Page 345 - Beyond Decommissioning

Case studies of nuclear redevelopment 321

access and housing in this former nuclear site are quite possible in the near future.
Details on the remediation works and redevelopment objectives are given in
Safegrounds (n.d.).
To determine the best practicable environmental option (BPEO) for site contam-
ination, an environmental assessment process was conducted in collaboration with
the National Radiological Protection Board. A set of alternatives were defined prior
to consultation with regulators, local authorities, and other stakeholders, including:

l no action;
l capping the wastes; or
l full removal.
The winning BPEO was the full removal of all waste from the site. The objectives of
the remediation were:
l Physical—To cleanup the land to a condition suitable for unrestricted public use, for example,
to make the site safe for children to live and play on. To this end, the risk assessment methods
were used to establish risk-based clean-up levels (RBCLs) for chemicals and radionuclides.
6
These were derived from an annual risk target of 1 10 .
Psychological—The SSA was a sensitive site with some local controversy. It was considered
l
necessary not only to make the site suitable for public access but also to exhibit timeliness
and transparency. The second objective was, therefore, the removal of doubt/blight.
l Redevelopment—The United Kingdom has a policy for the development to take place on pre-
viously used land, rather than to use “Greenfield” land. The demand for new housing in the
Harwell area is high and so the reuse of the land for a mix of housing and recreation was
established with the local government planners.
Following a review of available historical information (and interviews with former
staff to compensate for missing documentation), the characterization of the site
was undertaken, beginning with walkovers and trial pit investigations. Characteriza-
tion went on with monitoring for radioactive and chemical contamination in field,
gamma and gross αβ analysis, high-resolution gamma spectroscopy of bulk samples,
groundwater monitoring, etc. The general land areas of the SSA were of low hazard.
2
Typical contamination was <10Bq/g of Cs 137 in patches up to a few m . Chemical and
radioactive contamination was mostly at the surface but could also occur randomly in
underlying ground. The approach was to dig over every part of the SSA down to base
geology in layers 300mm deep. Before digging in an area, the next layer was surveyed
and sampled. Physical remediation onsite included excavation, and removal and seg-
regation of contaminated materials above predefined RBCLs. The extent of munitions
finds was much larger than expected and gave rise to extra cost and delay. Some 1200
bombs, 13,000 small arms munitions, 30 landmines, etc. were discovered. Three
munitions burial pits were found and munitions were otherwise scattered across the
SSA. Several large unexploded aerial bombs were unearthed (500 and 750kg). The
first of these led to the evacuation of the school and nearby residences. All munitions
were removed from the site for destruction.
All of the pits were dug inside a ventilated enclosure with an exhaust ventilation air
being high-efficiency particulate air (HEPA)-filtered, monitored, and discharged via
stacks. Airborne dust concentration, vapor, and odor controls were utilized as impact