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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on YbPu3 by Materials Project

Pu3Yb is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are three inequivalent Pu sites. In the first Pu site, Pu is bonded to eight Pu and four equivalent Yb atoms to form PuYb4Pu8 cuboctahedra that share corners with four equivalent YbPu12 cuboctahedra, corners with fourteen PuYb4Pu8 cuboctahedra, edges with six equivalent YbPu12 cuboctahedra, edges with twelve PuYb4Pu8 cuboctahedra, faces with four equivalent YbPu12 cuboctahedra, and faces with sixteen PuYb4Pu8 cuboctahedra. There are a spread of Pu–Pu bond distances ranging from 3.35–3.52 Å. There are two shorter (3.40 Å) and two longer (3.44 Å) Pu–Yb bond lengths. In the second Pu site, Pu is bonded to eight Pu and four equivalent Yb atoms to form PuYb4Pu8 cuboctahedra that share corners with four equivalent YbPu12 cuboctahedra, corners with fourteen PuYb4Pu8 cuboctahedra, edges with six equivalent YbPu12 cuboctahedra, edges with twelve PuYb4Pu8 cuboctahedra, faces with four equivalent YbPu12 cuboctahedra, and faces with sixteen PuYb4Pu8 cuboctahedra. All Pu–Pu bond lengths are 3.35 Å. There are two shorter (3.40 Å) and two longer (3.44 Å) Pu–Yb bond lengths. In the third Pu site, Pu is bonded to eight Pu and four equivalent Yb atoms to form PuYb4Pu8 cuboctahedra that share corners with four equivalent YbPu12 cuboctahedra, corners with fourteen PuYb4Pu8 cuboctahedra, edges with six equivalent YbPu12 cuboctahedra, edges with twelve PuYb4Pu8 cuboctahedra, faces with four equivalent YbPu12 cuboctahedra, and faces with sixteen PuYb4Pu8 cuboctahedra. There are one shorter (3.36 Å) and one longer (3.52 Å) Pu–Pu bond lengths. There are two shorter (3.40 Å) and two longer (3.44 Å) Pu–Yb bond lengths. Yb is bonded to twelve Pu atoms to form YbPu12 cuboctahedra that share corners with six equivalent YbPu12 cuboctahedra, corners with twelve PuYb4Pu8 cuboctahedra, edges with eighteen PuYb4Pu8 cuboctahedra, faces with eight equivalent YbPu12 cuboctahedra, and faces with twelve PuYb4Pu8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

