Idaho National Laboratory, Oregon State University, Nexant, USA

XVII — 1. Introduction

The multi-application small light water reactor (MASLWR) is a 150 MW(t) modular nuclear reactor that uses natural circulation for primary loop cooling. The MASLWR system was designed by the Nuclear Energy Research Initiative (NERI), a program of the United States’ Department of Energy (DOE). Other collaborators included Idaho National Engineering and Environmental Laboratory (INEEL), Oregon State University (OSU), and NEXANT-Bechtel, all in the United States of America. The design philosophy was to use existing pressurized water reactor (PWR) knowledge to develop a safe and economical small power source using only natural circulation in the primary system. Through economic considerations, the project moved towards design of factory-fabricated modules, designed to operate in a power farm of 30 units producing 1050 MW(e), although a fraction of that, down to a single module, could also be used in a given location. A single MASLWR module produces 35 MW(e), using 8% enriched fuel and can last for 5 full-power years without replacement.

Figure XVII-1 shows a single power generation module for the MASLWR design. MASLWR implements an integrated reactor vessel with an internal helical coil steam generator. The reactor vessel is enclosed in a high pressure steel containment vessel that is partially filled with water to serve as a suppression pool. The containment vessel in turn resides in a large exterior cooling pool that acts as the ultimate heat sink.

FIG. XVII-1. Schematic of the MASLWR exterior cooling pool and turbine-generator set.