ML17138A530

Rept Translated from German:Tests on Mixed Condensation W/Model Quenchers

ML17138A530
Person / Time
Site:	Susquehanna
Issue date:	05/15/1973
From:	Melchior, Simon, Werner PENNSYLVANIA POWER & LIGHT CO.
To:
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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-E3-2593, NUDOCS 7903150316
Download: ML17138A530 (119)

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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 KBAFTWERK UNION AG (KWU) ~

The PROPRIETARY information deletion s 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.

i)

...." with a mass flow density oft'~ Kg/m2s... ";

ii)

QMM~ mm iii)...." should be kept below ~<Zw% atm."

iv)

M 8/17/78

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Kraftwerk Union ace Date Technical Report KWU/E 3 - 2593 File number E

3 E 1 GKT - Dr. Me/do KWU - E 3

E 3 and E

1 epartment Authors Werner Dr. Melchior Dr. Simon Countersignature /s/

Title:

Tests on mixed condensation vith model quenchers Key words (max.

12) to identify the report's content:

, Condensation, model tank, quenchers, perforated pipe Pages of text Figures Circuit diagrams Diagr./oscillogr.

Tables Reference list 32 26 Summary To investigate the processes in the suppression chamber of BWR power

plants, blowdown and condensation tests were performed vith v

'ous quencher geometries.

A model tank with inside dimensions of 560 1600 x 3000 mm was used as the tank.

ar As a basis for comparison vith the results obtained in other test

stands, reference tests vere first performed with a pipe open at the bottom and having an inside diameter of 24 mm.

The study of different quencher geanetries with differently fine subdivision of the primary steam flov lead to the result that the imposed require-ments can be satisfied vith the simple geometry of a perforated pipe.

By means of various detailed studios, relationships vore found between the hole distribution density of the pipe surface, the hole dismeter and the hole configuration.

The results of these studies are being incorporated into the design of the quencher geometries for tests in the GKM test stand.

The influence of special tank geometries and problems in measuring pressure oscillations in vater are being investigated in accompanying tests.

/s/

(Werner) s Dr. Melchior)

Aut or s s1gnature Exam1ner ass1 1er ZZ Plass For information (cover sheet only):

Additional distribution according to attached list Distribution list:

lx KWU/GA 19 Erl lx

/PSW 22 Ffm lx E 3/Library 2x E 3/E 1/LP lx E 3

E 1 Pro'ect Mana er Transmission or dunlication of this document, exploitation or commu-n1cation of its cohtont not permitted unless expressly authorised, Znfringers liable to pay damages.

All rights to the award of patents or registration of ut3.laity patents reserved.

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NONLIABILITYCLAUSE This report is based on the current technical knowledge of Kl&FTWE1tK UNION AG.

However, KZUQTWERK UNION AG and all persons acting in its behalf make no guarantee.

In particulaz, they are not liable for the correctness, accuracy and completeness. of the data contained in this report nor for the observance of thizd-pazty rights.

This reservation does not apply insofar as the report is delive ed in fulfillment of contractual obligations,

@or with respect to licensing authorities or the expels appointed by the.=.

lGUEFTWERK UNION AG reserves all rights to the technical infozma-tion contained in this report, particularly the right to apply 4

for patents.

Further dissemination of this report and of the knowledge con-tainod therein requires the written approval of KRAFTWERK UNION AG.

Noreovez, this report is communicated under the assumption that it will be handled confidentially.

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Distribv.tion list (internal)

E 3

E 3/0 E 3/V E 3/V E 3/V E 3/V E 3/V E 3/V E 3/V E 3/V E 3/V E 3/V E '3/'V E 3/C E 3/L' E 3/}'.

