Office for Nuclear Regulation

Permissioning inspection - Technical assessment guides

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.

Official sensitive

Those civil nuclear industry dutyholders who need a document containing sensitive nuclear information, should contact


Should you have any feedback on our guidance, please email

NOTE: ONR operates a robust governance process for the review, and update as appropriate, of our regulatory standards and guidance. As a regulator, we are involved in the management of a range of relevant international standards and guidance, including International Atomic Energy Agency (IAEA) Safety Standards and Security Guidance, and the Western European Nuclear Regulators Association (WENRA) Safety Reference Levels (SRL). We ensure that all relevant expectations are reflected in the appropriate ONR internal guidance once those international documents are formally published.

In some cases, our guidance documents are updated in advance of the stated formal review date (because of a significant change in relevant good practice, updated international standards or guidance, or amendments to UK legislation). In other instances, where we have judged that there have been no changes that would materially affect our guidance and it therefore remains appropriate to continue use of the existing version, then the formal review date may be passed. 

Where published documents have passed their formal review date, we confirm that there are no significant changes in relevant good practice, modifications to international standards or guidance, or amendments to UK legislation that might significantly alter the content of that internal guidance. Consequently, this has no impact on our robust regulation and our inspectors continue to hold the industry account against the high standards required under UK law.

Any documents that have passed their review date remain subject to our review processes, as stated on our website, and the review dates will be updated in due course.

Document ID Review date Title
Nuclear safety
NS-TAST-GD-002 (Issue 8.1) July 2028 Radiation Shielding
NS-TAST-GD-003 (Issue 9.2) September 2024 Safety Systems
NS-TAST-GD-004 (Issue 8) April 2028 Fundamental Principles of safety assessment
NS-TAST-GD-005 (Issue 11.2) December 2023 Guidance on the Demonstration of ALARP (As Low As Reasonably Practicable)
NS-TAST-GD-006 (Issue 5.1) October 2025 Design Basis Analysis
NS-TAST-GD-007 (Issue 5.1) August 2027 Severe Accident Analysis
NS-TAST-GD-009 (Issue 7) November 2028 Examination, Inspection, Maintenance and Testing of Items Important to Safety
NS-TAST-GD-010 (Issue 7.1) December 2024 Early Initiation of Safety Systems
NS-TAST-GD-011 (Issue 2) Currently under review The single failure criterion
NS-TAST-GD-013 (Issue 9) October 2028 External hazards
NS-TAST-GD-014 (Issue 7.1) October 2026 Internal Hazards
NS-TAST-GD-015 (Issue 3.1) May 2025 Electromagnetic Interference
NS-TAST-GD-016 (Issue 7) April 2025 Integrity of Metal Structures, Systems and Components
NS-TAST-GD-017 (Issue 4.1) November 2025 Civil Engineering
NS-TAST-GD-018 (Issue 8) October 2023 Criticality Warning Systems
NS-TAST-GD-019 (Issue 5.1) April 2024 Essential Services
NS-TAST-GD-020 (Issue 6.1) May 2025 Civil Engineering Containments for Reactor Plants
NS-TAST-GD-021 (Issue 6) June 2024 Containment: Chemical Plants
NS-TAST-GD-022 (Issue 8.1) June 2027 Ventilation
NS-TAST-GD-023 (Issue 6.1) August 2024 Control of Processes Involving Nuclear Matter (SAP - ENM. 1 to 8)
NS-TAST-GD-024 (Issue 7.2) December 2023 Management of Radioactive Material and Radioactive Waste on Nuclear Licensed Sites
NS-TAST-GD-026 (Issue 5.2) September 2023 Decommissioning
NS-TAST-GD-027 (Issue 7) December 2027 Training and assuring personnel competence
NS-TAST-GD-028 (Issue 6.1) October 2024 Control and Instrumentation Aspects of Nuclear Plant Commissioning
NS-TAST-GD-029 (Issue 5) November 2023 Graphite reactor cores
NS-TAST-GD-030 (Issue 7) April 2024 Probabilistic Safety Analysis
NS-TAST-GD-031 (Issue 7) May 2028 Safety related Systems and Instrumentation
NS-TAST-GD-033 (Issue 7.1) February 2024 Duty Holder Management of Records
NS-TAST-GD-035 (Issue 7) March 2028 The Limits and Conditions for Nuclear Safety (Operating Rules)
NS-TAST-GD-036 (Issue 6) October 2028

Redundancy, Diversity, Segregation and Layout of Structures, Systems and Components

