ML20012A070

Safety Evaluation Concluding That Walls of Diesel Generator Vaults & Oil Tank Compartment Capable of Withstanding Tornado Wind Generated Loadings

ML20012A070
Person / Time
Site:	Oyster Creek
Issue date:	02/26/1990
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20012A048	List: ML20012A047 ML20012A070
References
NUDOCS 9003080241
Download: ML20012A070 (3)

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WASHINGTON, D. C. 20555 SAFETY EVALUATION.BY THE OFFICE.0F. NUCLEAR. REACTOR. REGULATION GPU NUCLEAR. CORPORATION AND JERSEY CENTRAL. POWER 5. LIGHT.CDMPANY 1

OYSTER CREEK. NUCLEAR. GENERATING. STATION L

DIESEL. GENERATOR. VAULTS-AND.01L TANK.COMPARTM' INT-5Ul3JECTED TO TORNADO GENERA 1 ED LOADING-DOCKET.NO. 50 219 1.0 -INTRODUCTION In reference 1, the staff had indicated that if GPU Nuclear Corporation -

(GPUN/ licensee) provided (as committed) a portable pump in a protected area and a hose connection to a protected water supply to be used in conjunction with the isolation condensor to achieve the hot shutdown, an i

analysis to determine if the diesel generator vaults and oil tank l

compartment can withstand tornado generated loadings is not warranted.

However,1after a detailed field walkdown'and line loss analysis of an existing system interconnection between the! core spray and the condensate

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and Deminer.lized Water Transfer. Systems, the licensee determined that the l

existing plant configuration is capable of supplying make-up water to the isolation condenser from the suppression chamber and is, therefore, sufficient to achieve the hot shutdown. The staff, after its detailed 1

review, concluded that the use of the existing system is acceptable if-the diesel generators, which~ power the core spray pumps upon a loss of off-site f

0 power, is protected from the tornado associated loadings.-

E This evaluation, thus, addresses the capacity of the diesel generator vaults and the oil tank compartment under tornado associated loadings.

-2.0 EVALUATION

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During the Systematic Evaluation-Program (SEP) reviews, it was recognized that the safety related structures of older plants could not withstand the loadings associated with the present generic criteria (i.e. R.G. 1.76)

.for tornado associated loadings. For these cases, the review practice had been to conservatively estimate the frequency of occurrence of tornadoes

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-(site specific), and to verify that as a minimum, the safety related structures could withstand the tornad probabilityofexceedance(PE)of10'ges(andassociatedloadings)having Figure 1 shows tornado and wind

. hazard probability model for the Oyster Creek site constructed by the licensee.-:The staff had' superimposed its own estimate of the hazard as indicated in Figure 1 as "NRR Estimate." Figure 3.2.3 of reference 4 indicates the plant to be in a region where the vector sum of the tan-gential, radial, vertical and translation mph corresponding to a probability of 10"g1 windspeed components is 150

. per year.

In.this evaluation,

.however the "NRR estimate" has been used in assessing the acceptability.

In reference 2, the staff had concluded that the diesel generator vaults and oil tank compartment are capable of withstanding 300 miles per hour (mph) wind and 2.0 psi depressurizat1 event would correspond to a PE of 10~9n load. From FiDure 1 such an-per year. However, no evaluation was made to evaluate the effects of. tornado generated missile loads in load combinations involving tornado wind-loads, for the structures.

-The exterior reinforced concrete walls (the potential target areas) of the subject structures are lft. 61n. thick, and the reinforced concrete roof is Ift. Oin. thick. The roof of each diesel generator vault has two grated openings and one stack opening. In 1983, the licensee had submitted a report (reference 3) entitled "0yster Creek Tornado Missile Risk Analysis." In addition to the wind hazard analysis, the report includes the tornado missile penetration analysis using the TORMIS simulation methodology. The results indicate that the mean probability of a missile hitt approximately.10~jng the exhaust stack openings or-roof gratings is per year. However, the mean missile-

-probabilityofthesubjectwallywasfoundtobe4.6x10'gtrike-L per year for penetration missile and 9.4x10~ for vehicle impact.

The licensee performed the structural calculations for the critical walls of the. diesel generator vaults and the oil tank compartment, and found that the walls can withstand the impact of the most damaging missile (hard missile with large kinetic energy) 1.e. a utility pole, together withthewigdloadingsassociatedwith168mphwind. Figure 1 indicates a p

PE of 7X10' per year associated with such a tornado wind speed. The stack openings, gratings and 12in. thick reinforced concrete roof panels of the subject structures are vulnerable to missile strike. The licensee r

calculations of 12in. thick roof panel indicated that it can withstand a p'

direct (end on) strike of an utility pole brought about by 88 mph wind.

