Medical and industrial sources

Types and volumes of waste from applications of radionuclides in research, medicine and industry vary extensively in radiochemical, chemical and physical content. Table 1.4 shows some waste types from non-NFC institutions.

Research establishments are often involved in monitoring the metabolic or environmental pathways associated with materials as diverse as drugs, pesticides, fertilisers and minerals. The radionuclides most commonly employed in studying the toxicology of many chemical compounds and their associated metabolic pathways are 14C and 3H, as they can be incor­porated into complex molecules with considerable uniformity. 125I has proved valuable in protein labelling. A spectrum of other radionuclides is available for research. Most of the radioactive waste generated by nuclear research centres contains mainly short-lived radionuclides although long — lived radionuclides such as MC, fissile radionuclides and transuranic ele­ments may also be present.

The main applications of radionuclides in medicine are in radio-immu­noassays, radio-pharmaceuticals, diagnostic procedures and radiotherapy. The radionuclides used in hospitals for medical diagnostic procedures and treatments are very short-lived, and the waste generated is usually stored for decay before further treatment as non-radioactive waste. Positron emis­sion tomography (PET), for example, incorporates cyclotron-generated 11C (20 minute half-life) or 18F (110 minute half-life) in a molecule such as sugar which is intravenously administered to the patient and is detected during its circulation around the body. Some radionuclides used in medical applica­tions, however, have longer half-lives including i7Co (271.7 days) used in clinical measurements and iH (12.3 years) and MC (5,730 years) used in radio-labelling (Ojovan and Lee, 2005). Medical applications of radio­nuclides such as for bone densitometry, manual brachytherapy and whole blood irradiation not only may use small quantities of unsealed sources and liquid solutions, but also of highly radioactive sealed radioactive sources (SRS) housed in shielded assemblies. Spent SRS are extremely hazardous as they may contain large quantities of radionuclides. Programmes to

Table 1.4 Waste types from radionuclide applications

Solid

Aqueous

Organic liquids

Highly active

Metallic scrap,

Effluents from

Pump oils,

Sealed

brickwork, sorbents

laboratories, hot

scintillation

radioactive

including ion-

cells, fuel storage

liquids,

sources,

exchange resins,

pool, sump,

extraction

radium

glassware, filters,

decontamination;

solvents such

needles,

cardboard, plastics,

rinsing waters,

as tributyl

reactor-

paper, swabs,

mining-milling

phosphate

irradiated

tissues, protective

raffinates.

(TBP), kerosene

materials.

clothes, gloves.

and amine.

collect, consolidate, store and dispose of SRS are being developed (Ojovan et al, 2004; IAEA, 2005, 2008a).

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