ML20137Q230

Containment Issue Isolation Transient

ML20137Q230
Person / Time
Site:	Grand Gulf
Issue date:	07/31/1983
From:	Atwell J, Hwang H, Srivastava H GENERAL ELECTRIC CO.
To:
Shared Package
ML20137Q185	List: AECM-85-0376, Submits Info Re Wier Wall Overflow,Per 851021 Request.Topics Addressed Include Overflow Effect Upon Uninsulated Drywell Piping & Evaluation of Recirculation Piping Relative to Predicted Water Level.Ge Rept Re Containment Issue Encl ML20137Q230
References
123-8324, DRF-124-98, TAC-55759, TAC-57139, TAC-57140, NUDOCS 8512050195
Download: ML20137Q230 (7)

Text

. . __ _ _ --

. GENERAL ELECTRIC CO.

NUCLEAR ENERGY DIVISION SAN JOSE, CA 9512S DESIGN MEMO #123-8324 DRF #124-98 CONTAINMENT ISSUE ISOLATION TRANSIENT Prepared by: i V N* 1 II[I1 H. M. Srivastava, Principal ' Engineer Plant Piping Design l

i l

Reviewed by: N*k- maw H. L. Hwang, Principa10 Engineer i

Plant Dynamic Methods & Applications l-i r

7_/2.l&)

Approved by: .C ,

. C. Atwell, Manager Plant Piping Design l

l

' JULY 1983 0512050190 PDR ADOCK h PDR h 16 l

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_ . _ - - _ _ . - - _ _ _ , - _ _ --_ _ _ _1.__._._._.__--_____.__- _ . _ _ _ _ _ _ _ _ _ . . _ _

CONTENTS .

f*81

1.0 INTRODUCTION

. . . . . . . . . . . . . . . . . . . . . I 2.0 PURPOSE . . . . . . . . . . . . . . . . . . . . . . . 1 3.0 CLASSIFICATION OF EVENT . . . . . . . . . . . . . . . 1 4.0 DRYWELL PLOODING TRANSIENT STRESS EVALUATION . . . . . 1 4.1 RECIRCULATION PUMP . . . . . . . . . . . . . . . 1 4.2 RECIRCULATION PIPING . . . . . . . . . . . . . . 1 S.O RESULTS . . . . . . . . . . . . . . . . . . . . . . . 2 5.1 RECIRCULATION PUMP . . . . . . . . . . . . . . . 2

.; S.2 RECIRCULATION PIPING . . . . . . . . . . . . . . 2

6.0 CONCLUSION

S AND RECO M NDATIONS . . . . . . . . . . . 3

7.0 REFERENCES

. . . . . . . . . . . . . . . . . . . . . . 4 APPENDIX A - LION 401 - COMPITTER PROGRAM . . . . . . . S e

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.i, 1,0 INTRODUCTION.

Various Scenarios lead to conditions where suppression pool water may overflow / backflow over the weir, splashing onto, or partial immersion of, recirculation pumps and piping become possible. 1hezzal shock, and resulting fatigue, will add to the system imposed (Service Levels A and B) fatigue life for the recirculation piping system and.may consume'all remaining useful life. Occurrence of any other concurrent, or subsequent, loading could result in a recirculation break LOCA.

2.0 PURPOSE.

The purpose of this report is to show that if this incredible event, were to occur it would not damage the piping system to an extent whereby loading could cause a recirculation break LOCA.

3.0 CLASSIFICATION OF EVENT.

Drywell flooding is"a rare event and it is postulated to occur only once or twice during a 40 year plant life. This event can be classified as Service Level C or Service Level D event (Reference 7.1) and no

• fatigue analysis is required. .

4.0 DRYWELL FLOODING TRANSIENT STRESS EVALUATION.

Although this event is classified as Service Levels C or D event, simplified fatigue analyses were made (Reference 7.2) for the pump casing and a typical BWR-6 recirculation piping system subjected to this postulated transient. The assumptions for this evaluation were as follows.

4.1 RECIRCULATION PUMP The present capability of the recirculation pumps as documented by the Byron Jackson stress report, states the pump casing can withstand a 0

maximum temperature gradient of 350 F without any fatigue evaluation.

However, a fatigue evaluation was made with a pump casing temperature gradient of 4500F.

4.2 RECIRCULATION PIPING A fatigue evaluation was made for this event end the stresses were added to the piping stresses due to system loading and thermal transients.

