Appendix CRF - Part 3 - Northamptonshire County Council

8.7 Pre Closure and Aftercare Period – not certain to occur
Exposure from Leachate - Spillage
8.7.1 The dose criteria are the legal limit to workers of 20 mSv/yr, the site criterion of 1
mSv/yr for workers, the dose guidance level of 0.02 mSv/yr for the public and the
dose constraint for the public of 0.3 mSv/yr.
8.7.2 Notwithstanding any radioactive components, landfill leachate poses a hazard to
the environment if spilt and any road accident involving loss of an entire load
would be subject to mitigation measures. Leachate that did enter water
resources would also become diluted. For this assessment, it is conservatively
assumed that an entire tanker load of leachate (30 m 3 of leachate) reaches a
small reservoir (2 x 10 6 m 3 ) that is used for drinking water, irrigation and fishing.
8.7.3 The scenario is addressed in Annex B, table 5.5.
8.7.4 The worst case is if the leachate comprises only Ra-226. The public dose
constraint of 0.3 mSv can be used because this event is low probability and
clean-up actions would in reality be taken to largely mitigate the event altogether.
The resulting radiological capacity for the crops exposure case is then 71E6 MBq
or 356,000 tonnes at 200 Bq/g. Given the mitigation measures noted above this
scenario does not constrain radiological capacity.
8.8 Pre Closure and Aftercare Period – not certain to occur
Exposure from Aerosols
8.8.1 The dose criteria are the legal limit to workers of 20 mSv/yr, the site criterion of 1
mSv/yr for workers, the dose guidance level of 0.02 mSv/yr for the public and the
dose constraint for the public of 0.3 mSv/yr.
8.8.2 There is potential, during leachate management or spillage, for the production of
aerosols which could lead to doses via the inhalation pathway.
8.8.3 The assessment is presented in Annex B, table 5.6. The results are presented in
terms of specific dose (μSv y -1 per MBq per hour). The worst case result is if the
leachate aerosol comprises only Ac-227, for public exposure. Assuming 1600
hours exposure per year and a dose guidance level of 0.02 mSv/yr, the resulting
leachate discharge limit would be 7002 MBq/yr. This case results in levels which
are orders of magnitude higher than the case considered in section 8.6 above
and hence this scenario is not a constraint on either radiological capacity or
leachate discharge concentration.
Application for disposal of LLW including HV-VLLW under RSA 1993,
for the East Northants Resource Management Facility:
Supporting Information
July 2009
71
WS010001/ENRMF/CONSAPPCRF 390