Epithermal and Fast Neutron Radiography Using Photoluminescent Imaging Plates and Resonance and Threshold Activation Detectors

Epithermal and Fast Neutron Radiography (FNR) are complementary to the conventional radiography with high energy gamma-rays or brems-strahlung radiation and which iarecommonly used for the inspection of thick metal objects. The advantage of using high energy neutrons for radiographic examination of thick metal objects is their higher penetration power and improved contrast sensitivity. Rather low detection sensitivity of direct and indirect epithermal fast neutron imaging methods using photographic films often poses a problem for FNR for NDT of thick objects. Resonance and fast neutron imaging method based on photoluminescent imaging plates (IP) in combination with activation detectors as converter screens in transfer exposure technique was successfully tested at the Budapest KFKI research reactor. The threshold activation detectors were the reactions In(n, n) In, Zn(n,p) Cu, Fe(n,p)Mn, Mg(n,p) Na and 27Al(n.α) Na. These threshold reactions cover the fast neutron energy region between 0.7 MeV and 12 MeV. The detectors for resonance neutron detection were activation reactions 115In(n,γ)116mIn, 3Cu(n,γ)64Cu and 164Dy(n,γ)165Dy. The very high sensitivity of IP , the linearity of their response over 5 decades of exposure dose and the high dynamic digitalisation latitude (12 bit) enable practical EN/FN radiography using neutron beam of a research reactor (Φn≈ 10 n/cms, RCd ≈ 2). The image quality of novel FNR method is comparable to the quality one encounters in thermal