The probabilfty of such a strike has been indicated (ref. 3) to be in the l'

order of 10" per year. A similar conclusion has been made by the licensee regarding a missile strike on a part of the diesel fuel supply line located outside the-north wall of the diesel oil tank compartment.

A 31n. diameter diesel fuel supply line for diesel oil tank and a valve are installed outside the north wall of the diesel oil tank compartment. The line penetrates the wall at approximately a foot above the grade level.

Though the supply line could be shown to have a low probability of being L

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l hit by a' tornado associated missile, it can be damaged by a number of j

ctber extraneous causes prior to or during a tornado event.

It needs to be adequately protected to assure its function when it is most needed.

In reference 3, the licensee had also submitted a tornado missile consequence analysis. Scenario 1 of the analysis considered a loss of.

4 offsit of 10~y power accompanying an initiating tornado event having a frequency -

s per reactor year. The analysis assumed that both the diesel.

generatorsfailduetotornadogeneratefgmissiles. The resulting 1

core melt frequency was found to be 10~

per reactor year. Though the J

staff has not considered the results of the consequence analysis in its.

i evaluation, a very low core melt frequency in case of a low probability e

tornado event provides confidence in staff conclusion regarding the Y

adequacy of the existing diesel generator facilities.

3.0 CONCLUSION

i Based on the prior reviews by the staff (1983 to 1988), the recent resper.ses to the staff reouests for additional information, and audit of some of the licenste calculatiers, the staff concludes that the wall of th ciesel geraretor vaults end the oil tank compartment are capable of J

withstarting the loeds generatec by a tornedo having a windspeed of 16E rph. Tbc staff agrees with the licensee contention that the prcbability of Irissile hittirs the ro9).or entry through the roof targets is very low f

(i.e. in the order of 10' The PE associated wit the tornado wind speed of.168 mph is estimated by the staff as 7x10~g per year.

Thus, the subject structures are acceptable.from the standpoint of tornado associated l

loadings. However,-the staff requires that the licensee provide adeounte d

L protection of the outside diesel fuel supply line against missile strike-irrespective of the probability consideration. Another reliable means of-assuring.that fuel will be supplied to the diesel generators in the event

~of a supply line break can also be acceptable.

4.0 REFERENCES

1.

Integrated Plant Safety Assessment Report (IPSAR) for Oyster Creek Generating Station, Supplement 1, NUREG-0822, July 1988 2.

IPSAR Section 4.3, Wind and Tornado Loadings-attached to the letter L

from J.A. Zwolinski (NRC) to P.B. Fiedler-(GPUN), dated March 8,1986 l

L 3.

PLG-0276, "0yster Creek Tornado Missile Risk Analysis," attached to the GPUN letter dated September 16, 1983.

4 ANSI /ANS-2.3, "American National Standard for Estimating Tornado and Extreme Wind Characteristics at Nuclear Power Sites."

Principal Contributor: H. Ashar l

Dated: February 26, 1990 r:

February 26. 1990 i

D.ocket'No. 50 219 r

Mr. E. E. Fitzpatrick i

Vice President and Director Oyster Creek Nuclear Generating Station s

Post Office Box 388 fcrked River, New Jersey 08731

SUBJECT:

EVALUATION OF DIESEL GENERATOR BUILDINGS SUBJECTED TO TOPNADO.

WIND GENERATED LOADING - OYSTER CREEK (TAC NOS. 49392 AND 49394)

The NRC staff has completed the review of the Diesel Generator Vaults and Oil Tank Compartment subjected to tornado wind generated loadings.

i Based on the prior reviews by the NRC staff (1983 to 1988) the recent i

responses to the staff request for additional information and audit of some ofGPUNuclearCorporation's(GPUN) calculations,thestaffconcludesthatthe w611s of the diesel generator vaults and the oil tank compartment are capable of withstandir.g the loads generated by a tornado having a windspeeo of 160 miles per hour. The staff agrees with GPUll's contention that the probability of a rissile hitting the 10p or entry thrcugh the roof targets is yrry low (i.e.,intheorderof10'9). The probability of exceedance assccieted with the tornado wind sgeed of 168 miles per hour as estimated by the staff is in the creer of 7x10' per year. For an SEP plant such as Oyster Creek this is acceptable. However, the staff requires that GPUN provide adequate protection of the outside fuel supply line against the potential missile strike irrespective of the probability consideration. Another reliable method.of assuring that fuel will be supplied to diesel generators in the event of a supply line break can also be acceptable. Our Safety Evaluation regarding this matter is enclosed.

