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3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Chemical characterisation of degraded nuclear fuel analogues simulating the Fukushima Daiichi nuclear accident

The Fukushima Daiichi accident generated degraded nuclear fuel material, mixed with other reactor components, known as molten core-concrete interaction (MCCI) material. Simulant MCCI material was synthesised, excluding highly radioactive fission products, containing depleted U, and incorporating Ce as a surrogate for Pu. Multi-modal µ-focus X-ray analysis revealed the presence of the expected suite of U-Zr-O containing minerals, in addition to crystalline silicate phases CaSiO 3 , SiO 2 -cristobalite and Ce-bearing percleveite, (Ce,Nd) 2 Si 2 O 7 . The formation of perclevite resulted from reaction between the U-Zr-O-depleted Ce-Nd-O melt and the silicate (SiO 2 ) melt. It was determined that the majority of U was present as U 4 , whereas Ce was observed to be present as Ce 3+ , consistent with the highly reducing synthesis conditions. A range of Fe-containing phases characterised by different average oxidation states were identified, and it is hypothesised that their formation induced heterogeneity in the local oxygen potential, influencing the oxidation state of Ce.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce2Nd2O7 by Materials Project

Nd2Ce2O7 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eight inequivalent Nd3+ sites. In the first Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nd–O bond distances ranging from 2.28–2.45 Å. In the second Nd3+ site, Nd3+ is bonded to seven O2- atoms to form distorted NdO7 hexagonal pyramids that share an edgeedge with one CeO7 hexagonal pyramid. There are a spread of Nd–O bond distances ranging from 2.33–2.50 Å. In the third Nd3+ site, Nd3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Nd–O bond distances ranging from 2.22–2.44 Å. In the fourth Nd3+ site, Nd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Nd–O bond distances ranging from 2.33–2.47 Å. In the fifth Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nd–O bond distances ranging from 2.29–2.43 Å. In the sixth Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nd–O bond distances ranging from 2.29–2.44 Å. In the seventh Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nd–O bond distances ranging from 2.29–2.42 Å. In the eighth Nd3+ site, Nd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Nd–O bond distances ranging from 2.30–2.56 Å. There are eight inequivalent Ce4+ sites. In the first Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.29–2.59 Å. In the second Ce4+ site, Ce4+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ce–O bond distances ranging from 2.22–2.40 Å. In the third Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.30–2.55 Å. In the fourth Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.34–2.54 Å. In the fifth Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.29–2.67 Å. In the sixth Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.29–2.57 Å. In the seventh Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.29–2.54 Å. In the eighth Ce4+ site, Ce4+ is bonded to seven O2- atoms to form distorted CeO7 hexagonal pyramids that share an edgeedge with one NdO7 hexagonal pyramid. There are a spread of Ce–O bond distances ranging from 2.25–2.41 Å. There are twenty-eight inequivalent O2- sites. In the first O2- site, O2- is bonded to three Nd3+ and one Ce4+ atom to form a mixture of edge and corner-sharing OCeNd3 tetrahedra. In the second O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form a mixture of distorted edge and corner-sharing OCe2Nd2 tetrahedra. In the third O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with fourteen OCe3Nd tetrahedra and edges with four OCeNd3 tetrahedra. In the fourth O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with twelve OCe3Nd tetrahedra and edges with five OCeNd3 tetrahedra. In the fifth O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form OCe3Nd tetrahedra that share corners with thirteen OCe3Nd tetrahedra and edges with six OCe2Nd2 tetrahedra. In the sixth O2- site, O2- is bonded to three Nd3+ and one Ce4+ atom to form OCeNd3 tetrahedra that share corners with fourteen OCe3Nd tetrahedra and edges with five OCeNd3 tetrahedra. In the seventh O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form OCe3Nd tetrahedra that share corners with thirteen OCe3Nd tetrahedra and edges with six OCe2Nd2 tetrahedra. In the eighth O2- site, O2- is bonded to four Ce4+ atoms to form OCe4 tetrahedra that share corners with fifteen OCeNd3 tetrahedra and edges with five OCe3Nd tetrahedra. In the ninth O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form OCe3Nd tetrahedra that share corners with fourteen OCe2Nd2 tetrahedra and edges with six OCe3Nd tetrahedra. In the tenth O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form OCe3Nd tetrahedra that share corners with fourteen OCe2Nd2 tetrahedra and edges with five OCe3Nd tetrahedra. In the eleventh O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form a mixture of edge and corner-sharing OCe3Nd tetrahedra. In the twelfth O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with fifteen OCeNd3 tetrahedra and edges with five OCe2Nd2 tetrahedra. In the thirteenth O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form OCe3Nd tetrahedra that share corners with fourteen OCe3Nd tetrahedra and edges with six OCeNd3 tetrahedra. In the fourteenth O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form OCe3Nd tetrahedra that share corners with thirteen OCe3Nd tetrahedra and edges with six OCe2Nd2 tetrahedra. In the fifteenth O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with thirteen OCe3Nd tetrahedra and edges with five OCe2Nd2 tetrahedra. In the sixteenth O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with twelve OCe3Nd tetrahedra and edges with six OCeNd3 tetrahedra. In the seventeenth O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form distorted OCe3Nd tetrahedra that share corners with fourteen OCe3Nd tetrahedra and edges with six OCeNd3 tetrahedra. In the eighteenth O2- site, O2- is bonded to one Nd3+ and three Ce4+ atoms to form distorted OCe3Nd tetrahedra that share corners with fourteen OCe3Nd tetrahedra and edges with five OCe2Nd2 tetrahedra. In the nineteenth O2- site, O2- is bonded to three Nd3+ and one Ce4+ atom to form OCeNd3 tetrahedra that share corners with fourteen OCe2Nd2 tetrahedra and edges with five OCe3Nd tetrahedra. In the twentieth O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form a mixture of distorted edge and corner-sharing OCe2Nd2 tetrahedra. In the twenty-first O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with thirteen OCe3Nd tetrahedra and edges with five OCe2Nd2 tetrahedra. In the twenty-second O2- site, O2- is bonded to three Nd3+ and one Ce4+ atom to form OCeNd3 tetrahedra that share corners with fifteen OCeNd3 tetrahedra and edges with three OCe3Nd tetrahedra. In the twenty-third O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form a mixture of edge and corner-sharing OCe2Nd2 tetrahedra. In the twenty-fourth O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form distorted OCe2Nd2 tetrahedra that share corners with thirteen OCe3Nd tetrahedra and edges with five OCe2Nd2 tetrahedra. In the twenty-fifth O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with twelve OCe3Nd tetrahedra and edges with six OCeNd3 tetrahedra. In the twenty-sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Nd3+ and two Ce4+ atoms. In the twenty-seventh O2- site, O2- is bonded to two Nd3+ and two Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with twelve OCe3Nd tetrahedra and edges with five OCe2Nd2 tetrahedra. In the twenty-eighth O2- site, O2- is bonded to three Nd3+ and one Ce4+ atom to form OCeNd3 tetrahedra that share corners with thirteen OCe3Nd tetrahedra and edges with four OCe2Nd2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce3Nd2O9 by Materials Project

