ML17340B409

Forwards IE Bulletin 80-04, Analysis of PWR Main Steam Line Break W/Continued Feedwater Addition. No Written Response Required

ML17340B409
Person / Time
Site:	Humboldt Bay
Issue date:	02/08/1980
From:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:	Crane P PACIFIC GAS & ELECTRIC CO.
References
NUDOCS 8003110287
Download: ML17340B409 (14)

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+@V STFA4l GENERATOR MATER HN9L~R TECHNICAL EVALUATION TURKEY POINT UNIT NOS.

3 AND 4 January 1980 EG&G Idaho, Inc.

sooszsoZ g '7

CONTENTS Io INTRODUCTION~

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II.

MATER HAMMER EXPERIENCE.

III.

MEANS TO.REDUCE THE POTENTIAL FOR MATER HAMMER.

IY.

OPERATING EXPERIENCE AND MATER HAMMER SUSCEPTIBILITY.

Y.

CONCLUSIONS AND RECOMMENDATIONS.

VIo REFERENCES ~

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I.

INTROOUCTION An evaluation was performed for the Turkey Poi'nt Power Station (TPPS) Unit Nos.

3 and 4 feedwater system.

The purpose of this evalution was to access the susceptibility-'of the feedwater system to water hammer during operating transients and situations that could result in conditi'ons conducive to water haaner.

Steam-water slugging resulting in water hamner in the steam generator feedrings and adjacent feedwater piping was considered in this review.

This type of water hammer is generally referred to as steam generator water hammer.

The information for this evaluation was obtained from:

1) discussions with the licensee,

2) licensee submittals to NRC of Duly 3, 1975, and January 3, 1978,

3) the "Turkley Point Unit 1

2 Nos.

3 and 4 Final Safety Analysis Report, 4)

"An Evaluation of PMR Steam Generator.

Mater Hanmer",

NUREG-0291, and 5)

"HRC requi"ments for Auxiliary Fe~dwater Systems at the Turkey Point Power Station ".

A review of steam generator water hanmer events at TPPS is presented in Section II.

The means to reduce the potential for water, hamner at this facility are presented in Section III.Section IV presents descriptions of the feedwater system geometry and operation pertaining to the susceptibility of the system to steam generator water hammer.

Conclusions and recomnendations are presented in Section V concerning the susceptibility of the feedwater system at this facility.to steam generator water harnner.

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II.

MATER HAMMER EXPERIENCE There are thre known occurrences of wate~ banner prior to feedring pipi~ modifications in 1974 in the feedwater piping at TPPS Unit Nos.

3 and 4.

The first occurrence was indicated by body-to-bonnet leakage and slight elongation of some body-to-bonnet bolts on the 3B.feedwater check valve.

The second occurrence was indicated by the same kind of leakage and bolt elongation on the 4B feedwater check valve.

The third acurrence was indicated by the following deformations discovered inside containment du~ing an outage of Unit No. 4.

They occurred on the 'A" steam generator feedwater piping.

1.

Some expansion boIts for two 'hydraulic pipe restraints had been pulled approximately one inch out of a, concrete wall.

2.

Two spring hanger mounting plates had been deformed.

3.

A 90 elbow located in the piping leading to the. steam 0

generator feedwater nozzle experienced plastic deformation.

Subsequent to the 1974 feedwater piping modifications, no steam generator water hanmers have occurred.

III.

MEANS TO REDUCE THE POTENTIAL FOR WATER HAMMER In 1974 the effective horizontal length of main feedwater piping adjacent to any steam generator was modified not to exceed eight feet.

The corrective action was to minimize the length of feedwater piping which could drain into the steam generator through the feedring.

This was done by shortening the horizontal length of pipe at the level of the feedring inlet nozzle.

As a result of these modifications, the piping turns downward through a 90 elbow approximately five feet from the steam generator.

These modifications were performed on the "A" and "B" steam generator feedwater piping for both units.

The feedwater piping for the "C" steam generator was not modified because the eight foot horizontal length at the nozzle elevation was evaluated and found to be acceptable.

There has been no evidence of water hammer occurrences in any steam generator feedwater piping since completion of the modifications.

Auxiliary feedwater flow is manually controlled to the Wa imum necessary to meet oper ating requirements.

However, specific administrative

means, or other positive means, such as top discharge feedrings or administrative auxiliary feedwater flow limitations, have not been incorporated into plant design or procedure.

Based on past experience, steam generator water hammer would be most likely during startup,

shutdown, and low power situations when feedwater is under manual control and the flow rates are insufficient to maintain uncover ed feedrings full of water.

To. avoid admission of steam and possible slugging during these operational conditions, the fe drings est remain covered with water.

IV.

