Selection of materials as diluents for burning of plutonium fuels in nuclear reactors

Kleykamp, H.

doi:10.1016/s0022-3115(99)00144-0

Cited by 152 publications

(62 citation statements)

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“…The volume fraction V V of the MgO and Nd 2 Zr 2 O 7 heterogeneities was determined by counting the number of points formed by the intersections of the vertical and horizontal lines that lay on the phase heterogeneities for each phase and dividing it by the total number of points according to the equation V V  P P P (1) where P P is the number of points that fell on the phase of interest and P is the total number of points. The number of heterogeneity interceptions per unit length N L was also calculated according to N L  N i L (2) where N i is the total number of heterogeneities intercepted of the phase of interest and L is the total lineal length of the grid.…”

Section: Quantitative Stereologymentioning

confidence: 99%

“…However, the aqueous-based synthesis methods magnetic bar stirring and ball milling transform MgO into Mg(OH) 2 through a hydration reaction with the deionized water during mixing. In an attempt to mitigate the formation of Mg(OH) 2 during mixing alcohol and acetone were also used as ball milling solvents, but XRD of the mixed powder showed that MgO still transformed to Mg(OH) 2 in the alcohol and acetone based slurries. The XRD profiles in Figure 3b show that an extra calcination step is added after mixing and before sintering in the aqueous processing methods to transform the Mg(OH) 2 back into MgO before sintering.…”

Section: Powder Characterizationmentioning

confidence: 99%

“…1,2 Magnesium oxide (MgO) is a promising candidate for inert matrix (IM) materials due to its high melting point (2827 °C) 2 , high thermal conductivity (13 W/K·m at 1000 °C) 2 , good neutronic properties, and irradiation stability 3,4 However, MgO reacts with water and hydrates easily, which prevents it from being used in light water reactors (LWRs) as an IM. To improve the hydration resistance of MgO-based inert matrix materials, Medvedev 5 and coworkers have recently investigated the introduction of a secondary phase that acts as a hydration barrier.…”

Section: Introductionmentioning

confidence: 99%

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Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Nino¹

2009

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The following is a technical report summarizing all the procedures, experiments, simulations and technical findings of this NERI project. For additional information, details or technical questions regarding this project, please contact jnino@mse.ufl.edu MgO and NDZ......................................................................69 8.4. Grain Size Dependence of MgO and NDZ Polycrystal Thermal Conductivity75 8.5 2009 Composite Processing and Characterization IntroductionIn order to reduce the current excesses of plutonium (both weapon grade and reactor grade) and other transuranium elements, a concept of inert matrix fuel (IMF) has been proposed for an uranium free transmutation of fissile actinides which excludes continuous uranium-plutonium conversion in thermal reactors and advanced systems. 1,2 Magnesium oxide (MgO) is a promising candidate for inert matrix (IM) materials due to its high melting point (2827 °C) 2 , high thermal conductivity (13 W/K·m at 1000 °C) 2 , good neutronic properties, and irradiation stability 3,4 However, MgO reacts with water and hydrates easily, which prevents it from being used in light water reactors (LWRs) as an IM. To improve the hydration resistance of MgO-based inert matrix materials, Medvedev 5 and coworkers have recently investigated the introduction of a secondary phase that acts as a hydration barrier. An MgO-ZrO 2 composite was specifically studied and the results showed that the composite exhibited improved hydration resistance than pure MgO. However, ZrO 2 is insoluble in most acids except HF, which is undesirable for fuel reprocessing. Moreover, the thermal conductivity of ZrO 2 is low and typically less than 3 W·m at 1000 °C. 6 In search for an alternative composite strategy, Nd 2 Zr 2 O 7 , an oxide compound with pyrochlore structure, has been proposed recently as a corrosion resistant phase, and MgO-Nd 2 Zr 2 O 7 composites have been investigated as potential IM materials. at 1000 °C for the MgO-Nd 2 Zr 2 O 7 composite with 90 vol% MgO was recently calculated and reported. 8,9 Other simulations proposed that the MgO-pyrochlore composites could exhibit higher radiation stability than previously reported. 10 Final optimization of the composite microstructure was performed on the 70 vol% MgONd 2 Zr 2 O 7 composite that burnup calculations had shown to have the closest profile to that of MOX fuel. Theoretical calculations also indicated that a homogeneous 70 vol% MgO composite could achieve the desired microstructure that would result in satisfying the dual requirements of good thermal properties. Experimental Procedures Composite Synthesis Solid State Synthesis of Nd 2 Zr 2 O 7Stoichiometric ratios of Nd 2 O 3 (Alfa Aesar 99.9%) and ZrO 2 (99.7%) were added to spherical 3 mm and 10 mm yttria stabilized zirconia (YSZ) milling media in a PTFE (polytetrafluoroethylene) ball mill jar with 100 ml of deionized water and 3 ml of ammonium polyacrylate dispersant (20 vol% Darvan 821A in deionized water). The slurry was milled for 24 hours on the ball mill at 85 rpm ...

