NUREG/IA-0187

International 

Agreement Report 

RELAP5/MOD3 Analysis of 

BETHSY Test 6.9c: Loss of 

RHRS: SG Manway Open 

Prepared by 

G. R. Kimber, M. A. George 

AEA Technology 

A32 Winfrith 

Dorchester, Dorset DT28DH 

UNITED KINGDOM 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001 

August 2000 

Prepared as part of 

The Agreement on Research Participation and Technical Exchange 

under the International Code Application and Maintenance Program (CAMP) 

Published by 

U.S. Nuclear Regulatory Commission
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NUREG/IA-0187

International 

Agreement Report 

RELAP5/MOD3 Analysis of 

BETHSY Test 6.9c: Loss of 

RHRS: SG Manway Open 

Prepared by 

G. R. Kimber, Mý A. George 

AEA Technology 

A32 Winfrith 

Dorchester, Dorset DT28DH 

UNITED KINGDOM 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001 

August 2000 

Prepared as part of 

The Agreement on Research Participation and Technical Exchange 

under the International Code Application and Maintenance Program (CAMP) 

Published by 

U.S. Nuclear Regulatory Commission
ABSTRACT

Accidents associated with a loss of the Residual Heat Removal System (RHRS) during PWR 

shutdown operation have received attention in recent years. Typically such events occur at low 

pressure and low core power. 

A series of tests, 6-9a-d, has been performed in the BETHSY Integral Test Facility at Grenoble, 

France, to address the safety issues posed in this type of incident. The data from Tests 6.9a,c & d 

are available to the AEA Technology through its membership of the BETHSY Club. 

Tests 6.9a & d have been analyzed in previous years. Test 6.9c, the subject of this report differs 

from previous tests as it simulates plant conditions following a loss of RHRS when the primary 

circuit is open in two places; one at the pressuriser manway and the other at the steam generator 

outlet plenum. There is thus the potential for a large inventory loss from the primary circuit and a 

deep core uncovery. This did in fact occur. The analysis of this test is directly relevant to PWR 

thermal hydraulics safety issues associated with loss of RHRS. 

The analysis has been performed using the latest release version of RELAP5, i.e. MOD3.2. The 

main phenomena occurring during this rest are well represented by the calculation. The calculated 

primary circuit peak pressure matches the experimental value. The reduction in pressure following 

the peak is, however, delayed due to water draining from the steam generator and being entrained 

into the pressuriser. 

The cladding temperature rise is delayed and the start of the gravity feed is about 150s late. 

Ultimately, however, the experimental peak clad temperature is matched to within 15oC. The mass 

error associated with the calculation is less than 10% for most of the transient. 

It is concluded that the broad characteristics of the transient would be experienced in a similar 

scenario for PWR plant. The analysis will also form the UK submission for the International 

Standard Problem 38 being hosted by AEA Technology at Winfrith.

iii
CONTENTS 

1. Introduction ............................................................... 1 

2. Rig configuration .......................................................... 2 

3. RELAP5 model ............................................................. 3 

4. Initial conditions ........................................................... 3 

5. The transient and RELAP5 calculation comparison .............................. 4 

5.1 Phase I (Os - 2670s) ..................................................... 4 

5.1.1 Pressure response ................................................... 4 

5.1.2 Flow in control rod guide tubes ....................................... 5 

5.1.3 Core bypass recirculation ............................................ 5 

5.1.4 Hot leg I conditions ................................................. 6 

5.2 Phase 2 (2670s to 5660s) .................................................. 7 

5.3 Phase 3 (t=5660s to 9044s) ................................................ 7 

5.4 M ass error ............................................................. 8 

6. Implications for large PW R plant ............................................. 8 

7. Conclusions .................................................. ............. 9 

Acknowledgement .......................................................... 10 

References ................................................................ 11 

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LIST OF FIGURES 

Fig. 1. Schematic diagram of rig circuits 

Fig. 2. Primary cooling system - Plan view 

Fig. 3. Primary cooling system - Elevations 

Fig. 4. Pressure vessel - General view 

Fig. 5. Pressuriser manway configuration 

Fig. 6. SG1 outlet plenum manway configuration 

Fig. 7. Identification of transducers in the vessel 

Fig. 8. Identification of transducers in the loops 

Fig. 9. RELAP5 noding scheme for BETHSY integral facility 

Fig. 10. RELAP5 noding for BETHSY vessel 

Fig. 11. RELAP5 noding for BETHSY loop 1 

Fig. 12. RELAP5 noding for BETHSY loops 2 & 3 

Fig. 13a. Hot leg 1 void fraction (0.0 to 4000s) 

Fig. 13b. Hot leg 1 void fraction 

Fig. 14. DP in surge line 

Fig. 15. DP in pressuriser 

Fig. 16. DP in hot leg 1 vertical section 

Fig. 17. DP in SG 1 inlet plenum 

Fig. 18. DPinSG 1tubes 

Fig. 19. Upper plenum pressure 

Fig. 20. DP in intermediate leg 1 - pump side 

Fig. 21. Total mass flow through upper head - downcomer link 

Fig. 22. Steam mass flow through upper head - downcomer link 

Fig. 23. Flow through core bypass 

Fig. 24. Core inlet temperature 

Fig. 25. Liquid fractions in hot leg 1 volumes 

Fig. 26. Integrated mass flows near surge line 

Fig. 27. Integrated mass flows in hot leg 1 

Fig. 28. Pressuriser manway discharge rate 

Fig. 29. SG outlet plenum manway mass discharge 

Fig. 30. DPs in intermediate leg 1 

Fig. 31. Gravity feed mass flow rate 

Fig. 32. DP in core 

Fig. 33. Primary circuit mass 

Fig. 34. Peak clad temperature 

Fig. 35. Mass error(l), cpu time (2), & relative mass error (3) 

Fig. 36. Primary circuit mass with mass error correction

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1. Introduction 

A safety issue of primary concern is the management of PWR plant following the loss of the 

Residual Heat Removal System (RHRS), particularly if the primary circuit is open and 

partially drained. The system pressure will be low, typically < 3 bars, and core power will 

be about 0.5% of its nominal value. The analysis of such situations has not hitherto received 

as much detailed attention as other transients. Following an incident at the PWR plant at 

Vogtle in 1990 the USNRC commissioned studies by INEL[1 & 2] to investigate the key 

phenomena involved in this type of event Subsequent PSA, both in France and the USA, 

highlighted the importance of cold shut down scenarios as a contributor to core melt 

frequency. The scenario is also important in considering plant management during refuelling 

and maintenance. 

