ONR has established its Safety Assessment Principles (SAPs) which apply to the assessment by ONR specialist inspectors of safety cases for nuclear facilities that may be operated by potential licensees, existing licensees, or other duty-holders. The Security Assessment Principles (SyAPs) apply to the assessment of security plans which include site security plans and transport security statements. The principles presented in the SAPs and SyAPs are supported by a suite of guides to further assist ONR's inspectors in their technical assessment work in support of making regulatory judgements and decisions.
This page contains Technical Assessment Guides (TAGs). These primarily provide guidance to ONR inspectors on the interpretation and application of the SAPs and SyAPs. However, some also contain guidance relevant to principles underlining the enforcement of licence condition compliance, which supplements the Technical Inspection Guides. Thus the TAGs have relevance to all inspectors within ONR, regardless of function. The TAGs also provide information to licensees and dutyholders regarding ONR's expectations of the nature and content of relevant technical elements of safety cases and security plans.
The TAGs provide guidance in particular technical areas, and they are to be used at the discretion of inspectors.
Responsibility for the maintenance of TAGs is shared between ONR's Professional Leads for individual technical areas and the Regulatory and Technical Standards sub programme within ONR's Technical Division.
The guides available below are the latest issues. As revised versions are produced they will replace the older versions.
Those civil nuclear industry dutyholders who need a document containing sensitive nuclear information, should contact cns.support@onr.gov.uk
Should you have any feedback on our guidance, please email contact@onr.gov.uk
NOTE: As part of a recent update to our internal quality control arrangements, we have updated the terminology related our document publication process. Previously, documents were marked with a ‘Revision number’ – denoting the next number in the lifecycle of the document. However, we have recently changed this term to ‘Issue number’ in order to avoid conflicts with our internal document management processes. New or updated documents will be marked with an ‘Issue number’ as opposed to a ‘Revision number’, however, the number sequence will not be effected by this change. Should you require more information relating to this change in terminology, please contact us.
| Document ID | Review date | Title |
|---|---|---|
| Nuclear safety | ||
| NS-TAST-GD-002 (Rev 8) | July 2023 | Radiation Shielding |
| NS-TAST-GD-003 (Rev 9) | October 2022 | Safety Systems |
| NS-TAST-GD-004 (Rev 7) | April 2023 | Fundamental Principles |
| NS-TAST-GD-005 (Rev 11) | March 2023 | Guidance on the Demonstration of ALARP (As Low As Reasonably Practicable) |
| NS-TAST-GD-006 (Rev 5) | October 2025 | Design Basis Analysis |
| NS-TAST-GD-007 (Rev 4) | September 2020 | Severe Accident Analysis |
| NS-TAST-GD-009 (Rev 6) | October 2023 | Examination, Inspection, Maintenance and Testing of Items Important to Safety |
| NS-TAST-GD-010 (Rev 6) | September 2021 | Early initiation of safety systems |
| NS-TAST-GD-011 (Rev 2) | Withdrawn pending review | The single failure criterion |
| NS-TAST-GD-013 (Rev 8) | October 2023 | External hazards |
| NS-TAST-GD-014 (Rev 6) | November 2024 | Internal Hazards |
| NS-TAST-GD-015 (Rev 3) | May 2025 | Electromagnetic Interference |
| NS-TAST-GD-016 (Rev 7) | April 2025 | Integrity of Metal Structures, Systems and Components |
| NS-TAST-GD-017 (Rev 4) | November 2025 | Civil Engineering |
| NS-TAST-GD-018 (Rev 8) | October 2023 | Criticality Warning Systems |
| NS-TAST-GD-019 (Rev 5) | April 2024 | Essential Services |
| NS-TAST-GD-020 (Rev 6) | May 2025 | Civil Engineering Containments for Reactor Plants |
| NS-TAST-GD-021 (Rev 6) | June 2024 | Containment: Chemical Plants |
