Combined method of determining the neutron fluence for control samples in VVER-1000

A method of using diamond, which enables verifying activation-method indications obtained with 54 Fe, to determine fast-neutron fluence is described. The procedure is especially effective for investigating the behavior of VVER-100 vessel steel. An advantage of the method is that there are no requirements concerning data on the start and termination of irradiation or stopping of reactor operation. The diamond sensor retains information on the neutron fluence for a long time after irradiation; it is especially effective for irradiation times longer than 3 yr, when information obtained about the neutron flux by means of 54 Mn actually vanished because of the short half-life. The procedure for using diamond is simple and based on determining the expansion of its crystal lattice. Data obtained simultaneously by means of the activation method are used to compensate for the drawbacks of the diamond method.