Radon-based assessment of stability effects on potential radiological releases

It is a requirement of nuclear energy and research facilities to conduct continuous and comprehensive atmospheric monitoring in order to better forecast public or environmental exposure to routine or accidental releases of radioactive substances to the atmosphere. A key aspect of such monitoring programs is the assessment of the atmospheric mixing state (or “stability”). Whether these facilities are in dense urban areas, or surrounded by heavily vegetated exclusion zones, local roughness heterogeneity can hamper attempts to accurately categorise stability by conventional meteorological techniques. Based on an analysis of 8 months of hourly climatology and atmospheric radon observations from a 60 m tower at the IFIN-HH nuclear research facility (Bucharest, Romania), we develop and apply a continuous (i.e. not categorical) radon-based scheme for the classification of the nocturnal atmospheric stability state. We demonstrate the superior performance of the radon-based technique to Pasquill-Gifford or bulk Richardson number stability typing at this site where heterogeneous roughness elements reach to 15 m a.g.l. Under stable nocturnal conditions the Pasquill-Gifford scheme overestimates the atmosphere’s capacity to dilute pollutants with near-surface sources by 20% compared to the radon-based scheme. Under these conditions, near-surface wind speeds drop well below 1 m s-1 and nocturnal mixing depths vary from ~25 m to less than 10 m a.g.l. Climatological parameters are characterised by season and 4 arbitrarily-defined nocturnal stability categories. Benchmarks (based on 10/50/90th percentile distributions) of 30-60 m wind and temperature gradients are devised for each stability category for evaluation of model performance. Lastly, nocturnal radon-derived effective mixing depth estimates constrained by tower observations are used to better-constrain the seasonal variability in the Bucharest regional radon flux: 13 mBq m-2 s-1 (winter), 18 mBq m-2 s-1 (summer)

Romanian Tritium for Nuclear Fusion

The demand for tritium is expected to increase when ITER (the International Thermonuclear Experimental Reactor) begins operation in the mid-2020s. Romania is expected to detritiate its CANDU (Canada Deuterium Uranium) units at Cernavoda starting 2024, with the goal of improving radiological safety and reactor performance. Detritiation will result in a significant quantity of tritium being produced and thus Romania has an opportunity to supply tritium for fusion. In this assessment, ITER has been used as a reference device requiring tritium, as the projected tritium extraction schedule from Cernavoda aligns favourably with ITER operation. The findings suggest that Romania is capable of providing a total of 6.2 kg of tritium to ITER over its 20 year operation, generating a potential revenue of $186 M (USD). Opportunities associated with the supply of Romanian helium-3 are also considered as a hedging option, which has the potential to generate$120 M (USD) in the case of zero tritium sales. Greater involvement in future fission-fusion tritium-related activities through experience in tritium technologies is also discussed as a unique opportunity for Romania

Modelling H-3 and C-14 transfer to farm animals and their products

The radionuclides {sup 14}C and {sup 3}H may both be released from nuclear facilities. These radionuclides differ from most others in that they are isotopes of macro-elements which form the basis of animal tissues, feed and, in the case of {sup 3}H, water. There are few published values describing the transfer of {sup 3}H and {sup 14}C from feed to animal derived food products. Approaches are described which enable the prediction of {sup 14}C and {sup 3}H transfer parameter values from readily available information on the stable H or C concentration of animal feeds, tissues and milk, water turnover rates, and feed intakes and digestibilities. It is recommended that the concentration ratio between feed and animal product activity concentrations be used as it is less variable than the transfer coefficient (ratio between radionuclide activity concentration in animal milk or tissue to the daily intake of a radionuclide)

Magnetic properties of a new molecular-based spin-ladder system: (5IAP)2CuBr4*2H2O

We have synthesized and characterized a new spin-1/2 Heisenberg antiferromagnetic ladder: bis 5-iodo-2-aminopyridinium tetrabromocuprate(II) dihydrate. X-ray diffraction studies show the structure of the compound to consist of well isolated stacked ladders and the interaction between the Cu(2+) atoms to be due to direct Br...Br contacts. Magnetic susceptibility and magnetization studies show the compound to be in the strong-coupling limit, with the interaction along the rungs (J' ~ 13 K) much greater than the interaction along the rails (J ~ 1 K). Magnetic critical fields are observed near 8.3 T and 10.4 T, respectively, establishing the existence of the energy gap.Comment: 10 pages, 4 figures, submitted to Phys. Rev. B Figure 4 did not print. *.eps files replaced with figures.ps fil

