Operation and safety

Rogue sources

30 November 2006

Anyone who doubts that resources should be invested into finding lost radioactive sources should look to the recent death of Russian dissident Alexander Litvinenko. By Deirdre Mason

If there are those who doubt whether the time, effort and resources invested in tracking down lost or orphaned sources of nuclear radiation is well spent, the tragic case of Alexander Litvinenko demonstrates only too clearly why this work is crucial. The former KGB officer, living in London at the time, died on 23 November 2006 after apparently ingesting polonium-210 in sufficient quantities to kill him painfully within a fortnight. Since his death, several premises known to have been visited by Litvinenko shortly before his death have become contaminated with the isotope, indicating its power.

Although polonium occurs naturally in small quantities, medical specialists such as Dudley Goodhead at the UK Medical Research Council radiation and genome stability unit point out that a dose sufficient to kill someone has to be man-made and is likely to originate from a defunct particle accelerator or a nuclear reactor.

Malevolent use of spent radioactive or nuclear materials has been an international concern since the middle of the last century. However, the terrorist attacks in the USA on 11 September 2001, have increased public concern about the security of radioactive sources worldwide. The most significant sources, from a safety and security point of view, are found in industrial radiography, radiotherapy, industrial irradiators and thermo-electric generators, according to the International Atomic Energy Agency (IAEA). These contain large amounts of radioactive material such as cobalt-60, strontium-90, caesium-137 and iridium-192, all of which can be used to build ‘dirty’ bombs.

Because of the wide distribution of sources, these materials can be found almost anywhere in the world and controls vary widely. According to the IAEA, more than 100 countries may have inadequate control and monitoring programmes to prevent or even detect the theft of these materials. Sometimes the sources are lost or missing, at other times their location is known but nobody has assumed control, leaving them ‘orphaned’.

Bringing countries like this into the safety net of strong control and monitoring has been a continuing programme for agencies such as the IAEA, Interpol, the World Customs Organization and the European Commission along with individual governments, but the events of 11 September 2001 undoubtedly boosted the importance of a secure international control system. Following that event, the overall international strategy was widened to include malevolence and terrorism, and the IAEA set up a collaboration with the US Department of Energy and the Russian Federation’s Ministry for Atomic Energy in the form of a tripartite working group on securing and managing radioactive sources. As a result, officials from the three sides agreed to develop a coordinated and proactive strategy to locate, recover and secure radioactive sources throughout the former Soviet Union.

IAEA priority

“What is needed is cradle-to-grave control of powerful radioactive sources to protect them against terrorism or theft,” IAEA director general Mohamed ElBaradei has stressed. “One of our priorities is to assist states in creating and strengthening national regulatory infrastructures to ensure that these radioactive sources are appropriately regulated and adequately secured at all times.”

The key, however, to such an ambitious programme’s effectiveness is expertise, and that is what so many of the countries with problems still lack. Skill and experience in locating lost or orphaned sources is what the IAEA can offer, and a key part of its work is the ability to help countries by sending, at their request, expert teams to help them develop national strategies or to advise on dealing with disused sources.

Carolyn Mac Kenzie is a radiation source specialist, who normally works for the Livermore National Laboratory in California. For the past two years, she has been with the IAEA and has completed around 17 missions in a variety of countries. Her most recent work involved Georgia, once part of the former USSR and since independence, in need of help for upgrading levels of radiation safety and securing orphan sources.

“Georgia was different. We were assisting them to search locations suspected of having orphan sources. Normally, we go to help and try to put together a picture of what might be lost, and then do an assessment. With Georgia, we played a more active part in finding it,” she said.

The Georgia search and recovery mission, funded by the USA through the IAEA technical cooperation programme, covered the mountainous region of Racha, which is about 300km northwest of the capital Tbilisi. The mission was concentrating on former industrial centres in the valley of the Rioni River and was one of the last areas of Georgia to have gone unchecked for orphan sources. The approach to tracking down missing or orphaned sources has to be methodical.

Mac Kenzie said: “First, we carry out a paper search. We try to dig up old records of what might have been there. We look at these and check old telephone books on what industries were in place and which of these might have used radioactive sources, such as mining.

“Then we look at the current inventory and try to find out what might be missing. The quality of these inventories varies considerable from country to country. If officials haven’t laid eyes on sources for three to five years, we try to verify these inventories.”

Normally, the countries themselves carry out the actual searches, once IAEA experts have trained the teams concerned, which is why the degree of IAEA involvement in actual searches in Georgia is atypical. Mac Kenzie continued: “There are only a few of us at IAEA involved. So we have to train people in their own countries and empower them so that they can find the sources. We teach them the techniques for using different radiation detectors.”

Search techniques

These techniques can vary from an airplane search, which needs sensitive equipment, to sensors mounted on vehicles and powerful backpack-mounted equipment, down to handheld equipment.

