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Tuesday, 29 May 1984
Page: 2097

(Question No. 735)


Senator Chaney asked the Minister for Resources and Energy, upon notice, on 27 March 1984:

(1) (a) What tonnage of black coal is required to be mined in order to fuel a 1000 megawatt coal-fired power station for a period of one year; and (b) what tonnage of uranium ore is required to be mined in order to fuel an equivalent capacity uranium powered power station for the same period.

(2) What quantity of radon would be released in: (a) the mining and processing of the quantity of coal referred to in question 1 (a) above; and (b) the mining and processing of the quantity of uranium referred to in question 1 (b) above.

(3) What quantity of radioactive matter would be released to the environment in : (a) the normal operation of a 1000 megawatt coal-fired power station over the period of one year; (b) the normal operation of a 1000 megawatt nuclear-fired power station over the same period.

(4) What quantity of other trace elements, such as cobalt, thorium, arsenic, lead, chlorine, mercury and other toxic hazards, would be released into the environment in the normal operation of a 1000 megawatt coal-fired power station using Australian black coal over the period of one year.

(5) What procedures are there to minimise or otherwise treat these radioactive and other wastes released from coal-fired power stations, either directly into the atmosphere or in cinder and fly ash, and how do these procedures vary from the treatment of radioactive wastes from nuclear power stations.


Senator Walsh —The answer to the honourable senator's question is as follows:

(1) Assuming that the 1000 megawatt power station operates at full power for 70 per cent of the time:

(a) A coal-fired station using a typical New South Wales black coal consumes approximately 2.5 million tonnes in a year, as mined.

(b) A typical light water reactor (LWR) station requires the mining of about 90 ,000 tonnes of uranium ore. This assumes an ore assay of 0.2 per cent uranium- that is, typical of Australian uranium ore bodies and that the uranium fuel is enriched to 3 per cent uranium-235.

(2)-

(a) Coal contains trace quantities of uranium and thorium and their radioactive daughter products including radium and radon. No data are available for the release of radon during mining and processing of coal. However the radium content of New South Wales coals range from 15-50 milli becquerels per gram- about 1/1000 of the amount in uranium ore-and levels of radon-a decay product of radium-would be extremely low.

(b) Typical radon release data for 90,000 tonnes of ore are as follows:

Mine-14,000GBq*

Mill-620 GBq

Tailings-7,000 GBq for each year thereafter.

* Footnote: The Becquerel (Bq) is the unit of measurement of radioactivity and is equal to 1 disintegration per second. 1 GBq = 1000 million Becquerels = 0.027 Curies (former unit of measurement).

The actual figures depend markedly on the design of the mine, the milling characteristics of the ore and, in particular, the method of tailings disposal practiced. For comparison, the average annual radon emission from land areas in Australia is approximately 1,200 GBq per square kilometre.

(3)-

(a) Based on New South Wales coals, it is estimated that a 1000 MWe power station consuming 2.5 million tonnes of coal in one year would discharge approximately 105 GBq of radon and other radionuclides to the atmosphere. In addition a further 550 GBq of radioactivity-principally lead-210, radium-226, uranium-238, thorium-228 and radium-228-would be retained in the solid residues.

(b) Radioactivity escaping from fuel elements to the coolant during reactor operations is largely removed in the coolant clean-up plant, but some radioactive gases-predominantly isotopes of the noble gases argon, xenon and krypton-are discharged to the atmosphere. For a 1000 MWe light water reactor, the average figure for the annual release of these gases ranges from 290,000 GBq for a pressurised water reactor, the most common reactor type, to 3 million GBq for a boiling water reactor.

(4) The trace element content of 2.5 million tonnes of a typical Australian black coal is

tonnes

Cobalt 5 2 micrograms per gram

Thorium 15 6 micrograms per gram

Arsenic 1.75 0.7 micrograms per gram

Lead 27.5 11 micrograms per gram

Mercury 0.125 0.05 micrograms per gram

Chlorine 1300 520 micrograms per gram

Most of the trace elements are retained in the solid wastes, that is, fly and furnace ash, produced in the power station. Commonwealth Scientific and Industrial Research Organisation has measured the total amounts of some trace elements being deposited in the environs of a power station but has not yet been able to determine how much of this is from power station emissions and how much from other sources, such as wind blown soil.

(5) The main procedures used in coal fired power stations to minimise discharges to the atmosphere involves removal of fly ash from flue gases. The radioactive and trace element content of solid wastes produced in power stations using Australian black coal is within the range of naturally occurring soils, as might be expected from their similar elemental composition, and no special precautions need to be taken on this account. Fly ash and furnace ash may be used as a construction material or as landfill.

Gaseous and liquid wastes arising from the operation of nuclear power plants are subject to extensive control systems to reduce the levels of radioactivity prior to discharge to the environment. Contaminated gases are filtered and sorted in pressurised tanks to allow short-lived radionuclides to decay, and radioactive noble gases are removed by absorption on cooled charcoal although a proportion is released to the atmosphere-see 3 (b) above; gases are dispersed through tall stacks to ensure radiation doses to individuals are well within the limits recommended by the International Commission on Radiological Protection. It should also be noted that the noble gases are chemically inert and biologically inactive and thus do not concentrate in the food chain or in the body. Liquid wastes are filtered and evaporated or their radioactive content adsorbed onto ion-exchange resins.

Solid wastes from these processes include filter sludges, evaporation concentrates and contaminated resins, and are categorised as either low or intermediate level wastes. These wastes are generally incorporated into inert material such as cement and bitumen prior to long term storage or disposal in special purpose waste repositories. Some of these wastes have also been disposed of at sea in the past but sea dumping operations are not currently being undertaken pending completion of reviews of scientific data on their environmental effects.