We request that you respond within 30 days of receipt of this letter indicating your intent to comply with this requirement and submit the details of your intended action for staff review.

Sincerely,

/s/

Alexander W. Dromerick, Senior Project Manager Project Directorate I.4 Division of Reactor Projects. I/II Office of Nuclear Reactor Regulation

Enclosure:

As stated cc/w enclosure:

See next page DISTRIBUTION Docket File NRC & Local PDRs Plant File S. Varga (laE4)

ACRS (10)04A2)

5. roger S. Norris A. Dromerick OGC E. Jorder. (itEB 3302)

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OfflCIAL KtGURD CUPT

Pr.'E. E. Fitzpatrick Oyster Creek Nuclear

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' Oyster Creek Nuclear Generating Station Generating Station tc:

Ernest L. Blake, Jr.

Resident Inspector Shaw, Pittman, Potts and Trowbridge e/o U.S. NRC 2300 N Street, NW-Fost Office Box 445 Washington. 0.C.

20037 Forked River, New Jersey 08731 J.B. Liberman, Esquire Commissioner Bishop, Liberman, Cook, et al.

New Jersey Department of Energy 1155 Avenue of the Americas 101 Commerce Street New York, New York 10036 Newark, New Jersey 07102 Kent Tosch, Chief Regional Administrator, Region 1 New Jersey Department of Environmental U.S. Nuclear Regulatory Commission Protection 475 Allendale Road Bureau of Nuclear Engineering King of Prussia, Pennsylvania 19406 CN 415 Trenton, New Jersey 08625 BWR Licensing Manager GPU Nuclear Corporation 1 Upper Pond Road Parsippany, New Jersey 07054 Deputy Attorney General State of New Jersey Department of Law and Public Safety 36 West State Street - CN 112 Trenten, New Jersey 08625 Mayor Lacey Township 818 West Lacey Road Forked River, New Jersey 08731 Licensing Manager Oyster Creek Nuclear Generating Station Mail Stop: Site Emergency B1dg.

P. O. Box 388 Forked River, New Jersey 08731 l

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%, *'... *,o SAFETY EVALUATION BY TNE OFFICE 0F.WUCLEAR. REACTOR. REGULATION GPU NUCLEAR. CORPORATION AND JERSEY GENTRAL. POWER 5-LIENT.CorPANY OYSTER CREEK. NUCLEAR. GENERATING. STATION DIESTL. GENERATOR. VAULT 3 AND.01L.TANL GQNPARTM ;NT 3V5J;CTED.TO TOENADQ GENERAI ;p LQAp Hii DOCKET.WO. 50 219 1

1.0 INTRODUCTION

l In reference 1. the staff had indicated that if GPU Nuclear Corporation (GPUN/ licensee)provided(ascommitted)aportablepumpinaprotected area and a hose connection to a protected water supply to be used in conjunction with the isolation condensor to achieve the hot shutdown, an analysis to determine if the diesel generator vaults and oil tank l

compartment can withstand tornado generated loadings is not warranted.

However, after a detailed field walkdown and line loss analysis of an existing system interconnection between the core spray and the condensate and Deminerlized Water Transfer Systems, the licensee detemined that the existing plant configuration is capable of supplying make-up water to the

?

isolation condenser from the suppression chamber and is, therefore, i

sufficient to achieve the hot shutdown. The staff, after its detailed review, concluded that the use of the existing system is acceptable if the diesel generators, which power the core spray pumps upon a loss of off-site power, is protected from the tornado associated loadings.

l

~

This evaluation, thus, addresses the capacity of the diesel generator vaults and the oil tank compartment under tornado associated loadings.

2.0 EVALUATION

[

During the Systematic Evaluation Profram (SEP) reviewsolderplantscouldno it was recognized that the safety related structures o t

the loadings associated with the present generic criteria (i.e. R.G. 1.76)

L for tornado associated loadings. For these cases, the review practice had been to conservatively estimate the frequency of occurrence of tornadoes l

f j hf S

4'

[

(site specific), and to verify that as a minimum, the safety related structures could withstand the tornad probabilityofexceedance(PE)of10'ges(andassociatedloadings)having i

Figure 1 shows tornado and wind hazard probability model for the Oyster Creek site constructed by the licensee. The staff had superimposed its own estimate of the hazard as indicated in Figure 1 as "NRR Estimate." Figure 3.2.3 of reference 4 indicates the plant to be in a region where the vector sum of the tan-gential, radial, vertical and translation mphcorrespondingtoaprobabilityof10'g1windspeedcomponentsis150 l

per year.

