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Open problems in radiological risk assessment of Tritium emissions including climate changes
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Acronym: OPTRAS
Contracting Authority: Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI)
Number / Date of the contract: PN-III-P4-ID-PCE-2016-0218 / 2017-07-12
PN-III-P4-ID-PCE
Project Manager: Anca Melintescu
Partners:
Starting date / finishing date: 2017-07-12 / 2019-12-31
Project value: 850000 RON
Abstract: In order to prove the enhanced safety and reduced costs, nuclear energy needs robust radiological impact assessment models. In Romania, developing CANDU technology, tritium is the main radioactive pollutant. Once emitted into environment as tritiated water (HTO), tritium enters the life cycle and is transformed in plants in exchangeable and non-exchangeable organically bound tritium (E-OBT and NE-OBT). The residence time of NE-OBT in plants and animals is longer and the health impact (radiological dose) is higher than that of HTO and E-OBT. For normal operation of the nuclear facilities, the present models under estimate the tritium concentration in plants comparing with the experimental results. For short term and intense emissions (incidents) the present dynamic models have an unacceptable large range of predictions for tritium concentration in plants. Similar processes for tritium transfer in environment are involved in both situations (normal operation and incidents), but for OBT formation in crops some processes are still not yet well understood, mostly at night. A novel conceptual model for OBT production at day and night was recently developed by IFIN-HH researchers. The project objective is to develop a new model for practical application in radiological risk assessment, considering the detailed dynamics of tritiated compounds formed in photosynthesis and the subsequent biochemical reactions at various time steps during the development stage of crops. The modelling of HTO concentration dynamics in leaves will be improved considering the balance between air and root pathways and the role of stomata conductance. The project will consider the main crops in Cernavoda area, including the effects of climate changes on HTO and OBT concentration in crops at harvest. The project will also consider the biota radioprotection as it was recently required by EC and will use concepts of animal adaptation to environment and the available data on carbon and caesium dynamics in biota.

Objectives: Development of an advanced process level oriented model for atmospheric tritium emissions in field conditions considering the fluctuating meteorological conditions and non-equilibrium situations of processes involved in tritium transfer between air, soil, plants, and animals (including biota), satisfying the general requirements regarding the data quality and applicability in operational cases for both routine and short term releases in case of incidental/accidental situations, based on the same processes involved in tritium transfer in environment, but taking into account different time scales (1 day for routine releases versus 10 minutes up to 1 hour for incidental/accidental releases).

THE STAGES OF THE PROJECT AND DELIVERY DATES
1. Development of conceptual model for HTO dynamics in leaves and OBT production in leaves with a time step of an hour. Model tests with experimental data for winter wheat (2017-12-15) Results
2. Model extension to other plants of interest for Cernavoda area, considering the specific characteristics of those plants and including the effects of climate changes (2018-12-15) Results
3. Uncertainty and sensitivity studies of the tritium model developed for various agricultural plants of interest for Cernavoda area. The improvement of tritium transfer model for biota radioprotection (2019-12-15)
RESULTS [Project Activity Report]
PUBLISHED ARTICLES
RESEARCH TEAM

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