Explanation?

June 23, 2017

Resin stuck on plutonium could be to blame for Ibaraki accident

http://www.asahi.com/ajw/articles/AJ201706230052.html

Gas produced when radiation caused an adhesive to decompose is believed to have led to the leak of a container holding plutonium that contaminated five workers, the Japan Atomic Energy Agency (JAEA) has announced.

The five workers at JAEA’s Oarai Research and Development Center in Oarai, Ibaraki Prefecture, were accidentally exposed to radioactive plutonium on June 6 when they were handling 26-year-old radioactive waste stored at the facility.

The tightly sealed polyethylene container wrapped in plastic bags contained radioactive substances including plutonium powder set in epoxy resin, JAEA staff said at a June 22 meeting with the special investigation team from the science and technology ministry set up to determine the cause of the accident.

JAEA said it is now investigating further the possibility that radiation may have decomposed the epoxy resin to produce gas that seeped out of the container and caused its plastic coverings to tear and contaminate the workers.

The agency found out about the resin by interviewing employees who were involved in experiments using radioactive substances and disposal of used test samples in 1991, when the container that caused the accident was first sealed.

According to the JAEA report, researchers at the facility conducted experiments to analyze the atomic structure of plutonium using X-rays in 1991. To do that, plutonium powder was mounted on a sheet of aluminum using the epoxy resin as adhesive.

After experiments, the piece of resin was removed from the aluminum sheet and placed in the polyethylene container. Then, it was wrapped in the plastic bags and placed in a stainless steel storage container.

JAEA did not inspect the state of the contents of the stainless steel container for the next 26 years.

The agency plans to submit a detailed report on the cause of the accident to the Nuclear Regulation Authority (NRA) and other parties as early as late July.