Feasibility study of a prestressed-concrete containment vessel for a novel GFR nuclear reactor

The latest modern nuclear energy systems currently researched and developed are the Generation IV (Gen IV) nuclear reactors, and one of the more promising Gen IV designs is the Gas-cooled fast reactor (GFR). Among the number of challenging problems of the design of GFR, the development of passive safety systems ensuring passive decay heat removal (DHR) during loss-of-coolant-accidents (LOCA) is of the highest importance. The currently proposed DHR strategy relies on intentionally increasing pressure inside a gas-tight guard vessel containing the reactor to approximately 4 bar. This, however, presents a significant engineering challenge as the vessel must be capable of withstanding high pressure of up to 10 bar, due to pressure spikes and safety coefficients, while also withstanding increased temperatures during the LOCA. As no GFR guard vessel has ever been designed, this paper presents a feasibility study establishing whether such vessel can be designed. The feasibility study is aimed at the assessment of a preconceptual design of a prestressed concrete vessel previously created by the authors. In the study, stresses in the structure induced by normal-operation loads and LOCA loads are calculated for three types of extreme constraint conditions covering all possible real constraints of the structure. The calculations are based on heat transfer equations, Euler–Bernoulli theory, and Lamé equation implemented in a in-house Python code. In the results, stresses in the vessel are presented and compared to design criteria. The main conclusion of the paper is that the vessel can be designed; however, certain adverse phenomena which complicate the design process, such as non-linear creep of concrete and occurrence of tensile stress up to 1MPa, will have to be addressed and considered during future detailed design. Following on from this affirmative conclusion, the authors will create the detailed design using advanced three-dimensional modelling in their future work. •The novel GFR reactor ALLEGRO requires an especially resistant containment vessel.•A prestressed-concrete containment vessel can withstand gas pressure of up to 10 bar.•The high pressure needed for the safety systems proposed for ALLEGRO can be maintained.•Non-linear creep of concrete may occur and must be considered in a detailed design.