NNSS Soils Monitoring: Plutonium Valley (CAU 366) FY2019

Desert Research Institute (DRI) conducted a field assessment of the potential for radionuclide-contaminated soil to be transported from the Plutonium Valley Dispersion Sites Contamination Area (CA) because of both wind and storm water runoff. This activity supported U.S. Department of Energy (DOE) Environmental Management Nevada Program (EM NV) efforts to establish post-closure monitoring plans for the Plutonium Valley Dispersion Sites Corrective Action Unit (CAU) 366. The DRI task was intended to identify the likely mechanism(s) of transport and determine the meteorological conditions that might cause the movement of radionuclide-contaminated soils. The emphasis of the work was on collecting sediment transported by channelized storm runoff and measuring airborne dust concentrations and associated wind conditions. These data will facilitate an appropriate post-closure monitoring program. In 2011, DRI installed meteorological monitoring stations north and south of the Plutonium Valley CA—known as Pu Valley North and Pu Valley South, respectively—as well as a fluvial sediment sampling station within the CA. Since installation, temperature, wind speed, wind direction, relative humidity, precipitation, solar radiation, barometric pressure, soil temperature, volumetric soil moisture content, and airborne particulate concentrations have been collected at both meteorological stations. The maximum, minimum, and average or total (as appropriate) for each of these parameters were recorded for each 10-minute interval. The sediment sampling station included an automatically activated sampling pump with collection bottles for suspended sediment, which was activated when sufficient flow was present in the channel, and passive traps for bedload material that was transported down the channel during runoff events. This report presents data collected from these stations during fiscal year (FY) 2019. During the FY2019 (October 1, 2018, through September 30, 2019) reporting period, the warmest month was July and the coldest month was February. Monthly total solar radiation was highest in June or July (depending on the station) and lowest in December. Monthly mean wind speeds were highest during February. At the Pu Valley North station, winds were commonly northerly, northwesterly, and southerly. At the Pu Valley South station, the wind direction was more variable and winds frequently came from most directions, excluding westerly and northwesterly winds. Winds above 15.0 miles per hour (mph) (24.1 kilometers per hour [km/hr]) were frequently southerly at both stations, and less-frequent strong winds were northerly (at the Pu Valley South station) or northwesterly (at the Pu Valley North station). Monthly average relative humidity ranged from 18 percent in August to 62 percent in January and February. Monthly total precipitation ranged from zero at both stations in September to 2.23 inches (in) (56.6 millimeters [mm]) during February at the Pu Valley South station and 2.09 in (53.1 mm) during March at the Pu Valley North station. From October 1, 2018, through September 30, 2019, the total precipitation was 8.23 in (209 mm) and 8.15 in (207 mm) at the Pu Valley South and Pu Valley North stations, respectively. The largest daily precipitation totals of 1.46 in (37.1 mm) and 1.14 in (29.0 mm) occurred at the Pu Valley South and Pu Valley North stations, respectively, on March 6, 2019. However, the ISCO autosampler was not activated during any storm event in FY2019 because the channel water depth measurements were insufficient for suspended sediment sample collection. Additionally, because no significant flow through the channel was indicated, no bedload samples were collected. Light breezes of 0.0 mph to 5.0 mph (0.0 km/hr to 8.0 km/hr) occurred most frequently (approximately 55 percent to 57 percent of the time). The frequency of occurrence diminished exponentially as the wind speed increased such that winds in excess of 25.0 mph (40.2 km/hr) occurred less than 0.01 percent of the time. Winds in excess of 15.0 mph (24.1 km/hr) were most commonly southerly, which is likely controlled by the topography of the valley because topographic highs define the east and west sides of the valley and converge toward the north.The concentrations of PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 micrometers [μm]) and PM10 (particulate matter with an aerodynamic diameter ≤10 μm) in the air generally increase as wind speed increases. However, the particle profiler at the Pu Valley South station regularly malfunctioned, which resulted in poor data quality and a limited period of record within FY2019. Therefore, discussion of the annual dust observations is mostly limited to the Pu Valley North station. At the Pu Valley North station, significant increases in windblown dust concentrations were observed when wind speeds exceeded 15.0 mph (24.1 km/hr), especially during southerly winds. When all wind speeds were considered, high dust concentrations at the Pu Valley North station were frequently associated with northerly, northwesterly, or southerly winds. The majority of PM10 transport at the Pu Valley North station occurred when winds were blowing northerly and northwesterly because of the high frequency of winds up to 15.0 mph (24.1 km/hr). The ratio of PM10 to PM2.5 is a qualitative indicator of the proximity of dust sources to the observation point and the values of the PM10 to PM2.5 ratio tend to be higher nearer to the source. The PM10 to PM2.5 ratio increased from 1.2 to 2.8 with higher wind speeds at the Pu Valley North station. This increase suggests that some locally sourced PM10 was present in the air when local winds exceeded 15.0 mph (24.1 km/hr). Local dust suspension is interpreted during major dust events when peaks in the PM10 to PM2.5 ratio occur simultaneously with the maximum wind speed and the peak PM10 concentration. Analysis of the five major dust events in FY2019 revealed that northerly winds were dominant in three events and southerly winds were dominant in two events. Local suspension of dust within Plutonium Valley is suspected to have occurred during two of the five major events (April 9, 2019, and September 28 to 29, 2019), and a nonlocal source of dust is presumed for the three other major dust events (October 14, 2018; May 16, 2019; and September 2, 2019). The three suspected regional dust transport events exhibited winds that typically did not exceed the 15.0 mph (24.1 km/hr) wind speed threshold for local dust transport and featured PM10 to PM2.5 ratios that indicate large-scale regional dust transport. Similar event characteristics (e.g., wind speed and PM10 concentration) were observed at air monitoring stations approximately 70 mi (113 km) to the northwest within the Tonopah Test Range (TTR). Therefore, these three regional events may not reflect transport from the Plutonium Valley CA. Routine monitoring of meteorological and hydrologic parameters at Plutonium Valley has been discontinued at the request of EM NV, effective at the conclusion of FY2019. Environmental data acquisition has been completed, and both Pu Valley North and Pu Valley South meteorological stations within Plutonium Valley as well as the ISCO autosampler station within the CA were removed on October 14, 2019.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on Pu2TcB6 by Materials Project

