- Date released
- 9 January 2024
- Request number
- 202312004
- Release of information under
-
Environmental Information Regulations (EIR)
Information requested
- What is the assessed overall frequency of events that would lead to releases requiring the declaration of an offsite incident?
- What is the assessed overall frequency of events that would require the evacuation of people from homes and businesses and how far downwind do the assessments show the potential need for urgent and subsequent evacuation?
- What would be the radionuclide composition and physico-chemical form of the released material? What inhalation categories are assumed (using the categories F, M and S as defined in ICRP Publication 66, but detailing any non-standard parameterisation, e.g. to represent aerosols intermediate between ICRP classes).
- How might the released inventory vary with the circumstances of the event? Is the UPAZ based on an upper bound of a variable potential release? If several different release sequences have been addressed, what were the magnitudes and time-courses of the releases for each release sequence? Specifically, what fraction of the total release is assumed to occur in each time interval following the declaration of the occurrence or anticipated occurrence of a release?
- Is the release modelled as having initial momentum or thermal buoyancy due to explosion/temperature and/or initial volume resulting from the explosive distribution?
- What release height is assumed? If momentum or thermal buoyancy is significant, how is this taken into account, e.g. by computing an effective release height?
- Is the release treated as a point release or is building entrainment taken into account?
- What assumptions are made about particle size distribution and settling velocity? Specifically, is a lognormal distribution of sizes of the released aerosol assumed? If so, what is the Activity Median Aerodynamic Diameter (AMAD) and the geometric standard deviation of the distribution?
- Is the preferential deposition of larger particles during downwind dispersion taken into consideration?
- Is dispersion modelled using a Gaussian Plume model or is a more complex model, such as ADMS, used? How is the model parameterised, e.g. in respect of windspeed, inversion height and roughness length?
- How inhalable are the particles? Would a Covid-style face mask be expected to make a contribution to reducing inhalation dose?
- How is deposition to soil and other surfaces modelled? For example, is a dry deposition velocity used? If so, what deposition velocities are adopted for different types of surface?
- How is resuspension modelled, e.g. using a resuspension factor or a mass loading approach? Is the time-dependence of resuspension taken into account?
- What capability exists to measure contamination in the environment? (Time to first measurement, sample throughput, minimum level of detection etc.) Specifically, how will contamination by alpha emitters be quantified both for hard surfaces and for soils? Are there any useful measurements that can be made in field conditions, or will reliance be entirely on radiochemical procedures undertaken in laboratory conditions?
Information released
We confirm that we do not hold the information you have requested.
This information is held by AWE on their secure network. However, it is important to note that this information is security-classified information and unlikely suitable for release into the public domain.
Exemptions applied
N/A
PIT (Public Interest Test) if applicable
N/A