E 3/E E 3/E E 3/E E 3/E E 3/E E 3/R E 3/R E 3/R E 3/R E 3/P E 3/R E 3/R 3

4 4/Evv 4/Era 4/Kla 4/'zre 4/EE I 4/GKT 5

1 1/a:

1/Ep 2

2/SA 3

4 x 5 x 2 x 1

2 2/KL 3

5 2 x Sclsz etariat Heron Goldstcrn Ease~

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$ 1 l

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DISTRIBUTION LIST (external)

TUV North Germany TUV Baden TUV Bavaria IRS, Cologne IRS-FB, Dr. Lummersheim, Cologne BMFT, Mr. Seipel, Bonn RKS - Members and subcommittee Boiling Water Reactor" 22x Ministry of Labor and Social Affairs, Baden-WQrtembg.,

Stuttgart Ministry of Economics, Baden-WQrtemberg, Stuttgart Ministry for Labor, Social Affairs and Distribution, Riel Ministry for Economics and Transportation, Kiel Bavarian State Ministry for Agricultural Development and Environ-mental Protection, Munich Austrian Study Company for Atomic Energy, Vienna Ministry for Health and Environmental Protection, Vienna HEW, Project Management, Nuclear Power Plants KKI 3-4

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TABLE OF CONTENTS Page 2 ~

2,1 2 '

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2.4 Introduction Construction of the test stand Mechanical construction of the model tank Installation of the model quenchers Steam boiler Instrumentation and data acquisition 3-9 3-11 3-11, 3-12 3-12 3-13 2.4.1 Determination of steam flow rate 3-13 2.4.2 Pressure and temperature transducers in the tank 3-14 2.4.3 2.4.4 Determination of the total tank load Data recording 3-15 3-15 2.4.5 Optical recording of the test procedure 3-15 2.5 3

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Test execution General characterization of the quenchers investigated 3-17 3-18 4.

Investigated blowdown geometries and tests performed 3-20 5.

5.1 5.

2'esults Results for various quenchers Optimization of hole configurations 3-24 3-25 3-27 5.3 Influence of the test tank on the measurement values 3-31 5.4 6.

Results of the comparison studies with different pressure transducers Qualitative conclusions for the design of quenchers 3-32 3-38 7

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Outlook and problems remaining open 3"41 Pigures 3"5

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List of Fi ures Figure 1

Construction and spatial configuration of the model condensation test stand in the Nuclear Energy Experimental Pacility in Grosswelzheim Figure 2

Side vt.ew and top view of the test tank Fi e

3 Piping and instrumentation diagram gure Figure 4

Instrumentation diagram for the model tank when testing the disk nozzle Figure 5

Arrangement of instrumentation for testing the

~ cross-shaped perforated-pipe quencher in a miniaturized vater volume Pi.gure 6

Instrumentation diagram for testing the hole arrays Figure 7

Diagrananatic illustration of the forked nozzle vith

)acket Figure 8

Stepped pipe vith ci.rculating )acket Pigure 9

Single slot vith )acket 1

Figure 10 Single slot vith )acket 2

Pigure 11 Disk nozzle Figure 12 Stepped hammer 3" 6

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Pigure 13 Perforated pipe 1

Pigure 14 Perforated pipe 2

Figure 15 Perforated cross pipe Figure 16 Arrangement of perforated pipei e 3 in the model tank for testing the hole arrays f the hole arrays with temperature Pigure 17 Arrangement o

e measurement points for perforated pipe 3

Figure 18 D

amic loading of the load cells vith different quenchers

- p as a function Figure 19 Bottom pressures hp>

p~

- pBmi of vater temperature for diffeient quenchers Figure 20 Temperature difference betveen infloving vater and

'on of the temperature middle of hole array as a function o of the infloving water.

The hole di diameter is 3.5 mm for all throe hole arrays.

Figure 21 Temperature difference betveen inflowing water and middle of hole array as a function of the temperature of the inflowing vater.

The hole diameter is 6

mm for all throe hole arrays.

Figure 22 Dependence of the pressures at the side wall as a function of vater pS5 pS5max.

pS5min.

temperature for different occ p cy cu an densities of the hole arrays.

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Figure 23 Dependence of the bottom pressures hp

~ p B

Rmx.

p~.

as a function of the wate tmnperature for the perforated cross pipe with restricted and normal water volume Figure 24 Copy of the recorder strip for comparison of pressure transducers at a water temperature of H C Figure 25 Copy of the recorder strip for comparison of pressure transducers at a water temperature of Q$ C Figure 26 Copy of the recorder strip for comparison of press re transducers at a water temperature of Q.QC 3-8

l. Introduction The good experience achieved with the temporary aquarium test stand in the study of blowdown and condensation processes led to the design of an enlarged, more stable and better instrumented model test stand.

The purpose of that improved test stand was to confirm and broaden the knowledge obtained previously in the "aquarium" and to serve as a test stand for model quenchers, which were then to be tested in already optimized form in large-scale tests in GKM.

