On 1st January 2018 Ionising Radiations Regulations 2017 replaced IRR99.

Under the new regulation employers must apply to the Health and Safety Executive (HSE) for certain work they do with ionising radiation. Importantly, all practices have to register with HSE by February 5th 2018 and any practice which uses an open source will have to obtain additional consent 

Background information is available at the HSE website here 

The Ionising Radiation Regulations 2017 Approved Code of Practice and Guidance is available here