Unfolding of polonium distribution in depth of irradiated lead–bismuth eutectic from α-particle pulse-height distribution

The α-particle pulse-height distribution measured from irradiated LBE is determined from the polonium distribution in it. The unfolding of vertical polonium distribution in irradiated LBE ingot is performed with the unfolding code UFOQ. The code uses quadratic programming to consider the constraint that polonium distribution does not have negative values. The response function defined as normalized α-particle pulse-height distributions caused by α-particles emitted from polonium in surface region, which is divided vertically to thin layers, of LBE ingot is calculated by Monte Carlo method. The polonium distribution around surface of irradiated LBE ingot is obtained clearly with the response function calculated for the surface region divided narrowly. Also, the polonium distribution in deeper layer of the surface region is obtained consistently with the response function calculated for the surface region divided widely.