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.

Aftermath of Indo-US nuclear deal

The deal virtually lifted the de-facto international ban on the trade of nuclear materials and equipments related with the nuclear industry. The deal and other related agreements were signed in October 2008. However, nothing much has changed in the Indian nuclear scenario.

India is still unable to buy nuclear fuel from nuclear material abundant countries like Australia. Indian nuclear facilities are not able to buy nuclear related equipments, monitoring instruments and systems from western countries.

Now, in a major breakthrough it is reported that US has permitted US firms to collaborate with Indian companies to manufacture nuclear related components. Even Australia which till now reluctant to sell uranium to India, is willing to sell uranium to boost its economy! Good for India, because price of uranium has fallen from $140 (2007) to $50 a pound after the Fukushima nuclear disaster.

The developments will help the seller countries to boost their sagging economies, and for India to buy the uranium fuel for the reactors and much needed equipments for the safe operation of nuclear fuel cycle facilities.

Tritium exposure - Kalpakkam

This has reference to the news item in the Times of India dt. 17 October, 2011: “Staff exposed to nuclear radiation – Tritium risk for some Kalpakkam workers”.

The news item states that some workers are exposed to nuclear radiation above permissible levels.

By going by the report, none was exposed to doses above permissible. Exposure to Investigation Levels which are 3/10th of the permissible levels is not an issue at all. In fact, tritium is the least radiotoxic radioisotope and hence least harmful. As a matter of abundant precaution, these levels of exposures are also investigated and corrective actions taken.

It is unfair to the nuclear industry to misquote the report and raise hue and cry on this normal exposure situation in any nuclear reactor.

Suppression of experimental evidence against LNT

This has reference to the article “Will the LNT Controversy ever be solved?” appeared in the July issue of the Express Healthcare. The following information appeared in HINDU (dated 22nd Sept. 2011) supports the view expressed in the article.

American geneticist Hermann J. Muller was awarded the 1946 Nobel Prize in medicine for his discovery that X-rays induce genetic mutations. In his Nobel Prize Lecture of December 12, 1946, Muller argued that the dose–response for radiation-induced germ cell mutations was linear and that there was “no escape from the conclusion that there is no threshold”. Muller and Curt Stern (the other geneticist) had done many of the key experiments. The fruit fly germ cell mutations experimental results at the University of Rochester failed to support the linear dose-response model at low exposure levels. However, in Muller's speech, he insisted there was "no escape from the conclusion that there is no threshold." Stern raised no objection. It is reported that the two successfully suppressed last-minute evidence against the LNT from the fruit fly experiments.

According to the Edward J. Calabrese, a Professor of Toxicology at the University of Massachusetts, School of Public Health, Amherst, uncovered the correspondence between Muller and Stern. He said, Muller’s decision not to mention the key scientific evidence against his position has had a far-reaching impact on our approach to regulating radiation and chemical exposure. In fact, Calabrese’s career research shows that low doses of some chemicals and radiation are benign or even helpful.

Within a year, National Academy of Sciences (NAS) was forced to accept the linear model for gonadal mutations, the practice was extrapolated to somatic cells and cancer. Twenty years later, NAS adopted the linear approach for chemicals. Soon thereafter, the U.S. Environmental Protection Agency announced it would use the linear model for risk assessment. The International Commission of Radiological protection also assumed the LNT as the basis for giving the recommendations for radiological protection.

If the truth was to be told, probably the nuclear industry could have drastically different exposure standards today, and far less fear about exposures to radiation. The resources, world-wide, spent on over-protection could have been better spent on healthcare in under-developed countries.

Annual average global human exposure to radiation

Radiation is a fact of life. The background radiation (cosmic radiation from space, radiation emitted from the natural radioactive elements present in soil/rocks, like uranium and thorium) contributes significantly to the total population dose. Totally, they contribute about 79 % of the annual average global human exposure to radiation. Out of remaining 21%, 20% is contributed from medical exposures from X-rays and scans and only 1% from all other man-made radiation sources, including nuclear power.

In India, major part (over 98%) of the average annual human exposure is from natural sources, about 1.93% from medical exposures and only about 0.37% from man-made sources. The large difference in medical exposures in the global average and Indian values, is due to enhanced medical care provided in developed countries as compared to India. More scans – more dose.

This information should be made available to the public so that risk from man-made sources is seen in proper perspective. Any activity or industry, which give more benefit than risk are easily accepted by the public. Transparency is the key to public acceptance.