4. Combined technology measurements
ANTECH instruments often combine different measurement technologies to provide an optional measurement solution.
These combined instruments usually include neutron and gamma measurements in a single system for waste assay and nuclear safeguards measurement applications.
3. Calorimetry measurements
Calorimetry measures the thermal energy released from a sample. It is applied in two areas:
- The measurement of plutonium in relatively large quantities. Thermal energy is generated through alpha particle decay.
- The measurement of tritium in relatively large quantities. Thermal energy is generated through beta particle decay.
Alpha and beta particles have a relatively short range inside the sample materials so the bulk of the energy released in the decay process is deposited locally in the sample. ANTECH calorimeters determine the rate of energy release by the samples through these decay processes.
Calorimeters are configured as single instruments, unlike gamma ray and neutron instruments in which the detector and counting electronics can be separated. The thermal element (or detector component) uses temperature sensitive materials such a nickel wire or thermocouples as a means of measuring temperature. It uses electrical heating elements as a means of depositing thermal energy for temperature control. The electronic coupling components are similar to electrical voltage and current measuring devices.
ANTECH employs two different calorimeter technologies: Isothermal calorimeters employ the power replacement method and achieving adequate measurement precision. Twin-cell heat-flow calorimeters are applied where high accuracy and precision measurement are required.
2. Neutron measurements
Neutrons are emitted by the decay of Special Nuclear Materials (SNM) and transuranic elements. Neutron measurement is the process of counting the neutrons emitted in nuclear fission. It is normally used to quantify uranium and plutonium. It is a sensitive technique that can be used to measure large or small quantities. The neutron measurement process can be passive or active. In PASSIVE measurement neutron emissions from the sample are measured by the detector and counting system. In ACTIVEmeasurement the sample is interrogated with neutrons from a neutron source or a neutron generator. The neutrons emitted from this induced fission are measured by the detector and counting system. ANTECH neutron counting electronics record the three different rates of neutron emission.
- Singles: the total neutron count rate arising from a sample (neutron totals counting)
- Pairs: the rate of emission of two neutrons in coincidence (neutron coincidence counting)
- Triples: the rate of emission of three neutrons in coincidence (neutron multiplicity counting)
ANTECH neutron instruments employ neutron detectors including fission chambers, boron proportional counters and helium-3 (He3) detectors.
1. Gamma ray measurements
Most radionuclides decay by gamma ray emission. Gamma ray measurement is the most common and widely used method for measuring nuclear material. It can be used to determine three different qualities of a sample:
- Total dose rate (commonly used for medical purposes)
- Ratio of the constituents of the sample
- Total radionuclide content of a source, either in terms of activity of the mass of a particular radionuclide
The gamma ray measurement process can be passive or active. In PASSIVE measurement the gamma rays emitted form radioactive decay are measured by appropriate detectors and counting electronics. In ACTIVE measurement gamma rays are used to interrogate samples and the attenuation of these interrogating gamma rays is measured. This is used to determine the ability for transmission through samples and thus the degree of attenuation in the sample material and the matrix in which it is contained.
ANTECH instruments perform gross gamma counting using ion chambers and plastic scintillators, and spectroscopy using low-resolution spectrometers (sodium iodide scintillators) or medium and high-resolution spectrometers (LaBr3scintillators and high purity germanium detectors). ANTECH instruments are configured to perform far field measurements to view entire objects, and segmented and tomographic gamma scanning for more complex samples.