ML19208C050
| ML19208C050 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/17/1979 |
| From: | Shepard R OAK RIDGE NATIONAL LABORATORY |
| To: | |
| Shared Package | |
| ML19208C045 | List: |
| References | |
| NUDOCS 7909240461 | |
| Download: ML19208C050 (3) | |
Text
o Enclosure S Ii Three Mile Island - 2 Technical Support I'
Instrumentation
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R. L. Shepard
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Problems:
- 1) Six of 52 in-core thermocouples are reading significantly higher than
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the others.
Can these readings be validated and/or can failure mechanisms t
be posculated to c.. plain the readings?
loop be calibrated.: sing Johnson noise measurem:nts or other techniques?
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- 3) Can a method be developed for using the RTD in the pressurizer for I,
indicating pressuri:er water level?
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- 4) Diagnose the condition of the in-core thermocouples using Time Domain Reflectrometry or other techniques.
Descrintion of h'ork Perfomed:
- 1) Possible failure modes were considered by several thermocouple experts. The most likely failure mechanisms-melting of the sheath or ingress of moisture into the insulation-could not cause readings higher i*
h than the true temperature.
The location of the thermocouple junction may g
have been displaced by melting along the sheath.
- 2) Methods are not sufficiently developed for using Johnson noise for field calibration of RTD's.
- 3) Methods have been developed for measuring in-sitt time response of RTD's using loop current step response (LCSR) and for using electrical selfheating for detecting the presence or absence of water in contact with 7909240 % [
P00R OR TNK 1006 55
2 i
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t the sheath of an RTD.
I The mett.ods are of questionabic applicability to TMI because of the massive (1.4 inch 0.b.) stainless steel well which ho t
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l the RTD.
Calculations were made to predict the sensitivity.
Rosemont
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J Engineering Company cooperated by determining the maximum safe heating i
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current that could be used.
i Idaho National Engineering Lab (INEL) made g
a sinulation using tippabic autoclave and a well similar to the one at Till.
Temperature differences of only 5"F were obtained between a wetted and um.ated w ell.
On April 2S, Shepard and Carroll went to TMI, then to Davis-Desse lg to try the selfhcating method in place.
The method was found to be
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unsuitable due to lon; time constants (greater than 3000 seconds) and i
Iow sensitivity.
Temperature changes due to water spray and heaters in the t.
pressuri er would mas: the levc1 change.
A bridged heater method of determining pressuri:cr level, using 4 of the 40 or more heater elements was devised by B5W with assistance by ORNL
- 4) Experiments were performed at OkNL to determine if Time Domain Reflectrometry could be used to verify the integrity of the in-core j
thermocouples.
1 It was determined that the technique was unsatisfactory because of the large electrical resistance and long extension wires used
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on the thermocouples.
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_ Conclusions and Results:
f It was concluded that:
- 1) The in-core thermocouples are probably accurate in spite of experiencing temperatures above 200*F.
- 2) Time Domain Reflectrometry is not a useful diagnostic tool for long high-resistance'thermocouples.
1006 256 00RDull#J
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- 3) The RTD might have been a useful indicator of pressurizer water i
level if the well had been less massive.
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- 4) There is a general need in PWR's for diverse measurement techniques s
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of process parameters, such as pressuri:cr water level.
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Nork Reouested By.
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- 1) NRC-TMI; Meted-D I; Mar 31.
- 2) NP.C-Ecthesdt ( U ')', Ap ri l 2.
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- 3) NRC-IAG-TMI (Ackerman) April 3.
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- 4) NRC-IAG-T"I (Ackerman) April 13.
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Results Reported To:
Same as above plus:
V Tom Murley, NRC April 6 Billy Jo Sheperd (B5U), B!I April 6 A review of activities was presented to David Cain and Alex Long at EPRI on May 10, 1979.
Work Performed By:
i D. Agouridis, ORNL l
R. M. Carroll, ORNL
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J. L. Horton, ORNL T. W. Kerlin,LTr I
Don Matychuk, Rosemont T. E. Mott, TEC
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R. L. Shepard, OR'?L
)
Marlin Stanley, INEL l
Wylie Stanse11, Tektronix e
P00R ORIGliUL 1006 257
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