Dissolution experiments of commercial PWR (52 MWd/kgU) and BWR (53 MWd/kgU) spent nuclear fuel cladded segments in bicarbonate water under oxidizing conditions. Experimental determination of matrix and instant release fraction

The denominated instant release fraction (IRF) is considered in performance assessment (PA) exercises to govern the dose that could arise from the repository. A conservative definition of IRF comprises the total inventory of radionuclides located in the gap, fractures, and the grain boundaries and, if present, in the high burn-up structure (HBS). The values calculated from this theoretical approach correspond to an upper limit that likely does not correspond to what it will be expected to be instantaneously released in the real system. Trying to ascertain this IRF from an experimental point of view, static leaching experiments have been carried out with two commercial UO2 spent nuclear fuels (SNF): one from a pressurized water reactor (PWR), labelled PWR, with an average burn-up (BU) of 52 MWd/kgU and fission gas release (FGR) of 23.1%, and one from a boiling water reactor (BWR), labelled BWR, with an average BU of and 53 MWd/kgU and FGR of 3.9%.; One sample of each SNF, consisting of fuel and cladding, has been leached in bicarbonate water during one year under oxidizing conditions at room temperature (25 +/- 5) degrees C. The behaviour of the concentration measured in solution can be divided in two according to the release rate. All radionuclides presented an initial release rate that after some days levels down to a slower second one, which remains constant until the end of the experiment. Cumulative fraction of inventory in aqueous phase (FIAPc) values has been calculated. Results show faster release in the case of the PWR SNF. In both cases Np, Pu, Am, Cm, Y, Tc, La and Nd dissolve congruently with U, while dissolution of Zr, Ru and Rh is slower. Rb, Sr, Cs and Mo, dissolve faster than U. The IRF of Cs at 10 and 200 days has been calculated, being (3.10 +/- 0.62) and (3.66 +/- 0.73) for PWR fuel, and (035 +/- 0.07) and (0.51 +/- 0.10) for BWR fuel. (C) 2015 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (author's final draft

Portuguese media discourse on nuclear energy before and after Fukushima: prepared for the EFDA Workprogramme 2012 WP12-SER-ACIF-1

This report presents the results of the analysis of nuclear related content in Portuguese print media. The report is submitted to the first step of the research task untitled Public Discourse about Nuclear Fusion before and after the Fukushima accident, as part of the Socio-Economic Research on Fusion under the general coordination of EFDA Workprogramme 2012

Japan as a Clean Energy Leader

Over the past several decades, Japan’s energy strategy had positioned it as the world’s leader in clean and efficient electricity production and usage. This strategy, heavily dependent on nuclear energy, was essentially destroyed by one of history’s largest earthquakes, followed by a tsunami which overwhelmed five nuclear reactors on March 11, 2011. As of April 2012, all of Japan’s 54 nuclear reactors have been shut down and it is uncertain when and how many may be restarted. This paper examines Japan’s options for crafting a new way forward with an energy policy to power the world’s third largest economy while taking into account the lack of domestic sources of fuel, high government debt, antinuclear sentiments and looming power shortages

Conversion of electron spectrum associated with fission into the antineutrino spectrum

The accuracy of the procedure that converts the experimentally determined electron spectrum associated with fission of the nuclear fuels ^{235}U, ^{239}Pu, ^{241}Pu, and ^{238}U into the $\bar{\nu}_e$ spectrum is examined. By using calculated sets of mutually consistent spectra it is shown that the conversion procedure can result in a small $\sim$1% error provided several conditions are met. Chief among them are the requirements that the average nuclear charge as a function of the $\beta$ decay endpoint energy is independently known and that the $\bar{\nu}_e$ spectrum is binned into bins that are several times larger than the width of the slices used to fit the electron spectrum.Comment: Accepted for publication in Phys. Rev.

Substitution and technological change under carbon cap and trade : lessons from Europe

The use of carbon-intense fuels by the power sector contributes significantly to the greenhouse gas emissions of most countries. For this reason, the sector is often key to initial efforts to regulate emissions. But how long does it take before new regulatory incentives result in a switch to less carbon intense fuels? This study examines fuel switching in electricity production following the introduction of the European Union’s Emissions Trading System, a cap-and-trade regulatory framework for greenhouse gas emissions. The empirical analysis examines the demand for carbon permits, carbon based fuels, and carbon-free energy for 12 European countries using monthly data on fuel use, prices, and electricity generation. A short-run restricted cost function is estimated in which carbon permits, high-carbon fuels, and low-carbon fuels are variable inputs, conditional on quasi-fixed carbon-free energy production from nuclear, hydro, and renewable energy capacity. The results indicate that prices for permits and fuels affect the composition of inputs in a statistically significant way. Even so, the analysis suggests that the industry’s fuel-switching capabilities are limited in the short run as is the scope for introducing new technologies. This is because of the dominant role that past irreversible investments play in determining power-generating capacity. Moreover, the results suggest that, because the capacity for fuel substitution is limited, the impact of carbon emission limits on electricity prices can be significant if fuel prices increase together with carbon permit prices. The estimates suggest that for every 10 percent rise in carbon and fuel prices, the marginal cost of electric power generation increases by 8 percent in the short run. The European experience points to the importance of starting early down a low-carbon path and of policies that introduce flexibility in how emission reductions are achieved.Energy Production and Transportation,Energy and Environment,Environment and Energy Efficiency,Carbon Policy and Trading,Markets and Market Access