Dear subscribers of J-PARC Project Newsletter,

As most of you have been already aware of, there was the radiation 
leak accident at the Hadron Experimental Facility at J-PARC on May 
23. Since then all J-PARC facilities have been shutdown and we are 
making every effort to restore the trust from users and also related communities.
Here, we are sending the English version of "J-PARC News" of which 
Japanese version has been published the end of May.

We are trying to make our every effort to keep updating the 
information on the accident and also the J-PARC status. You can reach 
them at the J-PARC homepage (

Yumiko Watanabe, Ph.D.
Leader, International Relations
J-PARC Center
Tokai-mura, Ibaraki, Japan


The Accident at the J-PARC Hadron Experimental Facility
                                    31 May 2013
                                    Yujiro IKEDA
                                    Director, J-PARC center

We would like to express all our deepest apologies for any 
disruptions and concerns that may have been caused by the leakage 
accident of radioactive material at the Hadron Experimental Facility 
of Japan Proton Accelerator Research Complex (J-PARC) in Japan.

On 23 May, due to a malfunction of the beam extraction system of the 
50 GeV synchrotron, a proton beam was delivered to the gold target of 
the Hadron facility within a very short time. As a result, the gold 
target is considered to have momentarily reached an extremely high 
temperature and part of the target was damaged. Radioactive material 
then leaked into the hadron experimental hall and some workers 
externally and/or internally exposed to radiation.

Operation of ventilation fans of the hall resulted in the leak of 
radioactive material out of the radiation controlled area of the 
Hadron Experimental Facility. The data logs of radiation dose rates 
at monitoring posts in the Nuclear Science Research Institute showed 
no signatures. However, at the three monitoring posts and stations of 
the neighboring JAEA facility, momentary increases of the radiation 
dose rate were observed. It is assessed that the released radioactive 
material was diluted and attenuated as it dispersed in a narrow strip 
towards the west. The maximum integrated radiation dose has been 
estimated even at the site boundary closest to the Hadron 
Experimental Facility was 0.29 µSv (preliminary).

All the J-PARC facilities have been shutdown since the accident. A 
full investigation of the cause of the accident is now underway along 
with the complete review of safety practices and emergency procedures 
at all J-PARC facilities. Our first priority is to restore public 
trust in the facility by developing and implementing measures to 
prevent the reoccurrence of an accident and to provide a safe 
experimental environment for users and workers.

We would deeply appreciate your understanding and continuous support.