The advantages of a model test stand in comparison to a large-scale test stand are evident. If for the time being we disregard the economic aspects, we are left with greater flexibility, smaller expenditure of time and personnel for tests and reconversions, and especially the capability for optical observation.

The latter ia a prerequisite for clarifying the phenomena that transpire during vent clearing and condensation.

A theoretical description of them is necessary for transposition analyses.

The success of the theoretical description depends primarily on whether it is based on correct physical concepts.

Another advantage of a model test stand is the capability for sub-stantially optmizing quencher geccnetries in the model before going to large-scale tests with them.

Of course, such a test stand does not make large-scale tests superfluous, since only from a comparison of similar types of experiments at small and lar'ge scales can we 3-9

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obtain information about the transposability of results and phenomena that were observed in the small-scale test stand to the large-scale test stand and the reactor plant.

Such a model test stand, as is available in the Nuclear Energy Experimental Facility of KWU in Grosswelzheim, is therefore uncon-ditionally necessary for a phenomenological clarification of the physical processes and in order to perform the large-scale tests only with previously optimized geometries, thereby keeping the costs for such large-scale tests within reasonable economic bounds.

Not least of all, information about transposability is obtained from the interplay between small-scale and large-scale test stan" results.

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2.

Construction of the test stand The basic construction of the model test stand and its spatial configuration in the Grosswelzheim Nuclear Energy Experimental Facility is shown in Figure 1.

The test stand consists of a water tank (model tank),

a steam generator and the necessary piping, valves and measuring instruments.

For pure air-blowdown tests there is an additional air storage tank which can be connected optionally to the blowdown geometry.

2.1 Mechanical construction of the model tank The model tank (Figure

2) consists of a rectangular tank 3

m high, 1.6 m wide and 0.596 m deep, which is supported by a steel frame.

Up to a height of 1.5 m the tank is provided with glass disks on the front and back in order to be able to observe the vent clearing and condensation processes, optically.

For safety reasons, the test stand is placed in a sheetmetal trough which can hold the tank's water content in the event of a hroak of the glass disks.

The sheetmetal trough is also shielded by movable positioning walls made of Plexiglas in order to protect personnel and instruments from the outflbwing hot water in the event of a glass break.

Steam is supplied from a steam boiler (see Section 2.3) via a 50 mm pipe with measuring nozzle to a membrane valve actuated by 3-11

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pressurixed air, with which opening times of 70-100 ms can be realised.

After the valve there is a reduction of the pipe dia-meter to NW 24 for connection to the model quenchers.

At the bottom of the tank there is a twist-proof strip used for installation of measurement transducers.

Screwable openings on the narrow sides of. the tank are used to hold additional measure-ment sensors.

2.2 Installation of the model enchers Beginning at the membrane valve, steam is supplied through a NV 24 pipe.

This pipe is suspended independently of the test stand and normally leads into the middle of the tank.

After the clamp above the test stand there is only a loose guide at an adjustable height.

By means of a screw connection, a pipe adapter and a tensioning device< connection of the individual blowdown geanetries to be studied is accomplished.

Different bottom distances can be adjusted by arbitrary variation of the pipe adapter.

2.3 Steam boiler As the steam generator there is available an oil-fired boiler having a steam capacity of 1 t/h of saturated steam at 8 kg/cm

[gauge).

The steam boiler can be controlled either automatically in 4 stages or manually in 7 stages.

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Since the boiler is designed as a single-pipe evaporator, it guar-antees a fast start-up and shutdown and also a quick adjustment of the desired steam condition.

In the planned second extension

stage, the high-pressure boiler of the experimental facility is being connected to the test stand.

Then it will be possibleto inject steam flow rates of up to ca.

30 t/h at 70 bar pressureefore the valve.

2.4 Instrumentation and data ac isition A thorough and sufficiently sensitive instrumentation of the tes stand and diligent acquisition of all data were the conditions fo" determining all the parameters in the tests.

In particular, it was necessary to measure and record pressures, temperatures, loads and steam flow rates.

The instrumentation installed permanently for all tests can be N

seen in the piping plan of the test stand in Figure 3.

Figures 4

to 6 provide examples of the instrumentation for individual tes s.

