Development of novel assays for ‘difficult-to-measure’ radionuclides in materials produced during nuclear decommissioning activities

Research output: Other contribution

Abstract

When a nuclear reactor enters in a decommissioning phase, large amounts of materials are
generated. Dismantled materials such as concrete or graphite have to be characterized for their
radioactive content to prove conformity with regulations related to unconditional or conditional
release and final disposal. Gamma emitters such as 60Co or 137Cs, easy to measure radionuclides (ETM),
can be quantified by using gamma-ray spectrometry. However, in the case of pure beta- and alphaparticle
emitters, called difficult to measure radionuclides (DTM), a radiochemical separation is needed
to obtain the required selectivity of the analysis method. Moreover, the radiotoxicity, mobility and
half-lives of the radionuclides are important factors to consider in the waste disposal repositories from
the safety point of view. Scaling factors are commonly applied to estimate the activity of DTM
radionuclides based on the measurement of ETM radionuclides, but the disadvantage of this method
is the large uncertainty on the results.
This research focuses on analytical method development for several important DTM radionuclides,
including 36Cl, 129I, 79Se, 41Ca, 151Sm and 147Pm. All these radionuclides are beta-particle emitting
radionuclides and are considered in radiological safety assessments for waste management. 36Cl and
41Ca are neutron activation products in graphite and concrete respectively, while 79Se, 129I, 151Sm and
147Pm are fission products.
The objectives of the project are: (1) development and optimization of sample decomposition
techniques and (2) development of individual or sequential radiochemical separation methods and (3)
application of automated of radiochemical separation systems. Different type of samples such as soils,
sediments, vegetation, graphite, concrete, filter and water are considered in this project. For the
sample decomposition, fusion (Katanax K3 automated fusion fluxer) and pyrolysis (RADDEC pyrolyser)
techniques will be investigated. Liquid scintillation counting (LSC) will be used to determine the activity
concentration levels of all the selected radionuclides (considering beta interferences) and triplequadrupole
inductively coupled plasma mass spectrometry (ICP-QQQ) will be used for quantifying the
mass concentration of mainly 79Se, 151Sm and 41Ca (considering isobaric interferences).
Thus, with these newly developed methodologies, it will reduce the uncertainies with respect to
the inventory estimation for these DTM radionuclides, and thereby facilitate more accurate waste
characterization and cost-effective waste management in nuclear decommissioning.
Original languageEnglish
TypePhD Day presentation SCKCEN
Media of outputStreaming/Youtube
Publication statusPublished - 13 Nov 2020

Keywords

  • DTM, LSC, ICP-QQQ

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