Critical Examinations
A critical examination of a system generating radiation is a series of tests to demonstrate that the safety features are functioning correctly and that the external dose rates comply with legal requirements .
The requirement for critical examinations on installed articles was first introduced under Section 6 of the Health and Safety at Work , etc . Act 1974 ( HSWA ), which imposes general duties on manufacturers etc . regarding the safety of articles and substances for use at work . The requirement first appeared in Section 32 ( 2 ) of the Ionising Radiations Regulations 1985 , and remains under the Ionising Radiations Regulations 2017 ( IRR17 ). Additional guidance on compliance is given in paragraphs 607-616 of the HSE Approved Code of Practice ( ACoP ), L121 , 2018 .
The Radiation Protection Adviser ( RPA ) involved in the critical examination may either be the RPA appointed by the erector or installer , or the user ' s own RPA . However , the erector or installer and the user should agree before the installation commences which RPA will be involved with the critical examination . The critical examination required for most installed articles will require the involvement of an appointed RPA who is a specialist in radiation protection matters specific to the type of equipment concerned .
The purpose of the critical examination is to ensure , in general , that the installation as a whole satisfies the performance standards for restricting exposure to ionising radiation which were specified by the designer , and in particular that :
• any safety features and warning devices provided , such as those listed in the ACoP which support the regulations , operate correctly
• sufficient protection , for example by shielding , has been provided for persons likely to be exposed to ionising radiations when the article is in use , as specified by the designer .
The critical examination may form part of the acceptance or commissioning test for the installed system . However , it need not include consideration of the intrinsic safety of the equipment as designed and manufactured , since this is the legal responsibility of the supplier under Section 6 of the HSWA , as modified by IRR17 regulation 32 ( 1 ).
The examination should generally include the following :
• Positive verification that all the safety features and warning devices operate correctly
• Consideration of whether safety features and warning devices are located in appropriate positions given the intended use of the article ( e . g . can the output from a radiation generator be easily terminated without undue exposure of the operator , and can warning devices be seen / heard at all relevant positions )
• Measurement and evaluation of all accessible dose rates , or other relevant parameters , and comparison with the criteria or performance standards specified by the designer of the installation
• A written record of the outcome of the critical examination , agreed by the RPA
Some manufacturers have a pre-printed check list that they use for their installations and regular maintenance of equipment .
12 Radiation Protection Today www . srp-rpt . uk