The decommissioning schedule is similar to that of existing PWR and BWR units and may include the following stages

• fuel assembly unloading,

• dismantling and breaking up of in-vessel highly radioactive structures,

• dismantling and breaking up of the RPV,

• dismantling of low radioactive and non radioactive equipment,

• radioactive equipment and spent fuel removal from plant site

Alternatively, the relatively large reactor vessel can be used for storage of all active components for about 50 years until their activity has reduced to a low level for easy handling for ultimate disposal This option is especially attractive if the vessel is below ground allowing removal of many structures above ground

4 CONCLUSIONS

In the technical committee meetings, a diversity of viewpoints and opinions was offered on the design and development of integral reactor concepts Consensus exists on many aspects of integral reactors The following are the conclusions

6 1 The presentations confirm the engineering validity and sound advancement of the integral design approach for advanced light water reactors (ALWR) Presentations have also covered new issues, areas and designs not covered previously

4 2 Integral reactor design activity is strong in many Member States Some designs have been built, some are in the detailed-engineering stage and most are in the conceptual design stage

6 3 For further development, a clear definition of user requirements is necessary, which will clarify design criteria and specifications

7 4 There are many similar designs for which realization in construction is unlikely Concentration of effort on fewer projects for the detailed design stage would be beneficial and cost effective

7 5 Integral designs cover from low to medium power range Low power reactors generally use natural circulation These designs may be more applicable than loop type designs for district heating and in remote locations

7 6 International cooperation is strongly recommended in carrying out further development of this type of reactors The efforts should include computer code validation and simulation of accidents in integral reactors, noting the specific problems of modeling natural circulation and the effect of non-condensables in accident condition

7 7 Other areas that should receive special attention include

a) Economic comparison of different integral reactor systems and identification of benefits covering the whole of the life cycle.

b) Ways to maximize the safety of integral reactors, especially to enable their siting near population centers

c) Requirements for plants in remote areas where more stringent restrictions on operation may be needed.

d) Decommissioning of integral reactors

e) Design of compact steam generators

f) Survey of market potential for integral reactors.