| NS-TAST-GD-022 (Rev 7) | December 2024 | Ventilation |
| NS-TAST-GD-023 (Rev 6) | August 2024 | Control of Processes Involving Nuclear Matter (SAP - ENM. 1 to 8) |
| NS-TAST-GD-024 (Rev 7) | June 2023 | Management of Radioactive Material and Radioactive Waste on Nuclear Licensed Sites |
| NS-TAST-GD-026 (Rev 5) | September 2022 | Decommissioning |
| NS-TAST-GD-027 (Rev 6) | December 2021 | Training and assuring personnel competence |
| NS-TAST-GD-028 (Rev 6) | October 2024 | Control and Instrumentation Aspects of Nuclear Plant Commissioning |
| NS-TAST-GD-029 (Rev 5) | November 2023 | Graphite reactor cores |
| NS-TAST-GD-030 (Rev 7) | April 2024 | Probabilistic Safety Analysis |
| NS-TAST-GD-031 (Rev 6) | April 2023 | Safety related Systems and Instrumentation |
| NS-TAST-GD-033 (Rev 7) | February 2024 | Duty Holder Management of Records |
| NS-TAST-GD-035 (Rev 6) | December 2022 | The Limits and Conditions for Nuclear Safety (Operating Rules) |
| NS-TAST-GD-036 (Rev 5) | Withdrawn pending review | Diversity, redundancy, segregation and layout of mechanical plant |
| NS-TAST-GD-038 (Rev 9) | November 2022 | Radiological Protection |
| NS-TAST-GD-041 (Rev 7) | January 2024 | Criticality Safety |
| NS-TAST-GD-042 (Rev 5) | September 2023 | Validation of Computer Codes and Calculation Methods |
| NS-TAST-GD-043 (Rev 6) | July 2024 | Radiological Analysis - Normal Operation |
| NS-TAST-GD-045 (Rev 6) | April 2024 | Radiological analysis - Fault conditions |
| NS-TAST-GD-046 (Rev 6) | October 2023 | Computer Based Safety Systems |
| NS-TAST-GD-048 (Rev 6) | July 2023 | Organisational Change |
| NS-TAST-GD-049 (Rev 7) | November 2023 | Licensee Core Safety and Intelligent Customer Capabilities |
| NS-TAST-GD-050 (Rev 8) | October 2025 | Periodic Safety Reviews (PSRs) [NS-TAST-GD-050] |
| NS-TAST-GD-051 (Rev 7) | December 2024 | The purpose, scope and content of safety cases |
| NS-TAST-GD-056 (Rev 7) | February 2023 | Nuclear Lifting Operations |
| NS-TAST-GD-057 (Rev 6) | October 2022 | Design Safety Assurance |
| NS-TAST-GD-058 (Rev 4) | March 2023 | Human Factors Integration |
| NS-TAST-GD-059 (Rev 5) | December 2022 | Human Machine Interface |
| NS-TAST-GD-060 (Rev 4) | March 2022 | Procedure Design and Administrative Controls |
| NS-TAST-GD-061 (Rev 4) | March 2022 | Staffing levels and task organisation |
| NS-TAST-GD-062 (Rev 4) | October 2025 | Workplaces and Work Environment |
| NS-TAST-GD-063 (Rev 5) | July 2022 | Human Reliability Analysis |
| NS-TAST-GD-064 (Rev 4) | December 2021 | Allocation of Function between Human and Engineered Systems |
| NS-TAST-GD-065 (Rev 4) | January 2023 | Function and Content of the Nuclear Baseline |
| NS-TAST-GD-067 (Rev 2) | February 2022 | Pressure Systems |
| NS-TAST-GD-072 (Rev 4) | July 2022 | Function and Content of a Safety Management Prospectus |
| NS-TAST-GD-075 (Rev 3) | September 2025 | Safety of Nuclear Fuel in Power Reactors |
| NS-TAST-GD-077 (Rev 6) | July 2024 | Supply Chain Management Arrangements for the Procurement of Nuclear Safety Related Items or Services |
| NS-TAST-GD-079 (Rev 6) | April 2024 | Licensee Design Authority Capability |
| NS-TAST-GD-080 (Rev 4) | January 2023 | Challenge Culture, Independent Challenge Capability (including an Internal Regulation function) and the Provision of Nuclear Safety Advice |
| NS-TAST-GD-081 (Rev 4) | June 2024 | Safety Aspects Specific to Storage of Spent Nuclear Fuel |
| NS-TAST-GD-083 (Rev 2) | November 2023 | Land Quality Management |
| NS-TAST-GD-087 (Rev 2) | June 2022 | Control of Property Transactions on Licensed Sites |
| NS-TAST-GD-088 (Rev 3) | January 2024 | Chemistry of Operating Civil Nuclear Reactors |
| NS-TAST-GD-089 (Rev 1) | February 2026 | |
| NS-TAST-GD-093 (Rev 2) | Withdrawn pending review | Guidance for undertaking Leadership and Management for Safety Reviews |
| NS-TAST-GD-094 (Rev 2) | July 2024 | Categorisation of Safety Functions and Classification of Structures and Components |