“We teach them techniques for gridding out an area. You can’t scan a whole country, so we pick a site where we suspect a source may exist and walk over it with radiation detection equipment.”

The teams check an area for background radiation and then zone in as they get more information. It is crucial to be careful and not to blunder in to an unknown dangerous situation: “You approach it slowly,” Mac Kenzie stressed.

Training generally involves two or three teams, each with typically three to five people. “Our courses are put on for between 10 and 20 people per country. It involves a week’s specific search training. We ask the country to pick qualified people with a physics background with knowledge of the subject, so they are specialists to start with,” Mac Kenzie said.

In the countries of the former USSR, there is still considerable need for specialist teams and for continuous training. “It’s not a question of going in once and saying that the job is done,” she said.

However, Georgia and the other former Soviet countries are by no means alone in their ability to lose track of dangerous materials. Over the years, IAEA records show an extraordinary array of lost and often, very dangerous radiation sources that have turned up in the most unlikely places. One lost source in the USA (before the present regulatory regime) was traced to a pig, which had been rooting around on a waste tip and swallowed a discarded brachytherapy radioactive needle, used to deliver minute radioactive ‘seeds’ deep into the heart of cancerous tissue. Some sources have turned up in bank vaults, or else have been recycled into jewellery.

A worrying problem involves imported scrap metal that includes radioactive material. The route can be very difficult to trace back and if the scrap is recycled as a building material, this can lead to contamination of an entire industrial plant and the surrounding environment, with serious environmental consequences. In Mexico, a discarded cobalt source was once unknowingly recycled into building materials for housing, which then had to be destroyed and the entire area decontaminated.

Medical equipment

Another problem arises from the export to developing countries of obsolete medical equipment such as cobalt-60 teletherapy units, formerly used in radiotherapy and now replaced by accelerators. Unless information is exchanged between exporting and importing regulatory authorities, these can all too easily become yet more orphan sources. There are problems, too, going back decades when discarded radioactive medical equipment was simply buried on site instead of being sent for proper disposal.

However, even today’s tighter regulations cannot catch everything in their net. As recently as 2005, a package containing highly enriched uranium (HEU) went missing in New Jersey, USA, and a neutron flux detector containing 0.0017g of HEU was lost at a nuclear power plant in Fukui, Japan.

Although the amounts were minute and of little interest to terrorists, these incidents showed security weak points at facilities handling HEU. During the most recent mission in Georgia, the joint Georgian Ministry of Environment and the IAEA team found a powerful source of radioactivity in a pile of dirt on the floor of a derelict factory in Iri – a village in the isolated mountain region of Racha. The lost source was tracked down once checks established that background radiation levels in the village were 12 times above normal.

The team also found a second, smaller source inside a house in the village of Likhaura, kept in a tin of nuts and bots above a work bench. Only a thin, wooden wall separated this source from the family bedroom.

The radioisotope in both sources was caesium-137, a powerful gamma emitter and among the most common isotopes in industrial use for instrumentation to check materials for flaws and for industrial measurements. The search team’s new backpack mounted instrumentation helped to reveal and locate both sources.

Because there were no records, the search team leaders said that they had no clear knowledge of the origin of the sources. Georgia has a considerable problem with lost and orphaned sources, with as many as 300 recovered since the mid 1990s. Abandoned mines and factories, and medical clinics that lose their funds, are all part of the problem. At least one person has died and many people have had radioactive burns as a result, the IAEA said.

Mac Kenzie added: “We have people who die or are seriously injured every year from accidents where they handle a source. They take off the protective lead covering to sell it, and become exposed and killed or injured as a result.”

Protecting people from this type of exposure is “paramount”, she said. “These sources need to be controlled. It is very important to the countries concerned, and we’re here to help them.”

Even more worrying than the sources most recently recovered have been strontium-90 sources that powered radioisotope thermoelectric generators (RTGs). Some RTGs, originally located in remote areas as stand-alone electrical generators are still unaccounted for.

“There may be no solution in the country to dealing with the waste arising from these discarded facilities,” Mac Kenzie explained. However, she added, governments are now coming up with repositories for radioactive waste. “You can’t just find sources and then not have somewhere to put them, so we do a review of the country’s waste repositories. These may be cargo containers, or a small building that can be secured. We do not ship radioactive waste out – there are not too many countries willing to accept another country’s radioactive waste,” she stressed.

Diplomacy plays a part, too: “We've convinced Russia to take back some of their original large sources from countries that don’t have facilities to handle these and the USA is also taking back some of its sources.” This, however, only works when the source can be traced back to a specific country.

Mac Kenzie, who has worked alongside many different governments, will be with the IAEA for a further year, putting together plans to get teams out in the field. Collecting data on sources and what they find is hard work, she admits, but there have been particular success stories in countries of the former Yugoslavia: Bosnia, Herzegovina and Montenegro. There are plans to go into Africa, China, and, when the situation permits this, Iraq.

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