MEDICAL WASTE MANAGEMENT

Zaidi M. K., Idaho State University, Pocatello, USA

The safe custody of radioactive waste (RW) is of great importance due to the fact that it is in high demand by the terrorists as they are keenly interested to get it and experiment a dirty bomb. The RW can be classified into five different categories: Low-level waste (LLW), High-level waste, Transuranic wastes, Mine and mill tailing, and Spent fuel. Here we will discuss the LLRW which satisfies 3 conditions: it must not be high-level waste, contains less than 10 nCi/g of transuranic elements, and must not be mine or mill tailings. LLRW can be solid, liquid, or gaseous. Commercial suppliers of radiopharmaceuticals generate RW by using a nuclear reactor or a particle accelerator to produce the radionuclide. LLRW covers all of the waste products of a typical nuclear medicine clinical or research laboratory. LLRW is also obtained from a variety of radioactive material (RM) used in diagnostic and therapeutic procedures, medical laboratories, and research in medical, commercial, and industrial processes. LLRW includes routine waste products, such as paper, filters, piping, tools, rags, and glass contaminated with small amounts of radioactivity. The generation of substantial amounts of LLRW started after World War II when RM were introduced into the civilian sector for research and development. In the beginning, all RW in the USA was handled by the federally owned disposal sites. In 1960, some commercial sites were opened for shallow land burial disposal of LLRW. The volume of LLRW in the USA continued to increase tremendously. RW was also brought in from other parts of the world. A law was passed in the USA in 1980 called the Low-Level Radioactive Waste Policy Act. This Act states that each state is responsible for disposal of LLRW generated within its boundaries, except for waste produced from the activities of the federal government. In 1988, the Medical Waste Tracking and Management Act, 40 CFR 259, was introduced and the U.S. Nuclear Regulatory Commission (NRC) became involved in the management of RW generated at places other than hospitals and the IAEA on international level. U.S. Environment Protection Agency (EPA) established a waste tracking system. It set out rules for its segregation, packing, storage, labeling, and marking requirements. RW defined by EPA is any solid waste, which is generated in the diagnosis, treatment, immunization of human beings or animals, in medical research, or in the production or testing of biological products. Regulated waste may be destroyed after being treated to reduce or to eliminate its potential for causing disease. The storage of RW must conform to three conditions: 1) stored in a manner, and at a location, that maintains the integrity of the packing and affords protection from water, rain, and wind, 2) maintain in a nonputrescent state, and 3) meet specific labeling and marking requirements. The generator is responsible for managing its waste from «Cradle to Grave», the generator can store the LLRW at the Satellite Accumulation Area (SAA). The NRC regulation dictates that the RM must be placed in a secured area. In the isotope preparation area, the access must be controlled and any unnecessary exposure be avoided. Shields used in a hot lab generally have a thickness of one or two lead bricks. The adequacy of shielding should be determined by the measurements performed by the health physics staff. The disposal of RW constitutes the major waste disposal concern for persons working in nuclear medicine.

Three modes of disposal are common in nuclear medicine waste management:
1. DILUTE AND DISPENSE: The waste containing amounts of radionuclides below regulatory concerns may be disposed without regard to radioactivity concern in air or water. The concentration that may be discharged into air or a sanitary sewer are listed in the maximum permissible concentration (MPC) tables, CFR-20, Chapter 10. Patient excreta is exempted from regulation as LLRW.
2. STORE AND DECAY: Many agencies require that it must decay at least 10 half-lives. The waste contaminated with 131I must be kept for 80 days and 125I for 600 days. It is feasible to store isotopes with half-lives of 60–90 days. The storage area should be secure and be in an area with relatively little traffic. The LLRW should be stored in steel drums, made of 15 H or 17 H steel. The steel wall of the drum will absorb low energy betas. However, it may be a source of bremsstrahlung from high energy betas (32P). Drums should be checked for surface contamination and exposure levels before being removed. Federal transport limits the exposure rate on the surface of the drum to be 200 mR/h. If exceeded, the drum has to be repacked until the radiation exposure is below.
3. CONCENTRATE AND BURN: Incineration is recommended to destroy the potentially infectious nature of the waste. After incineration, the ash is collected, surveyed, and disposed of at a landfill. The incinerated remains should be surveyed with a 5 diameter NaI(Tl) detector by examining a few samples of 750–1,000 g to check for microspheres labeled with gamma-emitting radionuclides. LLRW can be buried in shallow land burial sites at remote locations with controlled access. The ambient radiation at a burial site should essentially be at the background levels. A person, if living on a RW burial site after 100 years, should not receive more than 500 mrem/yr.
Waste Management (WM) is an applied science and developments are used at the point of generation, at the centralized treatment facility, and at the disposal site. Some of the important factors that affect are sources of waste, classification of waste, waste treatment and conditioning, minimization of waste, laws and regulations governing waste and present and future issues. WM has become a career with a promising future as the cost of waste disposal increases tremendously. The waste management has become a career with a promising future as the cost of LLRW disposal increases. Scientists and others involved have started working on waste minimization. RW disposal should be approached in an analytical manner. Latest developments to handle RW professionally will be presented.

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Zaidi Mohammed K., Affiliate Faculty, College of Engineering, Idaho State Universitа`, 121, North 18th Avenue, Pocatello, ID 83201-3345, USA. Tel. (208) 234-11-30, fax (208) 282-45-38. E-mail

Последние изменения внесены 11.08.08