Solid Radioactive Waste Strategy Report.pdf - UK EPR

EPR UK
N° NESH-G/2008/en/0123
REV. A PAGE 165 / 257
10.3.1 Identification of Safety Features
Prior to selection of a safety system the first step in the selection process will be to determine
whether a hazard can be eliminated. If the hazard cannot be eliminated then further assessment
shall determine if the hazard can be reduced, for example, by reduction of the hazardous
inventory used in a process. If a hazard cannot be reduced then an isolation measure shall be
incorporated where practicable to isolate the operator from the hazard for example by the use of
remote operations. If ‘eliminate’, ‘reduce’ or ‘isolate’ are judged not to be practicable only then
should a control measure or engineered safety measure be deployed.
During the design of the waste and spent fuel management facilities we shall apply the following
hierarchy of controls is applicable:
a) Accident Prevention
a. Passive safety measures that do not rely on control systems, active safety
systems or human intervention;
b. Automatically initiated active engineered safety measures;
c. Active engineered safety measures that need to be manually brought into service
in response to the fault;
d. Procedural safety measures that act to prevent a fault from progressing.
b) Consequence Reduction
a. Safety measures that act to mitigate the consequence of a fault.
From the list above it can be seen that the design will incorporate passive safety systems in
preference to active systems. Reliance will be placed on procedural controls only if provision of
an engineered system is not practicable. Therefore the emphasis will be placed on hazard
avoidance and then control rather than mitigation of an event once it has occurred.
10.3.2 Generic Hazards from Operations of the Waste and Spent Fuel Management
Buildings
In the paragraphs that follow, the generic hazards that relate to the waste and spent fuel
management buildings are described, together with a description of the safety features that may
be used to control or mitigate the hazard. Details of safety features peculiar to a particular
waste management facility or spent fuel facility are outlined later with the description of that
facility.
10.3.2.1 Direct radiation
Radioactive waste (in particular ILW) and spent fuel emit penetrating gamma rays and neutrons.
Employees and members of the public must be protected from exposure.
Doses from direct radiation can be minimised by reducing exposure time, increasing distance
from the radiation source and provision of shielding. In reducing exposure time and increasing
distance from the source there is a preference for provision of engineered controls and design
features where reasonably practicable. Remote operations may be implemented where
appropriate to remove the operators from the radiation source. Both fixed and mobile shielding
may be provided. In practice dose reduction will be achieved by a combination of the above
measures.