Stress and strain evaluation of the heat transfer tubes in the intermediate heat exchanger for the HTTR

An intermediate heat exchanger (IHX) with a heat capacity of 10 MW for the High Temperature Engineering Test Reactor (HTTR) uses helically coil heat transfer tubes. The stress and strain evaluation for the heat transfer tubes which are used in over 900degC is performed by an elastic or creep analysis during the possible abnormal events. This paper describes an evaluation procedure of the heat transfer tube, creep analysis method and evaluation results. The results showed that inelastic strain and creep fatigue increased rapidly in 1-2nd cycles of 850degC or 950degC operations, however, they did not increase in the following cycles. Therefore, they did not exceed the allowable limits for HTTR life time of 20 years. Primary stress is also under the limit in every abnormal event. (author)