The data below are the 'raw' extracts from the documents and/or papers. Please refer to the last column for the reference and obtain the full text if required. Please also let me know if there are any mistakes here.
No
Data
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1
USA
Estimated annual doses from in rare earth and zirconium industries - worker 2.0-5.0 mSv, public - 0.1 mSv
Worker gamma dose from storage or disposal of rare earths and zirconium is in order of 0.01 mSv/year
S-06
2

European Union
Most common ores - zircon (ZrSiO4) & baddeleyite (ZrO2). Sand is pre-processed by gravimetric and electromagnetic separation techniques. Refractory components are made by mixing zircon sand with alumina and sodium carbonate and smelting at high temperature.
General ranges of activity (Bq/g): Th-232 0.2-40.0, U-238 0.2-74.0, Ra-226 0.2-74.0, Pb-210 0.2-400.0
Doses
Normal conditions, min act conc 0.01 mSv/y, Normal conditions, max act conc 270.0 mSv/yr
Unlikely conditions, min act conc 0.08 mSv/y, Unlikely conditions, max act conc 580.0 mSv/yr
(Nick's additional note needed here: theoretically-generated doses like 270 & 580 mSv/year are a bit "over the top", I think. From my personal point of view, this is just plain impossible in the real life... Just compare them with the other information on this page. I would like to see the real situation where dose may be more than 10..., please let me know if you are aware of one)
D-02
3
UK
Manufacture of zirconia
Baddeleyite is heat treated to alter its crystalline structure to form zirconia. After treatment the product is milled to achieve a range of small particle sizes. P-b210 & Po-210 are volatile and are driven off during the heat treatment to deposit in the cooler parts of the effluent system. In particular they occur in furnace flue dusts.
Zircon as a refractory
In steel foundries where a layer of zircon is used as the inner surface of a mould.
Zircon & zirconia in the manufacture of refractories
Typical concentrations (Bq/g):
Zirconia/baddeleyite: Th-232 0.3, Ra-228 6.0, U-238 7.0, Ra-226 7.0, Pb-210 7.0, Po-210 7.0;
Zirconia flue dusts: Th-232 0.5, Ra-228 8.0, U-238 3.0, Ra-226 3.0, Pb-210 200.0, Po-210 200.0;
Zircon: Th-232 0.6, Ra-228 0.6, U-238 3.0, Ra-226 3.0, Pb-210 3.0, Po-210 3.0
Estimated typical doses (mSv/y): Production of ZrO2: 2.8, Fume: 0.8, Zircon: 0.0.
G-01
4
European Union
Bags with ore (Africa). Baddeleyite - Th-232 was found not in the secular equilibrium, reasons unknown. Total activity 150-2500 Bq/g, dose rate 1.0-45.0 microSv/hr
A-04
5
USA
Zircoloy sand from New Mexico was used in wellbore fracturing studies in Texas. Large volume of waste material - zirconium silicate - zircon.
Material: U-238 series: Ra-226 3.9-4.0 Bq/g, Pb-214 1.9-2.0 Bq/g; Th-232 series: Ra-224 0.14-0.40 Bq/g, Pb-212 0.14-0.4 Bq/g. dose rate 1.0-1.2 microSv/hr (Background = 0.1 microSv/hr)
Zircoloy sand isotopes:
U-238 chain not in secular equilibrium, Th-232 chain is. Reason: zircoloy sand is a porous loose material. This allows for Rn-222 gas to escape and thus lower the ratio of the decay products to the parent radioisotope. In Th-232 series Rn-220 has only 55-seconds half-life, this prevents it from escaping even in porous materials.
A-05
6
European Union
Foundry sands - zircon sands 1-5 Bq/g
J-02
7
UK, zircon processing
Th-232 0.5-1.0 Bq/g; U-238 1.0-5.0 Bq/g
External exposure - gamma 1-2 microGy/hr, internal - particle size is too large to be inhaled. However, milling creates very fine particles. Precautions - in dry milling dust extraction systems are necessary.
Doses: 0.6 mSv/yr if reasonable precautions are taken, 6.0 mSv/yr - if no precautions are taken
N-01
8

Australia
Potential radiation levels in process plants depend on the type of zircon and amount of dust in the air. The maximum possible annual levels of radiation - 5 mSv/yr. Estimated levels in process plants with dust management programs - ~0.5 mSv/yr.
A-06
9