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Section: Quantitative Stereologymentioning

confidence: 99%

Section: Powder Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Nino¹

2009

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“…Zirconium nitride was chosen as a primary candidate for the inert matrix not only for its physical properties but also because it is somewhat of a surrogate for a TRU-N. Due to the similar atomic radii and chemical similarities between the actinide elements and zirconium the radiation tolerance of ZrN may be used as a predictor for the tolerance of TRU-N to fission products and irradiation displacement damage [6,7,8].…”

Section: Zrn As An Inert Matrix and Surrogatementioning

confidence: 99%

“…Post-reactor requirements are that it must be able to be reprocessed to extract the minor actinides, and it must be compatible with the coolants used, and sodium as a thermal bonding agent [6,29,8,30,31].…”

Section: Sintered Pelletmentioning

confidence: 99%

Radiation Damage and Fission Product Release in Zirconium Nitride

Egeland

2005

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Zirconium nitride is a material of interest to the AFCI program due to some of its particular properties, such as its high melting point, strength and thermal conductivity. It is to be used as an inert matrix or diluent with a nuclear fuel based on transuranics. As such, it must sustain not only high temperatures, but also continuous irradiation from fission and decay products. This study addresses the issues of irradiation damage and fission product retention in zirconium nitride through an assessment of defects that are produced, how they react, and how predictions can be made as to the overall lifespan of the complete nuclear fuel package.Ion irradiation experiments are a standard method for producing radiation damage to a surface for observation. Cryogenic irradiations are performed to produce the maximum accumulation of defects, while elevated temperature irradiations may be used to allow defects to migrate and react to form clusters and loops. Cross-sectional transmission electron microscopy and grazing-incidence x-ray diffractometry were used in evaluating the effects that irradiation has on the crystal structure and microstructure of the material. Other techniques were employed to evaluate physical effects, such as nanoindentation and helium release measurements.Results of the irradiations showed that, at cryogenic temperatures, ZrN withstood over 200 displacements per atom without amorphization. No significant change to the lattice or microstructure was observed. At elevated temperatures, the large amount of damage showed mobility, but did not anneal significantly. Defect clustering was possibly observed, yet the size was too small to evaluate, and bubble formation was not observed.Defects, specifically nitrogen vacancies, affect the mechanical behavior of ZrN dramatically. Current and previous work on dislocations shows a distinct change in slip plane, which is evidence of the bonding characteristics. The stacking-fault energy changes dramatically with lowered nitrogen stoichiometry, resulting in widely spaced partial dislocations in ZrN with high nitrogen vacancy concentration.The wide range of nitrogen stoichiometry in the phase field shows that ZrN may accept nitrogen defects readily. Explanations for this are suggested based upon the bonding structure of these cubic nitrides. This structure allows for a solid framework to remain on one sublattice, while at the same time allowing defects on the other sublattice. This allowance for defects allows significant damage from irradiation yet also decreases the drive for cluster growth. This is evidence that the structure will be acceptable for long-term use as a nuclear reactor fuel.

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Diffraction and Thermal Expansion of Solids

Tyagi

Achary

2010

Thermodynamic Properties of Solids

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Thermal expansion of materials is a topic of age-old interest to mankind in view of the chronological development of several devices and technologies [1,2]. The concept of thermal expansion and knowledge of thermal expansion coefficient of materials remain important for any structural materials experiencing a temperature gradient. The structural materials include any material used in technology to build a mechanically or electronically integrated physical entity. In particular, the thermal properties are of interest when any structural assembly faces a temperature variation. Thermal expansion effects have been well considered right from the metals and ceramic parts of cookwares to the highly sophisticated mechanical structures, such as buildings, bridges, air/spacecraft, vessels, kilns, furnaces, and so on. In particular, metals such as steel, copper, and so on that are important structural parts show a significant expansion with temperature. Thus, in all these materials, thermal expansion was exploited either to enhance or to nullify any temperature-induced dimensional instability, for example, the utilization of thermal expansion in automatic cut-off switch using bimetals is well known. The discovery of Invar (an alloy of 35% Ni and 65% Fe) and subsequent modified compositions as Elinvar, Kovar, Alnico, and so on have found immense applications in modern technologies, such as design of high-accuracy clocks, shadow mask in television screen, and so on [3]. In addition, low thermal expansion in fused silica and controllable thermal expansion in materials with glass and glass-ceramic compositions have been discovered and used in precise optical instruments, mirror substrates, glass-metal junctions [4,5]. A large number of crystalline materials with low thermal expansion are also discovered [6]. Thermal expansion data of ceramics have been a prime consideration in the designing of electrolyte and electrodes of solid oxide fuel cells [7]. Similarly, thermal expansion data of nuclear fuel materials are significant in preventing detrimental effects of fuel-clad interaction and unwanted swelling of fuel pins [8]. Nuclear reactor performance is mainly restricted by the thermal expansion and thermal conductivity of the fuel pellets under irradiation conditions. In these j197 applications, the material property is more significant than the structural assembly and hence the structural materials are tuned as per their thermal expansion behavior. However, the thermal expansion behavior of electronic materials causing temperature-induced dimensional instability leading to circuit failure also needs to be dealt with. Considering such aspects, several Invar-type alloys and metal matrix composites are developed in recent years [9]. Thus, the thermal expansion data of any material are the first requisite for the development of most of the technologies.In general, it is known that all materials expand or contract with the rise or fall of temperature. The thermal expansion of any material is explained as a relative change in dimens...

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Selection of materials as diluents for burning of plutonium fuels in nuclear reactors

Cited by 152 publications

References 62 publications

Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Radiation Damage and Fission Product Release in Zirconium Nitride

Diffraction and Thermal Expansion of Solids

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