OPERATING EXPERIENCE AND WATER HAMMER SUSCEPTIBILITY The conditions most conducive to steam generator water hammer occur when the steam generator'eedrings are uncovered and steam enters the feedrings and attached horizontal feedwater piping.

Steam-water slugging and subsequent.

water haneer may occur when incoming feedwater mixes with the steam in the piping and rapid condensation occurs.

These conditions could conceivably occur during certain operating conditions for facilities with bottom discharge feedrings because of large drainage rates.

Since the piping modifications in 1974, TPPS Unit Nos.

3 and 4

have experienced numerous reactor trips.

A reactor trip almost always results in feedr ing uncovery in all steam generators.

The drop or

".shrinkage" in water level and subsequent fe dring uncovery is the result of interrupted reactor power production causing the collapse of

. steam voids within the secondary side of the steam generator s.

A similar situation would be experienced during events such as

'toss of main feedwater,

',oss of offsite power, steam line break, or

'II loss-of-coolant accident.

Normal startups and shutdowns with feedwater under manual control could also result in a substantial number of feedring uncovery events even with the administrative steam generator water level controls.

Our review of the operating history shows that drainage of the feedrings and adjacent piping has been experienced at TPPS Unit Nos.

3 and 4.

Although we would expect steam generator water harmer to occur under certain operating conditions, no steam generator water hmaer has be n experienc d at the acility sine

. 1974.

This has demonstrated that subsequent to the eedwater piping modifications, the acility at the Turkey Point site has an apparently low susc ptibility to steam generator water hamner under all conditions.

V.

CONCLUSIONS AND RECOMMENDATIONS Me have reviewed the operating history of the TPPS Unit Nos.

3

& 4 pertinent to steam generator water hamner 'and the related operational and procedural characteristics of the feedwater system.

The review has shown that conditions conducive to steam generator water hammer have occurred at the TPPS Unit Nos.

3 4 4 but no water hammer events have been observed subsequent to the 1974 steam generator feedwater piping modifications.

The conditions have been encountered during normal operating transients and startup and shutdown operation.

Such conditions would also be expected in the future during the normal and accident operating situations addressed in the review.

Based on this review we have concluded that the potential for steam generator water harrmer. is sufficiently low to permit continued operation of this facility.

Y1.

REFERENCES 1.

Robert E. Uhrig (FPL), letter to George Lear, NR', Subject-

"Mater Hanmer in PMR Feedwater System", July 3, 1975.

2.

Robert E. Uhrig (FPL), letter to George Lear, NRC, Subject-

"Mater Hamner in PMR Feedwater Systems",

January 3, 1978.

3.

Final Safet Anal sis Report, Turkey Point Units 3 and 4, Florida Power and Light Company, NRC Oocket Nos.

50-250 and 50-251.

4.

J.

A. Block, et al, An Evaluation of PMR Steam Generator Ma er

Hamner, Creare, Inc.

NUREG-0291 (December 1976).

.5.

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G. Eisenhut letter to R. E. Uhrig, FPL, Subject - "NRC Requirements for Auxiliary Feedwater Sys ems at Turkey Point Un'its 3 and 4", Qctober 16, 1979.

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Sc lltrnltKr l423 4 'i'tonsure FRM 2000 1042-l06 PUBLT.C VOUCP.Lt'R FOR REFUNDS Voucher No.................

,COG~9-00 Sehe'e No...---.-------------

NUCLEAR REGULATORY.CO! tMISSION U..S (llcvlnnlcat or. l'.stnblisbtncat, lturcnu or Ot0co)

WASHINGTON D

C 20555 Locaf>onr....

Appropriafion or Fund:........

31X 4675 PAIO BY Address FL PWR R LIGHT 'CO PO BOX 529100 MIAMI FL 33152 4ATTN ROBERT E

UHRIG Deposit received from thc above-named depositor on

, 19.....

for has been applied as herein stated and fhc balance indicated is returned herclvith:

Amount of deposit Applied as explained in "Remarks" belotv.........

Balance authorized fo bc refunded........

1~I 00 00 Remarks:

THE FEES RELATED TO A SEPT 20n 1979 APPLICATION BY FL PWR R LIGHT CO WHICH HAS BEEN REVIEWED AND FOUND NOT TO BE SUBJECT TO FEES BECAUSE THE NRC IS WAIVING FEES FOR CERTAIN TYPES OF FIRE PROTECTION AHDTS.

Turkey Pt.

3 8

4 Application 9/20/79 DISTRIBUTION:

Docket File (2)

Refund File Reactor File (2)

Activity File DOCKET 50-250, 50-251 (Sign original only)

T'fle Refund by Check No..

(Signa turc C'sh, $..............on..............

of payee)

Ofhcr method, $.

(Sign original only)

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