Accident at J-PARC Hadron Experimental Facility

Announcement

Accident at J-PARC Hadron Experimental Facility

May 27, 2013

High Energy Accelerator Research Organization (KEK)

At 11:55 of May 23, 2013, an accident took place at the Japan Proton Accelerator Complex (J-PARC), which is jointly operated by the High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA). In its Main Ring, a bunch of proton beam was extracted in an anomalously short period of time, and hit the primary target made of gold at the Hadron Experimental Facility (HEF), likely due to a malfunction of the beam extraction system. As a result, the target is suspected to have partially evaporated. Immediately after this, radioactivity escaped from the beamline into the HEF hall, and the researchers working there were subjected to internal radiation exposure(*).

In addition, due to the usage of exhaust fans, the radioactive particles in the air were brought out of the HEF building, and caused a subtle increase of the environmental radiation level as observed by monitoring posts on the perimeter of the radiation control area around the facility. The radiation level at the monitoring posts along the site border of Nuclear Science Research Institute stayed normal. A monitoring post and a monitoring station in the neighboring Nuclear Fuel Cycle Engineering Laboratories showed a momentary increase of the environmental radiation level by 6 nGy/h, over the typical average, 70~130 nGy/h. The amount of radioactive substances released into the atmosphere is under investigation.

Due to the slow progress in investigation and assessment on these matters, reporting of this accident to the local communities, local agencies, national agencies and other related parties could not be delivered until late evening of May 24, 2013.

More on this incident are posted as follows:
[1] http://j-parc.jp/ja/topics/20130525press.html
  (First report from J-PARC, in Japanese, May 25, 2013)
[2] http://j-parc.jp/en/topics/20130525presse.html
  (First report from J-PARC, in English, May 25, 2013)
[3] http://j-parc.jp/researcher/ja/safety/HDtrouble20130525.pdf
  (Tentative explanation of the accident from J-PARC in Japanese, May 25, 2013)
[4] http://www.kek.jp/ja/NewsRoom/Release/20130525200000/
  (First report from KEK, in Japanese, May 25, 2013)
[5] http://j-parc.jp/ja/topics/HDtrouble20130526.pdf
  (Status of radioactive exposure of workers at HEF, from J-PARC in Japanese, May 26, 2013)

KEK is the organization which is primarily responsible for design, construction, operation and management of the Hadron Experimental Facility at the J-PARC. Currently, KEK, along with JAEA at J-PARC, is conducting close investigations on the radiation exposure of the personnel, release of radioactive materials and causes of this accident.

We at KEK would like to extend our sincere apologies to those who felt concerned about this accident and to the members of the communities in the neighborhood of J-PARC.

Atsuto Suzuki
Director General, High Energy Accelerator Research Organization

(*)As detailed in [5], as of May 26, measurement with a whole body counter has been completed on 49 individuals out of the 55 who were present at the HEF, and 30 have been found to have a dose level of internal exposure above detection threshold.