Determination of the 6.13 MeV photon emission from the Pu(α, n)13 source and half life of 16N

To control the safe operation of the nuclear power plant Temelín in the Czech Republic an apparatus registering the presence of 16N is installed in the secondary circuit. On the basis of 16N activity measurement any eventual leakage from the primary into the secondary circuit is determined using a calculational model. A critical factor is the correct calculation of the detector efficiency for 6.13 MeV photons. The correctness of the calculations was verified by comparing calculated and measured efficiencies for photons emitted by 137Cs, 60Co, 24Na and 232Th sources of known activities and for 6.13 MeV photons produced due to the 13C(α, n)16O reaction in a Pu(α,n)13C neutron source with a certified emission rate for 6.13 MeV photons. Both the calculations and measurements were done in a very simple geometrical arrangement for NaI(Tl), BGO and HPGe detectors by means of various Monte Carlo codes. The difference between the calculated and measured values was used to derive the estimated uncertainty of the 6.13 MeV photon emission. lf life of 16N was checked experimentally because of a large scatter of data found in literature.