Early Experience With Resistance Temperature Detectors in PWRs - The 1960s and 1970s

Very likely some of the manufacturers are still in business, so I will not disclose any identifications (at this time). 

Anyway, as a "side task" the boss told me to set up a test rig to screen RTDs for subsequent installation in the Company's PWRs that were being built for several utilities.  RTDs had been failing in service and replacement was costly (although I believe that in the long run the consumers of electricity paid the bills).

So, in my monthly report of November 1968:

SCC-156  NOK-320  Resistance Thermometer Testing

Failure of resistance thermometers due to water inleakage at PWR plant sites has been extremely costly.  Therefore, a test program  for operation of these units in pressurized water has been initiated.

The test consists of cycling the water temperature from 50 F to 570 F while pressure is maintained at 2000 psi.  The failure rate of the resistance thermometers has been high (over 50 percent) and the margin of reliability is therefore unknown for the units which have not leaked in this testing. 
The main  problem appears to be in the welds associated  with the thin wall (0.010 inch) tubing at the tip of the resistance thermometer.  

Oh well, a meeting was set up with the supplier. Here are soon excerpts from the report of that meeting.

From page 1:  "Because of the special conditions and the available data, ______ will not formally consider any of the units from _____ as failures to be returned to ___________."

From page 6:  "In view iof the total picture it must be noted that R. Leyse's statements made (but unrecorded) at our December 11 meeting were oput of context and based on a very limited sampling of RTDs. ... We apologize for those statements."

That above was a fantastic report indeed.  It appears that the very heavy costs associated with RTD failure must have ultimately been paid by the consumers of electricity.  Otherwise, the hordes of RTD failures would not have been tolerated.

On January 15, 1971, the Company issued a SERVICE INFORMATION REPORT that reported, "In early 1969, it became evident that the RTDs furnished by our RTD supplier (hereafter referred to as A) were experiencing abnormally high failure rates at all operating ___________ PWRs at which they were in use."

Finally, here is a paragraph from the publication Nuclear Plant Experience, Vol. PWR-2, November 1972:

RTD FAILURES

Ginna

The plant has experienced a series of failures of the primary loop RTDs.  As of mid 1971, 25 of them had been replaced.

It is likely that several hundred RTDs at several nuclear power  plants were replaced at high cost.  Ultimately the problems were corrected based on costly experience and the ratepayers likely paid the bills. 

As I have reported in prior entries, in the case of Upper Head Injection, neither the Nuclear Regulatory Commission nor  EPRI's Nuclear Safety Analysis Center believed there was anything wrong with placing defective equipment in service and then correcting the problems based on operating experience at the plants. Of course, competent engineering in advance of placing the equipment  in service might not have been as profitable.