NS-TAST-GD-038 (Issue 10) November 2027 Radiological Protection
NS-TAST-GD-041 (Issue 7) January 2024 Criticality Safety
NS-TAST-GD-042 (Issue 5.1) September 2024 Validation of Computer Codes and Calculation Methods
NS-TAST-GD-043 (Issue 6) July 2024 Radiological Analysis - Normal Operation
NS-TAST-GD-045 (Issue 6) April 2024 Radiological analysis - Fault conditions
NS-TAST-GD-046 (Issue 6) October 2023 Computer Based Safety Systems
NS-TAST-GD-048 (Issue 7) July 2028 Organisational Change
NS-TAST-GD-049 (Issue 7.1) July 2024 Licensee Core Safety and Intelligent Customer Capabilities
NS-TAST-GD-050 (Issue 8.1) October 2025 Periodic Safety Reviews (PSRs) [NS-TAST-GD-050]
NS-TAST-GD-051 (Issue 7.1) December 2024 The purpose, scope and content of safety cases
NS-TAST-GD-056 (Issue 7.1) October 2028 Nuclear Lifting Operations
NS-TAST-GD-057 (Issue 7) May 2027 Design Safety Assurance
NS-TAST-GD-058 (Issue 5) March 2026 Human Factors Integration (HFI)
NS-TAST-GD-059 (Issue 5.2) December 2024 Human Machine Interface (HMI)
NS-TAST-GD-060 (Issue 5) December 2027 Procedure Design and Administrative Controls
NS-TAST-GD-061 (Issue 5) June 2028 Staffing Levels and Task Organisation
NS-TAST-GD-062 (Issue 4.2) October 2025 Workplaces and Work Environment
NS-TAST-GD-063 (Issue 6) December 2027 Human Reliability Analysis
NS-TAST-GD-064 (Issue 5) May 2028 Allocation of Function between Human and Engineered Systems
NS-TAST-GD-065 (Issue 5) July 2028 Function and Content of the Nuclear Baseline
NS-TAST-GD-067 (Issue 3.2) June 2027 Pressure Systems Safety
NS-TAST-GD-072 (Issue 4.1) July 2027 Function and Content of a Safety Management Prospectus
NS-TAST-GD-075 (Issue 3.1) September 2025 Safety of Nuclear Fuel in Power Reactors
NS-TAST-GD-077 (Issue 6.2) July 2024 Supply Chain Management Arrangements for the Procurement of Nuclear Safety Related Items or Services
NS-TAST-GD-079 (Issue 6.1) July 2024 Licensee Design Authority Capability
NS-TAST-GD-080 (Issue 5) January 2028 Nuclear Safety Advice and Independent Challenge
NS-TAST-GD-081 (Issue 4.1) June 2024 Safety Aspects Specific to Storage of Spent Nuclear Fuel
NS-TAST-GD-083 (Issue 2.2) November 2024 Land Quality Management
NS-TAST-GD-087 (Issue 2.1) July 2027 Control of Property Transactions on Licensed Sites
NS-TAST-GD-088 (Issue 3) January 2024 Chemistry of Operating Civil Nuclear Reactors
NS-TAST-GD-089 (Issue 1.1) February 2026 Chemistry Assessment
NS-TAST-GD-093 (Issue 2) Document replaced - TD-HOC-GD-002 - Leadership and Management for Safety Reviews Guidance for undertaking Leadership and Management for Safety Reviews
NS-TAST-GD-094 (Issue 2) July 2024 Categorisation of Safety Functions and Classification of Structures and Components
NS-TAST-GD-096 (Issue 1.2) November 2027 Guidance on Mechanics of Assessment
NS-TAST-GD-097 (Issue 2) April 2025 Criticality Safety Assessment of Transport Packages
NS-TAST-GD-098 (Issue 2.1) October 2024 Asset Management
NS-TAST-GD-099 (Issue 2.2) August 2027 Transport Engineering Assessment
NS-TAST-GD-100 (Issue 2) October 2024 Shielding and Dose Rate Safety Assessment of Transport Packages
NS-TAST-GD-101 (Issue 1.3) March 2028 Geological Disposal
NS-TAST-GD-102 (Issue 2) June 2028 General Guidance for Mechanical Engineering Specialism Group
NS-TAST-GD-103 (Issue 1.1) October 2023 Emergency Power Generation
NS-TAST-GD-104 (Issue 1) February 2025 Corporate Governance for Safety
NS-TAST-GD-105 (Issue 1) June 2028 The Assessment of the Nuclear Reactors (Environmental Impact Assessment for Decommissioning) Regulations Submissions
NS-TAST-GD-107 (Issue 1.2) April 2027 Safety Leadership

