Conceptual design and estimated cost of buried ''berm contained'' nuclear power plants. Executive summary

A conceptual study has been made of the the technical feasibility and cost of berm-contained nuclear power plants (a berm-contained plant has all, or part, of its structure covered with soil). A principal objective of this study was to achieve a design that would reduce the potential release of radioactivity that could result if accidents of the very severe nature, involving a melting of the reactor core, were to occur. These are termed Class 9 accidents by the Nuclear Regulatory Commission and are not now a design-basis requirement for nuclear power plants because of their probability of occurrence has been estimatd to be very low. A number of core-melt accident scenarios were considered by ERCDC in developing the facility design requirements for this study. These postulated accidents were selected with the goal of enveloping the range of expected core-melt characteristics in order to ensure the adequacy of the design of the systems required to mitigate their consequences. One of the most severe scenarios for the Class 9 accidents included permanent and total loss of all ac power, both onsite and offsite. The probability of such a power loss extending for the long periods of time associated with such a severe accident is very low. The utilization of such a scenario in this study is typical of the application of the conconcept of specifying an envelope of limiting accident conditions for design of accident mitigation systems for the berm-contained facilities. The design requirements for these very severe, very low probability, core-melt accidents were specified in terms of containment pressure, energy, and temperature time-histories which comprised the basis for the development of structural design and accident-management systems design. From these results, first-order cost estimates were prepared for baseline designs and for a number of parametric site characteristic variations