Nuclear safety: Why India relies on Cesium-137

Much of the international nuclear establishment has moved away from Cesium-137 because of the dangers associated with this radiological source, especially its potential theft and use by terrorists. But India’s nuclear establishment has bucked the trend and is instead deepening its dependence on Cesium-137. However, India’s choice is not as surprising as might seem at first glance: there are very good reasons for it.

First, some context. There has been a global effort to find an alternate technology to highly radiological sources in an effort to strengthen security of radiological materials. Nuclear and radiological materials falling into terrorist hands or those of criminal gangs has remained a serious concern especially since the 9/11 terrorist attacks on the United States. The US Energy Policy Act of 2005 created an Interagency Task Force on Radiation Source Protection and Security to undertake this task. The Task Force has produced four reports, containing its evaluation and recommendations to the President and Congress, on the level and type of threats that emanates from potential terrorists. The Task Force has looked at a range of threats including theft, sabotage, or use of a radioactive source in an RDD or RED. The last report of the Task Force came out in October 2018. The report of the Task Force in 2014 and 2018 has reported that though “the viability of alternative technologies for some applications has improved significantly, there are still limitations to the widespread implementation of most applications.” The US Department of Homeland Security in a September 2019 report stated that there are “significantly increased concerns related to the security of sealed sources and their potential use in a radiological dispersion device (RDD), which disperses radioactive material over a large area, or a radiation exposure device (RED), which could be hidden in a public area to expose people to radiation.” Since concerns meant that there have been consistent efforts within the US and around the world to find alternatives for some or all the functions in sectors that are currently using radiation sources. This is a challenge faced by a number of countries including India. The limitations in the case of India include economic feasibility and availability of alternative technologies.

India has by and large ensured secure practices while handling radioactive sources, but it had an incident with one of the high-risk radiological sources in 2010.

Not all radiological sources are the same in terms of their potency and risks. The riskier ones include Cobalt-60, Cesium-137, Iridium-192, Strontium-90, Americium-241, Californium-258, Plutonium-238, and Radium-226. The radiation effects are not the same even among these high-risk sources. There are several factors including type of exposure, and the kind of radiation emitted, whether it is alpha, beta or gamma. In India, the Atomic Energy Regulatory Board (AERB), India’s nuclear regulator, is responsible for the complete inventory of all radiation sources used within the country. Some of the more frequently used sources within India are Cesium-137, Cobalt-60, Tritium (H-3), Sodium-24, Bromine-82, Anthanum-140, Iodine-131, Molybdenum-99, Scandium-46, and Krypton-79. These have been used in several sectors including medicine, agriculture and industry.

India has by and large ensured secure practices while handling radioactive sources but it had an incident with one of the high-risk radiological sources in 2010. In early 2010, the disposal of a gamma unit using Cobalt-60 by the University of Delhi without following the recommended procedures led to the unit landing up in the hands of a scrap dealer in West Delhi. The incident resulted in the death of one person and seven persons suffered from radiation injuries. The AERB during interviews conducted by the author stated that they have made the rules and regulations more stringent in the wake of the Mayapuri incident. The AERB is also reported to have worked with the higher education body in India, the University Grants Commission (UGC), in tightening the procedures while handling radiological sources. After the Mayapuri episode, the AERB has apparently conducted several awareness camps in an effort to educate scrap dealers and other locals in broad terms about radiological security.

In the aftermath of the Mayapuri incident, there have been concerted efforts within India to move away from the use of Cobalt-60 to explore other options. One such source that India has been exploring is Cesium-137. Cesium-137 has been used in the medical sector as well as for well-logging purposes in the oil and gas sector. India’s Cesium-137 is “being recovered from the high level waste arising from reprocessing spent fuel from thermal reactors.” Though the global community is shifting from Cesium-137 to other sources and technologies, India is replacing Cobalt-60 with Cesium-137 because India’s nuclear establishment sees it as a viable option. In 2015, Bhabha Atomic Research Centre (BARC) scientists concluded that Cesium-137 can be recovered from the nuclear waste discarded by the atomic power plants and that this can be used to meet the demands in the medical and industrial sectors. Following this determination, Dr. Sekhar Basu, the chairman of the Atomic Energy Commission, said, “This technology is being used for the first time in the world in commercial domain.” C.P. Kaushik, an engineer at the BARC too endorsed the idea saying, “The new Caesium based irradiator is more economical and requires lesser handling so it is safer.”

In the aftermath of the Mayapuri incident, there have been concerted efforts within India to move away from the use of Cobalt-60 to explore other options.

The Indian atomic energy establishment has preferred Cesium-137 as an appropriate alternative because its half-life is longer (30 years) than that of Cobalt-60 (5.27 years). Short half-life generally would mean transportation, loading and unloading, and handling the source on multiple occasions, increasing the overall security risks. Nevertheless, acknowledging the security risks posed by Cesium-137, especially in its traditional powder form, the Indian nuclear establishment has set up a separate facility to develop vitrified Cesium-137 pencils which are used for blood irradiation. Indian nuclear scientists agree with their global counterparts about the danger of Cesium-137 because in powder form, it is “highly soluble in water and the powder can get easily dispersed resulting in release of activity during accidental conditions.” But, they argue that they have resolved the danger to a large extent by using it in vitrified pencil form.

It may appear surprising that India is moving from Cobalt-60 to Cesium-137 at the same time that the global community is moving away from Cesium-137 to other safer materials. So, India should expect the global nuclear community to continue to focus on India’s surprising preference for Cesium-137 despite the dangers associated with it. The Indian nuclear establishment can also be expected to reiterate its view: that the risks associated with Cesium-137 when used in vitrified pencil form are lesser; that since it is harvesting its Cesium-137 from nuclear waste, it is reducing the overall nuclear security dangers; and that the longer half-life of Cesium-137 actually makes it safer.

• Privacy & Data Protection
• India
• Atomic Energy Commission
• Atomic Energy Regulatory Board
• Cesium-137
• Cobalt-60
• Indian Nuclear Establishment

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