#FISSION URANIUM AKTIE UPDATE#– It is essential to monitor and verify how the neutrons and the fuel material in general behave in the reactor, Klara explains, – such data has never been collected before for these particular fuel types and is vital in order to qualify the fuel for commercial application as well as to calibrate and update our simulation software, she says. A vital part of her work – and also the most exiting – has been the ongoing Thor Energy irradiation campaign in the OECD Halden research reactor, now in its third year. Klara’s thesis was on necessary steps for a successful commercialization of thorium fuels as well as simulations of how various mixes of thorium fuel perform in the reactor. Both open and closed thorium fueling options exhibit higher proliferation resistance than their corresponding uranium based cycles, as assessed by internationally recognized methodologies. Thorium fuel cycles are highly resistant to nuclear proliferative actions. Modelling shows that the decay profiles for dose rates from thorium-plutonium spent fuels are essentially the same as those for uranium-based fuels, but there are fewer chemical pathways for thorium fuels to be dissolved – especially in oxidizing environments. Thorium-plutonium fuels have good long-term radio-toxicity credentials. Thorium oxide would therefore serve as a good matrix for once-through fuel designed specifically to ‘burn’ plutonium. It is highly insoluble, it is non-oxidizable and it retains both fission products and actinides extremely well within its lattice. Thorium-plutonium fuel can be designed with a priority to maximise plutonium consumption – by maximizing the extent to which neutrons are moderated in the reactor.Ĭeramic thorium oxide has excellent properties as a waste-form in its own right even after irradiation. Thus, a thorium-plutonium fuel will achieve much greater net plutonium consumption than a regular MOX fuel (which makes new plutonium as it burns). Thorium itself generates essentially no plutonium, and no minor actinides as it burns – unlike uranium fuel. To this end, the design and licensing of uranium-plutonium (MOX) fuels has “paved the way” for thorium-plutonium fuels since it is only the added plutonium component that makes MOX fuels different from simple enriched uranium fuels. It is possible to design viable thorium-plutonium fuels for LWRs balancing intersecting issues of fuel reactivity, safety margins and reactor operability. This implies that thorium oxide fuels should be able to operate safely to high burn-ups. Thorium oxide fuels can therefore operate with lower internal pellet temperatures and exhibit less fission gas release than uranium fuels (including MOX). Ceramic thorium oxide (ThO 2) has excellent material properties for serving as a nuclear fuel. ThO 2 has a higher thermal conductivity and a higher melting point than uranium oxide and it is better able to retain fission products within its crystal lattice. Thorium will absorb neutrons in a thermal reactor and its reactivity will increase as its 233U content grows. It is possible to achieve net ‘breeding’ of 233U in thorium fuels in faster-spectrum variants of light water reactors (LWRs) and in heavy water reactors. #FISSION URANIUM AKTIE DRIVER#Reactor grade plutonium is a very good fissile driver since it is available from today’s spent nuclear fuel inventories. As the fuel operates, thorium is transmuted to uranium-233 which is an excellent fissile material that then yields energy in the fuel. In order to create a reactive thorium fuel capable of producing energy, some form of fresh or recycled fissile material is needed as a ‘driver component’. This is achieved by operating the fuel in a reduced-moderation core environment (lower hydrogen-to-heavy-metal-ratio), resulting in higher production of 233U and hence a slower rate of fissile depletion in the fuel.” Maximizing the cycle length for the reactor-fuel system. This is done by operating the fuel in a core environment with high neutron-moderation (a high hydrogen-to-heavy-metal ratio). Thorium-MOX fuels can be designed according to two distinct objectives: Maximizing the utilization – and hence the incineration – of plutonium. The main prerequisites for this work are that normal, cylindrical oxide fuel pellets are used, supporting our view that this fuel should be deployable in operating LWRs with a comparatively small licensing effort. To further characterize these advantages, fuel design work is underway. Thorium-MOX proved to be a viable and in many respects advantageous option. Thor Energy has undertaken a number of studies aiming to compare thorium-plutonium oxide fuel (Thorium-MOX) with other fuel types, uranium- and thorium-based.
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