The RAPID-L, RAPID-LAT (L: Lunar base, A: Automatic，T: Thermoelectric) is a micro nuclear reactor concept conceived as a powerhouse for colonies on the Moon and Mars.
The study was funded by the Japan Atomic Energy Research Institute (JAERI) in FY 1999–2001.
Inspired by SP-100, the Alkali Metal Thermoelectric Converter (AMTEC), JAERI's own high-temperature gas-cooled reactor (HTGR) High-temperature engineering test reactor from 1990, and CRIEPI's RAPID & RAPID-A projects from 1993 & 1995 among others JAERI commissioned the RAPID-L study.
[3] The study followed a three-year plan: The RAPID and RAPID-L designs were developed by the Central Research Institute of Electric Power Industry (CRIEPI) of Japan.
The RAPID-L design is a liquid metal fast breeder reactor (LMFBR) concept meant to prevent accidents due to human errors.
The goal was to create a long-life core that is inherently safe due to being maintenance free.
The bias factors were used to determine the number of LEM and LIM needed in the core to achieve fully automated operation.
This RAPID concept has neither diagrid nor core support structure since they are integrated in a fuel cartridge.
The simple reactor container would make the most important In-Service Inspection (ISI) easier.
The reactor subsystem is characterized by the RAPID refueling concept to eliminate conventional fuel handling systems.
Reactor power will be in proportional with the primary coolant flow rate due to LEMs reactivity feedback.
The LRMs enable an automated reactor startup by detecting the hot standby temperature of the primary coolant.
All these systems use Li6 and are actuated by highly reliable physical properties (volume expansion of Li6 for LEM, and frozen seal melting for LIM and LRM).
[1] Toshiba has been often cited to be involved in the research and development of the RAPID-L, however, this could not be confirmed in any of the Japanese documentations nor in contemporary science or press news.