Abstract
Here we report the analysis of some of the test property data from the AGC-1 creep capsule. Specifically, we report analysis of the electrical resistivity (ER) and coefficient of thermal expansion (CTE). AGC-1 was operated at ~640°C and we measured the irradiated specimen CTE (α) over the temperature range 25°C to 550°C. Consequently, we have analyzed the mean CTE value for the temperature rage 25°C – 500°C. Both the ER and α(25-500°C) have been examined as a function of specimen dose (control specimens) and creep strain, %, (creep specimen). A direct comparison of the property changes has been made for the creep and control specimens by plotting their respective fractional changes as a function on neutron dose. Statistical “t” testing has been applied to any observed differences in property (ER or CTE) as a function of dose for the creep and control specimens of each graphite grade in the AGC-1 capsule. For electrical resistivity the irradiated value was shown to be greater than the unirradiated value for all graphite grades. However, the additional change due to creep strain was not found to be statistically significant. The coefficient of thermal expansion was seen to increase with dose for both the creep and control specimens. This increase was clearly seen in the fractional changes in CTE plot. The creep specimens were seen to increase their CTE above that noted for the control samples. The values of α(25-500°C) was statistically “t” tested and the differences between the creep and control CTE increases were shown to be statistically significant. Thus, creep strain is shown to have no additional effect upon ER but does increase the CTE over that observed from dose alone. The additional increase of CTE due to creep, is attributed to the closure of a larger fraction of the aligned porosity by compressive creep.