Pu2TcB6 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Pu+3.50+ sites. In the first Pu+3.50+ site, Pu+3.50+ is bonded in a 2-coordinate geometry to three equivalent Tc1- and fourteen B1- atoms. There are a spread of Pu–Tc bond distances ranging from 3.02–3.15 Å. There are a spread of Pu–B bond distances ranging from 2.61–2.76 Å. In the second Pu+3.50+ site, Pu+3.50+ is bonded in a 12-coordinate geometry to one Pu+3.50+, two equivalent Tc1-, and twelve B1- atoms. The Pu–Pu bond length is 2.63 Å. There are one shorter (2.97 Å) and one longer (2.98 Å) Pu–Tc bond lengths. There are a spread of Pu–B bond distances ranging from 2.63–2.69 Å. Tc1- is bonded in a 10-coordinate geometry to five Pu+3.50+ and ten B1- atoms. There are a spread of Tc–B bond distances ranging from 2.34–2.40 Å. There are six inequivalent B1- sites. In the first B1- site, B1- is bonded in a 8-coordinate geometry to six Pu+3.50+ and two B1- atoms. Both B–B bond lengths are 1.68 Å. In the second B1- site, B1- is bonded in a 3-coordinate geometry to four equivalent Pu+3.50+, two equivalent Tc1-, and three B1- atoms. There are a spread of B–B bond distances ranging from 1.78–1.81 Å. In the third B1- site, B1- is bonded in a 3-coordinate geometry to four Pu+3.50+, two equivalent Tc1-, and three B1- atoms. The B–B bond length is 1.82 Å. In the fourth B1- site, B1- is bonded in a 9-coordinate geometry to four Pu+3.50+, two equivalent Tc1-, and three B1- atoms. There is one shorter (1.75 Å) and one longer (1.80 Å) B–B bond length. In the fifth B1- site, B1- is bonded in a 3-coordinate geometry to four Pu+3.50+, two equivalent Tc1-, and three B1- atoms. The B–B bond length is 1.82 Å. In the sixth B1- site, B1- is bonded in a 9-coordinate geometry to four Pu+3.50+, two equivalent Tc1-, and three B1- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu3In by Materials Project

Pu3In is Uranium Silicide structured and crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are three inequivalent Pu sites. In the first Pu site, Pu is bonded to eight Pu and four equivalent In atoms to form distorted PuPu8In4 cuboctahedra that share corners with twelve equivalent PuPu8In4 cuboctahedra, edges with eight equivalent InPu12 cuboctahedra, edges with sixteen PuPu8In4 cuboctahedra, faces with four equivalent InPu12 cuboctahedra, and faces with fourteen PuPu8In4 cuboctahedra. There are six shorter (3.07 Å) and two longer (3.08 Å) Pu–Pu bond lengths. All Pu–In bond lengths are 3.07 Å. In the second Pu site, Pu is bonded to eight Pu and four equivalent In atoms to form distorted PuPu8In4 cuboctahedra that share corners with twelve equivalent PuPu8In4 cuboctahedra, edges with eight equivalent InPu12 cuboctahedra, edges with sixteen PuPu8In4 cuboctahedra, faces with four equivalent InPu12 cuboctahedra, and faces with fourteen PuPu8In4 cuboctahedra. There are two shorter (3.07 Å) and two longer (3.08 Å) Pu–Pu bond lengths. All Pu–In bond lengths are 3.07 Å. In the third Pu site, Pu is bonded to eight Pu and four equivalent In atoms to form distorted PuPu8In4 cuboctahedra that share corners with twelve equivalent PuPu8In4 cuboctahedra, edges with eight equivalent InPu12 cuboctahedra, edges with sixteen PuPu8In4 cuboctahedra, faces with four equivalent InPu12 cuboctahedra, and faces with fourteen PuPu8In4 cuboctahedra. All Pu–In bond lengths are 3.08 Å. In is bonded to twelve Pu atoms to form InPu12 cuboctahedra that share corners with twelve equivalent InPu12 cuboctahedra, edges with twenty-four PuPu8In4 cuboctahedra, faces with six equivalent InPu12 cuboctahedra, and faces with twelve PuPu8In4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmPu3 by Materials Project

Pu3Pm is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are three inequivalent Pu sites. In the first Pu site, Pu is bonded to eight Pu and four equivalent Pm atoms to form PuPm4Pu8 cuboctahedra that share corners with four equivalent PmPu12 cuboctahedra, corners with fourteen PuPm4Pu8 cuboctahedra, edges with six equivalent PmPu12 cuboctahedra, edges with twelve PuPm4Pu8 cuboctahedra, faces with four equivalent PmPu12 cuboctahedra, and faces with sixteen PuPm4Pu8 cuboctahedra. There are a spread of Pu–Pu bond distances ranging from 3.39–3.57 Å. There are two shorter (3.46 Å) and two longer (3.48 Å) Pu–Pm bond lengths. In the second Pu site, Pu is bonded to eight Pu and four equivalent Pm atoms to form PuPm4Pu8 cuboctahedra that share corners with four equivalent PmPu12 cuboctahedra, corners with fourteen PuPm4Pu8 cuboctahedra, edges with six equivalent PmPu12 cuboctahedra, edges with twelve PuPm4Pu8 cuboctahedra, faces with four equivalent PmPu12 cuboctahedra, and faces with sixteen PuPm4Pu8 cuboctahedra. All Pu–Pu bond lengths are 3.40 Å. There are two shorter (3.46 Å) and two longer (3.48 Å) Pu–Pm bond lengths. In the third Pu site, Pu is bonded to eight Pu and four equivalent Pm atoms to form PuPm4Pu8 cuboctahedra that share corners with four equivalent PmPu12 cuboctahedra, corners with fourteen PuPm4Pu8 cuboctahedra, edges with six equivalent PmPu12 cuboctahedra, edges with twelve PuPm4Pu8 cuboctahedra, faces with four equivalent PmPu12 cuboctahedra, and faces with sixteen PuPm4Pu8 cuboctahedra. There are two shorter (3.46 Å) and two longer (3.48 Å) Pu–Pm bond lengths. Pm is bonded to twelve Pu atoms to form PmPu12 cuboctahedra that share corners with six equivalent PmPu12 cuboctahedra, corners with twelve PuPm4Pu8 cuboctahedra, edges with eighteen PuPm4Pu8 cuboctahedra, faces with eight equivalent PmPu12 cuboctahedra, and faces with twelve PuPm4Pu8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CePu by Materials Project

