Multiple-Scattering Budgets for Verification of Spent Fuel Dry Storage Casks by Muon Tomography

This paper computes the muon attenuation, exposure and resolution budget for imaging a spent fuel dry storage cask with cosmic-ray muons. Sight lines through 1.2 metres of steel, concrete and fuel assemblies at a density of 4.5 grams per cubic centimetre present an opacity of 540 grams per square centimetre (5.4 metres of water equivalent), which sets a minimum muon energy of 1.081 GeV and a transmitted vertical intensity of 74.75 per square metre per second per steradian. For a detector of 2 square metres with the stated acceptance and efficiency, divided among 120 image elements, the stated feature produces a flux contrast of 1.324 and reaches five standard deviations in 0.0001471 days of counting, while the target precision of 0.05 per image element requires 0.004129 days. A deployment of 14 days delivers a per-element precision of 0.0008587, corresponding to a thickness sensitivity of 0.00103 metres. The combined angular resolution is 63.3 milliradians, of which tracking contributes 0.4714 milliradians and multiple scattering at the threshold momentum 63.3 milliradians. The budget is compared with published muography of the same class of target, for which muon tomography experiments at Los Alamos and elsewhere have imaged the contents of a dry storage cask and reported sensitivity to the removal of a single fuel assembly. Every number is computed by the accompanying script from the stated inputs. Computed, not measured.