THORIUM AS AN ENERGY SOURCE - Opportunities for Norway ...

Thorium Resources in Norway
The thorium concentration in the Fen rocks is positively correlated with iron (Fe) [12]. Thus, the
white carbonate part of the Complex has low levels of thorium. The summary report from
previous investigations concluded that the thorium concentrations are:
• 0.4 wt% thorium in the iron ore.
• 0.2 - 0.3 wt% thorium in enriched zones in the iron-rich part of the ore.
• 0.13 - 0.17 wt% thorium in the iron-rich part in large volumes.
As shown in Table 3.1, the concentration of thorium (Th-232) is highest in rauhaugite and
rødberg [15]. The iron-rich part of the carbonatite, rødberg, was mined for iron from 1655 until
1927, and søvite was mined for niobium (Nb) between 1953 and 1965. The carbonate rock has also
been investigated for exploitation of phosphorus (P). Many pits and piles of tailings in the Fen
Complex reflect the previous extensive mining activities. Today, about 350 dwellings are located
within the Fen Central Complex.
Table 3.1: Activity Concentration of Thorium-232 (Th-232) in Rock Samples from the Fen Complex.
4 Bq/kg (Becquerel 1 /kg) Th-232 is Equivalent to 1 ppm Th.
Rock Type
Number of
Samples
Th-232
(Bq/kg)
Mean Range
Rödberg 9 3100 (390 - 5900)
Rauhaugite 9 600 (290 - 930)
Sövite 9 80 (20 - 190)
Fenite 8 130 (20 - 200)
Precambrian
Gneiss
3
66 (68 - 63)
Based on recent helicopter surveys made by the Geological Survey of Norway [16] using a large
NaI (Sodium Iodide) scintillator detector to detect the gamma radiation from the area, the
distribution of thorium in the upper soils and bedrocks of the Fen Complex has been identified
(Figure 3.2). Although thorium in deeper mineral deposits will not be included in the gamma
measurements, the map shown in Figure 3.1 corresponds well with the distribution of rødberg in
the bedrock of Fen. However, uranium is also present in a series of minerals present in the Fen
Complex. Based on the helicopter survey where gamma radiation was determined, gamma
energies from the Th-232 series and from the U-238 series could be differentiated. Thus,
information of the distribution of uranium in the upper soils and bedrocks of the Fen Complex has
also been obtained (Figure 3.3). Thus, traces of thorium-234 (Th-234), being a daughter of U-238
will also be present in the minerals. The distribution of thorium and uranium seems to correlate
well, which indicates that uranium and its daughters will be present in the raw materials and the
waste when mining and extraction of thorium is performed.
1 Radiation Emitted from a Source: Desintegration per Second = Becquerel (Bq)
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