing earing.

3. 2. 1 Test 'goal

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1.

The pressure build-u in p

the pipe connection between a quick-opening valve (relief valve) and a pipe'termi nat on geometry arranged in the water space (perforated-pipe quencher) wa

-p pe quencher) was to, be investigated (vent clearing pressure) 2.

The relation betw between the vent clearing pressure and the loads occurring at the bottom of the test tank was to be determined experimentall T

y.

he vent clearing pressure was to vary at least in a ratio of 1:3.

3.2.2 Special test set<<up

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The set-up corresponds essentially to the description under Item 2.

In orde In order to guarantee the comparability. of the model 9-23

tests with the QRH tests, a number of transposition parameters vere to be considered.

The corresponding data, are compiled in Table 4 and Fi ur gure 14.

The tests vere always performed vith an insert of the same dlameter to restrict the vater suiface area.

The steam vas supplied via a quick-opening valve with a succeed-ing exchangeable throttle>>nossle.

This throttle unit vas con-nected closer to the test tank.

The pipe section, which was shorter than in the earlier test series, could thereby be con-structed vith a larger diameter.

By this measure and the elec-trical auxiliary heating of the pipe also used here, greater condensation

'was prevented in this pipe.

Zn the part lying under vater, the corresponding effect was achieved by means of an internal Hostaflon lining vhich vas led as far as the stop of the perforated cross pipe.

Zn order to obtain the same resistance coefficients, the diameter of the individual holes is the same as the hole diameter for GKH and reactor quencher (see Figure 5).

Zt should be noted that in com-parison to the preceding test series the outlet cross-sectional area A for the perforated cross pipe 2 used here is only half as large as for perforated cross pipe 1.

To measure the velocity of the air/water phase boundary surface during the vater expul-sion process, electrical resistance measurements vere made at S points (Zl to 8S)

(see Figure 13).

3.2.3 Test execution

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Zn accordance vith the test goal, a largest possible range of 9-24

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vent clearing pressure was to be covered.

For that purpose, the pressure before the valve was varied between 10 and 100 bar.

The variation of the pressure before the throttle nozzle as a

I direct measure of the flow rate was 10.to 76 bar.

In order to extend the range of the clearing pressures set in this manner, two test series were performed with a different diameter of the

/

throttle nozzle.

The resulting mass flow density for the entire range covered was LM~~gQ kg/m s relative to the outlet 2

cross-section of the perforated cross pipe.

The submergence was 2.0 m in all tests.

The valve opening time was adjusted to the smallest possible value. It was 145 ms

+ 15 ms on the average.

The test duration'as about 3 s in each instance.

The sheet~etal insert was'led beyond the water level in order to decouple the internal and external spaces.

3.2.4 Test results

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The most important data from the test evaluation, indicating the relationship between vent clearing pressure and bottom load, are compiled in Table 5.

The measurement point P>4, which was located H

centrally under the outlet geometry, was used exclusively for the indication of the maximum bottom pressure.

This measurement point also indicated the highest values in all cases.

The variation of the maximum clearing pressure (hP~E

) is

- DE max illustrated in Figure 15 as a function of the initial pressure 9-25

before the throttle norsle and thus as a function of the inflow-ing steam rate.

Zn addition, the pressure value set at the mea-i surement point P~ at the same time was also indicated.

Basic-ally, the same dependence is shown in Figure 16, except that here,'.

the clearing pressure is illustrated as a function of the mass flow density relative to the pipe and outlet cross-section.

The most important result from these tests, the relation between clearing pressure and bottom load, is evident from Figure 17.

= From the mean-value

curve, a dependence of the change of the positive pressure amplitude at the bottom relative to the vent clearing pressure can be indicated in the form hPB c gDE in the upper, range.

Zf we extrapolate beyond the measurement

-,range, this value seems to decrease further.

A quantitative indication concerning the further decrease of c is not possible.

For'he positive pressure amplitudes, the range of double stan-dard deviation,was also plotted.

The reason for the larger scatter in the range hPDE

~

8 bar compared to the other DE max values surely lies in the fact that at this point there is a crossover of two measurement

'series with different prethrottling.

The highly variable initial pressure has effects which cannot be evaluated exactly and are responsible for the larger devia-tions from the mean value.