2.4.1 Determination of steam flow rate To determine the steam 'flow rate, a standard norrle is installed in the line connecting the steam generator to the test stand (see Figure 3}.

Two absolute pressure transducers and one differential pressure transducer are used to determine the differential pressure across the nossle.

The pressure drop up to the membrane valve and the pressure build-up in the blowdown pipe are determined by two 3>>13

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additional pressure transducers before the valve and in the blow-down pipe above the test tank.

Parallel to the nozzles, the stea=

temperatures are measured at the same points.

2.4.2 Pressure and tern rature transducers in the tank (Figures 4-6)

To determine the pressure waves emanating from the condensation

process,

-a row of pressure transducers is arranged along the bottom and two additional rows along one of the narrow sides of the tank.

Depending on the type of blowdown geometry and the submergence, the side pressure transducers are mounted at different heights.

Thermocouple elements are installed parallel to each pressure transducer for determination of temperature distributions.

To also be able to record the pressure and temperature at a smaller adjustable distance frcsn the blowdown geometry, a movable instru-ment carrier was installed and outfitted with the appropriate measurement transducers.

Zn accordance with the particular model quencher under consideration, additional temperature measurement points were arranged directly a the quencher so as to be able to evaluate the water flow to the steam outlet opening (see Figure 17).

Baaed on previous experience, membrane transducers with a back membrane were first used at all pressure measurement points on the test tank.

To be able to investigate the influence of different 3"14

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measurement techniques, membrane transducers with external mm"..-

brane and also piesoelectric transducers were used in a series of tests in parallel with the tests described previously.

A list of all measurement transducers used is contained in Table 1,

For. each measurement point it gives the abbreviated designation, the measured magnitude and measurement position, the measurement principle, the type of measurement. transducer and the measurement range

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2.4.3 Determination cf the total tank load To determine the loads acting on the test tank, force cells were placed under the four support points of the tank (see Table 1, K 1-4) and their sum signal was recorded.

2.4.4 Data recordin All data such as pressures, temperatures and forces were recorded by two Visicorders (light beam oscillographs) for later evaluation.

2.4.5 0 tical recordin of the test rocedure In addition to the data recording, all important tests were recorded completely with a video tape recorder.

Using the play-

~

'ack

device, the test can be reconstructed optically at any time.

In addition, special problems such as the formation and collapse of steam bubbles were studied with a high-speed camera.

A special time~rk transmitter guaranteed an exact time correlation between 3"15

TABLE l Compilation of measurement transducers used Ul D 4l tJ V Q

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Pcnon M p r wo 0 0't$

ca ce p N 'u c nnonw e ow g

Ol Ol o 4 lo ca M ch

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0

$r'u 0c' n B oooo XC e

g '0'0 M

g4 cia~

& r0

-~4Kc0 C0 Measurement point HeAstelle Rurz-

-..aichcn Rl'2 R3'4 "Bl-B6 51 S2 S5 B7 c8 PS.y2 t-4 R~TS Measurement point McAstollo Ort I Dampf-vufiihrung

~ Bodendruck Soitondruck

> Seitendruck Bodcndruck

~ Bodendruck 5 Soitendruck

< BehHltorbc-lastung g Rohrlei tung/

Versuchsbe-hHltcr Measurement technique NRohrdruck-aufnehmer Membran-Drucknuf-nehmer II Pieso w Hembran-Druck-aufnehmor Pleio Q Thermo>>

element T X pe Measurement range KRAFTNERK UNION AG PROPRIETARY INFORMATION

the Visicorder traces and the individual pictures.

2.5 Test execution Nost of the condensation tests were pe rformed with the maximum erator of 1 t/h.

That steam attainable capacity of the steam genera densit of 614 kg/m s rela-flow rate corresponds to a mass flow den y

tive to the NN 24 blowdown pipe.

The steam flow rate was measured wi,th a standard nozzle having a diameterer of 20 mm in the NN 50 supply line.

u to full power To prepare the tests, the steam generator was run p

the membrane valve (constructed and the steam was conducted through the m

as a three-way valve) into an exhaust steam line.

e valve.

The The test was initiated by reversing the membrane val at the b inning of the test water temperature in the test tank a was generally ca.

20 'C The steam injection heated the water.