Pu(Ce) crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded to six equivalent Pu and six Ce atoms to form PuCe6Pu6 cuboctahedra that share corners with twelve PuCe6Pu6 cuboctahedra, edges with twelve PuCe6Pu6 cuboctahedra, edges with twelve CeCe6Pu6 cuboctahedra, faces with six equivalent PuCe6Pu6 cuboctahedra, and faces with twelve CeCe6Pu6 cuboctahedra. All Pu–Pu bond lengths are 3.30 Å. All Pu–Ce bond lengths are 3.25 Å. In the second Pu site, Pu is bonded to ten equivalent Pu and six Ce atoms to form PuCe6Pu10 cuboctahedra that share corners with ten CeCe6Pu6 cuboctahedra, corners with twelve PuCe6Pu6 cuboctahedra, edges with eight CeCe6Pu6 cuboctahedra, edges with sixteen PuCe6Pu6 cuboctahedra, faces with sixteen equivalent PuCe6Pu10 cuboctahedra, and faces with eighteen CeCe6Pu6 cuboctahedra. There are a spread of Pu–Pu bond distances ranging from 3.30–6.59 Å. All Pu–Ce bond lengths are 3.25 Å. There are three inequivalent Ce sites. In the first Ce site, Ce is bonded to six equivalent Pu and six equivalent Ce atoms to form CeCe6Pu6 cuboctahedra that share corners with twelve CeCe6Pu6 cuboctahedra, edges with twelve equivalent PuCe6Pu6 cuboctahedra, edges with twelve CeCe6Pu6 cuboctahedra, faces with six equivalent CeCe6Pu6 cuboctahedra, and faces with twelve equivalent PuCe6Pu6 cuboctahedra. All Ce–Ce bond lengths are 3.30 Å. In the second Ce site, Ce is bonded to six Pu and six equivalent Ce atoms to form CeCe6Pu6 cuboctahedra that share corners with five equivalent PuCe6Pu10 cuboctahedra, corners with twelve CeCe6Pu6 cuboctahedra, edges with ten PuCe6Pu6 cuboctahedra, edges with twelve CeCe6Pu6 cuboctahedra, faces with six equivalent CeCe6Pu6 cuboctahedra, and faces with fifteen PuCe6Pu6 cuboctahedra. All Ce–Ce bond lengths are 3.30 Å. In the third Ce site, Ce is bonded to six Pu and six equivalent Ce atoms to form CeCe6Pu6 cuboctahedra that share corners with five equivalent PuCe6Pu10 cuboctahedra, corners with twelve CeCe6Pu6 cuboctahedra, edges with ten PuCe6Pu6 cuboctahedra, edges with twelve CeCe6Pu6 cuboctahedra, faces with six equivalent CeCe6Pu6 cuboctahedra, and faces with fifteen PuCe6Pu6 cuboctahedra. All Ce–Pu bond lengths are 3.25 Å. All Ce–Ce bond lengths are 3.30 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Direct analysis of cotton swipes for plutonium isotope determination by microextraction-ICP-MS

