Level 3 PSA - EDF Hinkley Point

HPC-NNBOSL-U0-000-RES-000028 Version 1.0
Level 3 PSA
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CF
= the dose risk conversion factor which is 5x10-2 Sv-1 for all dose bands other
than dose band 5 where a probability of death is assumed to be 1; i.e. for
DB5 (WDB x CF) = 1.
The list of Worker Release Categories together with the Dose Band allocation is shown
in Table 23.
Not all WRCs identified in Table 23 are used in the risk analysis because although they
represent credible accident scenarios, they currently do not have any accident
sequences associated with them.
5.5 Worker Cohorts
To gain a better understanding of the distribution of risk, three worker profiles or ‘cohorts’
have been defined as follows:
A generic worker - for the overall comparison against SDO-4, a generic worker profile
has been used. This profile assumes that there is a hypothetical individual worker
who could be present in any building on site when an accident occurs. The risk to
this worker from accidents in each building is therefore calculated taking into account
the probability (i.e. occupancy factor) that the worker would be in this building when
the accident takes place.
A Fuel Building worker – this worker profile represents a worker who spends all of
their time when on site carrying out fuel building operations [AS-012]. This group
therefore has a maximum risk of exposure to accidents in the fuel building, in
particular fuel handling accidents, and a negligible exposure to accidents occurring in
other buildings. This cohort represents the bounding case for all workers involved in
controlled processes such as lifting operations, where the occupancy factor is taken
as unity, whilst still representing a realistic worker group.
A Main Control Room (MCR) worker – this worker profile represents a worker who
has to remain present in the MCR throughout the duration of an accident anywhere
on site [AS-013]. This worker group therefore has the maximum risk of exposure to
the consequences in the MCR of all accidents which result in an external (on-site)
release, including severe accidents.
In addition, although not technically a separate worker cohort, the risk arising from the
performance of LOSAs has been evaluated separately. This risk represents the risk to
any individual worker if any accident requiring a LOSA occurs whilst they are on site and
they are required to perform the LOSA. The results of the worker Risk Analysis for all
worker cohorts, with and without the contribution from LOSAs, are presented in Sections
5.6.3 and 5.6.4.
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