ML20127J822

Informs of Acceptability of Devcon 5-minute Epoxy for Use in Cementing Resistance Temp Detector Temp Sensors to CRD Cavity & Motor,Based on Test & Inservice Exposure of Epoxy to High Temps

ML20127J822
Person / Time
Site:	Fort Saint Vrain
Issue date:	06/07/1985
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
P-85195, TAC-55294, NUDOCS 8506270115
Download: ML20127J822 (2)

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2420 W. 26th Avenue, Suite 1000, Denver, Colorado 80211 June 7, 1985 Fort St. Vrain Unit No. 1 P-85195 Regional Administrator Region IV )

bh U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000- M! hh Arlington, Texas 76011 ,

p Attn: Mr. E. H. Johnson .

Docket No. 50-267

SUBJECT:

Epoxy used to Cement the RTD Temperature Sensors to the CRD Cavity and Motor

Dear Mr. Johnson:

During control rod drive (CRD) refurbishment work at FSV, an epoxy was used to cement the RTD temperature sensors to various parts within the CRD cavity. The epoxy, Devcon 5-minute epoxy, has a vendor recommended maximum temperature of 200 degrees Fahrenheit.

However, an effort is underday to insure all components of the CRD assembly are rated for 300 degrees Fahrenheit.

Therefore, a nonconformance report, NCR-85-595, was generated in response to the use of the 5-minute epoxy. In order to disposition the NCR, various tests were performed to justify the use of the Devcon 5-minute epoxy in the reactor environment.

Control rod assembly serial #31, which was recently removed from the core for refurbishment had RTD temperature sensors installed during 1979 using the Devcon 5-minute epoxy. This CRD has been in service since 1979 except for a six month period and therefore the sensors and epoxy were subjected to varying power operating conditions in the reactor core. A test was performed under the auspices of Fuel Handling Procedure 100-31 in which the epoxy for 3 sensors was visually examined and was determined to be completely intact. A -

compression force gauge was used to measure the force required to scrape the epoxy off. Forces in the range of 25 to 75 pounds were 8 )g [,

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To further support the continued use of the epoxy, a test, T-288, was performed to subject the epoxy to high temperatures. A sample of.the epoxy was used to cement RTD wires to a metal plate for test T-288.

During testing, the temperature detecting device was found to be inoperable. Therefore the plate was heated to 400 degrees Fahrenheit in an oven to assure that it remained above the 300 degrees Fahrenheit qualification temperature during the pull test, which was .

performed outside of the oven. Since the RTD wires remained sufficiently cemented to the metal surface throughout the test, we conclude that the RTD sensors will remain in place during operating conditions. .

Following the current outage, we will be monitoring the RTD sensor readings and will be able to detect any significant changes in readings. In addition, the epoxy will also be included in the upcoming environmental qualification test on the CRD assembly.

Based on the above test and the inservice exposure, it is our conclusion that the Devcon 5-minute epoxy is acceptable for use in this application. The justification will be documented by a PSC change notice. If you have any questions please contact Mr. M. H. Holmes at (303) 571-8409.

Very truly yours, A0. yy. fYw nt%.u,y D. W. Warembourg, Man &ger Nuclear Engineering Division DWW/KD:pa E