This study demonstrates a method for determining the isotopic composition of low-level (sub-pg) plutonium (Pu) directly from a cotton swipe. Environmental sample (ES) swipes are routinely employed as a tool for monitoring activities in nuclear facilities. Traditional ES swipe analysis, as employed in nuclear safeguards, utilizes laborious ashing, digestion, and chemical separation procedures prior to mass spectrometric (MS) analysis. Here, an innovative sample introduction technique employing a microextraction probe to extract Pu directly from the swipe surface is described. The microextraction probe lowers onto the swipe surface, seals on a small area (8 mm 2 ), and delivers solvent (2% HNO 3 ) to extract actinide material that may be present. The extracted analyte is subsequently directed into a sector field inductively coupled plasma (ICP)-MS for isotope ratio determination. This microextraction-ICP-MS method successfully determined the isotopic composition ( 240 Pu/ 239 Pu and 242 Pu/ 239 Pu) of three Pu certified reference materials (CRM 136, 137, and 138) that were deposited (1 pg) onto ES swipes. The percent relative difference from the certified value, uncorrected for instrumental fractionation, was <2% for the 240 Pu/ 239 Pu ratio on all three CRMs and <10% for the 242 Pu/ 239 Pu ratio on CRM 136 and 138. Here, the percent relative standard deviation, an estimate of the sample-to-sample isotopic precision, was <4% for the 240 Pu/ 239 Pu and <15% for the 242 Pu/ 239 Pu. Method limits of detection were determined, based on measurements of an enriched 244 Pu material, to be ~7 fg. Additionally, a mixed uranium (U) and Pu deposition was made to determine the method's ability to simultaneously extract U and Pu and determine the isotopic composition of both analytes.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Materials Data on Pu5Rh4 by Materials Project

Pu5Rh4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Pu sites. In the first Pu site, Pu is bonded in a 7-coordinate geometry to seven Rh atoms. There are a spread of Pu–Rh bond distances ranging from 2.79–3.12 Å. In the second Pu site, Pu is bonded in a 7-coordinate geometry to one Pu and six Rh atoms. The Pu–Pu bond length is 2.57 Å. There are a spread of Pu–Rh bond distances ranging from 2.82–3.21 Å. In the third Pu site, Pu is bonded in a 8-coordinate geometry to two equivalent Pu and six Rh atoms. There are a spread of Pu–Rh bond distances ranging from 2.66–3.21 Å. There are three inequivalent Rh sites. In the first Rh site, Rh is bonded in a 10-coordinate geometry to eight Pu and two equivalent Rh atoms. There are one shorter (2.74 Å) and one longer (2.92 Å) Rh–Rh bond lengths. In the second Rh site, Rh is bonded in a 8-coordinate geometry to eight Pu atoms. In the third Rh site, Rh is bonded in a 4-coordinate geometry to eight Pu and two equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Plutonium reactive transport in fractured granite: Multi-species experiments and simulations

Plutonium (Pu) in the subsurface environment can transport in different oxidation states as an aqueous solute or as colloidal particles. The transport behavior of Pu is affected by the relative abundances of these species and can be difficult to predict when they simultaneously exist. This study investigates the concurrent transport of Pu intrinsic colloids, Pu(IV) (aq) and Pu(V-VI) (aq) through a combination of controlled experiments and semi-analytical dual-porosity transport modeling. Pu transport experiments were conducted in a fractured granite at high and low flow rates to elucidate sorption processes and their scaling behavior. In the experiments, Pu(IV) (aq) was the least mobile of the Pu species, Pu(V-VI) (aq) had intermediate mobility, and the colloidal Pu, which consisted mainly of precipitated and/or hydrolyzed Pu(IV), was the most mobile. The semi-analytical modeling revealed that the sorption of each Pu species was rate-limited, as the sorption could not be described by assuming local equilibrium in the experiments. The model was able to describe the sorption of the different Pu species that occurring either on fracture surfaces, in the pores of the rock matrix, or simultaneously in both locations. While equally good fits to the data could be achieved using any of these assumptions, a fracture-dominated process was considered to be the most plausible because it provided the most reasonable estimates of sorption rate constants. Importantly, a key result of this work is that the sorption rate constant of all Pu species tends to decrease with increasing time scales, which implies that Pu will tend to be more mobile at longer time scales than observations at shorter time scales suggest. This result has important implications for predicting the environmental impacts of Pu in the safety assessments of geologic repositories for radioactive waste disposal, and we explore potential mechanistic bases for upscaling the sorption rate constants to time and distance scales that cannot be practically evaluated in experiments.

58 GEOSCIENCES↗
DOE OSTI2020

Materials Data on Pu2IO10 by Materials Project

Pu2O10I crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two Pu2O10I sheets oriented in the (0, 1, 0) direction. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of Pu–O bond distances ranging from 1.77–2.61 Å. In the second Pu site, Pu is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of Pu–O bond distances ranging from 1.77–2.53 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Pu atom. In the second O site, O is bonded in a single-bond geometry to one I atom. The O–I bond length is 1.78 Å. In the third O site, O is bonded in a distorted trigonal non-coplanar geometry to two Pu and one I atom. The O–I bond length is 1.90 Å. In the fourth O site, O is bonded in a 3-coordinate geometry to two Pu and one I atom. The O–I bond length is 1.92 Å. In the fifth O site, O is bonded in a single-bond geometry to one Pu atom. In the sixth O site, O is bonded in a single-bond geometry to one Pu atom. In the seventh O site, O is bonded in a bent 150 degrees geometry to two Pu atoms. In the eighth O site, O is bonded in a distorted trigonal planar geometry to two Pu and one I atom. The O–I bond length is 2.37 Å. In the ninth O site, O is bonded in a single-bond geometry to one Pu atom. In the tenth O site, O is bonded in a distorted trigonal planar geometry to two Pu and one I atom. The O–I bond length is 2.48 Å. I is bonded in a 5-coordinate geometry to five O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CePu4Co3 by Materials Project

