ML19248D347
| ML19248D347 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/27/1979 |
| From: | Kirslis S Office of Nuclear Reactor Regulation |
| To: | Mattson R NRC - TMI-2 LESSONS LEARNED TASK FORCE |
| References | |
| NUDOCS 7908150642 | |
| Download: ML19248D347 (2) | |
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R MEMORANDUM F0F, Yoser Mattson, Dire a u Copy 6
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sons Learned Task Force g
FROM:
S. Stan Kirs ais, Fr vaeu Manager Environmental Projects Branch 1, DSE s
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SUBJECT:
TMI INSTRUMENTATION In your memorandum of May 31, 1979 you invited the staff to submit ideas for reducing the likelihood of a reactor accident such as occurred at Three Mile Island. The following notions may be useful.
1.
Thermocouples Inside the Reactor Core Voids, whether steam or hydrogen bubbles, could be rapidly detected by a series of thermocouples positioned along the length of a fuel element near the axis of tie reactor and extending several feet down into the The themoccuples adjacent to voids would read higher temperatures core.
than themocouples irrraersed in liquid water (The fuel element near the themocouples would be the source of heat for the thermocouples).
Besides locating the voids, the measurement of temperatures would warn of the approach to the conditions for hydrogen generation and fuel damage.
2.
A Hydrogen Diffuser Tube This device would be a small diameter closed tube (say 1/4" 0.D. and 3/16" I.D.) of stainless steel positioned near the axis of the core adjacent to a fuel element and extending several feet down into the core. The upper end of the tube would be connected to a gas handling manifold to which are attached a vacuum pump, a sensitive pressure gauge and a mass spectrometer designea to measure hydrogen gas.
Hydrogen gas diffuses readily through metals such as stainless steel or
- 4kel, and the rate of diffusion increases exponentially with the scal temperature. The mass spectrometer at nomal reactor temperature
,,ould give a reading corresponding to the hydrogen level from the radiolysis of water.
If the temperature of the tube increased, or if a zircaloy-water reaction generated hydrogen gas, the spectrometer (or pressure gauge) reading would suddenly increase.
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s Roger Mattson This device would have the virtue of establishing uriequivocally whether hydrogen gas was present in the reactor. Of course, this piece of information could also be detemined by analyzing the water in the pressurizer.
3.
Neutron or Gama Flux Measurements If voids form in the core, the shielding value of the displaced water is lost. This loss might be detected by counting instruments inside or outside the core.
4.
Dissolution of Hydrogen Gas in the Metal Walls of the Primary System The thick metal walls of the reactor vessel, the pressurizer, the steam generator, and the associated piping contain hundreds of tons of ferrous metals in which hydrogen gas has an appreciable solubility.
The rate of solution of hydrogen in this metal under hydrogen bubble conditions would be of interest for estimating the degree of hydrogen embrittlement of the metal.
There are, of course, many other ways than those suggested above for detemining the location and extent of voids in a reactor coolant system. However, those on the Lessons Learned staff with whom I have spoken are aware of these methods, so I will not repeat them here.
Y S. Stan Kirslis, Project Manager Environmental Project Branch 1 Division of Site Safety and Environmental Analysis G
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