ML20012F267
| ML20012F267 | |
| Person / Time | |
|---|---|
| Issue date: | 03/29/1990 |
| From: | Novak T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Goering G NORTHERN STATES POWER CO., WESTINGHOUSE OPERATING PLANTS OWNERS GROUP |
| References | |
| NUDOCS 9004110043 | |
| Download: ML20012F267 (2) | |
Text
o MAR 2 91933 Mr. Gerard T. Goerin Chairn,an WestinghouseOwnersbr,oup Northern 5tates Power 1737 Watonade Drive East Welch, MN 5$089
$UBJECT: 1.EOD STUDY ON THERKAL STRATIFICATION
Dear Mr. Goering:
We have recently completed a study of both U.S. and foreign operating experience associated with therm 1 stratification and its eff tets. This report also provides a brief discussion of sone of the corrective actions employed to reduce the potential of.therral stratification. Findings identified in the report include:
Thermal stratification has caused cracks, damated supports, and contributed to thermal fatigue in high erergy piping. Some cracks have resulted in unisolable leals of reactor coolant. Thermal stratification has occurred in presturized water reactors and boiling water reactors. As those locations susceptible to the effects of thermal plants age, ion are sub,iteted to an increasing number of thermal cyclest stratificat and the likelihood of cracks increases accordingly.
Interfacing sy:, tem leatage has a potential to cause thermal stratification in system piping and lentage through check valves, block valves, and isolation valvts h65 been comon.
Thus, an approach to minimize the potential for thermal stratification in many locations is to implement effective preventive and corrective maintenance of valves at system boundaries, i
We believe th6t this report would be useful to engineering support organiza.
tions at operating plants represented by the Westinghouse Owners Group and the incustry stneric SCATS (striping, cycling, and thermal stratification) program.
If you have any questionc reoarding the enclosed study, or would like further discussions of the issues, please contact me at 301-492-4484 or Dr. Nelson Su of my staff at 301 492-4434, ffJcir.a1 ni,.aa Lg Thomas MrNovak, Director Division of Safety programs Office for Analysis and Evaluation of Operational Data
Enclosure:
As steted cc W/ enclosure:
Mr. Mark Beaumont Westinghouse Electric Corporation, Rockville, MD Distribution:
pDR NSu EJordan Central file Glanil Dross A
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See previous Concurrence:
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SUBJECT:
AE00 STUDY ON THERMAL STRATiflCATION Dear Mr.
[
We have recently completed a study of both U.S. and foreign oper ing esperience associated with thermal stratification and its eff
- s. This report also provides a brief discussion of some of the corrective ions employed to reduce the potential of thermal stratification, findings entified in the report includet Thermal stratification has caused cracks, de ed supports, and contributed to thermal fatigue in high ener piping. Some cracks have resulted in unisolable leaks of reactor c ant. Thermal stratification has occurred in pressurized-water rtect s and boiling water reactors. As plants age, those locations susceptib to the effects of thermal stratification are subjected to en creasing number of thermal cyclest and the likelihood of cracks incre es accordingly.
Interfacing system leakage has potential to cause thermal stratification in system piping and leakage rough check valves, block valves, and isolation valves has been ron.
Thus, an approach to minimire the potential for thermal str ification in many locations is to implement effective preventive an corrective maintenance of valves at system boundaries.
We believe that this port would be useful to engineering support organizations at op ating plants represented by the (
customized
)
and the industry @' neric SCATS (striping, ding the enclosed stu cycling, and thermal stratification)
- program, if yo eve any questions regar or would like further discu ions of the issues, please contact me at 301-492-Dr. Nelson $y f say staff at 301 49?-4434 Thor.as M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data
Enclosure:
As stated Distribution:
PDR JRosenthal Central file EJordan ROAB R/F Dross DSP R/F TNovak NSu Glanik ROAB:DSP:A R0 P:AEOD C',OAB:DSP:AE00 P:AE00 NSu:nnk' Gk JRostnthal To k 3A//90 3/g/90 3// 8 90 3/g 90