page_title: Muon tomography
section_title: Los Alamos Concrete Reactor
hierarchical_section_title: Muon tomography / Muon scattering tomography / Los Alamos Concrete Reactor
caption_attribution_description: English: Left – Lead reactor core with conic void. Right – Observed core where average scattering angles of muons are plotted. The void in the core is clearly imaged through two 2.74-m concrete walls. The lead core of 0.7-m thickness gives an equivalent radiation length to the uranium fuel in Unit 1, and gives a similar scattering angle. Hot spots at the corners are artifacts caused by edge effect of MMT.
context_page_description: Muon tomography is a technique that uses cosmic ray muons to generate three-dimensional images of volumes using information contained in the Coulomb scattering of the muons. Since muons are much more deeply penetrating than X-rays, muon tomography can be used to image through much thicker material than x-ray based tomography such as CT scanning. The muon flux at the Earth's surface is such that a single muon passes through an area the size of a human hand per second.
  Since its development in the 1950s, muon tomography has taken many forms, the most important of which are muon transmission radiography and muon scattering tomography. Muon tomography imagers are under development for the purposes of detecting nuclear material in road transport vehicles and cargo containers for the purposes of non-proliferation.
  Another application is the usage of muon tomography to monitor potential underground sites used for carbon sequestration.
context_section_description: In the summer of 2011, a reactor mockup was imaged using Muon Mini Tracker (MMT) at Los Alamos. The MMT consists of two muon trackers made up of sealed drift tubes. In the demonstration, cosmic-ray muons passing through a physical arrangement of concrete and lead; materials similar to a reactor were measured. The mockup consisted of two layers of concrete shielding blocks, and a lead assembly in between; one tracker was installed at 2.5 m height, and another tracker was installed on the ground level at the other side. Lead with a conical void similar in shape to the melted core of the Three Mile Island reactor was imaged through the concrete walls. It took three weeks to accumulate 8 × 10⁴ muon events. The analysis was based on point of closest approach, where the track pairs were projected to the mid-plane of the target, and the scattered angle was plotted at the intersection. This test object was successfully imaged, even though it was significantly smaller than expected at Fukushima Daiichi for the proposed Fukushima Muon Tracker (FMT).
caption: Left – Lead reactor core with conic void. Right – Observed core where average scattering angles of muons are plotted. The void in the core is clearly imaged through two 2.74 m concrete walls. The lead core of 0.7 m thickness gives an equivalent radiation length to the uranium fuel in Unit 1, and gives a similar scattering angle. Hot spots at the corners are artifacts caused by edge effect of MMT.[23]