Very high rotational frequencies and band termination in 73Br

Rotational bands in 73Br have been investigated up to spins of 65/2 using the EUROBALL III spectrometer. One of the negative-parity bands displays the highest rotational frequency 1.85 MeV reported to date in nuclei with mass number greater than 25. At high frequencies, the experimental dynamic moment of inertia for all bands decrease to very low values, indicating a loss of collectivity. The bands are described in the configuration-dependent cranked Nilsson-Strutinsky model. The calculations indicate that one of the negative-parity bands is observed up to its terminating single-particle state at spin 63/2. This result establishes the first band termination case in the A = 70 mass region.Comment: 6 pages, 6 figures, submitted to Phys. Rev. C as a Rapid Communicatio

Making the most of what we have: Application of extrapolation approaches in radioecological wildlife transfer models

© 2015 The Authors. We will never have data to populate all of the potential radioecological modelling parameters required for wildlife assessments. Therefore, we need robust extrapolation approaches which allow us to make best use of our available knowledge. This paper reviews and, in some cases, develops, tests and validates some of the suggested extrapolation approaches.The concentration ratio (CRproduct-diet or CRwo-diet) is shown to be a generic (trans-species) parameter which should enable the more abundant data for farm animals to be applied to wild species.An allometric model for predicting the biological half-life of radionuclides in vertebrates is further tested and generally shown to perform acceptably. However, to fully exploit allometry we need to understand why some elements do not scale to expected values.For aquatic ecosystems, the relationship between log10(a) (a parameter from the allometric relationship for the organism-water concentration ratio) and log(Kd) presents a potential opportunity to estimate concentration ratios using Kd values.An alternative approach to the CRwo-media model proposed for estimating the transfer of radionuclides to freshwater fish is used to satisfactorily predict activity concentrations in fish of different species from three lakes. We recommend that this approach (REML modelling) be further investigated and developed for other radionuclides and across a wider range of organisms and ecosystems.Ecological stoichiometry shows potential as an extrapolation method in radioecology, either from one element to another or from one species to another.Although some of the approaches considered require further development and testing, we demonstrate the potential to significantly improve predictions of radionuclide transfer to wildlife by making better use of available data

A model approach for tritium dynamics in wild mammals

Tritium (3H) transfer into environment must be modelled differently than the transfer of other radionuclides released from nuclear reactors because hydrogen represents the building blocks of life. A solid understanding of 3H behaviour is essential because 3H may be released in large quantities from CANDU (CANada Deuterium Uranium) reactors and from future thermonuclear reactors. Recently, the authors published a complex dynamic metabolic model for 3H and 14C transfer in farm and wild animals, but the model applications for wild biota were restricted to too few examples and mostly for 14C transfer. In this study, the model is applied to few selected wild animals for 3H uptake. Despite the lack of any experimental data for wild animals, the results presented in this study are less uncertain than for many other radionuclides and can provide a useful estimation for biota radioprotection

A versatile model for tritium transfer from atmosphere to plant and soil

The need to increase the predictive power of risk assessment for large tritium releases implies a process level aproach for model development. Tritium transfer for atmosphere to plant and the conversion in organically bound tritium depend strongly on plant characteristics, season, and meteorological conditions. In order to cope with this large variability and to avoid also, expensive calibration experiments, we developped a model using knowledge of plant physiology, agrometeorology, soil sciences, hydrology, and climatology. The transfer of tritiated water to plant is modelled with resistance approach including sparce canopy. The canopy resistance is modelled using Jarvis-Calvet approach modified in order to directly use the canopy photosynthesis rate. The crop growth model WOFOST is used for photosynthesis rate both for canopy resistence and formation of organically bound tritium, also. Using this formalism, the tritium transfer parameters are directely linked to known processes and parameters from agricultural sciences. The model predictions for tritium in wheat are closed to a factor two to experimental data without any calibration. The model also is tested for rice and soybean and can be applied for various plants and environmental conditions. For sparce canopy the model uses coupled equations between soil and plants

Modelling the transfer of

Future development of nuclear energy in the frame of climate change and sustainable development needs an increased safety and consequently, robust models of environmental transfer of radionuclides. Tritium and Carbon are life elements and must be treated separately from trace elements. The IAEA promoted EMRAS (Environmental Modelling for Radiation Safety) project in order to decrease uncertainties in the predictive capability of environmental models, including the cases of aquatic and biota. To understand the processes and models reliability, nine scenarios have been developed. The Working Group contributed to the Revision of “Handbook of parameter values for the prediction of radionuclide transfer in temperate environments” TRS 364, as well. The main task of this paper is to propose ways for models' predictive power improvements, based on lessons learnt from EMRAS' exercises