To qualify the in-core cable for use in the in-core startup systems, cable samples were tested in an operating reactor. D-c electrical characteristics were measured before insertion and at intervals after insertion.

5. 4. 1 Cable Samples And Processing

A single sample of each of two types of cable was irradiated. Both short-term and long­term effects were noted. One cable consisted of a 0. 018-inch-diameter center wire of stainless — steel-clad copper (Sylvania Oxalloy 28). GE quartz fiber, 150 2/2, initially manufactured with a Dow-Corning 1053 binder (a silicone compatible binder), and an outer braid of 0. 004-diameter Type-304 stainless steel wire. The braid outer diameter was 0. 070 to 0. 076 inch. The second cable was identical to the first except that Owens-Corning S-994 glass (S-glass) fiber, 150 1/2 with silicone compatible binder, was used instead of quartz fiber. .

The binder is coated on the quartz and S-glass fibers at the time of their manufacture.

The coating, by providing lubrication, increases the strength and flexing tolerance of the fibers.

It would be virtually impossible to otherwise fabricate the cable; however, the binder must be completely removed before the cables can be used at high temperature and/or in intense radiation fields.

♦The photos at the amplifier input were of poor quality for reproduction, so photos taken with a terminating resistance of 2700 ohms were substituted for them. This results in a pulse whose slow component has a faster decay time but which otherwise has the same general appearance as that at the 5000-ohm amplifier input resistance.

The binder, being an organic material in nature, decomposes when heated to a high temperature and/or exposed to high radiation. Spme of the. decomposition products are carbon­aceous and can degrade the insulation, resistance to the point where thfe’cable is unusable.

■x The cables are cleaned by the cable manufacturer by baking them in air at 850°F for 8 hours. This treatment removes all the organic components that could cause difficulty in reactor service.

For purposes of this test, the cable samples were drawn into 1/8-inch-o. d.. Type-304 stainless steel tubes. The tubes were seal-welded on the end to be irradiated, and terminated with a hermetic electrical connector on the other end. Before the final seal weld was made, the tubes were evacuated to 0. 1 micron while at a temperature of 800°F. The tubes were then backfilled with reactor grade argon at 1 atmosphere, and sealed.