There is a series of BETHSY Tests (6.9a-d) which is directly related to this issue. The 

BETHSY test rig [3] is a 1/100 scale, 3-loop integral facility at Grenoble, France, and has the 

capability for tests relevant to a wide range of LOCA and non-LOCA transients starting from 

both full power and shutdown conditions. Figure 1 shows a schematic diagram of the rig 

circuits. The data for Tests 6.9a, c and d are available to the AEA Technology through 

membership of the BETHSY Club. 

The overall purpose of BETHSY Test 6.9c [4] was to study the accident transient following 

the loss of the Residual Heat Removal System during mid-loop operation with the primary 

circuit open at the pressuriser and steam generator outlet plenum manways. This is a more 

severe condition than Test 6.9a[5], analysed previously, where only the pressuriser manway 

is open and contrasts with Test 6.9d[6] where there were only very small vents open. There 

is a significant loss of primary mass inventory in Test 6.9c which results in core uncovery 

and heat-up. These are arrested by an emergency water supply to the primary circuit driven 

by gravity alone. 

The aims of the test (as specified by CEN, Grenoble) are to study: 

a) the entrainment and temporary retention of water in the pressuriser caused by the 

steam flow escaping via the pressuriser manway, 

b) the sensitivity of the entrainment phenomenon to steam velocity in the hot legs, 

c) the level swell in the upper head, 

d) the expulsion of water through the steam generator manway, 

e) the level of pressurisation, which could jeopardise the effectiveness of the gravity 

feed, 

f) the re-flooding and re-filling of the core from the gravity (and, if necessary, forced) 

emergency core cooling water injection.

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For the analysis the underlying objectives of this work are: 

* To assess the potential of RELAP5/MOD3 [7] in: 

a. addressing the key safety issues associated with accidents at shutdown, 

b. predicting the effects of possible accident management procedures. 

"* To provide a UK submission to ISP38 to benefit from the comparison of results with those 

of other participants. 

"* To provide UK input to the BETHSY club and to take full advantage of the benefits of 

the BETHSY club membership. 

"* To provide RELAP5/MOD3 assessment required as part of the UK commitments to the 

CAMP agreement. 

This particular programme of work includes: 

1. an analysis of the test procedures and the overall course of the transient; 

2. an assessment of RELAP5/MOD3 models for mid-loop operation at low pressure; 

3. an assessment of the implications for PWR plant accident analysis. 

This report describes the analysis of the transient with RELAP5/MOD3.2, the latest release 

version. The calculation will form the basis of the submission to ISP38. Previously, in the 

interim report [8] on this work, the transient had been calculated with the development version MOD3.1.2. Although it was found that there were differences in the results in detail, broadly the two calculations were very similar. It was, however, necessary to incorporate 

some changes in the noding for RELAP5IMOD3.2 so a direct comparison was not practical. 

The calculation with the new code version will be acceptable as a CAMP in-kind contribution. 

Furthermore, it is expected that the majority of participants to ISP38 will be using RELAP5IMOD3.2 so the comparison will be more meaningful. 

The rig configuration is described in Section 2 and the RELAP5 model changes for this test 

are outlined in section 3. The initial conditions for the test are explained in section 4. The transient is described in section 5 together with a discussion on the performance of RELAP5 

in modelling the test. The implications for PWR plant are highlighted in section 6 and 

finally, in section 7, conclusions are drawn based on the analysis of the test. 

2. Rig Configuration 

A schematic diagram of the BET-SY rig circuits is shown in figure 1 and their plan and 

elevation are shown in figures 2 and 3 with a more detailed diagram of the vessel in 4. 

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The basic configuration for this test can be summarised as follows. 

The manway openings were represented by calibrated orifices with fast acting valves 

downstream. The pressuriser manway was connected to the top of the pressuriser. The steam 

generator outlet plenum manway was connected to a branch in intermediate leg 1 just below 

the SG outlet plenum and 720 mm above the hot leg axis. The details of the manways are 

shown in figures 5 & 6. 

The pressuriser was connected to loop 1. 

All the steam generators were drained down and isolated. 

For reference, the positions and the identification of the primary circuit instruments are shown 

in figures 7 and 8. The identifications are on all the graphs showing the experimental results. 

3. RELAP5 model 

The same basic nodalisation scheme, figures 9 to 12 , as used for the calculation of Test 6.9a 

was employed in this calculation. The changes to the deck were relatively few and will be 

described here. 

The SG manway was represented by a horizontal pipe and orifice at the correct level in the 

SG side of the intermediate leg. The discharge coefficient of the orifice was set in agreement 

with the test report [4]. This was also done for the pressuriser manway. The gravity feed 

was represented by a time dependant junction with the pressure characteristic taken from the 

test report. 

The number of hydraulic cells in the core has been chosen to match the heater rod structures. 

All except the end nodes are 0.26m high. A reasonably fine noding was recommended at the 

recent CAMP meeting [9] for this type of transient. 

4. Initial Conditions 

The test represented a reactor in a shut down condition with the loops filled to the mid-loop 

level. In BETHSY, this means that at the start the hot legs were half full of water, but the 

cold legs, being at a lower elevation, were completely full. For this test there was only water 

vapour in the parts of the circuit above the liquid level. The pressure was close to 

atmospheric and the core power off. 

The heat losses (primary and secondary) were balanced by the rig trace heating. The trace 

heating on the primary circuit was maintained constant throughout the transient. The 

secondary side trace heating was controlled to maintain a constant wall temperature of 105°C 

for the lower part of the SG riser throughout the transient.

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The primary circuit temperatures were very near to saturation except in the cold leg where 

the temperature was about 10 00 subcooled due to the effect of the pump cooling and the 

instrumented section where there was no trace heating. During the drain down phase of the 

experiment (not modelled) cold water from the pump seal/bearing cooling tended to be drawn 

along the cold legs. 

For the calculation the initial conditions were set by starting with the primary circuit full and 

draining it down to mid loop level. It was necessary to provide a temporary cold feed to the cold legs just before the transient was started in order to establish the lower temperatures 

observed there. 

5. The Transient and RELAP5 calculation. 

The test was started by opening the manway isolation valves and increasing the core power 

to 138kW which represents about 0.5% of nominal reactor power. 

The overall course of the transient can be separated into three relatively distinct phases: 

"* in the first phase (0-2670 s) the two phase level in the vessel remained close to the 

level of the hot leg axis; 

"* in the second phase (2670-5660 s) the mixture level fell below the hot leg nozzle and 

started to uncover the core until the gravity feed was triggered; 

" in the third phase (5660-9044 s) the core refilled under the action of the gravity feed 

until the mixture reached the hot leg nozzles again. 

These phases will now be described individually and compared with the calculated results. 

5.1 Phase 1 (Os - 2670s) 

As the liquid was close to the saturation pressure at the start of the test, the increase of core 

power and the opening of the manways led to rapid boiling and the entrainment of water into hot leg 1, thence in to the surge line and pressuriser. Two phase mixture was also entrained 

into the vertical sections of the hot legs and into the up-flow side of the SGl u-tubes, (figures 

16 to 18). 

