Emailing n°2 :
Solution for Large Volume Nuclear Waste Non Destructive Assay
Introduction
Most of the conventional nuclear wastes are within large drum, typically 118L or 200L. For
recent nuclear waste, the radionuclide inventory is well known, but for old nuclear waste
radionuclide inventory can be inexistent or lost. Therefore waste characterization is
necessary. But using classic nondestructive assay technics (gamma-rays spectrometry and
neutrons counting) matrix effects and pure beta emitters can hindrance the right
characterization of large nuclear material. Calorimetry is the only complementary or used
alone method which can guarantee high level of confidence in the characterization of nuclear
waste
Nowadays, the calorimetric assay is:
3
• the only one Nondestructive Assay for quantification of pure beta emitter, such as H,
• the only one Nondestructive Assay with no matrix effect, such as neutron and gamma
rays interactions,
• Very accurate technic for radionuclide inventory combined with isotopic assay.
The issues
Calorimeters are precise devices which need precise temperature regulation. Until recently,
drum inspection for large volume was complicate or almost impossible due to
inhomogeneous distribution of nuclear material inside. Calorimetric assay was adapted for
sample from few liters up to 90 L. In order to answer to large volume problematic KEP
Technologies developed a new calorimeter (so called LVC1380) based on SETARAM
calorimeter knowhow.
Calorimetric technical achievements
The LVC1380 is a joint development between KEP Technologies and the French Atomic
Energy and Alternative Energies Commission (CEA) and features a unique sample reference
concept to deliver unique insulation from room temperature perturbations and delivering high
precision, low detection limits, rapid measurement times. It has been manufactured and
designed for the characterization of radioactive wastes and quantification of radioactive
elements (e.g. curium, plutonium and tritium) contained in a 200 liters (55 gallons) drum. It
can also be adapted for containers up to 385 liters.
The conception is based on heat flow measurement between a measurement cell and a
ghost reference cell (Patent CEA-KEP deposit S53023 ML-P). This new technology reduces
the size of the calorimeter and improves the thermal regulation, while keeping the good
analytical properties of the differential measurement.
Figure 1 – LVC 1380 view
www.kep-nuclear.com
Some results are presented in Table 1 and show a high level of precision between 10 mW
and 1W for experience with 200 liters drum.
Table 1 – Results of the LVC 1380.
Gamma heating estimation inside a calorimeter
KEP Nuclear can also offer MCNP modelling when in some special cases, due to neutrons
activation or release of fission products, gamma emitters can induce heating inside the
sample and the calorimeter. This gamma-heating can be evaluated in output power thanks to
gamma-ray spectrometry coupled with modelling. Such calculations are interesting when it is
needed for instance to quantify and discriminate tritium within activation products. Gamma
distribution inside a 20 liters calorimeter is presented on figure 2.
Figure 2 – Example of energy deposits inside a LVC 300 (MCNPX modelling).
Key element
Based on its calorimetric assay expertise, KEP NUCLEAR develops and combines also
different technologies for large nuclear waste characterization. A concept of characterization
line is presented on Figure 3 combining, calorimetry for overall heat measurement, gamma
spectrometry for radioisotope ratio determination and X-Ray scan for imaging of the drum
contain.
Figure 3 – Picture of the nondestructive characterization line.
www.kep-nuclear.com