In 2022–2024, the Sosny R&D Company successfully designed, manufactured and supplied two facilities for the nuclear material control and specific activity measurements of the drums with solid radioactive waste (SRW) to the FSUE Mayak Production Association.
These facilities are to check the presence and determine the mass (weight) of the nuclear materials in the SRW. They also intended to measure the specific activity of alpha, beta, and gamma emitting nuclides in the SRW generated during the cutting of the AMB spent fuel assemblies for further account of the SRW.
The categories of the SRW under control are intermediate level waste and high level waste.
Parameters of SRW under control:
| Maximum mass | 600 kg |
| Maximum outer diameter of the drum | 860 mm |
| Height | 860 mm |
| Drum wall thickness | 2 mm |
The facility comprises the nuclear material mass measurement unit and the SRW activity measurement unit.
The active neutron technique using the pulse neutron generator ensures detecting the mass of the nuclear material. The nuclear material mass measurement unit is a measuring chamber. Its walls are made of polyethylene and cadmium lined with the stainless steel from the outside. Three walls have 20 neutron detectors inside, which are arranged at a fixed pitch. They are intended to register the intrinsic neutron radiation and induced neutron radiation in the object under control. The emitter of the pulse neutron generator is at the fourth wall from the outside. One neutron detector (monitor) is for monitoring the intensity of the pulse neutron generator.
The measuring chamber has remote-controlled slide gates for protection from the background neutron radiation and reflected neutron radiation during the measurements.
The object under control (SRW drum) shall be hung up in the center of the measuring chamber. The target of the pulse neutron generator generates neutron pulses with an energy of 14 MeV. To form a set energy spectrum, the neutrons will be moderated by lead and steel bricks, and then by the material of the measuring chamber walls to the thermal energy and induce fission of the fissile nuclides in the SRW nuclear materials.
The layout of the neutron detectors was selected to minimize the effect of a heterogeneous distribution of the nuclear material within the SRW drum volume, with no need to rotate the drum being measured. The pulse time interval analyzer selects a time window after the end of neutron pulse when only epicadmium neutrons resulting from the fission of the nuclear fissile material in the object under control are registered. The mass of nuclear materials contained in the SRW drum under control is determined by the measured neutron count rate using the calibration factors obtained by numerical simulations of the matrix of the object under control and using the reference materials of the nuclear fissile materials.
The SRW activity measurement unit is arranged above the nuclear material mass measurement unit. The SRW activity measurement unit includes three measuring spectrometric devices, each comprising two CdZnTe gamma radiation detectors. Every measuring device has a 152Eu calibration source and a remote source positioning system.
The facility operation modes are controlled with the industrial computer monitors mounted in the control cabinets. These monitors are also to display the results of measurements of the nuclear material mass and the STW activity. In addition, they can transmit control results to the external display equipment and multi-functional automated information data system.
Specifications of the facility:
| Safety Class as per NP-016-05 | 4 |
| Nuclear material under control (if any SNF) | 235U, 239Pu, 241Pu |
| Minimum monitored total mass of fissile nuclides: | |
| if the burnup is 1 MW·day/kg | 20 g |
| if the burnup is 45 MW·day/kg | 10 g |
| Maximum monitored total mass of fissile nuclides (sum of 235U, 239Pu, 241Pu) | 100 g |
| Duration of measurement of the nuclear material in the SRW | ≤20 minutes |
| Duration of measurement of the neutron background | ≤10 minutes |
| Duration of measurement of the specific activity of the SRWper one orientation of the SRW drum | ≤20 minutes |
| Continuous operation time | ≥8 hours |
| Internal dimension of the measuring chamber in the horizontal plane | 900 mm |
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