5.1.1 Pressure response 

By comparing the calculation with the experimental data, figure 13a & b, it is clear that the 

void fraction in hot leg 1 is well matched. The entrainment in the surge line (as reflected in 

the DP measurements), figure 14, and the pressuriser, figure 15 are also well matched. After 

the start of the transient, less water is entrained into the pressuriser surge line from the hot leg. This allowed the water to drain down from the pressuriser into the surge line. It appears

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that only a limited amount of water (possibly none) escapes from the surge line before it is 

driven back up into the pressuriser again. The cycle is repeated three times before the pressure 

falls. This complicated behaviour is reproduced quite well by the code but an extra cycle 

arises and the pressure fall is delayed. 

The mixture also flows up into the SG inlet plenum and the SGI tubes (up-side) only. The 

amount of water present in the vertical portion of the hot leg is in good agreement with the 

experiment, figure 16, but the liquid held-up in the SG inlet plenum is low, figure 17. 

Initially the hold-up in the SG1 tubes (up-side) is slightly high, but the peak is correctly 

predicted, figure 18. There is, however, late emptying of these components (figs 16,17,18) 

The liquid entrainment in the pressuriser and surge line noted above leads to a rise in the 

upper plenum pressure during phase 1 of the transient. This is evident in figure 19 and it is 

seen that the calculation closely matches the initial pressure peak. As a consequence of the 

pressure rise, water is driven towards the SG manway from the cold legs. The DP 

measurement in the SG side of the loop seal is shown in figure 20. It is seen that the DP rise 

reaches 3.0xl04

Pa, the pressure required for liquid to flow out of the manway, but only for 

a short time (-200s) compared with 1000s in the test. It will be seen later, however, that the 

calculated flow through the manway over this short period is about the same as that over the 

longer period in the experiment. 

In both the calculation and the test, the system pressure rise is not sufficient to cause the loop 

seal to clear in loop 1. The calculation, however, comes nearer to a clearance. After 2000s, 

when the pressure falls and the water redistributes itself, the intact loops refill completely but 

the loop seal only partially refills because more water had been ejected through the SG 

manway. There is sufficient water left, however, to provide a seal and prevent steam reaching 

the SG manway via the cold leg. 

5.1.2 Flow in control rod guide tubes. 

Some of the vapour generated in the core escapes up the control rod guide tube and down the 

upper head - downcomer link where it condenses in the downcomer inlet and cold legs which 

are emptying. This vapour flow is important as it reduces the rate of energy discharge from 

the primary circuit. The experimental results indicate that the flow is only steam. The 

calculation over-estimates the mass flow, figure 21, due to the presence of some water being 

carried over but the mass flow of the steam only is well predicted, figure 22. At its peak this 

flow represents about 25% of the vapour being generated in the core. 

5.13 Core bypass recirculation 

A further feature of this part of the transient is the core recirculation which occurs around the 

core and the core bypass. The flow is downwards in the core bypass and leads to subcooled 

water reaching the bottom of the core. There is a resultant effect on the core void fraction 

profile and the vapour generation. The flow is not measured in the rig but the estimated 

magnitude is 5 kg/s. Figure 23 shows that the calculation predicts about half this value 

(downwards flow is shown as positive). Prediction of the flow in the bypass is not 

straightforward because of the presence of formers maintaining the shape of the core shroud,

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which protrude into the core bypass gap. The discrepancy, however, is not fully understood. 

But, as the calculated flow at 2.5 kg/s is significantly greater than the steam boil-off rate of 

-0.07 kg/s most of the water entering the core will be recirculated from the core bypass rather 

than drawn in from the lower plenum. Thus core inlet temperature will still be largely determined by the core bypass temperature. It can be seen, figure 24, that this is essentially correct: the main difference between the two curves occurs when the calculated pressure is 

higher than in the test. 

5.1.4 Hot leg 1 conditions 

The predicted conditions in the hot leg 1 have received some attention. Almost entirely throughout the transient horizontal stratified flow is calculated and this agrees with the 

interpretation of the gamma-densitometer beam traces from the test. Significant wave 

formation is not expected as the vapour flow is about 1/3 of the Kelvin - Helmholtz criterion 

for sustained wave production. The void fraction in hot leg 1 is well predicted although it 

remains at about 0.8 for about 1000s longer than in the test and doesn't empty completely as 

the experimental data appear to show. 

Figure 25 shows the liquid fractions at each of the calculation volumes along the horizontal 

section of hot leg 1, with the bottom curve representing the volume nearest to the vessel. The 

average liquid fraction here is significantly lower than at the far end of the hot leg where it 

is almost entirely above 0.5. Liquid surges emanating from the vessel (indicated by peaks in the curves) appear' to be carried along the length of the hot leg. But surges which appear 

to come from the far end of the hot leg are not generally seen as significant increases in the 

liquid fraction close to the vessel. This suggests that there is a tendency for liquid from the 

steam generator tubes and inlet plenum to be entrained into the surge line as it flows back 

along the hot leg. 

In figure 26 curves 1, 2 & 3 show the calculated integrated junction mass flows at the 

junctions before, after and at the surge line respectively. (Note: the vertical scale does not 

give a true value but the trends in the curves are correct and can be observed more easily). In curve 3 there are three short periods of a steep increase in the curve when a significant 

amount of water is entrained into the surge line. The first period is around 100s into the 

transient and is a result of the initial level swell as the liquid in the vessel boils. 

Subsequently there continues to be a flow along the hot leg, but there is no corresponding liquid entrainment into the surge line as the liquid fraction is too low. From around 750s 

water flows back from the steam generator for a short time but then there is a reversal of the 

flow and quite a sudden increase in the liquid fraction. This increase gives rise to a significant 

water entrainment into the surge line. Near 2000s there is a reversed flow along the hot leg and again further entrainment into the surge line. 

An indication of the liquid entrainment into and out of hot leg 1 can be seen in figure 27. 

Plotted together for comparison are the integrated value of the liquid mass entrained into the 

'The full resolution of these points is not possible at the plotting frequency of these 

graphs.

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hot leg nozzle, (curve 1), the pressuriser surge line (curve 2), the right angle bend at the end 

of the hot leg (curve 3) and the SG tube plate (curve 4). There is a significant entrainment 

into the hot leg nozzle, the surge line and the vertical part of hot leg 1 over the first 100s. but 

there is a delay of about 600s, while the SG inlet plenum is filling, before the liquid is 

entrained into the SG tubes. The reversed flow around 2000s (noted above) is seen to come 

from the emptying of the SG tubes and follows a reduction of entrainment into the hot leg. 