Zircon, ZrSiO4, occurs in nature with total Th and U concentrations that are usually in the range from 0 to 4000 ppm but in rare cases up to 6% by weight UO2+ThO2
(Another Nick's note: it's quite possible that in some cases when it is said that zircon contains THAT much of thorium and uranium, it's just has not been fully separated from monazite and still contains some...)
C-04
10
USA
decommissioning of ceramic manufacturing facility licences by NRC (used depleted uranium oxide)
Zirconium oxide activity concentrations: U-238 5.1-5.4 Bq/g, U-235 0.2-0.3 Bq/g, Th-232 0.3-0.4 Bq/g; >0.05% of U+Th by weight, above the classification is a "source material"
L-06
11

Netherlands
Radium concentration in zircon grains depends on grain size and decreases with increasing size. However it does not follow the surface to volume ratio. This suggests that radium distribution in zircon grains is neither homogenous, nor of a surface type but possibly with an outer layer of the grain higher in radium than the inner core.
T-06
12

South Africa
Ceramic tile glaze contains ~6% of ZrO2, 0.37 Bq/g U-238, 0.10 Bq/g Th-232
Extended floor or wall scenario - 0.057 mSv/yr, small room - 0.007 mSv/yr, external exposure + radon/thoron taken into account
S-07
13

some peculiar zircons...
Zircon from Ampagabe (Madagascar); UO2 - 1.85%, ThO2 - 1.35%
Zircon from Naëgy (Japan), associated with thorite: UO2 - 8.25%, ThO2 - 10.55%.
F-02
14

The term "metamict" describes an amorphous state of initially crystalline minerals reached by secondary displacement of atoms ("radiation" damage). The main cause of displacements of lattice atoms is not alpha radiation itself, but the recoil of heavy nuclei when emitting an alpha-particle.
Gem-quality zircon from Sri Lanka 530-560ppm U.
Four zircons studied:
Jack Hills, NW Yilgarn Craton of Western Australia, late Archaean granite, zircon - rounded, short-prismatic grains, U 277-870ppm, Th 381-962ppm
Mittweida, Germany, zircon - short and prismatic, partly rounded crystals, U 197-4489ppm, Th 63 - 4191ppm
Borlas, Germany, zircon vary widely ranging from long almost needle-like crystals to short and prismatic ones, the latter ones analysed: U 23-683ppm, Th 9-67 ppm
Weferlingen, Germany - oval, well-rounded shape, U 97-903 ppm, Th 2-150 ppm
N-02
15

Zircon typically contains 5-4000 ppm U, 2-2000 ppm Th
Zircon from gem gravels of the Ratnapura district in Sri Lanka:
Th 31 - 1340 ppm, U 26 - 3210 [M-07] or 7600 [E-04] ppm

E-04
M-07
16

Australia
Zirconia production waste 9.0 Bq/g radium
Foundry sands - used because of its suitable refractory properties, isolated from the public after use to minimise exposure. Foundry sands are frequently diluted with silica sand during their use, thus, activity concentrations in waste can be lower than that of pure zircon. No chemical treatment.
Zirconia production for use in advanced ceramic materials, radionuclide concentration factor = 1-2, no chemical treatment.
Zirconium produced by chlorination process. Zircon tetrachloride is formed and is reduced by magnesium to Zr. Concentration factor 1-3.
H-11
17

In high temperature processes such as smelting of zircon, fume may be enhanced in Po-210. An investigation carried out at an Italian zircon plant revealed a concentration of Po-210 in fume of 0.4 Bq/m3. Using the measured Activity Median Aerodynamic Diameter (AMAD) value of 0.3 microns, and assuming full-time exposure to this concentration results in an estimated dose of 3.4 mSv/year.
H-12
18

Bangladesh
Zircon, garnet, magnetite, ilmenite
Gamma 0.23-8.89 microSv/hr. Radon 20.5-252.6 Bq/m3. Dose estimate for workers ~6.9 mSv/year.
M-09
19

Italy
Zircon
U-238 series were virtually in secular equilibrium except possibly Po-210. Th-228/Th-232 activity ratio in the zircon sample was close to unity, and thus all thorium series members were probably in equilibrium with Th-232.
Baddeleyite
U-238 to Ra-226 - secular equilibrium. Pb-210 only about 60% of its Ra-226 precursor.
Th-232 not in equilibrium with daughters Th-228/Th-232 = 11.7. The smaller diameter of the particles sugests that sand has already been treated.
Explanation for Pb-210 depletion - partial loss of Rn-222 parents during extraction and milling. Excess of Th-228 could be due to a recent enrichment, probably through its Ra-228 precursor.
Zircon
Despite the high levels of natural radionuclides, which are about two orders of magnitude higher than those normally encountered in soil samples, U-238, U-235, Th-232 and their respective daughters are strongly bound to the matrix. This, coupled with the relatively large particle sizes, their high density results in low radon emanation rate from zircon sand.