In this evaluation, however, the "NRR estimate" has been used in assessing the acceptability.

i In reference 2, the staff had concluded that the diesel generator vaults and oil tank compartment are capable of withstanding 300 miles per hour (mph) wind and 2.0 psi depressurizat1 event would correspond to a PE of 10'9n load.

From Figure 1 such an per year. However, no evaluation was made to evaluate the effects of tornado generated missile loads in load combinations involving tornado wind loads, for the structures.

The exterior reinforced concrete walls (the potential target areas) of the subject structures are lft. 61n. thick, and the reinforced concrete roof is lft. Oin. thick. The roof of each diesel generator vault has two grated openings and one stack opening. In 1983, the licansee had submitted a report (reference 3) entitled "0yster Creek Tornado Missile Risk Analysis." In addition to the wind hazard analysis, the report includes the tornado missile penetration analysis using the TORMIS simulation methodology. The results indicate that the mean probability of a missile hittjng the exhaust stack openings or roof gratings is approximately 10' per year. However the mean missile probabilityofthesubjectwallywasfoundtobe4.6x10"gtrike per year for i

penetration missile and 9.4x10' for vehicle impact.

The licensee performed the structural calculations for the critical walls of the diesel generator vaults and the oil tank compartment, and found that the walls can withstand the impact of the most damaging missile (hard missile with large kinetic energy) 1.e. a utility pole, together r

with the wigd loadings associated with 168 mph wind. Figure 1 indicates a PE of 7X10' per year associated with such a tornado wind speed. The stack openings, gratings and 12in. thick reinforced concrete roof panels of the subject structures are vulnerable to missile strike. The licensee calculations of 12in. thick roof panel indicated that it can withstand a direct (end on) strike of an utility pole brought about by 88 mph wind.

The probabiljty of such a strike has been indicated (ref. 3) to be in the order of 10' per year. A similar conclusion has been made by the licensee regarding a missile strike on a part of the diesel fuel supply line located outside the north wall of the diesel oil tank compartment.

A 31n. diameter diesel fuel supply line for diesel oil tank and a valve are installed outside the north wall of the diesel oil tank compartment. The line penetrates the wall at approximately a foot above the grade level.

Though the supply line could be shown to have a low probability of being

r 1

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J

-3 I

n hit by a tornado associated missile, it can be damaged by a number of I

ctber extraneous causes pricr to or during a tornado event.

It needs to te. acequately protected to assure its function when it is most needed.

i in reference 3, the licensee had also submitted a tornado missile consequence analysis. Scenario 1 of the analysis considered a loss of offsit of 10'y power accomparying an initiating tornado event having a frequency per reactor year. The analysis assumed that both the diesel generatorsfailduetotornadogenerategmissiles. The resulting core melt frequency was found to be 10' per reactor year. Though the staff has not considered the results of the consequence analysis in its evaluation, a very low core melt frequency in case of a low probability tornado event provides confidence in staff conclusion regarding the adequacy of the existing diesel generator facilities.

i

3.0 CONCLUSION

Based on the prior reviews by the staff (1983 to 1988), the recent resper.ses to the staff recuests for aeditional information, and audit of some of the licetiste celculatiers, the staff concludes th6t the 6:a11 of the eitsel ger,tretor vaults er.d the oil tank corrpartitent are capable of i

withstercing the loads generateo by a tornado having a windspeed of 16P rrh. The staff agrees with the licensee contention that the prctability of Irissilt hittirg the ropf or entry through the roof targets is very low (i.e. in the order of 10' ).

The PE associated wit speed of 168 mph is estimated by the staff as 7x10'g the tornado wind per year. Thus, the subject structures are acceptable from the standpoint of tornado associated loadings. However, the staff requires that the licensee provide adequate protection of the cutside diesel fuel supply line against missile strike-irrespective of the probability consideration. Another reliable means of i

assuring that fuel will be supplied to the diesel generators in the event of a supply line break can also be acceptable.

4.0 REFERENCES

1.

Integrated Plant Safety Assessment Report (IPSAR) for Oyster Creek Generating Station, Supplement 1, NUREG-0822, July 1988 i

2.

IPSAR Section 4.3, Wind and Tornado loadings-attached to the letter from J.A. Zwolinski (NRC) to P.B. Fiedler (GPUN), dated March 8,1986 3.

PLG-0276, "0yster Creek Tornado Missile Risk Analysis," attached to the GPUN letter dated September 16, 1983.

4 ANSI /ANS-2.3, "American National Standard for Estimating Tornado and Extreme Wind Characteristics at Nuclear Power Sites."

• Principal Contributor: H. Ashar Dated: February 26, 1990

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