5.2 Phase 2 (2670s to 5660s) 

Throughout this phase the system pressure remains close to 1.02 bars because the pressuriser 

is empty. The core starts to uncover at about 3433s. There is no steam flow through the 

upper head bypass at this time. 30% of the vapour escapes through the pressuriser manway 

and 70% through the SG manway, via the SG tubes. Figures 28 & 29 show the calculation 

to be in good agreement during this phase. 

From figure 30 it is seen that there is a slightly greater pressure at the pump side of the 

intermediate leg than at the SG side, which is a measure of the pressure loss experienced by 

the steam as it flows from the core to the SG manway. The difference is correctly reflected 

in the calculation, although the levels are lower because more of the loop seal liquid has been 

ejected. The result is taken as confirmation that the friction loss in the pathway from the 

upper plenum to the SG manway via the steam generator is correct. 

At 5660s the core cladding temperature reaches 250 0C in the upper level of the core. At this 

temperature the gravity feed is triggered. The time is about 150s late in the calculation, figure 

31. The collapsed level at this time, as indicated by the DP measurement is low by about 

0.1m (figure 32), despite the fact that initially there is a significant under-prediction of the 

level. The actual mixture level is about 2 m above the bottom of the heated length. 

5.3 Phase 3 (t=5660s to 9044s) 

Since the system pressure is low the initial gravity feed is about at its maximum (0.125 kg/s) 

and this is approximately twice the estimated rate of boil off in the core. Thus there is 

sufficient flow to refill the core and primary circuit, figure 33. 

The injection is into cold leg 3 and this causes condensation to occur in the region of the 

downcomer inlet. The flow in the upper head - downcomer link then becomes re-established 

in the test and the value is well matched in the calculation. There is not a sustained reduction 

of the flow in the pressuriser manway as occurs in the test. The effect is, however, evident 

in the SG manway discharge. The condensation does, however, help to maintain a low 

pressure level (-0.97 bar) in the cold leg and so the gravity feed is sustained. The core 

becomes re-covered by 6805s. 

The maximum temperature reached by the heater rods was 305 0C, but this is over-predicted 

by 15 00 in the calculation, figure 34. The first peak in the calculation curve is at a level of 

2.7m above the start of the heated length. The second peak is at 3.6m and this is also the

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level of the experimental curve. 

In the calculation the temperatures at all the three upper zones i.e. >2.7m are similar whereas the experimental data show a peak of 450K at 2.7m rising to 575K at 3.6m. 

Finally, the test was terminated when the hot leg void fraction was about 0.8 at 9044s. The calculation was extended to 10000s but the primary inventory, see figure 33, was not 

recovered. 

5.4 Mass error 

A matter of concern with RELAP5 calculations at low pressure has been the occurrence of 

mass error. The mass error is known to be sensitive to pressure, time step, and, as identified recently by PSI [10], the bubbly/slug interfacial shear package. 

For the calculation presented here the run statistics are shown in figure 35. The mass error (curve 2) increases most rapidly during the first phase of the transient and after 6000 s. At its peak the mass error is about 20% of the primary mass inventory. If the mass error is added to the primary inventory then an almost perfect match to the experimental data results is obtained, figure 36. This confirms that the mass error is a 'mass loss'. Inspection of the 

output file shows that the cells which have had the largest error are widely distributed around the circuit The cell which recorded the largest mass error most frequently was in the 

intermediate leg for loop 22. 

6. Relevance to large commercial PWR plants 

It is noted that the BETHSY facility is a scaled (-1% by volume) representation of a 3 loop PWR. In constructing the facility some design compromises are inevitable which preclude an absolutely precise comparison with PWR plant. Further there are design differences between individual plant and the rig (the pressuriser surge line is one example) 

The implications for the management of a shut down event of the scenario analysed here has been discussed in previous reports ([11] & [12]) on the tests in this series. With the analysis made here more information is now available about the transient. The conclusions drawn in those reports, however, are still valid. It was that "the broad characteristics of the transient would be present in a similar scenario for the plant There are, however, design characteristics which would probably result in a higher pressure level in the plant and possibly 

a less effective gravity feed." 

It can now be seen that with the SG manway open the pressure rise in the primary circuit will be limited. Higher pressure may result from (say) an alternative siting of the pressuriser surge 

2 A calculation with a more recent development version of RELAP5, i.e. MOD3.2.1.2, 

shows the mass error reduced to -5% of the primary mass inventory. 

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AEA CS 16423592/V02jNAL REPORT
AEA/16423592/002/FINAL REPORT

line junction (e.g. at the bottom of the hot leg) since more water will be forced up into the 

pressuriser line. The peak pressure reached may well be higher but this will mean that the 

loop seal in the leg with the open SG manway will clear and open up another route for steam 

to escape from the primary circuit. There will thus be three paths by which vapour can 

escape from the circuit but the actual balance of flows will depend on the flow losses in each. 

The important point is that the pressure should not rise very high and so an effective gravity 

replenishment of the primary circuit inventory should be assured if no power was available 

to drive a forced feed. 

Further design differences concerns the bend at the end of the hot leg which may be inclined 

at less than the 900 of the BETHSY rig. The differences will be manifest in two ways. For 

the steam flow there will be less loss at the bend. The amount will depend on the radius but 

must inevitably reduce the losses in the steam path to the SG manway compared to the 900 

bend. For small pipes reference [13] suggests that there is no effect of pipe inclination on 

the onset of flooding although there are observed differences in flow patterns. It is reported 

in [14] that the Wallis correlation is not applicable for large pipe diameters. Although the 

CCFL model was activated at the bend for this analysis, the output from the calculation shows 

that the conditions did not arise for it to be applied. It is therefore unlikely to affect the 

response of the plant significantly. 

7. Conclusions. 

1. From the study of the experimental data it can be confirmed that the aims of the test 

were satisfied and good information is provided on the phenomena that were involved. 

The measurements are of the same high quality that has been evident in the analysis of 

previous tests. 

2. The full transient has been calculated with the latest release version of the code, 

RELA /MOD3.2. No code failures were encountered. 

3. The main phenomena in the test are correctly represented in the calculation. The primary 

pressure peak is well matched although the reduction in pressure is delayed. This 

appears to be due to water draining from the steam generator tubes and then being 

entrained up into the surge line. It is not possible to determine whether this effect 

occurred in the test. 

4. The mass error remains less than 10% of the primary mass for the early part of the 

transient until the gravity injection phase when it rises to a peak of 20%. The under

prediction of the primary mass is almost precisely accounted for by the mass error. 

5. The clad temperature rise is initially delayed but then is slightly more rapid than in the 

test. The gravity feed start is delayed by 300s but is still able to arrest the rise in 

temperature. The peak temperature is overestimated by 15 -C. 