S-09
20

UK
Batches of mineral are mixed with various additives and are then fused at high temperatures in an electric arc furnace. During this process fine dust and furnace fume are released and are collected by an extraction system. The dust typically contains the same radionuclides found in the raw material, but in slightly higher concentrations. The fume containds volatile radionuclides that condense and attach to dust particles in the extraction system - substantial increase in concentrations of Po-210 & Pb-210. The combined dust and fume is collected as a furnace dust collector fines or "furnace DCF".
Raw material (Bq/g): Th-232 0.3, Ra-228 2.0, Th-228 0.4, U-238 9.5, Th-230 1.3, Ra-226 10.0, Pb-210 10.0, Po-210 3.7.
Furnace DCF (Bq/g): Th-232 1.8, Ra-228 11.0, Th-228 3.6, U-238 16.0, Th-230 2.5, Ra-226 30.0, Pb-210 200.0, Po-210 600.0.
Products (Bq/g): Th-232 0.3, Ra-228 2.0, Th-228 0.5, U-238 8.0, Th-230 1.0, Ra-226 10.0, Pb-210 10.0, Po-210 3.0
Max possible dose in the past was >30mSv/year, average now ~2.5, highest possible ~5 msv/yr
S-11
21

Australia, zircon milling
Typical Th and U:
Australia U 1.8-3.6 Bq/g, Th 0.62-1.03 Bq/g
South Africa U 2.8-3.1 Bq/g, Th 0.82-0.90 Bq/g
USA U 2.4-3.0 Bq/g, Th 0.41-0.62 Bq/g
China U 14.3 Bq/g, Th 8.2 Bq/g
Measured in Australian plants:
External 0.1-0.4 mSv/yr, internal 0.27-0.73 mSv/yr, total 0.66-1.03 mSv/yr
H-13
22

Taiwan, ceramic tiles
The radioactivity is mostly from zircon used in glaze. 60 tile samples were investigated.
Different studies comparison for U series in tiles (Bq/g):
Netherlands, 1985: 0.04-0.09; Malaysia, 1990: 0.04-0.06; Canada, 1992: 0.04-0.12; Greece, 1994: 0.03-0.09; Taiwan, 2001: 0.04-0.32.
The same for Th series in tiles (Bq/g):
Netherlands, 1985: 0.05-0.08; Malaysia, 1990: 0.04-0.12; Canada, 1992: 0.03-0.15; Greece, 1994: 0.01-0.05; Taiwan, 2001: 0.05-0.20
The annual dose induced by the 60 samples are all within 0.05 mSv/yr, therefore no action is suggested. If any intervention - pay more attention on zircon related process.
L-08
23

Russia, metal zirconium production
Based on chemical metallurgy reprocessing of zircon mineral and products of its reprocessing. More than 90% of activity was transferred to wastes of zircon processing.
Raw material (Bq/g)
Zircon: U-nat 10.9; Ra-226 1.25; Th-232 0.22, Ac-227 0.09
Products (Bq/g)
Zirconium carbonate: U-nat 0.45, Ra-226 0.003, Th-232 0.013, Ac-227 0.015
Zirconium dioxide technical: U-nat 0.19, Ra-226 0.008, Th-232 0.012, Ac-227 0.007
Potassium fluorozirconate: U-nat 0.21, Ra-226 0.007, Th-232 0.015, Ac-227 0.013
Wastes (Bq/g)
Zr hydroxide (five different ones): Unat 1.05-3.8, Ra226 0.007-0.032, Th232 0.002-0.029, Ac227 0.007-0.049
Sands: Unat 0.25, Ra226 0.026, Th232 0.021, Ac227 0.020
S-13
24

Netherlands
Refractory material - zircon-alumina-casting - as measured in a Dutch glass furnace: about 1.7 Bq/g U-238 and daughters (corresponding to about 50 pCi/g) about 0.3 Bq/g Th-232 and daughters
R-05
25

