Analyzing & Testing Characterization of Nuclear Materials Methods, Instrumentation, Applications Leading Thermal Analysis Introduction The world demand for electricity is In addition, the nuclear reactors of projected to double by mid-century. current design are safe and, save a Because of the ever-increasing price natural disaster such as the magnitude of fossil fuels and the associated 9 earthquake east of Japan and environmental concerns such as carbon resulting tsunami, accidents are highly dioxide emissions, nuclear power unlikely. In spite of the accident at the generation is regaining popularity. Fukushima nuclear power plant caused Nuclear fuel is clean and relatively by the earthquake/tsunami, the strong inexpensive compared to fossil fuels. resurgence – so-called renaissance – of It is in fact the only source of clean, nuclear power is expected to continue. sustainable and affordable energy which can meet current and near-term This renaissance has led to the demands for electricity generation, formation of a multi-national if sufficient numbers of reactors of cooperation called the Global Nuclear current and advanced design can be Energy Partnership (GNEP). Two of the brought on line in a timely manner. stated aims of GNEP are to: 2 develop a new generation of nuclear development and the GEN IV reactors power plants – the so-called Genera- under consideration are of unique design tion IV systems (GEN IV) in which with respect to safety, performance and six different reactor types are under economics. The GEN IV reactors include consideration (both thermal and fast the Very High Temperature Reactor reactors), and (VHTR), the Sodium-cooled Fast Reactor (SFR) and perhaps the most unique, the reduce waste by recycling used Molten-Salt Reactor (MSR). Many of nuclear fuel using new technologies. these reactors will contain unique fuel systems and reactor materials. The history of commercial nuclear power generation reaches back to the mid-60s. The Generation III+ reactors now under Generation I Generation II Generation III Generation III+ Generation IV Early Prototype Commercial Power Advanced LWRs Evolutionary Highly Reactors Reactors Designs Offering Economical LWR-PWR, BWR Improved Enhanced Safety CANDU Economics Minimal Waste AGR for Near-Term Proliferation Deployment Resistant I II III III+ IV 1950 1960 1970 1980 1990 2000 2010 2020 2030 Time line for reactor development 3 Introduction Source: Idaho National Laboratory The major concern with nuclear power Long-lived I and Tc generation today is the safe disposal of Minor 0.1% used fuels. Because of storage-related Actinides 0.1% Cs and Sr problems, recycling of used fuel is of Plutonium 0.3% paramount importance. Fuel recycling 0.9% is not a new concept. In fact, used fuel Other Long-lived from light-water reactors (LWR) has Fission been reprocessed into (U,Pu)O2 – Products so-called MOX fuel – for some time by 0.1% Stable Fission various countries. This is economically Products 2.9% feasible because spent fuel contains not only fission products and minor actinides such as Americium, Neptunium and Curium, but a large percentage of U 95.6% (235U 0.5-1.0%) fissile Uranium and Plutonium isotopes Composition of used fuel as well. 4 Reactor/ Interim Fuel Fabrication UO2 Used Fuel Power Plant Fuel Storage UO2 Aged Used Fuel (U,Pu,Np)O2 Reconversion (Am,Cm)O2 Fuel Recycle/ UO2 Target Fabrication/ UF6 Separation Enrichment Waste UF6 UO2 Recycle Geological Conversion Repository U3O8 Uranium Mining & Milling F R O N T E N D B A C K E N D Closed fuel cycle with front end processing of UO2 and back end recycling/target fabrication It has been estimated that the effective reprocessed fuel or targets for capacity of geological repositories can transmutation/consumption. Several be increased greatly if the long-lived concepts have been proposed to realize minor actinides such as those this, some of which utilize fast reactors mentioned above plus Pu (transuranics) and others thermal reactors. are separated and fabricated into the 5 Introduction In addition, studies have shown that Of course, a prerequisite for the significant reductions in repository heat successful design of any new reactor or and radiotoxicity loads can be realized by fuel system as well as modernization of placing used fuel in interim storage for the existing reactor fleet is the accurate a few years to allow short-lived fission knowledge of the thermophysical products such as Cs-137 and Sr-90 to properties for the materials of interest. partially decay prior to separation. This will necessitate the measurement of the thermophysical properties for Interim storage also reduces the fresh, reprocessed and used fuels as well problems associated with reprocessing as irradiated and unirradiated reactor fuel containing Cm, but also increases component materials. the content of high-vapor-pressure Am-241 due to the β-decay of Pu-241. Assumptions Limited by 200°C Burnup: 50 GWd/MT 225.0 drift wall temp. Separation: 25 years at emplacement Emplacement: 25 years Closure: 100 years 175.0 94.0 Limited by 200°C drift 91.0 wall temp. at closure Limited by 96°C mid-drift temp. 54.0 >1600 yrs 44.0 5.7 10.5 10.3 5.5 10.0 0.001 1.0 4.4 1.0 0.01 1.0 1.0 Fraction Pu, 0.1 Am & Cm in 0.001 Waste 0.01 1 Fraction Cs & Sr in Waste 0.1 1 The calculated increase in repository capacity as a function of reduced Cs, Sr, Pu, Am and Cm content with separation after 25 years “Separations and Transmutation Criteria...