6. In considering the implications for PWR plant it is anticipated that the course of the

9 AEA Technaoky 

AEA CS 16423592=002/PINAL REPORT
AEA/16423592/002/FINAL REPORT

transient will be similar. Higher pressures may occur due to differences in detail design but the effects will be limited since only a small increase in pressure is necessary to 

clear the loop seal and provide a further route for steam escape. 

Acknowledgement 

This work was performed under contract to Nuclear Electric plc. 

The authors gratefully acknowledge the assistance of M R. Deruaz and M G. Lavialle of CEA 

Grenoble in clarifying particular points about the data and the test.

10 AEA Technolog 

AEA CS 16423592/V02/FJAL REPORT
AEA/16423592/002/FINAL REPORT

References 

[1] Consequences of the Loss of the Residual Heat Removal Systems in Pressurised Water 

Reactors. L W Ward et al NUREG/CR-5820 May 1992 

[2 ] Thermal Hydraulic Processes During Reduced Inventory Operation with Loss of Residual 

Heat Removal. S A Naff et al. NUREG/CR-5855 

[3] BETHSY General Description. CEN Note SETH/E/90-97 April 1990 

[4] BETHSY - Test 6.9c: Loss of Residual Heat Removal System during Mid-loop Operation. 

Pressuriser and steam generator outlet plenum manways open. Test Report. G Lavialle CEN 

Note STR/LES92-110. December 1993. 

[5] BETHSY - Test 6.9a: Loss of Residual Heat Removal System during Mid-loop Operation. 

Pressuriser Manway Open. Test Report. G Lavialle. CEN Note STR/LES/92-1 11. December 

1992. 

[6] BETHSY - Test 6.9d: Loss of Residual Heat Removal System during Mid-loop Operation. 

Primary system partly open. Test Report. B Noel CEN Note STR/LES/93-140. August 1993. 

[7] RELAPS/MOD3 Code Manual. Volumes I to VI. The RELAP5 code development team 

NUREG/CR-5535 June 1995. 

[8] RELAPSIMOD3 Analysis of BETHSY Test 6.9c Loss of Residual Heat Removal System 

Pressuriser and Steam Generator Outlet Plenum Manways Open. Draft report. G R Kimber 

AEA/16423592/001. November 1995 

[9] RELAPS. G Johnsen. Presentation at the CAMP meeting. Pennsylvania State University. 

October 1995 

[10] Effect of wet wall interfacial shear correlations on the mass error of RELAPS/MOD3.1 

G Th Analytis, Transaction ANS Winter Meeting San Francisco. October 1995. 

[11] RELAP5/MOD3 Analysis of BETHSY Test 6.9a Loss of Residual Heat Removal System 

Pressuriser Manway Open. G R Kimber AEA RS 5644 March 1994 

[12] RELAP5/MOD3 Analysis of BETHSY Test 6.9d Loss of Residual Heat Removal System 

Primary System Partly Open. G R Kimber AEA/CS/16401552/002 March 1995 

[13] Countercurrent flow limitation in inclined channels with bends. S M Ghiaasiaan et al. 

Nuclear Engineering and Design 152 (1994) 379-388. 

[14] The CCFL option in the Sizewell Project version of RELAP5/MOD2. M J Dillistone,W 

M Bryce. AEEW-M2574 1989.

11 AEA Techology 

AEA CS 16423592O2JF1NAL REPORT
= 

-

N N 47
Broken loop

stirge line

N SGI ACC :accumulator 

S nozzle 

I SI safety Injection 

nozzle 

NS : normal spray 

nozzle 

--. spool pieces SG3 pressurizer 

pump pressure vessel 

NS 

SIACC Sl downcomner • spool solpee pieces 

spool 

pieces 

SG2

SI 

Inloct loops NS

Figure 2 Primary Cooling System - 'Top View
Steam generator

Pressurizer 

20655

20371 

relief nozzle 

Pressure vessel 8724

rnD[ -8257.

3656

0 

C

18335 

16870 

7748

cold leg -- 4794 

(axis)

k )=, 2595 (axis) 

intermediate leg

V 

0 

V

_A- 0

~-2164

Figure 3 Primary Cooling System - Elevations 

15

cold 

leg
cold leg 

nozzle

BB View

thimbles

,upper core support plate 

hot leg nozzle

,upper core ani tie plates 

428 full le.gib HR 

cosine axid power 

17 x 17 desqn 

29 guides fimbles 

uniform

core by-pass

Figure 4 Pressure vessel - General view

16
Sicontrol system measurement only

Ball valve

or 

P* PB

Loss of R.H.R.S - Pressuriser Manway Arrangement.

towards 

atm. 

flow

cn 

'0

3

d~tail A

o 120

Figure 5
diaphragm o 41 C-i control system measurement only

(manway simulation)

-9000+

500

4 1 A424 

TP47 904A I-Hl904B 

I 9O1A 901B 

903A DPQBGV3 903B 

TPBGV DPQBGV1 

DPQBGV2

DPQBGV2

480

(through W" 

and 84 pipe:

Ball valve o 150

DPQBGV1

H.L. axis

904A/B

diaphgragm 0 41

0,3 

03

e6. SG1 outlet plenum manway configuration

09 W!

1225 (with

11i

DP12VGB z=15o 

DP12VGA 

z-680

70A

Figure
M• Control sysiam measurements only 

.. A 3 guide thimbles Instrumented 

with TC

DP034

- POZ 

OPORI/OPCUV

Q05B 

Q05

o Fluid TC * Struclure TC

Pressure vessel. Gauge and differential 

pressure measurements

Pressure vessel. Temperature (except 

HR cladding) and flow rate measurements

Figure Identification of transducers in the vessel 7.
SGI side

'-• IFI141 

tIL 

1WPIIV 

\ Pressure lop 

iumbe! ilg

- J Luntrol system measurement 

only

o iu1uiu iup 

Structure thermocouple 

o Fluid thermocouple 

I Turbo probe 

i - I loop I 

I - 2 loop 2 

I a 3 loop 3 

IIflfM. 

