EFFECT OF STEAM CORROSION ON CORE POST STRENGTH LOSS:I. LOW, CHRONIC STEAM INGRESS RATES

摘要

The purpose of this study was to assess the effect of chronic, low levels of steam ingress into the primary system of the HTGR on the corrosion, and consequent strength loss of the core sup¬port posts. The assessment necessarily proceeds through the following three steps:(l) The impurity composition in the primary system was estimated as a function of a range of steady ingress rates of from 0.001 to 1.0 g/sec, both by means of an analysis of the Dragon steam ingress experiment and a computer code, TIMOX, which treats the primary system as a well-mixed pot. (2) The core post burnoffs which result from 40-year exposures to these determined impurity atmospheres were then estimated using a corrosion rate expression derived from pub¬lished ATJ-graphite corrosion rate data. Burnoffs were deter¬mined for both the core posts at the nominal and the maximum sustained temperature, estimated to be 90°C above nominal. (3) The final step involved assessment of the degree of strength loss resulting from the estimated burnoffs.