Pu4CeCo3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 2-coordinate geometry to one Pu and four equivalent Co atoms. The Pu–Pu bond length is 2.82 Å. There are a spread of Pu–Co bond distances ranging from 2.45–3.17 Å. In the second Pu site, Pu is bonded in a 4-coordinate geometry to one Pu, two equivalent Ce, and six Co atoms. There are one shorter (3.17 Å) and one longer (3.19 Å) Pu–Ce bond lengths. There are a spread of Pu–Co bond distances ranging from 2.64–3.27 Å. Ce is bonded in a 4-coordinate geometry to four equivalent Pu and four equivalent Co atoms. There are two shorter (2.80 Å) and two longer (2.81 Å) Ce–Co bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 10-coordinate geometry to four equivalent Pu atoms. In the second Co site, Co is bonded in a 10-coordinate geometry to eight Pu and two equivalent Ce atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pu2Zn17 by Materials Project

Pu2Zn17 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded in a 12-coordinate geometry to eighteen Zn atoms. There are a spread of Pu–Zn bond distances ranging from 3.07–3.46 Å. In the second Pu site, Pu is bonded in a 8-coordinate geometry to twenty Zn atoms. There are a spread of Pu–Zn bond distances ranging from 3.09–3.42 Å. There are eight inequivalent Zn sites. In the first Zn site, Zn is bonded in a 1-coordinate geometry to one Pu and thirteen Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.71–3.04 Å. In the second Zn site, Zn is bonded to two equivalent Pu and ten Zn atoms to form a mixture of face, edge, and corner-sharing ZnPu2Zn10 cuboctahedra. There are two shorter (2.62 Å) and six longer (2.63 Å) Zn–Zn bond lengths. In the third Zn site, Zn is bonded to two equivalent Pu and ten Zn atoms to form ZnPu2Zn10 cuboctahedra that share corners with eighteen ZnPu2Zn10 cuboctahedra, edges with six ZnPu3Zn9 cuboctahedra, and faces with fourteen ZnPu2Zn10 cuboctahedra. There are four shorter (2.61 Å) and four longer (2.63 Å) Zn–Zn bond lengths. In the fourth Zn site, Zn is bonded in a 12-coordinate geometry to two Pu and ten Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.66–2.77 Å. In the fifth Zn site, Zn is bonded in a 12-coordinate geometry to two Pu and ten Zn atoms. There are a spread of Zn–Zn bond distances ranging from 2.66–2.76 Å. In the sixth Zn site, Zn is bonded to two Pu and ten Zn atoms to form a mixture of distorted face, edge, and corner-sharing ZnPu2Zn10 cuboctahedra. There are two shorter (2.71 Å) and two longer (2.75 Å) Zn–Zn bond lengths. In the seventh Zn site, Zn is bonded to three Pu and nine Zn atoms to form a mixture of distorted face, edge, and corner-sharing ZnPu3Zn9 cuboctahedra. There are one shorter (2.52 Å) and one longer (2.54 Å) Zn–Zn bond lengths. In the eighth Zn site, Zn is bonded to three Pu and nine Zn atoms to form a mixture of distorted face, edge, and corner-sharing ZnPu3Zn9 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Plutonium Redox Transformation in the Presence of Iron, Organic Matter, and Hydroxyl Radicals: Kinetics and Mechanistic Insights

Plutonium (Pu) redox and complexation processes in the presence of natural organic matter and associated iron can impact the fate and transport of Pu in the environment. In this work, we studied the fate of Pu(IV) in the presence of humic acid (HA) and Fe(II) upon reaction with H 2 O 2 that may be generated by photochemical and other reactions. A portion of Pu(IV) was oxidized to Pu(V/VI), which is primarily ascribed to the generation of reactive intermediates from the oxidation of Fe(II) and Fe(II)–HA complexes by H 2 O 2 . The kinetics of Pu(IV) oxidation is pH-dependent and can be described by a model that incorporates Pu redox kinetics with published HA-modified Fenton reaction kinetics. At pH 3.5, the presence of HA slowed Pu(IV) oxidation, while at pH 6, HA accelerated Pu(IV) oxidation in the first several hours followed by a reverse process where the oxidized Pu(V/VI) was reduced back to Pu(IV). Analysis of Pu-associated particle size suggests that Pu oxidation state is a major driver in its complexation with HA and formation of colloids and heteroaggregates. Our results revealed the H 2 O 2 -driven oxidation of Pu(IV)–HA–Fe(II) colloids with implications to the transient mobilization of Pu(V/VI) in organic-rich redox transition zones.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Plutonium Co-precipitation with Calcite