VP' 

Pompe I 

DPi2P P P I I 

i2PG 1 4 -

Hot leg n1l instrumentation

Accumulator 

nozzle, [ Sl nozzle on CLI

TFi21 

TPi 21

VI21

'Pressure top 

numbering

Cross over leg instrumentation

e8. Identification of transducers in the loops

Pressure 

vessel sil

SGI

Down comer 

side (DC)

12H

Figure
STEAM LINES

FEEDWATER 

SUPPLIES

N.3

cross-flow 

junction

< valve

time dependent junction

HPIS/1

HPISI2

LPIS

SAFETY INJECTION SYSTEMS

RELAP5 noding scheme for BETHSY integral facility Figure 9.
bypass orifice 

plate position 

upper head to 21 

downcomer 

bypass

2002 

cold legs 2003 

2004

guide tube 

orifice plate

1505 

1506 

1507

hot legs

upper plenum 

-• internal core 

bypass 

gion 

heater bundle

time dependent junction

FIG 10 RELAP5 NODING FOR BETHSY VESSEL

22
7 6- 7 5200 5492 5600 

32 4 9j 

S 3 5103 

134• Z_/[I 3 02 

S G Manway 145 440 501 

S133 14100 1505 

..... 1-3 hot lea cross-flow 

- 1420 nozleFjunction 

13602 146 47 .. 14801 13801 13802 2002 valve 

148 137 13870139 nozzle time dependent 

013601" junction 

04 071210 151 accumulator 

05 122 

FIG 11 RELAP5 NODING FOR BETHSY LOOP 1 

HPSI / LPSI
relief valve 

27700 atmosphere

x cross-flow 

junction 

valve 

- - time dependent junction

HPSI / LPSI

Figure 12. RELAP5 noding for BETHSY loops 2 & 3

24

26201 

26203 

27500

260 

235
WORK AREA 1: RELAP5/3.2 96-Jan-19 15:53:39 StripT 

WORK AREA 2: BETHSY PER RRA (PR BF)O Fri Nov 24 11:46:42 1995 BETTRA 

1.0 

0.9 

0.8 1 J f- - - -I- - -

V I I 

0.7-- - I 

IfI \r I I 

1 II II 

54 I 

1 0.5 -------- ------ J I - I

0 I I I I 

0 11 fI I I I I I I 

4 41- 0.4 --- -- t -- - '-- ------------------ I..----------I - - -I- - -

f .4 .* I I I I III 

I I I IIII 

>. 0.3 -- -------- -4 ------- 4------- 4--------------------

0 . - ! I -I - - -- -- - - - -- I -I 

21:lli -a~) ieWP RA 2 1 1 1 

SI I I I. IIII 

S0 .0 • -- 4 L- -I 

1 I I I I I I II 

0 50 100 150 200 250 30030040 

I I I I I I I 

S0.1 -I-: • 4 -4-- - -• ---- -- -- -

I I/ III III I I 

0. I - IIIII - 0. 50 10010 0020 4000 0030 

Time (s) 

Fig. 13a. Hot leg 1 void fraction (0.0 to 4000s)
WORK AREA 1: RELAP5/3.2 96-Jan-19 15:53:39 StripT WORK AREA 2: BETHSY PERRRA (PRBF)O Fri Nov 24 11:46:42 1995 BETTRA 

1.0 _-______ 

0.9 I 

1.0 • , , -- ----- -- ; ------- 4- -- -,, 

I I :' 

0.8 T -- - - -1 I - - - - -- i I ---- 

l-I - - - - - - - - -

4, 1 

0.5 - -- -, -' - J- - - - -

o !III -•i I I l 

.IJ I I I II I U i 

0.4 --------------- - ------- ---------- ------------

"0II I I 

I I 

0. 0-5 1 - - -1 -j ------ _ 

0II I I 

•>II I I 

I I I I 

0I I I 

II I II 

II II I I I 

Time (s) 

Fig. 13b. Hot leg 1 void fraction
WORK 

WORK AREA 2: 

2.5 . -

xlO0 

2.0

1.5 

1.0

0.5 

0.0

0

AREA 1: 

BETHSY

RELAP5/3.2 96-Jan-19 15:53:39 Stri T 

PER RRA (PRBF)O Fri Nov 24 11:46:42 199 - F - i 

-I-i-- (p( r=v13201)-p(v=v09301)) time-220.0 WORK AREA 1 

2 dp(])PDIM=DPP3) time WORK AREA 2 I I I 

I 1 I 1 I 

I I I I ---- ------ ---- - -- --------------.. I I II 

-I IJ

- -

II 

I I 

II 

I1I 

.III 

----------

I - - -7- - - - - -

I

I A9 m 

• I I

I - -- I --.----------.----------- 4------------I--------

2000 4000 6000 8000

Time (s)

Fig. 14. DP in surge line

BETTRA

--.i

a, 

54) 

0) 

P4 

0D

10000

I

I

I I I
WORK 

2.0 

xl04 

1.5

,-0

0-

1.0 

0.5

0.0 -

WORK 

AREA 2: a

I ' 

II 

II 

III I 

II

AREA 1: 

BETHSY

II 

ta 

Ig 

III

RELAP5!3.2 96-Jan-1.9 15:53:39 StripT PER -

RRA -ri(PRBF) 0 Fri Nov 24 11:46:42 1995 

i i I 

-- 1--- (p(v=v0.301)-p(v=v05501)) time-220.0 WOPId AREA 1 

2 dp (DPDIq=DPPI) time WORK, AREA 2

Ir

LUJI 

III 

Ijf I 

till 

Iilli

11P-1- .- i- I

0 2000

I I I I 

Si--------: 

I I I 

II I I 

It I I I 

II I I I 

It I I 

II I I I 

I I I I

4000 6000

-

I I

8000

BETTRA

10000

Time (s)

Fig. 15. DP in pressuriser

I I I I"I 

II---------- --------------------- -----------

III III Vil III 

-----------------

I 

I I 

I

I

I I

I I 

I 

I

I I 

I 

I
AREA 1: 

BETHSY

RELAP5/3.2 96-Jan-19 

PER RRA (PRBF)O Mon S- - " 

15:53:39 Stri T 

Aug 21 16:27:53 1995

SI I I 

-- 3--- (p (v=vl3301)-p (v=v13303)) time-220.0 WORPX AREA 1 

2 dp(DPDIq=DP11V) time WOR AREA 3 i R

WORK 

2.0 

xlO 

1.5

2000 4000 6000 8000

Time (s)

Fig. 16. DP in hot leg 1 vertical section

WORK 

AREA 3:

I I a I I 

I I 

I III ---------------. L---------.---------------

'a I I 

a a I a a a 

a' 1 a - al I' a 

al I a I SI I 

aa a a 

I I I 

. I |. -

BETTRA

1.0

04 

a,) $4 

0

0.5

0.o0 - - - -

0 10000

I
a4 

a) 

14 

aj 0) 

a1) 

0

WORK 

WORK AREA 2: 9N ,I

AREA 1: 

BETHSY

RELAP5/3.2 96-Jan-19 15:53:39 

PER RRA (PRBF)0 Fri Nov 24 11:46:42 - - 2 I I I 

-- i--- (p(v-v13303)-p(v=v13401)ý time-220.0 WORI AREA 1 

2 dp(DPDI4=DP41) time WORK1 AREA 2 

x10 4 I I II III 

II II 

II III 

1.5 - -.1I - - -- - - - --L - - - -- --III L - - - - -- - - - - -- - -- - - - -- -

1 - - - I III 

1.0 - II! --------------------------------------------

I I I I 

I. - IIII

0.5 

0.0

2000 4000 6000

Time (s) 

