FOR IMMEDIATE RELEASE
March 27, 2015
Cosmic-ray Muon Technology to be Used
To Image Debris Inside Fukushima Dai-ichi Reactors-Can image debris as small as 30-cm sizeTOKYO-Toshiba Corporation (Tokyo: 6502) and the International Research Institute for
Nuclear Decommissioning (IRID) today announced the development of a muon*1-based
technology for imaging and mapping nuclear fuel debris inside the reactor pressure vessel(RPV) of the Fukushima Dai-ichi Nuclear Power Plant. The system was developed as thepart of sub-project for “Development of Fuel Debris Sensing Technology for NuclearReactors” financed by the Agency for Natural Resources and Energy.
Dismantling the tsunami-damaged reactors at Fukushima Dai-ichi can be speeded up if therecovery team has a realistic estimate of the damage and the location of nuclear fueldebris in the core. In the case of Three Mile Island, it took 10 years before this could beassessed. At Fukushima, measurement of cosmic-ray muons seemed to offer a way
forward, but imaging resolutions achieved with conventional methods are not sufficient toidentify debris in the RPV.
The solution developed by Toshiba and IRID successfully measures the scattering of
cosmic-ray muons before and after they pass through the reactor core. Technicalevaluations and simulations have confirmed that actual measurements using muon trackers
can image debris as small as 30-cm in size. Imaging at Fukushima Dai-ichi Unit 2 will
start within FY2015, after completion of final testing and installation.
The high penetrative power of naturally occurring cosmic-ray muons has long been
known, and their use in obtaining density maps has been demonstrated with objects asdiverse as Egypt’s pyramids, a temple gate and the interior of volcanoes. However,standard muon transmission methods cannot be used at Fukushima as the rays arescattered too much by the thick concrete and steel walls of the RPV. It is impossible todistinguish between uranium and water in the core.
Toshiba and IRID have adapted a novel technology for measuring the scattering behaviorof muons penetrating objects, building on techniques originally developed by the Los

Alamos National Laboratory (LANL) in the United States. Two external detectors areplaced in parallel to one another on opposite sides of the reactor building, and cosmic-ray
muon trajectories, scatter and scatter angle are recorded. The scatter angle is directly
related to the atomic number of objects the muons collide with, and uranium can be
distinguished from surrounding structural objects with lower atomic numbers.
Toshiba has enhanced the detection process to the point where RPV fuel debris as small as
30cm can be imaged, by developing an electric circuit and algorithms that remove
gamma-ray noise from the high radiation background at Fukushima. By combining
Toshiba’s gamma-ray noise removal technology, which has been accumulated throughdevelopment of measurement instruments for inside the reactors, with the muon-scattering
method developed by LANL, the collaboration, started in 2013, will be put to practicaluse for Fukushima Dai-ichi.
Mamoru Hatazawa, Vice President of Toshiba Corporation Power Systems Company said,“All of us at Toshiba are pleased to have worked with LANL on development of thistechnology. We are confident that it will prove to be a useful tool for analyzing the interiorof the RPV, pinpointing the locations of fuel debris, and pointing the way forward in thedecommissioning of Fukushima Dai-ichi. We also hope that this innovative approach willfind applications in other areas”.
Duncan McBranch, the Chief Technology Officer of LANL said, “This collaboration has
helped to demonstrate an important new technique for mapping nuclear facilities.
Thanks to the partnership between Japan and the US Department of Energy, and to ourcollaborators at Toshiba and IRID, we have scaled up a technique that was originallydeveloped for detecting nuclear materials in shipping containers. We are hopeful that
this collaboration can accelerate the remediation work at Fukushima Dai-ichi”.
The detection technology will not only help to locate the debris, but provide essential data
for selection of efficient fuel removal method and for designing extraction equipment at
an early date. Toshiba and IRID will continue to contribute to R&D supporting thedecommissioning of Fukushima Dai-ichi.
*1 A cosmic-ray produced by collisions of high-energy electrons and protons with nitrogen and oxygen in theatmosphere.

Measurement Device:Settings at the Site (Image):###About Toshiba:
Toshiba Corporation, a Fortune Global 500 company, channels world-class capabilities inadvanced electronic and electrical product and systems into five strategic businessdomains: Energy & Infrastructure, Community Solutions, Healthcare Systems & Services,Electronic Devices & Components, and Lifestyles Products & Services. Guided by theprinciples of The Basic Commitment of the Toshiba Group, “Committed to People,Committed to the Future”, Toshiba promotes global operations towards securing “GrowthThrough Creativity and Innovation”, and is contributing to the achievement of a world inwhich people everywhere live safe, secure and comfortable society.
Founded in Tokyo in 1875, today’s Toshiba is at the heart of a global network of over 590
consolidated companies employing over 200,000 people worldwide, with annual sales
surpassing 6.5 trillion yen (US$63 billion).

To find out more about Toshiba, visit www.toshiba.co.jp/index.htm
Toshiba Press Contact:
Hirokazu Tsukimoto / Aya Oshima
PR & IR Office, Toshiba Corporation+81-3-3457-2100
media.relations@toshiba.co.jp

About IRID:
International Research Institute for Nuclear Decommissioning (IRID) was established on
August 1, 2013 as an organization to develop nuclear power plant decommissioning
technologies efficiently based on collective wisdom from Japan and abroad, composed of
18 member corporations such as electric companies, plant manufacturers and research
institutes.
Now IRID carries out research and development of the technologies required for thedecommissioning of the Fukushima Daiichi NPS as a matter of urgency and enhances thecollaboration with the international and national relevant organizations as well as
promotes human resource development for the research and development.
To find out more about IRID, visit http://irid.or.jp/en/
IRID Press Contact:
Tomohisa Ito
Corporate Communications Team, IRID
+81-3-6435-8607
tomohisa-ito@irid.or.jp