Nuclear waste disposal.

Mumbai University > Mechanical Engineering > Sem 7 > Power Plant Engineering

Marks : 5M

Year: May 2016

1 Answer

A multi barrier approach is followed in the disposal of radioactive solid wastes. The overall safety against migration of radionuclide is achieved by proper selection of waste form, suitable engineered barriers, backfill materials and the characteristics of the geo-environment of the repository site. Based on the nature and type of the radionuclide present in the solid waste and its concentration the repository could be near surface or in deep geological formations. Operation of various Near Surface Disposal Facilities (NSDF) has led to considerable expertise in this field. Our programme on site selection & host rock characterization is under evaluation for deep geological disposal.

Nuclear Waste Management

• Recently nuclear power has entered many discussions as world energy needs rise and oil reserves diminish.

• Most opponents of nuclear power point to two main arguments: meltdowns and nuclear waste.

• Nuclear waste is any form of byproduct or end product that releases radioactivity.

• How to safely dispose of nuclear waste is pivotal for the continued operation of nuclear power plants, safety of people living around dump sites, and prevention of proliferation of nuclear materials to non-nuclear states.

Nuclear Fuel Cycle

Most nuclear waste comes from the byproducts of the nuclear fuel cycle. The cycle typically is split into three sections: front end, service period, and back end. There can be intermediate stages that include the reprocessing of nuclear waste elements.

Nuclear Fuel Cycle (Cont.)

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• Nuclear waste is segregated into several classifications.

• Low level waste is not dangerous but sometimes requires shielding during handling.

• Intermediate level waste typically is chemical sludge and other products from reactors.

• High level waste consists of fissionable elements from reactor cores and transuranic wastes.

• Transuranic waste is any waste with transuranic alpha emitting radionuclides that have half-lives longer than 20 years.

Low Level Waste LLW

• Low level waste is any waste that could be from a high activity area.

• 90% volume of waste

• It does not necessarily carry any radioactivity.

• Split into four catagories: A, B, C, and GTCC.

Intermediate Level Waste ILW

• Intermediate level waste requires shielding when being handled.

• 7% volume of waste

• Dependent on the amount of activity it can be buried in shallow repositories.

• Not recognized in the United States.

High Level Waste HLW

• High level waste has a large amount of radioactive activity and is thermally hot.

• 3% volume of waste

• 95% of radioactivity

• Current levels of HLW are increasing about 12,000 metric tons per year.

• Most HLW consists of Pu-238, 239, 240, 241, 242, Np-237, U-236

Transuranic Waste TRUW

• Transuranic waste consists of all waste that has radionuclides above uranium.

• TRUWs typically have longer half-lives than other forms of waste.

• Typically a byproduct of weapons manufacturing.

• Only recognized in the United States.

Types of waste:

•Very low level radioactive waste

•Low level radioactive waste

•High level radioactive waste

•Uranium mill waste

•Transuranic waste from manufacturing of nuclear weapons

•Naturally occurring radioactive material.

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