What is nuclear waste and what are the challenges of handling it? | Explained Premium

India's nuclear power program faces challenges with nuclear waste and power tariffs, despite some progress in breeder reactor technology.

Only two countries in the world have persisted with a breeder reactor programme: Russia and India. Recently, India loaded the core of its long-delayed prototype fast breeder reactor (PFBR) vessel, bringing it to the cusp of stage II of its three-stage nuclear programme. At the end of this programme, India hopes to be able to use its vast reserves of thorium in reactors to produce nuclear power to sate the country’s surging energy demand and provide some energy independence. But there are two barriers to this realisation: nuclear waste and power tariffs.

When a nuclear fission reactor operates, it allows neutrons with a specific energy to bombard the nuclei of atoms of certain elements. When one of these nuclei absorbs such a neutron, it destabilises and splits into two (i.e. fissions). This event yields some energy and the nuclei of different elements. For example, when the uranium-235 (U-235) nucleus absorbs a neutron, it can disintegrate to barium-144, krypton-89, and three neutrons. If the ‘debris’ (barium-144 and krypton-89) constitute elements that can’t gainfully undergo fission, they become nuclear waste.

An important source of nuclear waste is the fuel itself, the substance that undergoes fission — such as the U-235. “The spent fuel contains all the radioactive fission products that are produced when each nucleus of uranium or plutonium breaks apart to produce energy, as well as those radioactive elements, including plutonium, that are produced when uranium is converted into heavier elements following the absorption of neutrons and subsequent radioactive decays,” M.V. Ramana, a professor and the Simons Chair in Disarmament, Global and Human Security at the School of Public Policy and Global Affairs, University of British Columbia, wrote in a 2018 paper.

Nuclear waste is often highly radioactive and needs to be stored in special facilities that are reinforced to prevent leakage into and/or contamination of the surrounding soil, air, and water.

The composition and quantity of nuclear waste produced depends on the nuclear reactions happening inside a reactor. This said, handling the spent fuel is the main challenge: it is very hot and radioactive, and needs to be kept underwater for up to a few decades. Once it has cooled, it can be transferred to dry casks for longer-term storage.

All countries with longstanding nuclear power programmes have accumulated a considerable inventory of spent fuel. For example, the U.S. had 69,682 tonnes (as of 2015), Canada 54,000 tonnes (2016), and Russia 21,362 tonnes (2014).

Depending on radioactivity levels, the storage period can run up to a few millennia. Thus, “they have to be isolated from human contact for periods of time that are longer than anatomically modern Homo sapiens have been around on the planet,” Dr. Ramana wrote in his paper.