Media, page-1704

I just spent a few hours looking further into this Thorium issue ?: here is what I found:

Dose limits ~ WHO Guidelines

The current limit of radiation exposure is 20 millisieverts (mSv) per year averaged over 5 years, and not more than 50 mSv received in any one year for effective (whole body) dose.

1rem=10mSv Therefore the limits are : over 5 years 2rem, with a maximum in any one year of 5rem

There is very little published on the dosage from mining Thorium, however I did find one paper (from an impeccable source) that extrapolates Th values from other studies done into Uranium dosages from mining operations. The "Theoretical" mine based on 500ktpa @ 0.5 % (5000ppm) ThO2, whereas Longonjo is 2.5Mtpa @ <1,000ppm. So the total loads are very similar certainly within the same ball-park..

Some extracts from the study done by the Oak Ridge Laboratory: https://www.osti.gov/servlets/purl/5536703
A word of caution for non-experts reading this ~ A thorough knowledge of the Units used for Radioactivity is required to understand the text.

2.1 Radiological Impacts During Operation

The study by Tennery et al.(*4) analyzes the potential impacts resulting from the operation of a facility involving an open-pit thorium mine and a model thorium mill and refinery.

The mine is an open-pit thorium mine producing 1600 metric tons (MT) of ore per day, containing an average thorium content equivalent to 0.5 wt % of Th02. The thorium mill is hypothesized to process 1600 MT of ore per day, producing 4500 MT of Th(N03)4•4H20 per year.

Radioactivity leaves the complex as 22 0Rn (55.6-s half-life) from the mine, ore storage pile, mill refinery, and tailings beach, and as airborne dust
from the mining and milling operations and the tailings. Besides 22 0Rn, radionuclides of interest are 228Ra , , 232Th 228Th , 224Ra , , 228Ac and .daughters of 220Rn, notably, 212Pb. After facility shutdown, the drying thorium-tailings area is assumed to be stabilized by covering it with earth, reducing erosion processes. Because of the .55.6-s half-life of 220Rn, however, only a thin covering of earth is necessary to reduce emanation rates of the gas to near zero. Since the 222Rn in the uranium decay chain has a half-life of 3.82 days, the doses associated with the retired thorium tailings pile will be very low in contrast to the impact of retired uranium tailings treated similarly.

"The following table should address every bodies concerns on what levels can be expected from Longonjo and for that matter the Peak Tailings dumps in Teeside":

Note well: These dosage units are in 'mrem' ie That (50 year) 2,4 mrem dose is just One Thousandth of the five year WHO limit,



Considering the mines themselves, the only significant radioactive release would be radon gas ~ 220Rn in the case of thorium and 2 22Rn in the
case of uranium. It has been estimated that the 220Rn release from the 12- acre open-pit model thorium mine would be ~37 Ci/day or ~1.35 x 104 Ci/yr. 7 Because of atmospheric dispersion and its rapid decay, the air concentration at a hypothetical site boundary of 800 m (0.5 miles) (~ ca. 1 x 10-6 ) would be ~8 x 10-12 ~Ci/ml. The 222Rn release from a model uranium mine was estimated at 3 Ci/day or 1095 Ci/yr.7 For similar conditions, the air concentration of 2 22Rn at the site boundary would be ~4 x 10-10 ~Ci/ml or two orders of magnitude higher. All concentrations are orders of magnitude less than the limits for an unrestricted area in 10 CFR 20.



5. Oak Ridges SUMMARY

Based on a review of the available literature and participation in related studies, it is our opinion that radiological impacts to the general public associated with routine releases of radionuclides from both thorium/uranium and uranium/plutonium recycle systems will be acceptably low. Technology to meet existing or anticipated radiological standards arise. The larger dose commitments associated with current uranium mine/mill facilities compared to hypothetical thorium facilities are clearly the major significant difference in radiological impact of the Th/U and U/Pu fuel cycles

My Summary

I hope that the above goes some way to settling peoples fears that Thorium may perhaps be a valid issue. Yes there is Thorium there, but No it is not an issue as the dosages experienced by those working at the mine will be several orders of Magnitude below the limits set by the WHO


*4. v. J. Tennery, E. s. Bomar, w. D. ~ond, L. E. Morse, H. R. Meyer, J. E. Till, and M. G. Yalcintas, Environmental Assessment of
Alternative FBR Fuels: Radiological Assessment of Airborne Releases from Thorium Mining and Milling, ORNL/TM-6474, October 1978