The mobility of plutonium (Pu) in the environment is affected by Pu–mineral interactions, such as adsorption–desorption and structural incorporation. Calcite (CaCO 3 ) is a common secondary phase in near surface environments and a major component of many rocks and soils and is expected to form as an alteration product of cement-based materials planned for use in geological repositories. The reactivity of the calcite surface and its ability to tolerate significant variations in its chemical composition through substitution of Ca for other cations make calcite a potentially important sink for environmental contaminants. Here, single crystals of calcite were synthesized from aqueous solutions in equilibrium with air containing Pu as either Pu(VI) or Pu(IV) and characterized using a combination of laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) and X-ray absorption spectroscopy (XAS). These data are used to assess the amount, structure, and oxidation state of Pu co-precipitated into calcite, providing insight into the potential for Pu sequestration in calcite precipitates. Overall, the XAS and LA–ICP–MS data support the co-precipitation of plutonyl [Pu(VI/V)] in the bulk calcite, although the exact nature of the co-precipitated Pu complex is difficult to elucidate in the synthesized material. Co-precipitated plutonyl could be incorporated in either distorted Ca lattice sites or defect sites, and we provide evidence to suggest that Pu(VI) is reduced mainly to Pu(V) in the precipitated solid. LA–ICP–MS additionally shows that the co-precipitation of Pu(VI/V) is favored over the co-precipitation of Pu(IV). Altogether, our results suggest that Pu sequestration in calcite under environmental conditions could immobilize Pu and isolate it from groundwater interactions in contaminated environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Thermodynamics of gallium-stabilized delta-plutonium: A high-temperature drop calorimetry study

Throughout the Cold War (1947–1991), both the United States and the former Soviet Union independently derived a phase diagram for the Pu-Ga system that has different implications on Pu phase stability. In the phase diagram produced by the United States, the Pu δ-phase is thermodynamically stable at room temperatures when Ga content is between 2 and 9 at. %. The diagram produced by the Soviet Union shows the δ-phase undergoing an eutectoid decomposition into the α-Pu + α-Pu 3 Ga at 7.9 at. % Ga and 370 K. This would suggest that Ga-stabilized δ-Pu is metastable with respect to α-Pu + α-Pu 3 Ga at 298 K. To investigate this, and the thermodynamic behavior of Ga in the FCC lattice of δ-Pu, we have utilized high-temperature drop calorimetry to study the enthalpy of formation of two δ-Pu 1−x Ga x compositions. In doing so, mixing models (regular and subregular) were developed to understand the thermodynamic behavior of Ga in the FCC lattice of δ-Pu and found a strong departure from ideal conditions, which suggests Ga ordering in the FCC lattice of δ-Pu. Overall, it was found that δ-Pu 1−x Ga x is enthalpically metastable with respect to α-Pu + Pu 3 Ga at 298 K.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Plutonium Oxidation State Distribution in the Presence of WIPP-Relevant Organics and Iron Corrosion Products