The test ended when water temperatures aboveve

'C were reached.

the test duration was 7-8 For an initial water height of 800 mm, th minutes at maximum mass flow density.

Zn tests with low mass flow densities for higher water level at ondin 1

longer test durations.

the beginning, there were correspo y

en ada ted to the particular steam The measurement nozzle was then a ap flow rate.

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3.

General characte isation of the enchers investi ated A common feature of all investigated quenchers in comparison to the pipe open at the bottom was the subdivision of the primary steam flow into tvo or more steam subflows in order to produce a

greatest possible surface area for condensation arid limit the maximum steam volumes at high water temperatures.

Since the main problem in condensation is to conduct sufficient quantities of cold vater to the steam throughout the entire tem-perature range under consideration, the quenchers can be roughly divided into tvo groups, according to the type of water supply:

quenchers vith circulating pipe quenchers without circulating pipe.

Xn quenchers with circulating pipe, the oondensation is to take place inside the circulating pipe and the water is supplied through the circulating pipe in the direction of the outflowing steam.

The vater is pumped by momentum transfer from the injected steam.

Zn the quenchers without circulating pipe, the condensation takes place outside the blovdown geanetry and the vater inflow is adjusted freely in accordance with the injector action of the stea-...

jet.

Since its length also depends on the vater temperature, the out-side dimension of a circulating or mixing pipe must be designed 3-18

for the maximum occurring water temperature in order to guarantee condensation inside the mixing pipe.

For quenchers with free inflow, optimisation involves a choice of the correct hole spacing as a function of the mass flow density and length of the hole rows.

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4. Investi ated blovdown eametries and tests rformed In accordance vith the available steam capacity of l t/h at 8 kg/cm (gauge),

an NW~+steam pipe (outside diameter Q mm) was use" for all tests.

That resulted in a maximum mass flov density of

++kg/m s.

In a few cases, additional tests were performed with low mass flow densi.ty.

An important parameter for the behavior of a blowdown gecxaetry during condensation is the mass flow density at the outlet cross-

section, which at constant mass flow rate is characterized only by the surface area ratio of the inflow surface area Fi to the in outflow surface area F ut.

This ratio is called the opening ratio in the folloving and is used to characterize the quenchers.

KRAFTWERK UNION AG PROPRIETARY INFORMATION In particular, the folloving geometries vere investigated:

a)

Open ~i e:

These tests vere used to try out the test stand and instm-mentation and also for comparison vith earlier aquar'iu=. tests.

guenchers with circulatinc i e:

b) Forked nozzle with acket:

(Figure 7)

The same model vas used as was used in earlier tests in the small test stand (aquarium).

3-20

c) Ste ed i e with circulatin acket:

(Figure 8)

In this model, the positive properties of a stepped pipe (see Report AEG-E3-2037) were combined with the desired water supply of a circulating jacket.

d) Sin le slot with acket 1:

(Figure 9)

To investigate the aspiration of water in the jacket pipe for quenchers with vertical slots, a single slot was tested here.

The lateral water inflow was impeded by partition plates in order to simulate the arrangement of slots in rows in the large-scale version.

e) Sin le slot with acket 2:

(Figure 10)

This version represents a further developcaent of the model described above..Since the stcam flowing out of the slot impedes the water inflow laterally around the slot, the steam outlet was shifted radially outward by means of baffle plates in order to guarantee the water inflow to the long sides of the slot.

enchers without circulatin i e:

f) Disk nozzle:

(Figure ll)

Division of the steam flow over a horixontal annular gap ~l,car.

in diameter and ~~" mm high.

g) Ste ed banner:

(Figure 12)

The principle of the stepped pipe blowing out vertically is

modified here into two stepped pipes blowing out at small angles KRAFTNERK UNION AG PROPRIETARY INFORMATION h) Perforated i e 1:

(Figure 13)

After it had been shown in earlier tests that perforated pipes with large opening ratios have unfavorable properties due to nonuniform outflow of steam through the hole area,~~~~~~~~

N obtained with that quencher was used primarily for comparison with other quenchers and to prepare for the later optimization of hole configurations.

i) Perforated i e 2:

(Figure 14)

This version represents a miniaturization of the perforated pipe tested in the GKN test stand.

Tests with this geometry served primarily to observe the steam-water flow at the pipe surface.

