Poor man's nuclear energy?

Actually, I wonder, for thermo-electric generators powered by Pu-238, does one do an isotopic separation on the plutonium to get pure Pu-238 ?

The nuclear infrastructure required to produce RPS is comprised of three major components: (1) The production of Pu-238; (2) the purification and encapsulation of Pu-238 into a fuel form; and (3) the assembly, testing, and delivery of the RPS to the Federal users. The three major components of the existing infrastructure, including their current status, are briefly described below:

Production of Pu-238: The Pu-238 production process consists of the fabrication of neptunium-237 (Np-237) targets, irradiation of the targets in a suitable irradiation facility, and the recovery of Pu-238 from the irradiated targets through chemical processing. In the past, Pu-238 was produced at DOE's Savannah River Site (SRS), using reactors that are no longer operating. After SRS stopped producing Pu-238, DOE satisfied its Pu-238 requirement by using DOE's available inventory in storage at LANL. This inventory was augmented by Pu-238 purchased from Russia for use in space missions. DOE analyzed the need for reestablishment of Pu-238 production capability in the Programmatic Environmental Impact Statement for Accomplishing Expanded Civilian Nuclear Energy> Research and Development and Isotope Production Missions in the United States, Including the Role of the Fast Flux Test Facility (NI PEIS) (DOE/EIS-0310), issued in December 2000. On the basis of the analysis in the NI PEIS, DOE issued a Record of Decision (ROD) (66 FR 7877, January 26, 2001) to reestablish Pu-238 production capability at ORNL using the Radiochemical Engineering Development Center (REDC) for the fabrication of targets and extraction of Pu-238 from the irradiated targets. The Advanced Test Reactor (ATR) located at the Idaho National Engineering and Environmental Laboratory (also referred to as the Idaho Site), supplemented by the High Flux Isotope Reactor (HFIR) located at ORNL, would be used in the irradiation of targets, and the irradiated targets would be returned to REDC/ORNL for extraction of Pu-238. This decision, however, has not yet been implemented and the DOE has expended no resources to establish the Pu-238 production at the Oak Ridge Site.

Np-237, the feed material for fabrication of targets for Pu-238 production, had been stored at the SRS where Pu-238 was historically produced. In the NI PEIS ROD, DOE decided to transfer this material to ORNL since the Pu-238 capability was planned to be reestablished there. However, Np-237 is a special nuclear material and, after the events of September 11, 2001, it required a higher level of security than could be reasonably provided at REDC/ORNL. Therefore, DOE amended the ROD for the NI PEIS to change the storage location for Np-237 from ORNL to the Idaho Site (69 FR 50180, August 13, 2004). Np-237, in the form of an oxide, will be shipped from SRS to the Idaho Site beginning in FY 2005 (and ending in FY 2006) for storage until needed for Pu-238 production.

Purification and Encapsulation of Pu-238: Pu-238 is purified and encapsulated in a metal capsule and welded closed. These fuel capsules are used as a heat source in the RPS. The purification and encapsulation work is currently conducted within the Technical Area-55 (TA-55) complex at LANL. The finished Pu-238 fuel capsules are shipped from LANL for assembly of the RPS at the Idaho Site.

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And now our enemies have the recipe they've longed for?

In fact, Pu-238 is something you want to LEAVE OUT OF a nuclear weapon - the Pu-238 doesn't
help in the fission reaction - and its radioactivity and heat just complicate matters.

It is not fissile in a thermal spectrum, but it is in a fast spectrum.

A nuclide can't be not "fissile" in a thermal spectrum but fissile in
a fast spectrum- by definition.

The word "fissile" means that the nuclide will fission with thermal neutrons.

If a nuclide like U-238 that will only fission with neutrons of energy above
a certain threshold - like with fast neutrons - those nuclides are termed "fissionable".

U-238 is NOT "fissile" - but it is "fissionable".

Dr. Gregory Greenman
Physicist

You are right concerning terminology. I should have said fissionable, not fissile.

I just wanted to point out that a big enough lump of Pu-238 will undergo just as well a fast power excursion (if you see what I mean) as a big enough lump of Pu-239, as its k_inf value is far above 1. (which is not the case for U-238 btw).