The oxidation state and solubility of plutonium (Pu) in high ionic strength synthetic WIPP (Waste Isolation Pilot Plant) brines as a function of pC H+ in the presence and absence of WIPP-relevant organic ligands (EDTA [Ethylenediaminetetraacetic acid], oxalate, citrate, acetate) and iron corrosion products (magnetite and metallic iron) at 𝑇 = 23 ± 2 ∘C was thoroughly studied by long-term batch solubility experiments (between approximately 800-1,100 days) from an undersaturation approach. The oxidation state of Pu in the WIPP environment has been a topic of interest since the initial Compliance Certification Application (CCA). This study aims to investigate the solubility of Pu under the expected WIPP conditions and to determine the oxidation state of the solid phase that will control the solubility. One of the most important results of this study is that the Pu oxidation state was analyzed both from the surface area of the corrosion products and in the precipitated solid. The analysis of the Pu oxidation state on the surface of the iron mineral from the ongoing undersaturated experiments is more relevant to the performance assessment of nuclear waste disposal than short term batch (plutonium-iron phase) experiments. The X-ray Absorption Near-Edge Spectroscopy (XANES) analysis showed that Pu oxidation state is different on the metal surface and in the precipitated solid. Pu(III) is the dominant oxidation state in the metallic iron (Fe 0 ) system in the presence and absence of organics. Pu(IV) is the dominant oxidation state in the magnetite system in the presence and absence of organics. Also, organics stabilize Pu(IV) in the magnetite system. Analysis of Pu in the precipitated solid by Extended X-ray Absorption Fine Structure (EXAFS) analysis showed that Pu formed an inner-sphere complex with iron with minor amounts of PuO 2 present. X-ray diffraction (XRD) results indicate that metallic iron and magnetite did not oxidize in three years in the alkaline and high ionic strength system. Under these conditions (8 < pC H+ < 10 at T = (22 ± 2) °C under nitrogen atmosphere, the solubility of Pu changes by up to three orders of magnitude (10 -5 and 10 -8 M). The spread in solubility is highest at pC H+ = 9. Pu(III) and Pu(IV) showed different solubility behavior in the synthetic WIPP brine. A summary of the data collected in this report will be submitted to Sandia National Laboratories as part of a parameter update report which will outline the changes to the OXSTAT parameter for the 2026 Compliance Recertification Application (CRA-2026). The experiments performed were done according to the U.S. Department of Energy (DOE) approved Test Plan entitled “Effects of Radiolysis, Organic Complexation, and Redox Conditions on the Speciation and Oxidation State Distribution of Pu(III/IV)” (LCO-ACP-25). All data reported were obtained under the Los Alamos National Laboratory-Carlsbad Office (LANL-CO) Quality Assurance Program, which is compliant with the DOE Carlsbad Field Office, Quality Assurance Program Document (CBFO/QAPD).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on Pu3Al by Materials Project

Pu3Al is Uranium Silicide structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded to eight equivalent Pu and four equivalent Al atoms to form PuPu8Al4 cuboctahedra that share corners with twelve equivalent PuPu8Al4 cuboctahedra, edges with eight equivalent AlPu12 cuboctahedra, edges with sixteen equivalent PuPu8Al4 cuboctahedra, faces with four equivalent AlPu12 cuboctahedra, and faces with fourteen PuPu8Al4 cuboctahedra. All Pu–Pu bond lengths are 3.09 Å. All Pu–Al bond lengths are 3.14 Å. In the second Pu site, Pu is bonded to eight Pu and four equivalent Al atoms to form distorted PuPu8Al4 cuboctahedra that share corners with twelve equivalent PuPu8Al4 cuboctahedra, edges with eight equivalent AlPu12 cuboctahedra, edges with sixteen PuPu8Al4 cuboctahedra, faces with four equivalent AlPu12 cuboctahedra, and faces with fourteen PuPu8Al4 cuboctahedra. All Pu–Pu bond lengths are 3.14 Å. All Pu–Al bond lengths are 3.09 Å. Al is bonded to twelve Pu atoms to form AlPu12 cuboctahedra that share corners with twelve equivalent AlPu12 cuboctahedra, edges with twenty-four PuPu8Al4 cuboctahedra, faces with six equivalent AlPu12 cuboctahedra, and faces with twelve PuPu8Al4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmPu3 by Materials Project

Pu3Tm is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Pu sites. In the first Pu site, Pu is bonded to eight equivalent Pu and four equivalent Tm atoms to form PuTm4Pu8 cuboctahedra that share corners with four equivalent TmPu12 cuboctahedra, corners with fourteen equivalent PuTm4Pu8 cuboctahedra, edges with six equivalent TmPu12 cuboctahedra, edges with twelve equivalent PuTm4Pu8 cuboctahedra, faces with four equivalent TmPu12 cuboctahedra, and faces with sixteen PuTm4Pu8 cuboctahedra. There are a spread of Pu–Pu bond distances ranging from 3.37–3.48 Å. There are two shorter (3.42 Å) and two longer (3.43 Å) Pu–Tm bond lengths. In the second Pu site, Pu is bonded to eight equivalent Pu and four equivalent Tm atoms to form PuTm4Pu8 cuboctahedra that share corners with four equivalent TmPu12 cuboctahedra, corners with fourteen PuTm4Pu8 cuboctahedra, edges with six equivalent TmPu12 cuboctahedra, edges with twelve equivalent PuTm4Pu8 cuboctahedra, faces with four equivalent TmPu12 cuboctahedra, and faces with sixteen PuTm4Pu8 cuboctahedra. There are a spread of Pu–Pu bond distances ranging from 3.37–3.48 Å. There are two shorter (3.42 Å) and two longer (3.43 Å) Pu–Tm bond lengths. Tm is bonded to twelve Pu atoms to form TmPu12 cuboctahedra that share corners with six equivalent TmPu12 cuboctahedra, corners with twelve PuTm4Pu8 cuboctahedra, edges with eighteen PuTm4Pu8 cuboctahedra, faces with eight equivalent TmPu12 cuboctahedra, and faces with twelve PuTm4Pu8 cuboctahedra.

36 MATERIALS SCIENCE↗