Paralava and clinker products of coal combustion, Yellow River, Shanxi Province, China

Grapes, Rodney,Zhang, Ke,Peng, Zhuo-lun Elsevier 2009 Lithos Vol.113 No.3

<P><B>Abstract</B></P> <P>Combustion of bituminous coal seams in a Carbonifeorus–Permian sequence of siltstone, quartzose sandstone, sideritic mudstone, kaolinite-rich and sulphide–ankerite rocks exposed on the left bank of the Yellow River, western border of Shanxi Province, China, has resulted in the formation of paralava and glassy clinker. Some paralavas have compositions similar to low alkali basalts and contain anorthite, low Ca-pyroxenes (clinoenstatite, pigeonite), ±minor augite, ±olivine, Fe–Ti oxides and K-bearing siliceous glass. In these paralavas the sequence of pyroxene crystallization was Mg-pigeonite→augite→Fe-pigeonite and Mg-clinoenstatite→borderline Fe-clinoenstatite/pigeonite. More siliceous paralava compositions contain anorthite, clinoenstatite, cordierite, Fe–Ti oxides and glass. Fused clinker consists of cordierite, anorthite, tridymite, mullite, Fe–Ti oxides and K-rich siliceous glass. Paralava liquidus temperatures range between ca. 1230 and 1120 °C and the generalized crystallization sequence in a “basaltic” composition was anorthite, pyroxene (low Ca-clinopyroxene, augite), Ti-magnetite, olivine with quench apatite in glass over a cooling interval of ∼345 °C. The liquidus temperature of clinker was ca. 1100 °C. In paralavas and clinker, subsolidus exsolution of hemo-ilmenite from Ti-magnetite occurred under log<I>f</I>O<SUB>2</SUB> =−9.0 to −13.9 at temperatures of 907–756 °C, with formation of almost pure ilmenite at lowest temperatures of 536–567 °C at log<I>f</I>O<SUB>2</SUB> =−24.9–21.9. Changes in the texture and habit of pyroxene in paralava adjacent clinker (porphyritic to skeletal/plumose towards clinker) reflect the effects of a cooling front moving into the paralava and changing bulk composition. Paralavas formed by melting of different combinations of siltstone, sideritic mudstone and ankerite-rich rock “end-members”, and there was also diffusion of Si, Al, Ti and K into paralava from fused clinker blocks within it.</P>

The eclogite-facies Allalin gabbro, Western Alps, Switzerland : a record of subduction zone hydration

Rodney Grapes,Kurt Bucher 대한지질학회 2007 대한지질학회 학술대회 Vol.2007 No.

Late-stage hydrothermal alteration and heteromorphism of calc–alkaline lamprophyre dykes in Late Jurassic Granite, Southeast China

Bratzdrum, Christian,Grapes, Rodney,Gieré,, Reto Elsevier 2009 Lithos Vol.113 No.3

<P><B>Abstract</B></P> <P>Three generations of calc–alkaline lamprophyre, occurring as patches or segregations in granite and as dyke swarms with a NNW–SSE trend, are associated with the Late Jurassic Shanqi–Xiaqi granite, SE China. They comprise coarse-grained, hornblende-dominated spessartite and two types of panidiomorphic kersantite: type-1 contains clinopyroxene and biotite phenocrysts, whereas type-2 is fine-grained and plagioclase-rich. The granite is characterised by large feldspar crystals and Al-rich annite. This rare occurrence of outcrops with no influence from atmospheric weathering allows the investigation of extensive alteration from hydrothermal interaction between lamprophyres and granite. At a depth of ca. 18 km, the breakdown of annite in the granite to magnetite+K-feldspar was the result of reheating above 670 °C at oxygen activities >10<SUP>−17</SUP> bar. In the lamprophyres, a variety of reactions due to autometasomatism include: breakdown of Ti-rich pargasites to chlorite, epidote, titanite; olivine to talc, tremolite, saponite, beidellite and Fe–Cr spinels; biotite to chlorite and titanite; calcic plagioclase to orthoclase, albite, epidote, chlorite and beidellite. Late-stage magmatic hydrothermal fluids from granite and lamprophyres resulted in redistribution of F, Ba, Sr, and CO<SUB>2</SUB> with the formation of calcite–fluorite veins. Amphibole-rich spessartite and biotite–diopside dominated kersantite exhibit heteromorphism in that they have similar geochemical characteristics but different mineralogies. The alkali-rich lamprophyric magmas are inferred to have been derived from melting in the mantle wedge during the subduction of the Kula Plate, and show typical backarc rift chemistry. Prior to intrusion of lamprophyre, underplating of large volumes of basaltic magma is thought to have enhanced partial melting in the overlying continental crust resulting in widespread granite magmatism in SE China.</P>

