Characterization of aerosols from RDD surrogate compounds produced by fast thermal transients

Figures & data

Table 1. Radionuclides of concern for RDD production (as reported in [11]).

Radionuclide	Typical physiochemical form	Application	Activity
^60Co	Metal	Sterilization irradiator	Up to 400 000 TBq
		Nuclear medicine	Up to 1000 TBq
^90Sr	Ceramic (SrTiO3)	Thermoelectric generator	1000–10 000 TBq
^137Cs	Salt (CsCl)	Sterilization irradiator	Up to 400 000 TBq
		Nuclear medicine	Up to 1000 TBq
^192Ir	Metal	Industrial radiography	Up to 5 TBq
^226Ra	Salt (RaSO4)	Nuclear medicine	Up to 5 TBq
^238Pu	Ceramic (PuO2)	Thermoelectric generator	Up to 5 TBq
^241Am	Pressed ceramic powder (AmO2)	Well logging source	Up to 1 TBq
^252Cf	Ceramic (Cf2O3)	Well logging source	Up to 0.1 TBq

Table 2. Samples tested in our studies, and the cladding materials investigated.

Sample	Cladding	Composition (%wt.)
Co	Tungsten	50/50, 30/70
	Stainless steel	50/50, 25/75
	Mixture	33/33/33, 22/71/7
CsCl	Tungsten	50/50, 25/75
	Stainless steel	50/50
	Mixture	33/33/33, 25/50/25
Ir	Stainless steel	50/50
SrTiO3	Tungsten	50/50, 87.5/12.5
	Stainless steel	50/50
	Mixture	33/33/33, 25/50/25

Table 3. Properties of the applied materials in the experiments.

			*Vapour pressure (Pa) at
Sample	Purity	Grain size (μm)	500 K	1000 K	2000 K	3000 K
Co	99.8	1.6	–	3.1 × 10^−6	2.1 × 10^3	9.5 × 10^5
CsCl	99.9		3.8 × 10^−8	97.3	1.24 × 10^6	–
Ir	99.9	<44	–	8.1 × 10^−25	3.3 × 10^−5	–
SrTiO3	99	5	–	–	0.22 ^†	5.0 × 10^4 ^†
W		74 < X < 105	–	–	2.4 × 10^−10	9.5 × 10^−3
				(1.4 × 10^−7)	(2.8 × 10^5)
Steel	99.9	15	–	–	37.4	5.6 × 10^4

*Vapour pressure data were obtained from literature data [12] and described for the relevant temperature region for our experiments. The values in parentheses for W refer to WO₃.

^†No data available. SrTiO₃ decomposes to SrO and TiO₂ during vaporization, as reported for PbTiO₃ in [13]. The vapour pressure values refer to SrO [12].

Figure 1. Aerosol size distribution for the Co sample and its mixture with the cladding materials, obtained by weighing the MOUDI impactor plates before and after the experiments.

Figure 2. Examples of aerosols from the Co sample, showing the different types of particles: in the first stages (top left, with cut-off sizes 1.8 < AED < 18 μm), individual spherical particles were found; in stage 5 (top right, with a cut-off size of AED 1 μm), agglomerated particles were observed (a magnified image of these agglomerates is shown in the bottom-left frame). Nanometric agglomerates were found in the last stages 6–8 (bottom right, AED < 0.56 μm).

Figure 3. Raman spectrum measured for mixed cobalt–tungsten aerosols, showing all the typical bands of CoWO₄, as reported in [17–19].

Figure 4. Examples of aerosols from a mixed cobalt–tungsten sample (50/50%wt.), showing the different particles collected: top, aerosols collected from the first stages (1.8 < AED < 18 μm), isolated big particles and externally mixed agglomerates; bottom, mixed agglomerates containing Co and W, in the smaller particles, a higher content of tungsten was detected by SEM/EDX. The table shows the average concentration together with the maximum value detectable by EDX.

Figure 5. Aerosol size distribution for the CsCl sample and its mixture with the cladding materials, obtained by weighing the MOUDI impactor plates before and after the experiments. The size distribution refers to a CsCl + W + Steel mixture (25/50/25 composition), with may explain the minimal shift of the peak to μ = 1.11 μm (σ = 600 nm).

Figure 6. Results from the Raman analyses on the aerosols produced from a mixture of CsCl and W, showing a chemical partitioning over the different stages. Smaller particles show the presence of WO₃. The middle stages show some modification in the spectra (e.g. 320, 700–780 and 900 cm⁻¹ bands) that are related to the formation of a new chemical compound.

Figure 7. Aerosol size distribution for the SrTiO₃ sample and its mixture with the cladding materials, obtained by weighing the MOUDI impactor plates before and after the experiments.

Figure 8. Raman spectra for the SrTiO₃ aerosols and pellets, showing the difference between the bulk material and the first-order bands related to the nanometric aerosols. In particular, the spectrum of the particles in the stage 5 (AED of 1 μm) is similar to the bulk material, indicating that this effect becomes evident only for smaller particles.

Figure 9. Typical Raman spectra for the aerosols collected from an SrTiO₃ sample with tungsten, showing a chemical partitioning with AED. In the smaller particles, the bands of WO₃ can be observed. The formation of SrWO₄ can be inferred from the band at 922 cm⁻¹.

Andersson KG, Mikkelsen T, Astrup P, et al. Estimation of health hazards resulting from a radiological terrorist attack in a city. Radiat Prot Dosim. 2008;131(3):297–307.

 PubMed Web of Science ®Google Scholar

Yaws CL, Prasad NR, Chaitanya G. The Yaws handbook of vapor pressure: antoine coefficients. Houston (TX): Gulf Publishing Company; 2007.

 Google Scholar

Kobertz D, Mueller M, Molak A. Vaporization and caloric studies on lead titanate. Calphad. 2014;46:62–79.

 Web of Science ®Google Scholar