14.3.1 Overview

During nuclear power production radioactive substances are generated as fission products, activation products and transuranic elements (which are also strictly speaking activation products). Most of the radioactivity, 99%, will be found in the spent fuel and in the structural components in the reactor core. The remaining 1% will be found in the process and technologi­cal waste, which is normally low-level waste.

The waste from nuclear power production can thus be classified as follows:

• Spent fuel elements, consisting of the fuel material (uranium oxide, plutonium oxide, fission products and transuranic elements), the fuel cladding and the structural components in the fuel element. As has been noted above, the spent fuel can also be considered a resource, as it con­tains components that can be further used as nuclear fuel.

• Core components, i. e. components that hold the core together and that direct the flow of water (or gas) through the core. Examples are the core grid and core barrel. Also control rods are included among the core components.

• Process waste, i. e. waste from systems used during reactor operation to clean the process water or gas or to limit the releases of radioactive substances during operation.

• Technological and maintenance waste, consisting of secondary waste generated during maintenance work and components from the reactor systems that have been replaced due to failure or wear or to renewal of the particular system.

• Decommissioning waste, with similar content to the technological and maintenance waste. It also includes the reactor pressure vessel and its internal components, which are similar to the core components.

Annually about 20-25 tonnes of spent nuclear fuel,[83] counted as uranium or uranium and plutonium (heavy metal (HM)), or 10-15 m3, is removed

from a 1000 MWe light water reactor, and about 100-200 m3 (after condi­tioning) of LLW is generated. The volume of ILW, mainly core components, varies depending on actions undertaken and is on average at least an order of magnitude less than the LLW.

During decommissioning a few thousand cubic metres of radioactive waste is generated. Most of this waste is VLLW and LLW, while some of the internal components are ILW.