Test Conditions ‘

The test facility consists of dry thimbles in an operating reactor core. The total length of the thimbles is about 30 feet. Half of this length is outside the pressure vessel; of the remaining half, the last 5 feet is actually in the core. The cable temperature external to the pressure vessel is about 80°F. Inside the pressure vessel but not in the core, the cable temperature is about 550°F. In the core, the cable temperature due to gamma heating, as well as ambient temperature, is about 650°F. ■ .

The profile of both the gamma flux level and the neutron flux level is roughly a cosine curve

with a zero intercept 1 foot beyond the end of the thimbles and 5 feet along the thimble. The peak

12 12 neutron flux was about 5×10 nv during the first portion of the test and 7. 5 x 10 nv during the

latter portion of the test. •

5.4. 3 Test Data ‘

•Figure 5^11 is a plot of the d-c leakage versus applied potential across the cable insulation for various levels of nvt. The d-c leakage of the quartz did not increase with increasing nvt. This was illustrated by measurements-of d-c leakage at 100 volts applied potential for various nvt values (see Figure 5-12). On the other hand, the leakage currents through the S-glass insulation generally increased with increasing nvt.