Spent Nuclear Fuel – A Waste or a Resource?

In any power plant, there is a need of fuel which needs to be burnt to generate heat which in turn is used to produce steam and ultimately to produce electricity. In fossil fuel based plants, the fuel is coal or gas. There are different types of fuels, such as heavy metal fuels like naturally occurring uranium, enriched uranium ²³⁵U, plutonium (Pu) or their appropriate mixtures can be used in nuclear reactors. The radioactive isotopes – ²³⁵U and ^239/240Pu are fissile materials, meaning that the radioisotopes can undergo fission reaction to produce energy, termed as nuclear energy. Very highly radioactive fission products (see the reaction below) are also produced in the fission reaction. The half-lives of these fission products vary from seconds to several years. In addition to the release of energy during fission reaction, the decaying fission produce in the fuel generates large amount of heat (termed as decay heat). The heat from the fuel is utilized to produce steam via suitable heat exchanger systems.

In nuclear reactors, this rate of fission reaction is controlled, by design, to ensure proper and safe utilization of the released energy.     

In the reactors, nuclear fission reaction is induced using a sub-atomic particle, neutron. For example, heavy metal, ²³⁵U absorbs a neutron in the reactor to become an unstable nucleus ²³⁶U, which splits into two lighter and highly unstable products fission products, three neutrons and a lot energy. The unstable fission products quickly decay to finally become ¹³⁷Cs (a beta-gamma emitter) and ⁹⁰Sr (a beta emitter) with half-lives of around 30 years.

The ²³⁸U isotope forms about 99.27% of natural uranium. In the nuclear reactors, due to the neutron absorption, a small percentage of the uranium isotope gets converted through nuclear reactions, to plutonium isotopes which are again good fissile materials and can be used in nuclear weapons, and as part of mixed nuclear fuel used in “breeder” reactors. The remaining portion of the spent fuel consists of depleted uranium (DU) where the percentage of fissile ²³⁵U is reduced due to the fission reaction in the reactor to below the existing level of 0.72% in natural uranium fuel.

After the useful life of the nuclear fuel in the reactor, the highly radioactive fuel is called Spent Nuclear Fuel (SNF). As such, SNF does not have further use as nuclear fuel.

In addition to the fission products, plutonium, depleted uranium, the SNF also contains minor actinides which include long-lived and relatively long-lived isotopes of neptunium (²³⁷Np), americium (²⁴¹Am and ²⁴³Am) and curium (²⁴²Cm, ²⁴⁴Cm). These are also useful radioisotopes. Efforts are underway to separate the fission product radionuclides chemically from the waste and use them as radiation sources in industrial applications of radioisotopes.   

In countries where nuclear power has a considerable share in electricity production and has adequate uranium resources, the SNF is considered as nuclear waste and is disposed of or stored safely in isolation from the biosphere.  In countries like India, where there is shortage of uranium and need plutonium as fuel for the future up-coming reactors, the SNF is the resource material which can be reprocessed chemically to separate the useful plutonium and depleted uranium from the spent fuel.  

It is reported that India now retains the right to reprocess the SNF in India, with all the safety aspects considered, from upcoming Kudankulam nuclear power plant instead of sending them away to Russia. 

IAEA Launches Database of Fukushima Radiation Information

The International Atomic Energy Agency (IAEA) on 7 September 2012 launched a database, Fukushima Monitoring database,  of radiation measurements collected in Japan following last year's accident at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company (TEPCO). The database, prepared by the IAEA’s Incident and Emergency Centre (IEC), consists of data on radiation measurements collected both near and far from the power plant since the Fukushima Daiichi accident began on 11 March 2011. It is reported that the database will be upgraded as and when additional information is received from Japan (source: IAEA News).

International Cooperation is vital for Global nuclear security

Protection of nuclear material in transport and storage and the protection of nuclear facilities against acts of terrorism are important from global nuclear security point of view.

According to the IAEA Director General Yukiya Amano attending the Nuclear Security Summit in Seoul, South Korea, national governments continue to have primary responsibility for nuclear security. He pointed out that more than 100 countries are reporting incidents of thefts or other illicit activities involving nuclear and other radioactive materials to the IAEA Illicit Trafficking Database, which now tracks several hundred incidents every year. Mr. Amano urged all countries to continue to share information on illicit trafficking with the IAEA in order to ensure that the world has a comprehensive overview of the threat and can respond effectively.

On strengthening nuclear security, Mr. Amano also stressed the importance of the "human element". Strengthening nuclear security is not just about spending money on guns, gates and guards, he said. Training specialist staff and transferring know-how are of equal importance.