Studies of void distributions using neutron tomography

The thermal hydraulics of two-phase flows of water and steam is of importance for Boiling Water Reactors (BWRs). Because of the low density of steam, it nearly completely lacks the moderating and cooling properties of liquid water. Therefore, the volume fraction of steam is called the void fraction.

The thermal hydraulics of BWR relevant two-phase flows are being studied at several test loops, where electrically heated mock-ups of BWR fuel bundles and simplified geometries are being studied. The STUNT project aims to develop a new non-invasive technique for measurements of the void distributions at such test loops.

The proposed measurement technique is fast-neutron transmission tomography using portable neutron generators (DD or DT). Here, the test-loop test section is irradiated and the penetrating intensity is measured. Tomographic techniques are applied to reconstruct the internal attenuation distribution, which is used to calculate the local void fraction.

Selected publications

P. Andersson, “Optimization of Equipment for Tomographic Measurements of Void Distributions using Fast Neutrons”,
Licentiate thesis, Uppsala University, May 2011

P. Andersson, S. Jacobsson Svärd, H. Sjöstrand, “Effects of proton escape on detection efficiency in thin scintillator elements and its consequences for optimization of fast-neutron imaging”, Nuclear Instruments and Methods in Physics Research Section A, 651(1), September 2011. doi: 10.1016/j.nima.2011.01.002

P. Andersson, E. Andersson Sundén, S. Jacobsson Svärd, H. Sjöstrand, “Correction for dynamic bias error in transmission measurements of void fraction”, Review of Scientific Instruments, 83 (12), December 2012. doi: 10.1063/1.4772704