China, zircon tiles
External gamma- and beta-radiation was measured at 5 cm from piles of zircon sand sacks: 11-49 microGy/hr, with an average of 21 microGy/hr. Average gamma radiation at the surface of tile stacks in shops is 1.5 times higher than background level.
Gamma dose rate was measured in 47 randomly selected dwellings decorated with glazed tiles. No elevated gamma was detected. Increased external radiation dose rate of glazed tiles is only from beta radiation. Radon exhalation rates were measured and elevated results were obtained.
(Nick's additional note: the values appear to be quite high, one possible explanation would be that some zircon in this study was slightly contaminated with monazite...)
D-04
26
 Australia, ceramic tiles
Gamma dose in a room decorated with tiles would be about 10 microSv/year (average value for Australian homes is 900 microSv/yr). The estimate is based on: exposure for 1 year in 3x3x3 m room gives a dose of 370 microSv, then 2-3% occupancy factor is applied.
Contribution of exhaled Rn-222 (5 Bq/m3) is comparable with annual average for Australian homes (12 Bq/m3) and is only a small fraction of action limit of 200 Bq/m3. Therefore, radon exhaled from tiles is not a significant risk.
Low exhalation rates of the zircon sands, stains and frits imply that the Rn-222 emanation coefficient for zircon is much lower than the theoretical value of 0.2. The structure of zircon grains is such that most of the Rn-222 produced by the decay of Ra-226 is trapped in the grains.
O-03
27
 China, ceramic tiles
Levels of natural radionuclides in zircon are between 2.1 Bq/g (for Australian material) and 12.8 Bq/g (for Chinese material) for Th-232, and between 5.5 Bq/g (for Australian material) and 15.6 Bq/g (for Chinese material) for U-238.
Ra-226 levels in glaze are up to 4.1 Bq/g and thorium levels - up to 1.3 Bq/g.
Rn-222 exhalation rate for ceramic tiles is higher than for other building materials. O'Brien method (ref.O-03) measured per unit mass, this study - per unit surface area. Average surface alpha was 0.88x10(-2) Bq/cm2, beta 0.21 Bq/cm2 - these values exceed the exempt limits of national criteria in China.
(Nick's additional note: it appears that no gamma measurements were made and the statement about the need for control of external exposure was made only on the basis of radionuclides concentrations in the glaze...)
Y-03
28
 USA, ceramic tiles
Ceramic tiles contain zircon, which in its turn contains thorium and uranium. These tiles could serve as large area calibration sources if it can be demonstrated that they have uniform surface-alpha emission rate. For a given type of tile, alpha contamination is fairly uniform on all tiles, but there was a significant difference (a factor of up to 3.5) between tiles of different types. A conclusion - tiles can serve as cheap, uniform, large area fixed contamination test beds - unlike conventional calibration sources that are expensive, require licensing, not readily available and are subject to deterioration.
D-05
29
 Australia, zircon milling
Five milling plants were studied. Theoretical doses are potentially up to 5.5 mSv/yr, measured doses are in the range between 0.66 and 1.03 mSv/yr. Upper limit of doses for dustiest operations is about 3 mSv/yr.
H-16
30

UK, refractories production
The raw material is imported in drums or bags and stored until required for production. Batches are mixed with various materials prior to fusing at high temperature in an electric arc furnace. This process releases fine dust and fume, which is collected in the extraction. The dust typically contains the same radionuclides found in the raw material, but with slightly enhanced activity concentration. The fume contains volatile radionuclides that condense and attach to dust particles in the extraction system. The volatilisation process substantially enriches (typically by two orders of magnitude) the concentration of Po-210 and Pb-210. The extraction system transports the fume and dust to a collection point where it is collected in drums. The combined dust and condensed fume is referred to as "furnace DCF". Typical activity concentrations in the raw material, furnace DCF and a typical product are shown in the table below:
 
Radioactivity concentration (Bq/g)
Radionuclide
Raw material
Furnace DCF
Products
Th-232
0.3
1.8
0.3
Ra-228
2.0
11.0
2.0
Th-228
0.4
3.6
0.5
U-238
9.5
16.0
8.0
Th-230
1.3
2.5
1.0
Ra-226
10.0
30.0
10.0
Pb-210
10.0
200.0
10.0
Po-210
3.7
600.0
3.0
All the materials listed may be regarded as radioactive when used in dusty operations or kept in bulk storage. The highest doses are received by persons working in the product milling and bagging areas. Average estimated doses for these workers in 1990 and 1991 exceeded 10 mSv/year. After a major program of engineering controls and employee education average doses for these workers in 1994-1997 were reduced to 2.5-4.0 mSv/year.
Disposal of Furnace DCF (Po-210 up to 600 Bq/g) represents a major problem. By 1998, over 200 tonnes of waste had been accumulated. The producer decided to pursue the stabilising option for the stored DCF. A purpose-designed plant was constructed to blend DCF with damp sand, in a ratio varied to suit the particular specific activity of the DCF.

D-23
31
 EU, zirconium and rare earths
Naturally occurring radioactivity levels in rare earths and zirconium ores and in associated products and wastes are generally around 10 Bq/g. Occupational exposures during the processing of these materials have been conservatively estimated to be in the region of a few mSv/yr, mainly from internal exposure. The dose to the public from liquid and airborne effluents from the processes have been shown to be low, though the estimated doses resulting from landfill disposal of the waste materials are more significant. Subsequent redevelopments at landfill sites could give rise to individual doses of about 0.1 mSv/yr.
E-08

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