Page 124 - Beyond Decommissioning

Relevant factors for redevelopment 105

International guidance on the long-term preservation of decommissioning-related
information (of which reuse is a major component) is given in International
Atomic Energy Agency (2008).

5.5 Radiological and non-radiological criteria
for the end state

Recent decommissioning projects have drawn attention to site end states (SESs),
clearance levels, and related definitions. Quite often erratic use of the terms describing
the post-decommissioning state of a facility/site has led to confusion and misunder-
standings (including litigation between parties). It is only recently that the interna-
tional community (with the IAEA having the leading role) has specifically
addressed this issue for general harmonization. Decommissioning companies and reg-
ulators have loosely used the terms of “Greenfield” and “Brownfield” for the planned
end state of a decommissioned site, without evaluating or specifying in detail the phys-
ical conditions targeted.
The term greenfield was coined when environmental considerations for
decommissioning were prevalent, and the aim was to restore a site into its pristine,
undisturbed condition. It was felt at the time that this was the only environmentally
acceptable end state of decommissioning. In actual facts, defining a “pristine” condi-
tion is uncertain and ambiguous. Moreover, the construction of the nuclear facility had
often improved the original site conditions, for example, by maintaining healthy
waterways and riparian land, improving the state of roads, and revegetating the site.
Furthermore, returning a site to its preconstruction state would not take account of the
socioeconomic factors of the local communities as these had changed during nuclear
operation. Finally, the financial and social costs of achieving greenfield conditions
can be extremely expensive.
The IAEA term for greenfield is “unrestricted (or unconditional) release” (see
Glossary). However, the definition refers only to the radiological characterization
of a site after decommissioning. Two main subcategories can be identified:
unrestricted release with or without structures remaining.
In case of full demolition, the extent of demolition may be nominally to 1m below
grade if all structures are bound to meet unrestricted release criteria, or to complete
removal of all subgrade structures of radioactive contamination extended to founda-
tions. In United States, examples of this strategy include NPPs at Big Rock Point
(Fig. 5.1), Maine Yankee, and Shippingport.
Unrestricted release with structures remaining involves the removal of radioactive
substances to clearance criteria without the demolition of facilities and structures.
Generally, the site environs are not restored, for example, restoring vegetation, etc.
In the United States, examples of this strategy include NPPs at Trojan (reactor build-
ing and auxiliary structures maintained intact), Elk River (the uncontaminated power
plant is reused as part of the existing fossil-fired power plant onsite), and San Onofre
Unit 1 reactor building and auxiliary structures maintained basically intact except as
needed to remove large equipment.