NGNP Composites R&D Technical Issues Study

Abstract

This study identifies potential applications and design requirements for ceramic materials (CMs) and ceramic composite materials (CCMs) in the NGNP high-temperature gas-cooled reactor (HTGR) primary circuit. Components anticipated for fabrication from non-graphite CMs and CCMs are identified along with recommended normal and off-normal operating conditions. The evaluation defines required dimensions and material properties of the candidate materials for normal operating conditions (NOC), anticipated transients, abnormal events, and design basis events. The report also identifies additional activities required for codifying the selected materials. The activities include ASTM Standard and ASME Code development and other work to support NRC licensing of the plant.Evaluation of the NGNP baseline design indicates components requiring either CMs or CCMs depend upon the reactor operating temperatures. For a reactor outlet temperature of 900 o C, four of the five evaluated components would benefit from either CMs or CCMs. Section 4 discusses candidate materials and Section 5 discusses a recommended development and codification process. Although some thermal and mechanical data exist for most of the candidate materials, they all need additional irradiation, thermal, and mechanical testing. Section 5.3 outlines the proposed testing program for CCMs. The recommended program will require an estimated four to six years, not including long-term tests, and cost around $80-120 million. The codification process must take into account the type of material and the geometry of components using either CMs or CCMs. The process requires close integration of the design and the research and development (R&D) program, which has already started by using preliminary control rod component designs as the basis for establishing specimen geometry and test conditions [13][14][15][16]. The remaining time and budget for completing the R&D program need further assessment.Designing the initial NGNP reactor for a lower outlet temperature (e.g., 750 o C) would reduce development risk inherent in the R&D process. Based on the 750 o C outlet temperature evaluation, the study recommends either CMs or CCMs for three of the five evaluated components: control rods, upper core restraint, and lower floor blocks. Designing for an initial lower outlet temperature could greatly reduce schedule and cost risks for the CM and CCM R&D program.