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Today marks the beginning of the 2012 nuclear security summit in South Korea. Ahead of the meeting, US President Barack Obama delivered a speech at Hankuk University in Seoul, in which he reiterated his hope for a world free of nuclear weapons.

Obama has been particularly worried about the ‘loose-nuke’ scenario, in which a terrorist procures some nuclear material and fashions it into a crude weapon. One source would be research reactors, many of which were built during the height of the cold war and run on highly enriched uranium-235 (HEU) — the same material used in basic nuclear weapons.

In 2010, I accompanied a group of American advisers as they spirited uranium out of the Polish Institute of Atomic Energy in Otwock-Świerk, 30 kilometres southeast of Warsaw. It was a big undertaking, and you can watch a shaky bit of video from my trip below.

The US National Nuclear Security Administration, which oversaw the operation, continues to work at converting research reactors and removing nuclear material. Today the agency announced the successful conversion of Mexico’s lone research reactor to the less dangerous low-enriched fuel.

It’s a positive step, but to really get the research-reactor problem under control, the US needs to work on Russia, which has dozens of HEU-fuelled research reactors (see diagram). After years of negotiation, Russia has agreed to do “feasibility studies” on the possibility of converting a handful of its reactors, according to Matthew Bunn, a non-proliferation expert at Harvard University in Cambridge, Massachusetts. But Russia, Bunn says, could do much more. The former superpower “has not yet committed even to do a study of which ones are still needed, and which could be converted or shut down.” Bunn has a new report out this month with a lot more detail on the research-reactor problem.

Russia is the biggest concern, but the West also has its fair share of research reactors running on HEU. One important use is the creation of medical isotopes for cancer treatments. Techniques involving low-enriched uranium are in development, and this morning Belgium, France, the Netherlands and the United States pledged to end the use of HEU processes by 2015.

You can read a lot more about the research-reactor problem in this feature about the ongoing US effort to secure HEU reactor fuel.

Image source: NNSA