The Design of Diagnostic Medical Facilities where ... - ResearchGate

Bench surfaces in areas where unsealed radionuclides or body fluids are handled should be coved against the
walls and lipped at the edges to prevent radioactive substances becoming lodged in any cracks between the
wall and bench or spilling onto the floor. It should be noted that the use of coving between walls and bench
tops could mean that hatches at bench level may not be flush with the bench thus necessitating items, which
are sometimes heavy or fragile, to be lifted through the hatch. Caution should be applied to the selection of
laminate finishes which although satisfactory in many respects can be susceptible to damage and may not
provide an optimal long-term solution. Durable materials should be used. Floors and benches must be strong
enough to support the weight of shielding materials.
6.3 Shielding in radiology department
6.3.1 Walls
For general X‐ray rooms, the lead equivalence required for a room of dimensions 6 m x 4 m x 3 m is typically
of the order of 2 mm at 150 kV (WHO, 1975) although a lead equivalence of 3-4 mm or more may be required
for angiography suites and multi-slice CT installations (NHS, 2001). This level of shielding is based on the assumption
that the radiation at the boundaries will be mainly scattered radiation. Additional shielding for the primary
beam is needed in situations where it is frequently directed towards a wall. For example, in the case of chest
radiography, a primary beam absorber (typically an additional 2 mm lead equivalent) is required behind the
chest stand/vertical Bucky (Photo 6.1). In practice the level of shielding required must be determined by the
RPA before construction. The walls of an imaging facility may be constructed from high density solid concrete,
concrete blocks, bricks or other materials provided due account is taken of the issues raised in Section 6.1.
As an alternative to using concrete, wall shielding may be provided using panels of lead plasterboard or lead
plywood. The internal walls of many modern buildings are composed of plasterboard attached to both sides
of metal or wooden framing. Lead plywood or plasterboard may be used on one side of the internal framing
to achieve the required shielding. Ideally it should be used on the side which will require the least perforation
(Appendix E). Lead plasterboard is less robust than lead plywood during handling; however it leaves a smooth
finish for decorating.
The shielding must not be compromised at the joints between panels and where nails, screws and other fixings
are used. Lead lined battens should be used at the joints. These are typically 50 mm wide and provide a secure
base for fixing the panels (BIR, 2000). Their lead thickness should be the same as that in the panels and they
should have a sufficient overlap with each panel to provide protection at the joint and for the nails and screws
(Appendix E). Steel nails and screws however generally attenuate radiation equally or more effectively than the
lead displaced by the nails, therefore steel nails or screws used to secure lead barriers may not need to be covered
with lead discs or supplementary lead. However, where the edges of two lead sheets meet, continuity must be
ensured at the joints with lead battens (NCRP, 2004, WHO, 1974).
Additional shielded battens may be provided in areas where items have to be fixed to the wall. Where service
perforations are required in walls, i.e. electrical socket outlets, light switches, service outlets, ventilation
grilles, installation of sinks, cabinets, light boxes, etc., additional lead shielding is required in place of the
shielding that is displaced. All joints, perforations, ducts, service outlets, etc. must be shielded as outlined in
Section 6.5.
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