ML20127C132
| ML20127C132 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 01/06/1993 |
| From: | Harris R NORTHEAST UTILITIES |
| To: | Stevenson T COLTEC INDUSTRIES, INC. |
| References | |
| REF-PT21-93 ED-RTH-92-231, NUDOCS 9301140003 | |
| Download: ML20127C132 (2) | |
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ED.RTil 92 231 January 6,1993 Mr. Ted Stevenson Collec industries Fairbanks Morse Engine Division 701 Lawton Avenue Beloit, WI $3511
- 1. Collec Engineering Report R 6.00 0260, dated 4/28/92:
- Millstone Unit No. I
References:
Cooling Capacity Analysis Perfonnance of Heat Exchangers Under Various Operating Conditions".
- 2. Collec Engineering Report R 6.00 0260, dated 1/10/92: " Millstone Unit No. 2 llent Exchanger Perfonnance System Perfonnance Under Cooling Water Flow Conditions outside the Design Basis Final Report".
- 3. Code of Federal Regulations, Title 10, Part 21 Dear Sir; it is the opinion of Nonheast Utilities Service Company (NUSCO) that the heat exchanger c performed by Coltec Industries /FMED for the Millstone Point Nuclear Power Station Un Emergency Diesel Generators (EDG) are in enor and that the actual cooling water Dow require are greater than specified in the referenced Collec Engineering Repor1s. Details of this error are described in the attachment to this letter.
As part of our responsibilities under 10CFR, Part 21, Collec Industries should evaluate all he 3
tr.msfer analyses perfonned for other NRC licensed or otherwise regulated nuclear facilities to determine if the NUSCO identified defects adversely efTect the conclusions of engineering analysis if the NUSCO identified defects are discovered to adversely effect supphed to other nuclear facilities engineering analysis supplied to other nuclear facilities, Coltec Industries should review 10C 21 and any internal procedures used to iraplement the requirements of 10CFR, Part 21 to dete reporting and notification requirements for these facilities Please call Peter Tirintoni at (203)665 3387 with specific technical questions or Tom Silko at (203)665 5241 with specific Licensing questions.
If you have any other questions, please do not hesitate to contact me.
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- n. T. iiarris, Director Engineering Department RTil/pli L J. Northolm, NRC. Chief Vendor inspection Branch e:
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o Attachment to ED RTil 92 231 Page1 ofI Collec Industries /Fairbanks Morse Engine Division has performed heat exchanger performance analysis to detennine the minimum required cooling water now to the Millstone Po'nt Nuclear Power Station Units I and 2 Emerger.cy Diesel Generators (EDG). This analysis was performed using &
commercial heat exchanger analysis program called Shell and Tube Exchangers, developed by the Thermal Analysis Systems Company. This analysis program utilized the Kern correlation for establishing the shell side film coemeient.
Northeast Utilities Service Company (NUSCO) has researched the Kern correlation and found that it was developed using test data from heat exchangers with a 25% baffle cut (bamo cut is defined as the fraction of a segmented bame or support plate that is cut off to allow passage of the shell side Guld, expressed as a percentage of the shellinternal diameter). The Kern method agrees well with test date for these heat exchanger (i.e. 25% bame cut), however it is limited in it's application since there are no conection factors to account for bame cuts other than 25%. With all other characteristics remaining consistent, the emeiency of a heat exchanger will be reduced as the bame cut increases, since less of the tube bundle will be in pure cross Dow.
The Millstone Point Units No. I and 2 EDO heat exchangers have bame cuts of 35% and 45%. If a 25% bame cut is assumed in analyzing the performance of these heat exchangers, then the shell side film cocmcient will be overpredicted, thus resulting in a non conservative minimum required cooling water Dowrote. For the case of the Millstone Unit No. 2 EDG heat exchangers, the Kern coce!ation predicted the shell. side film cocmcients to be 25% greater than predicted by correintions that account for various bame cuts. Correcting the shell side illm cocmcient for the appropriate bame cut inercases the minimum required cooling water flowrote by 40% compared to that specified by Coltec -
in the reference 2 tcport.
NUSCO also detected an apparent non conservatism in Collec's implementation of the Kern correlation The Kern correlation requires the viscosity be calculated at the b'ulk Huid temperature when determining the shell side Reynolds number, however,it appears that Coltee calculated the Guld viscosity using the shell side wall temperature. Although it is a common practice to neglect the viscosity correction term (the viscosity at the wall temperature divided by the viscosity at the bulk Duid temperature, raised to the.14 power), analyzing the fluid viscosity at the wrong temperature linearly impacts the calculated Reynolds number, Calculating a higher than expected Reynolds number will inflate the shell side film cocmcient, again resulting in a nosonservative minimum required cooling water dowrate.
Based upon these concerns, the Collec Engineering Reports provided for the Emergency Diesel Generators at the Millstone Nuclear Power Station Unit No.: I and 2 are considered to be in error.
This conclusion has been confirmed through an independent evaluation by a NUSCO consultant and by the Millstone 2 EDG heat cichanger manufacturer (BASCO), using the Heat Transfer Research Institute (llTRI) heat exchanger analysis computer code.
For the Emergency Diesel Generators at Millstone Units 1 and 2, NUSCO has performed subsequent heat exchanger analyses which account for the inemeiencies associated with the actual heat exchanger bame cuts (35% or 45%, as appropriate). Although these calculations establish a required cooling water Dowrate greater than that speciGed in the reference 1 and 2 Cottec Engineering reports, the cooling water now predicted to be available under degraded conditions exceeds the required Dowrate under the limiting system alignment for both Millstone Unit No.s I and 2.