“, Wigeland, et al., Nuc. Tech., 2006 6 Property measurements on fission of these properties on the materials use. All of these attributes are necessary products and/or their surrogates, glasses, mentioned above will necessarily be for instruments operating in harsh containment components and geological carried out in glovebox and hot cell environments such as gloveboxes and materials associated with long-term environments as well as in cold facilities. hot cells. Further, the modular design isolation in repositories are also of of our instruments makes them ideally paramount importance. The properties Over the past few years NETZSCH- suited for incorporation into these of interest include but are not limited Gerätebau GmbH has become the environments. Finally, the costs of to the thermal conductivity, thermal leading supplier of thermal analysis operating in hot cells and gloveboxes diffusivity, specific heat, transformation and thermophysical properties are extremely high, making downtime energetics, thermal expansion, bulk instrumentation to the nuclear industry. critical. Our exemplary global service density, solidus/liquidus temperatures This is because our instruments are is therefore one more reason for our and O/M ratio. Clearly, measurement reliable, robust, accurate and easy to success. 35 33000 MWd/MTIHM 75.5% 13% 95.3% 30 55000 MWd/MTIHM 242 (n,γ) 243 (n,γ) 244 (n,γ) 25 Cm Cm Cm 162.8 d (n,f) 29.1 y (n,f) 18.10 y (n,f) 20 24.5% 87% 4.7% 15 10 84% β (>83%) 5 (n,f) 242m Cm% in Am-Cm Fraction FPs Am 16% 0 141 y (n,γ) 0 20 40 60 80 100 9% Years after Removal from Reactor (n,β) 90% 34% 99.2% 20% α α α 241Am (n,γ) 242Am (n,γ) 243Am (n,γ) 244mAm 244Am (n,γ) 432.2 y (n,f) 16.02 h (n,f) 7370 y (n,f) 26 m 10.1 h (n,f) 1.0% 66% 0.8% 80% 92.6% 36.3% 99.8% 26% 98.7% 238Pu (n,γ) 239Pu (n,γ) 240Pu (n,γ) 241Pu (n,γ) 242Pu (n,γ) 243Pu (n,γ) 244Pu 87.7y (n,f) 2.41x104 y (n,f) 6563 y (n,f) 14.36 y (n,f) 3.733x105 y (n,f) 4.956 h 8.08x107 y 7.4% 66.7% 0.25% 74% 1.3% α α α α α 17% 242Pu 241Am 242Am 242 238 239 83% Cm Pu Pu 241Pu 242Pu 243Am 244mAm 244Cm “A G E D F U E L“ “Y O U N G F U E L“ Transmutation Benefits of Older Fuel “Closed Nuclear Fuel Cycle…”, Collins, et al., Atalante 2008 Int. Conf., 2008 7 Thermophysical Properties Introduction Thermophysical properties can be Thermodynamic properties include divided into two categories – transport specific heat, transition energetics and and thermodynamic. Transport thermal expansion (bulk density). properties include, but are not limited to, thermal conductivity, electrical resistivity and thermal diffusivity. Thermophysical Properties (Actually, thermal diffusivity is a hybrid transport/thermodynamic property.) Thermodynamic Thermal Transport Properties Diffusivity Properties Thermal Expansion Specific Heat Thermal Electrical (bulk density) and Enthalpy Conductivity Resistivity Classification of some thermophysical properties Thermal Conductivity ability of geological repositories and Specific Heat and Transition container material to dissipate heat Energetics The thermal conductivity is perhaps the heat transfer in multi-layer fuel single most important thermophysical systems, e.g. TRISO. The capacity of a material to store property and is paramount to the design energy is governed, in part, by the of any system operating at elevated or The complete list is quite long. The specific heat (sensible heat). It is made sub-ambient temperatures. It consists of thermal conductivity is greatly affected by up of lattice, electronic and defect a lattice and/or electronic component, corrosion, hydriding, fouling, O/M ratio, components, depending on the material. depending on the material (other fission product carry-over, irradiation This property is required for design of components are also possible). It is well damage, composition, porosity, etc. The any transient heat transfer process. It is known in the nuclear industry that the thermal conductivity/thermal diffusivity also used to quantify surface oxidation/ thermal conductivity controls: of almost all nuclear materials is most reduction and O/M ratio (defects) of efficiently measured by the laser flash fuels during processing.