Nuclear Monitor #939

Jan van Evert

NASA has unveiled an ambitious plan to build a permanent base in the Moon’s south polar region starting in 2030. The most striking part of this plan is a nuclear reactor to provide power for the base. The problem on the moon is that the lunar day lasts two weeks, and so does the night. This makes solar panels alone not enough to provide permanent power. NASA is working with the Department of Energy (DOE) and industry to design a nuclear fission power system that would provide at least 40 kW of electrical power. Obviously, building a concrete shell on the moon is not a realistic option so the nuclear power systems need to be a kilometre or more away for the radiation protection. That means the moon base will be very large. NASA plans to build the moon base in three phases:

Phase one, which runs from now through 2029, will gather detailed information and “secure reliable access” to the lunar surface.

Phase two will include power generation by radioisotope heater units and radioisotope thermoelectric generators (RTG’s). These contain plutonium that produces heat by radioactive decay. The heat is directly concerted into electricity. RTG’s have been used by NASA for decades in interplanetary probes such as the Voyagers, and recently, the Perseverance Mars rover. They can only produce a small amount of power, a few hundreds of watts. The RTG’s will mainly be used to help equipment survive the extremely cold lunar night.

Phase three, starting in 2030, will mean the beginning of a permanent human presence on the moon. That includes a nuclear fission rector. This is not as revolutionary as it seems: the United States already flew a reactor in space in the 1960s. Some companies already have matured designs and in some cases prototype systems. What type of fuel will be used is still undecided. It may be High Assay Low Enriched Uranium (HALEU) to potentially even highly enriched uranium based on mission demand.

Launching a nuclear reactor into space is easier said than done. There are no facilities yet to test nuclear systems in the same way that satellites are tested before launch. And using large amounts of nuclear material means the launch pad and its systems will have to be adapted extensively to protect the personnel against radiation. NASA hasn’t said a word either about the biggest risk: what if a launch fails and the reactor ends up on the bottom of the Atlantic Ocean? Plutonium is not only radioactive but also extremely toxic. It is totally unclear what safety measures will be taken to prevent the spreading of nuclear material across our planet in such a case.

It’s still unclear what NASA plans to do with the lunar base. The space agency even wants to build a nuclear powered spaceship that will be able to fly faster to Mars. Space Reactor 1 (SR-1) Freedom as it is called is planned to be launched as soon as 2028. NASA even plans putting nuclear reactors on the surface of Mars.