Fig. 17. DP in SG 1 inlet plenum

StripT 

19-95 BETTRA

0 8000 10000

I

I I I I

I 

I
PA 

Volume Pressure (Pa) 

o 0, I- x 

o .... 0 • 

0O 

-wr 000 

tlt 

-' ,=_ I l- )

""U C 

'4 4 

ONN 

I I 

ItI 

ItI I I 

CDI 

_ CDIe~
WORK AREA 1: 

AREA 2: BETHSY I a

RELAP5/3.2 96-Jan-19 15: 

PER RRA (PRBF)0 Fri Nov 24

I--1---p(v=v01.01) time-220.0 WORK AREA 1

53:39 StripT 

11:46:42 1995

2 p(p#dim=p#03B) time WORKIAREA 2 I II I 

-------------------------- ---------- 1--- ---- -4------ ---------- -----

-- I I I I ! I I! 

I! I I 

I I I II 

1" 1------.t----------1----------------------

I II 

1 .2 - %- . --------- ---------- ----- -, ----_ -.. 

-I I. I - - -I ' I' - -I I / 

"1.2 - - - - - S- I I 

II&II'II I ,v, -- II I 

I I 

III II

III II 

I ' I. I I

-a I I I I.

0 2000 4000 6000

Time (s) 

Fig. 19. Upper plenum pressure

8000

WORK 

1.5 , 

X10 

5 

1.4

1.3 -

BETTRA

1.

¢0 

ca~ (jD 

co 

r-4 

0

0.9 -

U.?,

10000

I I

I

I I I

I 

I !

I I I 

I
apls dtund - ~ I 2aauipatuialui U! dL[ 0Z -2i! 

00001 0008 0009 0~00 0O0o 0 

I I I I 0*0 

L-------------------------------.1-----------------T- * 

r~~ ~ ~ ~ -I - 4 IV I * 

I I I I I 

t - - - -I 1 

I I I I d) I&=A 

T

9LL 66T Cg*LZ9T TZ6n bri O~ N O('99id) vu daid XSHIL3G vaziv MOM 

Lt~jS 6CC:T 6T-UPP-96 Z*E/gdvqalU :1vau UV OM
t7c

KG/SEC 

Combined Liquid and Vapour flow Rate (kg/s)

0

""II - ••c =•.. --T--------------- r j ------- -TI ------ I-- --

I

II I I ------------------------- I----------- --------- -------- -I, 00 

I > II 

I-I I 

II I 

-I 4, I,,-,. I . 

I I I 

I I., I,,

------------------------ 4----------- --- ------- , 

, I,,. ,. 

I I , I I

,II IE , , I

"Is) 

W 

I 

0 

0o --- T I I

0 

tz > 

r0 

V.. 

c-n 

c.l 

tr 

to,

0 

0

p

S----------I-------I------- ' I I I I 

(I I I I 

I't-, I I I r- --. - - I I ' 

S-i"...... _ ,• ._ I I I .. . , --J-- -

_I I L I

N) 

(

00 

CD 

C', 

0O 

0> 1..

i I I I II I

I I 

I

I I 

I I

I 

I
WORK 

WORK AREA 2: 

0.020 1t

AREA 1: 

BETHSY

RELAP5/3.2 96-Jan-19 

PER RRA (PRBF)O Fri Nov - -7 - a

15:53:39 StripT 

24 11:46:42 1995

0.015

0.010 

0.005

0.000 

-0.005

4000 6000 

Time (s)

Fig. 22. Steam mass flow through upper head - downcomer link

BETTRA

U) 

u-i 0 

'-I 

.4-I 

U) 

U)

0 2000 8000 10000
Combined Liquid and Vapour flow Rate (kg/s) 

0 I I "I I-° , 

II I I"I --

SoI .. ... .J I 

I I II 

I I I IiI 

I II 

COI , * 

0II o .. . . . -J - L • I I 

I I E 

° I "CD 

I I I 1.C> 

I D 

oo 

0 IT 

CI-I 

C)D
WORK AREA 1: RELAP5/3.2 96-Jan-19 15:53:39 StripT 

WORK AREA 2: BETHSY PER RRA (PR BF)O Fri Nov 24 11:46:42 1995 BET 

3 90 i I 71 

S--1--- tempf(v-'v01201) time-220[0 WORK AREA 1 I 

382 tmp(tfdjr=tf012B) time WýRK AREA 2 

38 1 I I ' I 

IIII I 

III I I 

386 38 . I I I_ --------------------------- ---- i - ------------

384 2 -- .-- - JII I 

I I I I I 

3802 -- - - - - -- - - - ----------- t----------------------------

I I I I 

!1%I I ! 

376 ,- •! 

37 ----- "--". '• I -------------------------------- ---- ' 

II I!\ ...

I I 

370-, I III

0 2000 4000 6000 

Time (s) 

Fig. 24. Core inlet temperature

8000

'TRA

10000

a) 

4) 

I-' 

a) 

SlE-4 

.H 

0
5.0 

5 1 f (v131 e-22U I I , 2 1 0 V i V=1

-1 0 -22 5 1 

5 -3- 4 -. e fv-vl_ 3304H-t-------- ------ - - 4 (30+voidf(v=1 v13301)) time-2 0 1 

5 (4I0+voidf(vqv13301)) tuime-220 1 t g 4.0 I I I , I 4 II I I I I 

4, III I I I I 

o I I I -. I. I . . . -,-4 I I I I I I' I 

41 I I I I I 

1 441 

c3.0 

rZ43 II I I I I 

2.50 3 - - - - - --- ------- 

0 

1.0 

I I I I I I 

0.5 -- ----- -- - --- - ----. ----------- I -.. - - -------- - ------------------- -------

-,II I I I I I 

0 500 1000 1500 2000 2500 3000 3500 4000 

Time (s) 

Fig. 25. Liquid fractions in hot leg 1 volumes
2500

I 1 (vdidfj(j=j14i0000)*rho.fj (j=j,40 00)*velfj j=j1410000)*1.09360EL02) time- 20.0 

2 (v idfj(j=jO 0000)1 j( -0500 00)*velf j0500 *1.44500E03) time- 20.0 

3 (v idfj(j=jl 000) rho j=j 420 00)*velf 1 00 ) . tine- 20.0 

2000 ------------------- - ------ - - -

1 I I - I - I I I I II 

IIIII 

1000 .------------------.-- 1 -- 1----- ------ ------- I - -- -- -- L--- -- -- -L- - -L -

I II I I 

1 2 1 " 

I I I II 

0 I J - -I I -I 

I II II 

I I I II 

I III 

II.I 

-500 -1 F • 

0 500 1000 1500 2000 2500 3000 3500 4000 

Time (s)