$ ) Perforated cross i e:

(Figure 15)

To examine the influence of thin test tanks, tests were per-formed with this geometry in a narrowed water space and in a normal water space.

k) Perforated i e 3: (Figure 16)

To investigate the optimal distribution of holes on the su face 3-22

of the perforated pipe under reactor-like conditions, a short piece of pipe with a diameter of Q~~mm was inserted and was provided with a replaceable perforated plate.

Flow conditions

~ corresponding to the large-scale version are produced by the large dimensions of the carrier geanetry.

Table 2 contains a compilation of all investigated hole config-urations.

arith the exception of plate no.

6, they are all square hole-array configurations (see Pigure 17), as can be seen from the horisontal (a) and vertical (b) spacings between hole centers.

ln contrast, water lanes were formed between the hole rows in configuration 6 by reducing the vertical spacings.

The figures indicated in the last column indicate the distri-bution density n of the hole array.

This was defined as the ratio of the sum of all hole areas to the total area of the hole array:

Table 2

Com ilation of investi ated hole confi ations

.Number Plate no.

Hole dia.

of holes Platton Nr.

Loch g a

b Loch-d f'mme mm mm aahl Z

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6 KRAFTWERK UNION AG PROPRIETARY INFORQTZON 3-23

5. Results In the following we first illustrate the test results for the various blowdown geometries studied (5.1).

For the tested models of complete quenchers we aze not concerned primarily with the absolute values of the measured pressure amplitudes (the transposition ratio to reactor conditions is too large for that),

but rather with a qualitative comparison in conjunction with direct observation of the condensation process.

In the optimization of hole configurations carried out subsequen ly (5.2) the water flow and the pressure waves emanating from the condensation were studied under conditions that essentially correspond to the conditions in the GRM test stand and in the reactor.

The results obtained there can be transposed to the conditions prevailing for reactor versions of perforated-pipe quenchers, taking into consideration the restrictions listed later.

The actual condensation tests were accompanied by studies of condensation in narrow test tanks (5.3) in order to estimate the influence of the special geometry of the GEM test stand on the test results.

In parallel with the tests, different types of pressure transducers were compared (5.4).

The significance of a correct choice became

clear, since pressure transducers with internal membrane are able to indicate several times the actual pressure values.

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5.1 Results for various enchers Condensation tests were performed with a number of different model quenchers while recording the pressures at the tank bottom and also the total load on the tank.

Because of the large transposition ratio from the model test stand to the reactor, the measured absolute values ofthe pressure cannot be related to reactor conditions.

However, since the model quenchers were tested under identical conditions, a qualitative comparison is permissible.

The readings of the load cells and the measured bottom pressures are illustrated as a function of water temperature in Figures 18 and 19.

A calm behavior up to temperatures of ca.

k~QC is observed for all quenchers.

Above that the pressure and KRAFTWERK UNION AG PROPRIETARY INFORMATION With perforated pipe 1, the lowest pressure amplitudes are obtained by dividing the steam flow over individual holes in the form of W It is conspicuous that from the readings of 'the load cells (Figure

18) the lowest load is found for the disk nozzle,

. This can be

'explained well by observing the flow pattern in the tank:

The completely symmetrical expulsion of steam along the circumference 3-25

leads to a uniform circulation of water.

In contrast, despite lower pressure amplitudes the flow pattern with perforated pipe 1

is more nonuniform, resulting in higher readings of the load cells.

If for comparison we consider the stepped hammer with its two laterally directed, larger blowdown nozzles with which the steam is divided only into two single flows, then we recognize clearly the positive influence of a greater subdivision.

Expressed differently, it can be stated that a reduction of the cha acteris:ic dimensions (hole diameter, slot width) results in a reduction of the pressure amplitudes and tank loads.

The fact that the trans-position of this principle to large>>scale versions is subject to certain restrictions is discussed at length in Section 5.2.

For quenchers with.a circulating jacket, the worsening of the condensation above ~~C must be explained differently.

Up to that temperature there is a satisfactory condensation in the jacke:

'ipe.

There is a satisfactory aspiration and'ownflow of water.

A reduction of the water flow is observed at higher temperatures

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Due to the slower condensation, the outflowing steam occupies a

larger and larger fraction of the volume in the downflow and impedes the further inflow of water.

Zt can be clearly seen that at temperatures above Q~~C the condensation takes pjace prima"'ly outside the jacket.

