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Samples of graphite from a RBMK-1500 reactor at the Ignalina Nuclear Power Plant from different construction elements (stack, sleeve, and bushing) were analyzed by the instrumental neutron activation analysis (INAA) method (LVR-15 experimental reactor of the Research Centre Řež, Ltd.) using the prompt gamma activation analysis (PGAA) method (Heinz Maier-Leibnitz Zentrum) and with an inductively coupled plasma mass spectrometer (ICP-MS) (CPST, Lithuania). These measurements were performed with the aim of obtaining the missing information on the impurity distribution in the RBMK-type nuclear graphite constructions as well as for intercomparison purposes, with the results measured in the graphite sleeve samples previously obtained by INAA & GDMS (Glow Discharge Mass Spectrometry) at CEA Saclay, France, and ICP-MS (CPST, Lithuania) methods. Validation of the ICP-MS method for the nuclear graphite impurity concentration determination was proven. The experimentally obtained RBMK-1500 graphite impurity values in different graphite constructions were compared with other measurements and new limits of the possible maximal concentrations of nuclear RBMK graphite impurity concentrations were obtained.

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Poly(ethylene 2,6-naphthalate) (PEN) is promising as a new plastic scintillator, which emits deep-blue photons. Its photoluminescence emission peak (434–436 nm) and the decay time is of the order of 3 ns, as well as it is resistant to harsh environment. In this study, thin PEN film with high neutron cross section dopants was used for the thermal neutron detection. Iron boride, lithium tetraborate and lithium metaborate layers were coated on a 125 µm PEN film. Reaction particles from the boron neutron and lithium neutron reaction were detected by scintillation in PEN, and photomultiplier (PMT) pulses were registered and analysed. Energy deposition in the film samples was calculated using MCNP6 code taking into account losses in the source and air gap for the alpha particle source and incomplete energy deposition for the electrons. It was found that a small quantity of particles from the thermal neutron reaction could be detected in the strong neutron, gamma ray and recoil proton background.

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