In general, however, it can be stated that the pressure values at the bottom could be 9-26

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reproduced with an accuracy ofg~Q bar.

A statistical evaluation of the scatter was dispensed with for the negative pressure amplitudes at the bottan, because only slight deviations from the mean value occur, especially at the higher values.

The curve leads us to conclud'e that there is an, asymptotic approach to the value I~3 bar.

The measurements concerning the speed of the water surface pass-ing through the pipe during the vent clearing are evaluated in Figures 18 to 21.

The pathMependent change of the speed is il-

• lustrated for various clearing pressures in Figures 18 and 19.

Xn Figures 20 and 21, the speed is illustrated as a function of the time after the valve opening begins.

Copies of the Visicorder recordings together with the, measured pressure. values are included in Figures 22 to 25 for 4 tests.

The particularly interesting curves for FP07-0i, hp>E and 4P><

are specially emphasised.

The measurement<<point coverage of the. light-beam oscillographs used for this test series (Visi-corder) is shown, in Table 7 <<nd Table 8.

The'requency of the first air-water oscillation was ~~~~~~

Hz in all tests.

These relatively slight differences are caused by slightly different boundary conditions (temperature and moisture content of the air in the pipe before the test)

~

• The different clearing pressures quite obviously have no influences on the frequency.

9 27

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fiumma of results The vent clearing tests in the condensation model test stand in Grosswelzheim have demonstrated the direct relation between the pressure build-up in the pipe and the dynamic pressure loads on the bottom of tthe confining tank.

The clearing pressures in the pipe vary within a range of 4MM%i bar.

\\

Important observations concerned the influence on the bottom pressures exerted by the water space relative to the amount of air introduced during the clearing.

By parametrizing the cross-sectional area of the water apace, it was possible to obtain from these tests important information for the transposition of the qu'antltative results obtained in GKH tests to reactor conditions.

The influe influence of the stiffness of the surrounding tank walls on the wall load and bottom load was determined qualitatively.

A compliant" confining wall, which was loaded up to or beyond the permissible limit, resulted in values up to 60% lower than a

'noncczapliant'all.

Ho quantitative statement can be made about this dependence.

For all of the measured bottom pressures, it should be noted that no absolute values are transposable to reactor conditions.

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REPERERCES

/I' Werner,,Nelchior Tests of mixed condensation with model,quenchers lNU-E3-2596 Nay 1973

/2/ Backer, Hoffmann, Xnapp, Xraemer, Nelchior, Neyer, Schnabeel Vent clearing with the perforated-pipe quencher XWU"E3-2848 January 1974

/3/ Hoffman, Knapp, Neyer, Waldhofer, Werle Condensation and vent clearing tests in CKN with perforated pipes EWU-E3-2594 Nay 1973 0

0 29

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KRAFTWERK UNION AG PROPRIETARY INFORMATION 1.through 8

Table....'...

9-30 through 46

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High-pressure connection Hochdruck-AnschluA Arrangement and instrumentation Anordnung und Instrumentierung Throttle normal@

OrosseMGse FO 07-02 r

<<r FP 0743 olekfdsch boheizt electrically heated varioBer Einsah.

im Viasserraum - "

variable insert in water space P81 - PB6 Tc-Te

Main steam

5. Model test stand 2

3 ~

4.

Exhaust steam Outer wall Inner wall OT,,

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6. Outer

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8. Drain

9. Air

%5tl81) alO atu ~ kg/cm (gauge) 2

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I J. 220'0t 01 LOT Ol PL, 07 Ot Oyluh 7 io AOT OT XOT Oe 5 07 TO 42 OT Ce 41 07 OI

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Mass flow density of saturated steam flowing through throttle nozzles, relative to the area of A

~ 0.00157 m

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KRAFTNERK UNISON AG PROPRIETARY ENFOKCATXON 5

Fulgur e1

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Insert in water space Einsatz im Sasserraum p)

P2 Kreuzlochrohr 1

Perforated cross pipe l Model l - Kond - Versuchsstand Yersuchsserie 1/Einflu0 Behaltergeometrie Instrurneotierung des Abblaserohres Condensation Model Test Stand Test series 1:

Influence of tank geometry Instrumentation of the blowdown pipe Bild 6 Figure 6

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KRAFTWERK UNION AG PROPRIETARY INFO%CATION Fi9ure.

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