Material attractiveness of irradiated fuel salts from the Seaborg Compact Molten Salt Reactor

Mishra Vaibhav,Branger Erik,Grape Sophie,Elter Zsolt,Mirmiran Sorouche 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.9

Over the years, numerous evaluations of material attractiveness have been performed for conventional light water reactors to better understand the nature of the spent fuel material and its desirability for misuse at different points in the nuclear fuel cycle. However, availability of such assessments for newer, Generation IV reactors such as Molten Salt Reactors is rather limited. In the present study we address the gap in knowledge of material attractiveness for molten salt reactor systems and describe the nature of irradiated fuel salts which the nuclear safeguards community might be faced with in the near future as more and more such reactors enter commission and operation. Within the scope of the paper, we use a large database of simulated irradiated fuel salt isotopics (and other derived quantities such as gamma activity, decay heat, and neutron emission rates) developed specifically for a molten salt reactor concept in order to shed some light on possible weapons usability of uranium and plutonium present in the irradiated fuel salts. This has been achieved by proposing a new attractiveness metric that is better suited for quantifying attractiveness of irradiated salts from a model molten salt concept. The said metric has been computed using a database that has been created by simulating the irradiation of molten fuel salt in a concept core over a wide range of operational parameters (burnup, initial enrichment, and cooling time) using the Monte-Carlo particle transport code, Serpent. With the help of this attractiveness metric, the findings from this study have shown that in relative terms, molten salt spent fuel is more attractive than spent fuel produced by a conventional light water reactor. The findings also underscore the need for strengthened safeguards measures for such spent fuel. These results are expected to be useful in the future for regulatory authorities as well as for nuclear safeguards inspectors for designing a functional safeguards verification routine for irradiated fuel of such unique nature.

Material attractiveness of irradiated fuel salts from the Seaborg Compact Molten Salt Reactor

Vaibhav Mishra,Erik Branger,Sophie Grape,Zsolt Elter,Sorouche Mirmiran Korean Nuclear Society 2024 Nuclear Engineering and Technology Vol.56 No.9

Over the years, numerous evaluations of material attractiveness have been performed for conventional light water reactors to better understand the nature of the spent fuel material and its desirability for misuse at different points in the nuclear fuel cycle. However, availability of such assessments for newer, Generation IV reactors such as Molten Salt Reactors is rather limited. In the present study we address the gap in knowledge of material attractiveness for molten salt reactor systems and describe the nature of irradiated fuel salts which the nuclear safeguards community might be faced with in the near future as more and more such reactors enter commission and operation. Within the scope of the paper, we use a large database of simulated irradiated fuel salt isotopics (and other derived quantities such as gamma activity, decay heat, and neutron emission rates) developed specifically for a molten salt reactor concept in order to shed some light on possible weapons usability of uranium and plutonium present in the irradiated fuel salts. This has been achieved by proposing a new attractiveness metric that is better suited for quantifying attractiveness of irradiated salts from a model molten salt concept. The said metric has been computed using a database that has been created by simulating the irradiation of molten fuel salt in a concept core over a wide range of operational parameters (burnup, initial enrichment, and cooling time) using the Monte-Carlo particle transport code, Serpent. With the help of this attractiveness metric, the findings from this study have shown that in relative terms, molten salt spent fuel is more attractive than spent fuel produced by a conventional light water reactor. The findings also underscore the need for strengthened safeguards measures for such spent fuel. These results are expected to be useful in the future for regulatory authorities as well as for nuclear safeguards inspectors for designing a functional safeguards verification routine for irradiated fuel of such unique nature.