With the forked nozzle and the stepped pipe with circulating jacke=,

3-26

the flow direction was shifted in such a way that the steam also omerged upward from the )acket pipe.

This phenomenon was able to be observed still more clearly in the optimization tests with sing' slots.

KRAFTWERK UNION AG PROPRIETARY INFORMATION Improvements would probably be possible here also by means of parameter studies.

Eowever, the tests performed up to now have already demonstrated that considerable time would still be neces-sary for further optimization of a quencher with circulating pipe.

A special problem in such a developaent would be to keep within the maximum outside dimensions for quenchers corresponding to the large-scale version.

S.2 timization of hole confi urations As a supplement to the perforated pipe versions tested in the GEM test stand, special studies were performed in the model test stand 3-27

on the water inflow to a variety of hole array configurations.

As already stated, a piece of pipe4~3mm in di.ameter was inserted in the test tank for that purpose and was provided on one side with a replaceable perforated plate (perforated pipe 3; see Figures 6 and 17 for arrangement)

By varying the hole spacing and the size of the individual holes, the influence of the hole occupancy ratio holes 5acket area occupied by holes was investigated.

The effect of vertical lanes was analyzed with perforated plate 6.

For that purpose, the horizontal spacing between the holes was increased and the vertical spacing was reduced A cpecial aim of the study of hole arrays was to examine the temperature distribution in the water along a lane, since the water required for condensation h the middle of a lane must flow in frccn the edge.

Accord'ingly, over and above the normal instrumentation, several thermocouple elements were mounted closely together over the perforated plate in the space between two vertical rows of holes (see Figure 17).

Fran the temperature distribution along the water lane it is then possible to infer uniquely the water inflow to the steam holes in the middle of the bole array.

The results of those tests are sumnarized in Figures 20, 21 and 22.

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For various perforated plates, Figures 20 and 21 contain a

representation of the temperature difference T

- T alon middle edge the wate lane as a function of the temperature of the inflowing water.

KRAFTWERK UNION AG PROPRIETARY INFORMATION 3-29

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KRAFTWERK UNION AG PROPRIETARY INFORMATION

First, as was expected from the begin-ning, the hole occupancy density n plays a role:

The water inflow is improved if the spacing between adjacent holes is increased with otherwise identical conditions.

Zf, however, we now compare the temperature difference between perforated plates with identical occupancy ratio and identical ratio of hole spacing to hole dia-meter but different hole diameter, then the influence of the absolute value of the s acin between two rows of holes becomes clear.

KRAFTWERK UNION AG PROPRIETARY INFORMATION 3-30

I

KRAFTWERK UNION AG PROPRIETARY INFORMATION I

5.3 Influence of the test tank on the measurement values KRAFTWERK UNION AG PROPRIETARY INFORMATION 3-31

KRAFTWERK UNION AG PROPRIETARY INFORMATION 5.4 Results of the com arison studies with different ressure transduce"s Uniform pressure oscillations in the range of Q~MMBr <ith pronounced resonance phenomena provided a motivation for studying the behavior of different types of pressure transducers.

It was obvious to suspect that the higher pressure amplitudes occurring in that frequency range vere caused by resonance phenomena in the pressure transducers having a certain type of construction.

3-32

I

To clarify the origin of the resonance phenomena, three different types of transducers vere used:

l.

Membrane transducer with internal membranes g~~~~W Qi~M~~~4 (subsequently called DA type l).

2.

Hembrane transducer with external membrane Q~~~~~

(subsequently called DA type 2).

3.

Piezoelectric transducer, Using these pressure transducers, the folloving investigations vere performed in condensation tests vith the perforated cross pipe:

- Different types of transducers vere installed in parallel.

- The mechanical connection betveen the pressure transducers=

and the test stand vas interrupted by mounting the transducers on a bar pro)ecting from the roof of the building into the test

'tand.

Pressure transducers vere blocked off from the water space by means of a pipe vhich projected from the vater surface.

The results of these investigations can be summarized qualitatively as follows:

3-33

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KRAFTNERK UNION AG PROPRIETARY IHFOKQtTION 3-34

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KRAFTWERK,.UNION AG PROPRIETARY INFORMATION From the results illustrated here we can draw the following con-clusions:

- Pressure transducers with internal measuring system can form an intrinsically oscillatory system.

