Industrial relics with enhanced natural radioactivity

The intense industrial development in many parts of Germany since the middle of the 19th century also entailed uses of a number of raw materials containing enhanced amounts of uranium or thorium (for example bauxite, phosphorite). A variety of residues was produced which were, however, not further used at the time.

Under certain circumstances, the use of chemicals as well as the physicochemical conditions of the treatment process led to the accumulation or depletion of single radionuclides in different types of residues.

Often, they are accompanied by heavy metals or harmful organic materials and therefore, besides the radioactivity conventional contaminants have to be considered, as well.

Examples

Well known examples for industrial relics with enhanced natural radioactivity are the former factories Auer in Oranienburg and de Haën in Hanover:

• The Auer factory used monazite sand to produce incandescent gas mantles and radium paint.
• Using ores containing thorium and uranium minerals, the de Haën factory produced specialty chemicals and incandescent gas mantles as well.

At both sites production residues remained on the former premises, leading to enhanced natural radioactivity which gave rise to remediation measures.

Possibly radiologically relevant residues

In the past it was a common way of disposal to deposit residues on the company's premises in numerous industries. Depending on their consistency residues were deposited either on waste rock piles or in tailing ponds.

For lack of knowledge, possibly associated radiation protection problems had not been taken into account. As a result, radionuclides released into the environmental media, may cause radiation exposure of the population in case of unfavourable site and usage conditions thus requiring subsequent radiation protection measures.

Assessment by the Federal Office for Radiation Protection

An assessment by the Federal Office for Radiation Protection (BfS) revealed that residues from the following industrial sectors may be of importance due to the amount of residues with enhanced natural radioactivity deposited in Germany in the past:

• treatment of raw phosphate to produce phosphoric acid and fertilisers
• primary production of petroleum and natural gas
• processing of bauxite to produce aluminium (Bayer method)
• pig-iron metallurgy (recovery gas cleaning), and
• combustion of coal (flue gas cleaning).

Apart from these residues of which large amounts have arisen there may be a number of radiologically relevant residues with smaller volume but higher contents of natural radionuclides, such as:

• residues from the production of thoriated welding electrodes and of incandescent gas mantles
• residues from catalyst production for the Fischer-Tropsch method, and
• residues from the production of radium paint.

According to first estimations, the total volume of the residues deposited in Germany that could be relevant from the radiation protection point of view does probably not essentially exceed the amount of 100 million cubic metres.

As in the case of mining relics, with the evaluation of which much experience has been gained particularly in the Federal States of Saxony and Thuringia, remediation measures may not become necessary for industrial relics for radiation protection reasons in each individual case. The requirements of conventional soil protection have to be kept, as well.