Page 362 - 00. Complete Version - Progress Report IPEN 2014-2016

362 Nuclear Safety | Progress Report

work in order to contribute to the assessment the ejection of a thin layer of the material in
of the durability of cementitious materials in the form of plasma that cools down after fly-
a deep borehole for disposal of disused sealed ing a short distance from the ejection point,
radioactive sources. In the environment of a eventually resulting in an aerosol cloud. The
deep borehole for this waste, the aging hydrat- ablated material is captured by vacuuming
ed cement material is exposed to the radio- the surface during the ablation and collect-
lytic effects of the radiation field of the sourc- ing the particles in an air filter.
es, the high temperature determined by the
geothermal degree of the disposal site and The main advantage of laser ablation over oth-
the disposal depth, and is possibly exposed to er techniques is the low volume of secondary
aggressive chemical species dissolved in the waste generated in the decontamination pro-
ground water. Presently, the assessment of the cess. Indeed, laser ablation generates the low-
long-term behavior of cement materials can est volume of secondary waste that is the vol-
only be done by accelerated tests in laborato- ume of the filter used to collect the ablated
ry and modeling. The GRR’s work in this field material. Other advantages are the indepen-
is combining both methods, taking advantage dence of the process on different surfaces, the
of the availability of the Multipurpose Irradia- portability of the decontamination equipment
tor to irradiate cement specimens cast in lab- and the low cost.
oratory with the expected integrated radia-
tion dose delivered to the material until the As the dismantling and decommissioning of
sources are decayed. The effects of the radia- nuclear facilities generate high volume of ra-
tion, temperature and chemical species in the dioactive waste composed of pieces of equip-
cement specimens are evaluated by X-Ray Dif- ment and structures contaminated in the sur-
fraction and microtomography, among other face, the laser ablation is a technique that may
methods, to observe changes in the mineralo- be of interest as a decontamination tool. The
gy and microstructure of the material. The re- GRR is participating in a development proj-
sults of the accelerated tests in laboratory are ect together with the IPEN’s Center of Laser
important as input data to model the behav- Applications whose goal is to build an exper-
ior of cementitious materials under the con- imental laser-ablation decontamination tool.
ditions expected in a borehole repository and
to validate data used in the safety assessment Isotopic characterization of
of the disposal facility. radioactive waste drums

Use of laser for cleaning of GRR has built an automated system for isoto-
radioactively contaminated surfaces pic characterization of radioactive waste drums

using segmented gamma scanning (SGS). The
Laser ablation is a process of removing materi- figure 2 shows the equipment that resulted
al from a surface by irradiating it with a laser from the project. The detection system is com-
beam. This technique was previously tested posed of an HPGe detector and associated elec-
and showed to be effective in decontaminat- tronics. A PLC (Programmable Logic Controller)
ing the surface of radioactively contaminat- automates and controls the drum driving sys-
ed metal scrap produced in the dismantling of tem. This system allows controlling the eleva-
radioactive lightning rods. The energy of the tion and rotation of the base where the radio-
laser beam deposited in the surface produces active waste drum is positioned. The result is

Instituto de Pesquisas Energéticas e Nucleares