PHWR meaning

PHWR (Pressurised heavy water Reactor) describes, in nuclear regulation and energy contracting, a reactor type that uses heavy water (deuterium oxide) under pressure as the primary coolant and moderator, allowing the use of natural uranium fuel and on‑line refuelling via pressure tubes. The most common example is the Canadian candu reactor. The term is a descriptive technical expression rather than a defined term in UK or Irish legislation or case law. Legal practitioners encounter it in nuclear site licence and safety case materials (ONR, UK), environmental impact assessment and permitting documents, decommissioning and radioactive waste strategies, fuel supply and services contracts, and export control and nuclear safeguards compliance. The UK civil fleet comprises AGR and PWR units rather than PHWRs, but the term is relevant to cross‑border projects, vendor and component procurement, financing due diligence, and comparative safety assessments. Usage and meaning are broadly consistent across England and Wales, Scotland, Northern Ireland and Ireland. In Ireland (which has no nuclear power stations), PHWR references typically arise in transboundary consultation, emergency planning and the transport of radioactive material.