Energy Recovery from Nuclear Waste Generated by the French Nuclear Industry

Nuclear energy relies on an extraordinary energy density: the fission of a single gram of ²³⁵U releases approximately 82 GJ of heat, which is used to generate electricity with an efficiency of about 33% in the case of a PWR (pressurized water reactor). A PWR is a slow (or thermal) neutron reactor. Globally, this technology accounts for 67% of all slow neutron reactors that generate electricity. The raw material used to produce the fuel required to operate PWRs is natural uranium. Pressurized water reactor technology requires the use of uranium slightly enriched in ²³⁵U. Starting with natural uranium, part of the natural uranium will therefore be depleted in ²³⁵U and a small portion enriched during fuel preparation. For example, a 900-MW PWR consumes slightly more than 20 metric tons of uranium enriched to 3.5% annually. To produce this amount, 150 to 200 metric tons of natural uranium are required.

Nuclear energy can be harnessed in either an open or closed cycle:

• in an open cycle, the fuel is used only once. After it has been consumed, it is considered waste;

• in a closed cycle, spent fuel is reprocessed to recover valuable materials (uranium and plutonium) that can be used to manufacture MOX (Mixed Oxide) or fuel for fast neutron reactors. France uses a partially closed cycle in which spent fuel is reprocessed at the La Hague plant to separate uranium from plutonium. The plutonium is used to manufacture MOX fuel. The uranium from reprocessing is sometimes recycled after re-enrichment. The cycle would be slightly more closed if multi-recycling were implemented.

Waste is any solid, liquid, or gaseous substance that is produced or left behind in a process and is unusable for that process. Consider the case of pressurized water reactors. The initial raw material is natural uranium. From this, uranium enriched in ²³⁵U is produced. The remaining fraction, which constitutes the majority, is depleted uranium, which can be considered waste from the current nuclear fuel cycle. Enriched uranium is used to manufacture nuclear fuel for reactors. This fuel is “burned” in the reactor core. Once it is deemed to have been sufficiently burned, it is considered spent and is replaced. In an open cycle, spent fuel is considered waste.

With current technology (slow-neutron reactors), only a tiny fraction of the energy potentially contained in natural uranium is utilized. This represents a staggering waste of resources. In fact, the amount of natural uranium needed to power a PWR for 40 years could, in theory, power a series of fast-neutron reactors for nearly 5,000 years.

In an open cycle, what is therefore classified as waste according to the definition we provided above includes:

• depleted...