ML20012F265
| ML20012F265 | |
| Person / Time | |
|---|---|
| Issue date: | 03/29/1990 |
| From: | Novak T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Sterling E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR, C-E OPERATING PLANTS OWNERS GROUP |
| References | |
| NUDOCS 9004110039 | |
| Download: ML20012F265 (2) | |
Text
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MAR 2 91990 Mr. Edward Sterling, Chairman c
Combustion Engineering Owners Group Arizona Public Service Mail Station 9878 411 North Central Phoenix, AZ 85004
SUBJECT:
AE00 STUDY ON THERMAL STRATIFICATION i-
Dear Mr. Sterling:
We have recently completed a study of both U.S. and foreign operating experience associated with thermal stratification and its effects. This report also provides a brief discussion of some of the corrective actions employed to reduce the potential of thermal stratification, findings identified in the report include:
Thermal stratification has caused cracks, damaged supports, and contributed to thermal fatigue in high energy piping. Some cracks have resulted in unisolable leaks of reactor coolant. Thermal stratification has occurred in pressurized-water reactors and boiling-water, reactors. As plants age, those locations susceptible to the effects of thermal stratification are subjected to an increasing number of thermal cycles; and the likc-lihood of cracks increases accordingly.
Interfacing system leakage has a potential to cause thermal stratification in system piping and leakage through check valves, block valves, and isolation valves has been common. 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.
We believe that this report would be useful to engineering support organiza-tions at operating plants represented by the Combustion Engineering Owners Group and the industry generic SCATS (striping, cycling, and thermal strati-fication) program.
If you have any questions regarding the enclosed study, or would like further discussions of the issues, please contact me at 301-492-4484 or Dr. Nelson Su of sqy staff at 301-492-4434
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'Originni signed by 4 Thomas M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data
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Enclosure:
As stated o
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MS Mr. Charlie Brinkman, Combustion Engineering Co., Rockville, MD
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SUBJECT:
AE0D STUDY ON THERMAL STRATIFICATION l
Dear Mr.
We have recently completed a study of both U.S. and foreign oper ing experience associated with thermal stratification and its effe
- s. This report also provides a brief discussion of some of the corrective ions employed to l
reduce the potential of thermal stratification. Findings entified in the report include:
Thermal stratification has caused cracks, da 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 react s and boiling-water reactors. As plants age, those locations susceptib to the effects of thermal stratification are subjected to an i creasing number of thermal cycles; 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 anon. Thus, an approach to minimize the potential for thermal str ification in many locations is to implement i
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
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i and the industry neric SCATS (striping, cycling, and thermal' stratification) program.
If yo ave any questions regarding the enclosed study, or would like further discus ons of the issues, please contact me at 301-492-4484 or Dr. Nelson 5 of ray staff at 301-492-4434 Thomas 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- 0AB:DSP:AE0D
- AE0D NSu:nsnk GL osenthal k-3A//90 3/g/90 3/Jj/90 3/g.90
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