Fig. 26. Integrated mass flows near surge line
WORK AREA 1: RELAP5/3.2 96-Jan-19 15:53:39 StripT ,1800 i i I I I I I 

, 1 (vdidfj(j=j8O50200)*rhoTj(j=j8050£00)*velfj j=j8050 .)*1.09360EL02) time- 20.0 2 (vidfj(j=j 00000)*rho j(j=j0500 00)*velfj j=105_ 00 

'1600 -- 3---- 4 df. (-j-1 M4H0+ *- H-Y1--3 H *e1-f .=) -1.04 I time 0.0 4 (vqidfj(j=j1 40100)*rhofj(j=j1340 00)*vel j= 34010 )*1.03420E02) time- 20.0 

I I I I I 

1200 - -. - • - - "- L/ - -i 

1 I " ,A 1 1 I II 

-'- -,-±------------.....------__ 

800 - - - - - -- I I 

i i I ' I' I I I 

1000 -_L - - -, - - l- - -I_ -• -" .- . .. .. _ _,t_ , 

I •\ /I I \I I l\J I 4 -- - - I i - - - - -

200 -- - - - 1-" -- 4.' --• ---...-- - - 4 - -- - _- -...... _, -- -- .

r -" - - - - - - - - - - I 

6200 

0 500 1000 1500 20 00 2500 3000 3500 4000 

Time (s) 

Fig. 27. Integrated mass flows in hot leg 1
WORK 

AREA 2:

AREA 1: RELAP5/3.2 96-Jan-19 15:53:39 StripT 

BETHSY PER RRA (PRBF)0 Fri Nov 24 11:46:42 1995 I - -ri

I I I I 

-- i--- cntrlvai (x=x0853) time-2M0.0 WORK AREA I 

2 mfj (qmd4m=qmthp) time WOtUK AREA 2

I I I I I 

I I I I I *1----------.--------------------- 4------------------- I I I Ii

I I II 

I I III

I I I I I 

+----------9---------.-------------------t--------------- --- $------- ----------- I I I II 

I I I II 

I I I I

I I I I I 

-I --.--- I I 

. II I . . '

0 2000 4000 6000 8000

Time (s)

Fig. 28. Pressuriser manway discharge rate

WORK 

600 

500 -

ý4

0 

0:-

400 

300 

200 -

BETTRA

10000

I

! 

I

I

! I I I

I I I I I

"- - - - - -. -. . . -- - - - ----

f. - - ----- - -- - - - - - - -- - -- - -- - - - -

100 

0
WORK 

600 

500 

S400 

C1

4J 

(D• 

r• 

E- ,._30 

I-40 200 g P 

0 

0 

100 

0

WORK AREA 1: 

AREA 2: BETHSY

RELAP5/3.2 96-Jan-19 15:53:39 StripT PER RRA (PRBF)0 Fri Nov 24 11:46:42 1995

i I I 

S--1--- cntrlvai.(x=x0753) time-2.0.0 WORK AREA 

2 mfj(qmdlm=qmthb3) time WPRK AREA 2

I

I I I I ----------------------- 4-- -- 4------------ I I II ! I I II "i.

- --- 41--'-- 

-

- - - -

I I I 

I I I 

I I I 

I ~II 

I I - - - - - - - - --- 0 -4- i - - - - - - - - - - - - - - I I .I I 

I I II 

I I I" I 

"I II 

I ~II 

I I I" 

III 

III 

I I 

" " - - - - - - - - - - - - - - - - - - - - - -

I I I 

I I II 

I I I 

SI I II

0 2000 4000 6000 8000

BETTRA

10000

Time (s)

Fig. 29. SG outlet plenum manway mass discharge

I I

I I

I

I I V i•

I

- - - - - - - - - - - - - - - - -

I I 

I

I I 

I I I I

I I I
(aAZTJUI) OPIS 

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NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER 

(2-89) (Assigned by NRC, Add Vol., Supp., Rev., 

NRCM 1102, and Addendum Numbers, if any.) 

3201, 3202 BIBLIOGRAPHIC DATA SHEET 

(See instructions on the reverse) 

2. TITLE AND SUBTITLE NUREG/IA-0187 

RELAP5/MOD3 Analysis of BETHSY Test 6.9C: Loss of RHRS: 3. DATE REPORT PUBLISHED 

SG Manway Open MONTH YEAR 

August 2000 

4. FIN OR GRANT NUMBER 

5. AUTHOR(S) 6. TYPE OF REPORT 

G.R. Kimber, M.A. George Technical 

7. PERIOD COVERED (inclusive Dates) 

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (If NRC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address; if contractor, 

provide name and mailing address.) 

AEA Technology 

A32 Winfrith 

Dorchester, Dorset DT28DH 

UNITED KINGDOM

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC, type -Same as above-; dfcontractor, provide NRC Division, Office or Region, U.S. Nuclear Regulatory Commission, 

and mailing.address.) 

Division of Systems Analysis and Regulatory Effectiveness 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001

10. SUPPLEMENTARY NOTES 

11. ABSTRACT (200 words or less) 

Accidents associated with a loss of the Residual Heat Removal System (RHRS) during PWR shutdown operation have received 

attention in recent years. Typically such events occur at low pressure and low core power. A series of tests, 6-9a-d, has been 

performed in the BETHSY Integral Test Facility at Grenoble, France to address the safety issues posed in this type of accident. 

The data from Tests 6.9a, c&d are available to the AEA Technology through its membership of the BETHSY Club. Tests 6.9a & 

d have been analyzed in previous years. Test 6.9c, the subject of this report differs from previous tests as it simulates plant 

conditions following a loss of RHRS when the primary circuit is open in two places; one at the pressuriser manway and the other 

at the steam generator outlet plenum. There is thus the potential for a large inventory loss from the primary circuit and a deep 

core uncovery. This did in fact occur. The analysis of this test is directly relevant to PWR thermal hydraulics safety issues 

associated with loss of RHRS.

12. KEY WORDS/DESCRIPTORS (List words or phrases that wil assist researchers in locating the report.) 13. AVAILABILITY STATEMENT 

RELAP5/MOD3 unlimited 

BETHSY Test 6.9c 14. SECURITY CLASSIFICATION 

Loss of RHR (This Page) 

Critical Flow unclassified 

(This Report) 

unclassified 

15. NUMBER OF PAGES 

16. PRICE

NRC FORM 335 (2-89)
Federal Recycling Program
NUREG/IA- 0187 RELAP5/MOD3 ANALYSIS OF BETHSY TEST 6.9C: LOSS OF RHRS: 

SG MANWAY OPEN

AUGUST 2000

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

WASHINGTON, DC. 20555-0001

yeors