This Safety Guide, a revision of IAEA Safety Standards Series No. SSG-5, was initiated to provide recommendations on site evaluation, design, construction, commissioning, operation and preparation for decommissioning of conversion facilities and uranium enrichment facilities to meet the applicable requirements established in IAEA Safety Standards No. SSR-4, Safety of Nuclear Fuel Cycle Facilities, which incorporates the lessons learned from the accident at the Fukushima Daiichi nuclear power plant. The revised Safety Guide also reflects current operational practices at conversion facilities and uranium enrichment facilities. The recommendations in this publication are aimed primarily at operating organizations of conversion facilities and uranium enrichment facilities, regulatory bodies and designers.