Nd2Ce3O9 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Nd3+ sites. In the first Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nd–O bond distances ranging from 2.25–2.53 Å. In the second Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nd–O bond distances ranging from 2.25–2.52 Å. There are three inequivalent Ce4+ sites. In the first Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.30–2.48 Å. In the second Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.33–2.44 Å. In the third Ce4+ site, Ce4+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Ce–O bond distances ranging from 2.30–2.48 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Nd3+ and two equivalent Ce4+ atoms to form a mixture of edge and corner-sharing OCe2Nd2 tetrahedra. In the second O2- site, O2- is bonded to four Ce4+ atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the third O2- site, O2- is bonded to four Ce4+ atoms to form OCe4 tetrahedra that share corners with sixteen OCe4 tetrahedra and edges with six OCe2Nd2 tetrahedra. In the fourth O2- site, O2- is bonded to two equivalent Nd3+ and two equivalent Ce4+ atoms to form a mixture of edge and corner-sharing OCe2Nd2 tetrahedra. In the fifth O2- site, O2- is bonded to two equivalent Nd3+ and two equivalent Ce4+ atoms to form a mixture of edge and corner-sharing OCe2Nd2 tetrahedra. In the sixth O2- site, O2- is bonded to four Nd3+ atoms to form a mixture of edge and corner-sharing ONd4 tetrahedra. In the seventh O2- site, O2- is bonded to two equivalent Nd3+ and two equivalent Ce4+ atoms to form OCe2Nd2 tetrahedra that share corners with fourteen ONd4 tetrahedra and edges with five OCe2Nd2 tetrahedra. In the eighth O2- site, O2- is bonded to four Ce4+ atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the ninth O2- site, O2- is bonded to four Ce4+ atoms to form OCe4 tetrahedra that share corners with sixteen OCe4 tetrahedra and edges with six OCe2Nd2 tetrahedra.

36 MATERIALS SCIENCE↗