Under suitable axcitation, they exhibit pressure values that can amount to several times the pressure peaks that actually occur (see Figures 24>>26)

~

- Zf the use of such pressure transducers with internal membrane is unavoidable, then they can only be recommended for static pressures or low-frequency dynamic pressures.

- Only piesoelectric transducers or transducers with external membrane can be considered as pressure transducers for dynamic pressures of higher frequency such as occur during condensation.

3-35

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KRAFTNERK UNION AG PROPRIETARY INFORMATION 3

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KRAFTNERK UNION AG PROPRIETARY INFORMATION Table K 7 for table 3

3-37

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6.

ualitative conclusions for the desi n of enchers The following processes take place during the depressurizat'ion of a

BHR with wet containment:

Due to opening of the relief valves, steam enters into the relief

pipes, expels the water and air located in them and then the stea.-,

condenses in the water.

The expelled air executes oscillations in l

the water, leading to pressure loads on the tank walls.

In addition, formation of larger volumes of steam in the water can cause condensation hammering.

The steam outlet geometry (quencher) must therefore satisfy the following requirements:

l) Reduction of the initial shock due to distribution of the air over a larger surface area.

2) Condensation of the steam over a broad range of temperature and mass flow while avoiding condensation hammering

~

Por, the initial shock it is a matter of not expelling the air in a single volume but rather dividing it into as many individual bubbles as possible, which then can oscillate out of phase with each other.

The central problem in the condensation of steam in-water is to provide sufficient quantities of cold water to condense the steam immediately after it enters the water and to prevent the formation 3-38

l l

of large volumes of steam which can then collapse suddenly and produce high pressure peaks.

As qualitative results of the condensation tests in the model tank we can list the following points Chat must be observed in the design of a quencher to satisfy these requirements:

- Subdivision of a large steam flow into several steam subflows.

The subdivision may not be too fine, because for a given total outlet area the range of a single steam jet depends on the characteristic dimensions of the single outlet area and water inflow problems can arise.

'- Systematic arrangement of the individual steam outlet cross-.

sections so that there is a clear inflow of water to the steam (for example, formation oi rows of holes with water lanes when using perforated pipes).

- Zn no outlet opening should the mass flow density be smaller Chan the condensation rate of the steam, since otherwise water enters into the quencher and the condensation takes place inside the blowdown geometry.

Inside the quenche",

the rate of con-densation goes rapidly toward sero as the ingressed water, is heated up.

As a result, the water is expelled again.

The I

steam flowing after it forms large bubbles outside the quencher, which collapse suddenly when cold water is admitted and produce loads on the blowdown geometry and tank wall.

Then water enters the quencher again and the process is repeated.

3-39

i

- In quenchers with circulating pipes, the water inflow to the steam must be ensured inside the circulating pipe.

That can be accomplished by an arrangement Iike the one illustrated in Figure 10.

- Steam gets that blow out opposite one another must have a

large enough spacing that there is no combining of steam into a larger volume near the boiling point.

This point is especially important for cross-shaped perforated pipes with horizontal blowdown direction..

3"40 If

5 f

7. Outlook and roblems remainin o en Basic information concerning the condensation behavior with model quenchers and parts of larger quenchers were obtained with the avaihble test stand.

Extrapolation to the conditions existing in the reactor met with some difficulty due to the limited capa-city of the steam generator that was used.

To continue the work, the model test stand is being connected to a high-pressure steam boiler.

That will provide a capability for operating model quenchers with higher steam prepressures corre-sponding to reactor conditions.

Zn addition, much larger parts

'f actual quenchers can then be used.

To optimise the configuration of hole arrays, further tests are planned with perforated-pipe quanchors in which the water flow between longer rows of holes will be studied.

Of utmost importance here is the variation of the mass flow density in the individual hol.es.

A possible increase relative to the values used as a basis heretofore would permit a reduction of the required quencher dimensions.

The model test stand has proved very well suited for clarifying all the phenanena that occur during vent clearing and condensation, especially through its vd.sual observation capabili<ies.

It was also possible to interpret processes for which no explanation was found initially by measurements in the GKN test stand.

Purther investigations will make the results found heretofore more certain and will axtend the theoretical analyses over a wider range of parameters.

3-41

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