| NS-TAST-GD-096 (Rev 0) | April 2023 | Guidance on Mechanics of Assessment |
| NS-TAST-GD-097 (Rev 2) | April 2025 | Criticality Safety Assessment of Transport Packages |
| NS-TAST-GD-098 (Rev 2) | October 2024 | Asset Management |
| NS-TAST-GD-099 (Rev 1) | June 2021 | Transport Engineering Assessment |
| NS-TAST-GD-100 (Rev 2) | October 2024 | Shielding and Dose Rate Safety Assessment of Transport Packages |
| NS-TAST-GD-101 (Rev 1) | January 2023 | Geological Disposal |
| NS-TAST-GD-102 (Rev 1) | June 2023 | General Guidance for Mechanical Engineering Specialism Group |
| NS-TAST-GD-103 (Rev 1) | October 2023 | Emergency Power Generation |
| Civil Nuclear Security | ||
| CNS-TAST-GD-1.1 (Rev 1) | March 2025 | Security Governance and Leadership |
| CNS-TAST-GD-1.2 (Rev 2) | March 2022 | Organisational Security Capability |
| CNS-TAST-GD-1.3 (Rev 1) | March 2025 | Security Decision Making |
| CNS-TAST-GD-1.4 (Rev 1) | March 2025 | Organisational Learning for Security |
| CNS-TAST-GD-1.5 (Rev 1) | March 2024 | Security Assurance Processes |
| CNS-TAST-GD-2.1 (Rev 1) | March 2023 | Maintenance of a Robust Security Culture |
| CNS-TAST-GD-3.1 (Rev 2) | March 2022 | Analysis of Security Roles & Associated Competencies |
| CNS-TAST-GD-3.2 (Rev 2) | March 2022 | Identification of Learning Objectives and Training Needs |
| CNS-TAST-GD-3.3 (Rev 2) | March 2022 | Measurement of Competence |
| CNS-TAST-GD-3.4 (Rev 2) | March 2022 | Organisation of and Support to the Training Function |
| CNS-TAST-GD-4.1 (Rev 1) | March 2024 | Procurement and Intelligent Customer Capability |
| CNS-TAST-GD-4.2 (Rev 1) | March 2024 | Supplier Capability |
| CNS-TAST-GD-4.3 (Rev 1) | March 2024 | Oversight of Suppliers |
| CNS-TAST-GD-4.4 (Rev 1) | March 2024 | Commissioning |
| CNS-TAST-GD-5.1 (Rev 1) | March 2023 | Reliability and Resilience |
| CNS-TAST-GD-5.2 (Rev 1) | March 2023 | Examination, Inspection, Maintenance and Testing |
| CNS-TAST-GD-5.3 (Rev 1) | March 2022 | Sustainability |
| CNS-TAST-GD-6.1 (Rev 1) | April 2023 | Categorisation for Theft |
| CNS-TAST-GD-6.2 (Rev 1) | March 2022 | Categorisation for Sabotage |
| NS-TAST-GD-6.4 (Rev 1) | March 2022 | Vulnerability Assessment |
| CNS-TAST-GD-6.5 (Rev 1) | March 2022 | Adjacent or Enclave Nuclear Premises |
| CNS-TAST-GD-6.6 (Rev 1) | March 2024 | Nuclear Construction Sites |
| CNS-TAST-GD-6.7 (Rev 1) | May 2023 | Class A Carriers – Transport Security Statements and Plans |
| CNS-TAST-GD-7.1 (Rev 1) | March 2023 | Effective Cyber and Information Risk Management |
| CNS-TAST-GD-7.2 (Rev 1) | March 2023 | Information Security |
| CNS-TAST-GD-7.3 (Rev 1) | March 2022 | Protection of Nuclear Technology and Operations |
| CNS-TAST-GD-7.4 (Rev 1) | March 2022 | Physical Protection of Information |
| CNSS-TAST-GD-7.5 (Rev 3) | March 2024 | Preparation for and Response to Cyber Security Events |
| CNS-TAST-GD-8.1 (Rev 1) | November 2024 | Cooperation of Departments with responsibility for delivering vetting and ongoing personnel security arrangements |
| CNS-TAST-GD-8.2 (Rev 1) | November 2024 | Pre-employment Screening and National Security Vetting |
| CNS-TAST-GD-8.3 (Rev 1) | November 2024 | Ongoing Personnel Security Aftercare |
| CNS-TAST-GD-9.1 (Rev 1) | March 2024 | CNC Response Force |
| CNS-TAST-GD-9.2 (Rev 1) | March 2024 | Local Police Forces |
| CNS-TAST-GD-9.3 (Rev 1) | March 2024 | Security Guard Services |
| CNS-TAST-GD-10.1 (Rev 2) | October 2024 | CT Measures EP&R Planning |
| CNS-TAST-GD-10.2 (Issue 2.1) | October 2024 | Testing and Exercising the Security Response |
| CNS-TAST-GD-10.3 (Rev 2) | October 2021 | Clarity of C3 Arrangements for Nuclear Security Events |
| CNSS-TAST-GD-11.1 (Issue 1.2) | May 2026 | Guidance on the Security Assessment of Generic New Nuclear Reactor Designs |
| Safeguards | ||
| SG-TAST-GD-001 (Rev 3) | January 2023 | Safeguards technical assessment guidance |
| SG-TAST-GD-002 (Rev 1) | January 2022 | Nuclear Material Accountancy |