The thermal gradient was evaluated for this event using the LION 401 computer program. The surface temperature of the pipe was assumed to be 700 immediately after water reaches the pipe surface. The boundary temperature and heat transfer coefficient were conservatively assumed as follows: .

4 I

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Temperature " 528 - h" .  ;

'F BTU HR-FT *F

\

70 .

0  : Time (Sec) M H 0 15 Time (Sec)

TEMPERATURE PR0cILE HEAT TRANSFER COEFFICIENT Theheattransfegto,waterincreasesrapidlyin15secondsto 1000 STU/hr F Ft and partially destroy the insulation. This causes o

high thermal gradient in the pipe. ,

5.0 RESULTS.

The results of the evaluation (Section 4.0) were:

5.1 RECIRCULATION PUMP 5.1.1 The calculated allowable cycles for this transient were 150 cycles which gives a fatigue usage factor of 0.007 (1/150).

5.1.2 Distortion There is a chance the 4500F temperature difference would cause local yielding such that a dimensional check of the critical parts would be required. The recirculation pump motor cannot tolerate flooding without subsequent cleaning, oil change and drying its' winding.

These operations and check have to be done after this event.

5.1.3 Fracture Toughness ,

The pump casing is cast sustenitic stainless steel, so brittle fracture is not a concern.

The pump cover case bolts are ferritic steel. The mean temperature of the cover is: 1/2 (450) + 100 = 3500F. This temperature is above NDTT (Nil Ductility Transition Temperature) of ferritic steel.

5.2 RECIRCULATION PIPING .

5.2.1 The calculated maximum temperature gradients for this transient

• described in Section 4.2 were:

AT g = 354*F AT = 88'F 2

T'g,

= 46'F (Due to thick pump casing and thin pipe) 2

l c. .

The stresses due to the above thermal gradients were added to the

• - stresses due to the system loads and thermal gradients. The allowable cycles with these stresses were 900, which gives a fatigue usage factor of 0.001 (1/900).

5.2.2 Distortion .

The temperature gra' d ient may distort the pipe at the pipe to pump casing weld location which will not affect the function of the recirculation piping.

5.2.3 Fracture Toughness For the austenitic stainless steel recirculation piping, fracture is not a concern for this e.ent.

6.0 CONCLUSION

S AND REC 00NENDATIONS.

The above transient is similar to events of " Improper Start of a Cold Loop", except the temperature shock AT is 3980F instead of 4500F. So the transient is not totally new for the recirculation piping system design. This event is not a safety concern based on the fatigue 4 evaluation and the following reasons.

i 1) The stresses produced by the event are in a category (secondary 4 peak) that do not require evaluation except for Service Levels A 4 8 conditions. These peak stresses produced by the thermal shock are important only for fatigue and fatigue usage which, for a few rare events, is not required by the Code or by NRC rules.

2) If it were necessary to consider the fatigue usage due to this thermal shock, calculations show; based on worst case conditions, that significant fatigue usage would not result unless there were more than one hundred such cycles.

3) Under a worst case condition the potential damage to the piping could be slight distortion at the weld joints. The worst case condition is defined as the insulation being removed and a 4500 temperature difference between the outside and inside of the recirculation pipe. In the event that suppression pool water immersed part of the recirculation piping, we would recommend the insulation of the piping be removed and the weld joints connecting the recirculation piping to the recirculation pump be visually examined for deformation at the next shutdown.

Additionally, a dimensional and alignment check of the pump is recommended. The pump motor must be reconditioned by decontamination and drying the insulation, an electrical check, and,an oil change.

This assumes the motor was flooded.

t 3

4 ..

7.0 REFERENCES

7.1 ASE Boiler and Pressure Vessel Code,Section III Division I - 1980 Edition upto and including Winter 1982 Addenda.

7.2 Design Record File 8124-98, Recirculation flooding.

8 0 e e

.4.

APPENDIX A LION 401 PROGRAM LION 401 is a digital computer program which is used to solve the steady state or transient temperature distribution in any three-dimensional configuration.

The heat source may be externally conducted or internally generated.

In addition to the solving of heat conduction in structural eler.tnts, LION 401 may also be used in such cases as forced convection, free conver. ion, or radiation where the output will yield temperatures and heat fluxes for points representing the surface of the structure.

The program solves the transient heat conduction equations for a three-dimansional field using a first forward difference method.

Input to the program consists of structural geometry, physical properties, boundary conditions, internal heat generation rates and coolant flow properties and rates.

1

=

1 l

5-

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