The goal of the ENUBET project is to demonstrate that a precision of ∼1% on measurement of the absolute neutrino cross section at GeV scale can be achieved by monitoring the positron production in the decay tunnel coming from the three-body semileptonic decays of kaons. The baseline option for the tunnel instrumentation employs a fine-grained shashlik calorimeter with a 4.3 X0 longitudinal segmentation to separate positrons and pions coming from other decay modes of kaons. The system is complemented by rings of plastic scintillator doublets below the calorimeter acting as a photon veto to suppress the π0 background and to provide timing informations. SiPMs instrumenting the detector will be exposed to sizeble amounts of neutrons arising in ...