A shielding plan details the level of shielding that is installed to protect workers and members of the public. This can include a dental, veterinary, chiropractic, or other medical premises which use ionising radiation apparatus. The plan should include floor plans, estimated dose calculations and other details that relate to radiation protection.
You must prepare and submit a shielding plan with your registration for any source that’s installed in new or renovated premises. A copy of the existing shielding plan should be submitted for a replacement source that’s installed into existing premises that hasn’t been renovated.
Please submit your shielding plan as early as possible before construction to ensure it meets all the requirements. Radiation shielding must be inspected by HPS or an accredited tester during the construction phase and before being covered by paint, plaster, floor coverings or other fittings.
Please contact us or consult the National Standard for Limiting Occupational Exposure to Ionising Radiation. You may also find the National Council on Radiation Protection and Measurements (NCRP) Report No. 147 or Structural Shielding Design for Medical X-Ray Imaging Facilities useful.
Following a decision made by the ACT Radiation Council, in a move towards national uniformity, please note the following design constraints which should now be used in radiation shielding calculations:
- Controlled areas 2mSv/yr (40µSv/wk)
- Other areas 0.5mSv/yr (10µSv/wk)
A controlled area, in relation to a radiation source, is a limited access area:
- in which the exposure of persons to radiation is under the supervision of an individual in charge of radiation protection. This implies that access, occupancy and working conditions are controlled for radiation protection purposes; OR
- to which access is subject to control and in which employees are required to follow specific procedures aimed at controlling or monitoring exposure to radiation.
If a blanket design constraint is used for an entire practice or department then this should be 0.5mSv/yr (10µSv/wk).
Shielding design height requirements from the finished floor level are:
- no less than 2.1m for general radiography, fluoroscopy, mammography, BMD/DEXA, OPG, intraoral, dental CBCT and nuclear medicine; and
- no less than 2.7m or to the upper slab, whichever is the lower for CT, including SPECT/CT, PET/CT and all other non-dental CBCT unless a lower height has been authorised by the Radiation Council.
However, for high dose areas including CT and interventional radiology, shielding design depends on a number of site-specific factors so shielding designers are asked to refer to authoritative texts which deal with these cases such as [1] and to specify height requirements greater than those indicated above, where applicable.
[1] Sutton, D.G., Martin, C.J., Williams, J.R., Peet, D.J., Radiation Shielding for Diagnostic Radiology, 2nd Edition, British Institute of Radiology, London (2012).
Any penetrations to the shielding, such as for cables, power points, water pipes or light switches, need to be addressed with material equal to or greater than the lead equivalence of the material which was removed.
The additional material needs to extend beyond the edges of the penetration by at least twice the offset distance*. If the location of a stud or nogging makes this impossible the additional material must return along the stud or nogging to meet the original layer of material.
*The offset distance is the distance between the original material and the additional material.
The Radiation Council may request third party verification of installed shielding when considering a source registration application or re-application (renewal).