NS-TAST-GD-109 (Issue 1)

February 2028 Ageing and Degradation Management
Civil Nuclear Security
CNS-TAST-GD-1.1 (Issue 1) March 2025Security Governance and Leadership
CNS-TAST-GD-1.2 (Issue 2.1) April 2027 Organisational Security Capability
CNS-TAST-GD-1.3 (Issue 1) March 2025Security Decision Making
CNS-TAST-GD-1.4 (Issue 1) March 2025Organisational Learning for Security
CNS-TAST-GD-1.5 (Issue 1) March 2024Security Assurance Processes
CNS-TAST-GD-2.1 (Issue 2) March 2025Maintenance of a Robust Security Culture
CNS-TAST-GD-3.1 (Issue 3.1) April 2027Identification and Analysis of Security Tasks and Roles
CNS-TAST-GD-3.2 (Issue 3) April 2027Sufficiency and Competence of Personnel Delivering Security
CNS-TAST-GD-3.3 (Issue 3) April 2027

Workspaces, Equipment and User Interfaces

CNS-TAST-GD-3.4 (Issue 3) April 2027Procedures and Administrative Controls
CNS-TAST-GD-4.1 (Issue 1) March 2024Procurement and Intelligent Customer Capability
CNS-TAST-GD-4.2 (Issue 1) March 2024Supplier Capability
CNS-TAST-GD-4.3 (Issue 1) March 2024Oversight of Suppliers
CNS-TAST-GD-4.4 (Issue 1) March 2024Commissioning
CNS-TAST-GD-5.1 (Issue 2) March 2025Reliability and Resilience of the Security System
CNS-TAST-GD-5.2 (Issue 2) March 2025Examination, Inspection, Maintenance and Testing of Physical Protection Systems
CNS-TAST-GD-5.3 (Issue 2) March 2025Sustainability of Nuclear Security Arrangements
CNS-TAST-GD-6.1 (Issue 2) March 2025Categorisation for Theft
CNS-TAST-GD-6.2 (Issue 2) June 2025 Categorisation for Sabotage
CNS-TAST-GD-6.4 (Issue 1.1) April 2027 Vulnerability Assessments
CNS-TAST-GD-6.5 (Issue 1.1) April 2027Adjacent or Enclave Nuclear Premises
CNS-TAST-GD-6.6 (Issue 2) March 2025 Nuclear Construction Sites
CNS-TAST-GD-6.7 (Issue 2) March 2025Class A Carriers – Transport Security Statements and Plans
CNS-TAST-GD-7.1 (Issue 2) March 2026Effective Cyber and Information Risk Management
CNS-TAST-GD-7.2 (Issue 2.1) March 2027Information Security
CNS-TAST-GD-7.4 (Issue 2) April 2026Physical Protection of Information
CNSS-TAST-GD-7.5 (Issue 3) March 2024Preparation for and Response to Cyber Security Events
CNS-TAST-GD-8.1 (Issue 1) November 2024 Cooperation of Departments with responsibility for delivering vetting and ongoing personnel security arrangements
CNS-TAST-GD-8.2 (Issue 1) November 2024Pre-employment Screening and National Security Vetting
CNS-TAST-GD-8.3 (Issue 1) November 2024Ongoing Personnel Security Aftercare
CNS-TAST-GD-9.1 (Issue 1) March 2024 CNC Response Force
CNS-TAST-GD-9.2 (Issue 1) March 2024Local Police Forces
CNS-TAST-GD-9.3 (Issue 1) March 2024Security Guard Services
CNS-TAST-GD-10.1 (Issue 2) October 2024CT Measures EP&R Planning
CNS-TAST-GD-10.2 (Issue 2.1) October 2024Testing and Exercising the Security Response
CNS-TAST-GD-10.3 (Issue 3) March 2025Clarity of Command, Control and Communications Arrangements During and Post a Nuclear Security Event
CNSS-TAST-GD-11.1 (Issue 1.2) May 2026 Guidance on the Security Assessment of Generic New Nuclear Reactor Designs
CNS-TAST-GD-11.4.1 (Issue 1.1) January 2028 Secure by Design
CNS-TAST-GD-11.4.2 (Issue 1) April 2027 The Threat
CNS-TAST-GD-11.4.5 (Issue 1) April 2027 Functional Categorisation and Classification of Security Structures, Systems and Components
CNS-TAST-GD-11.4.6 (Issue 1.1) April 2027 Managing Changes to Security Standards, Procedures and Arrangements
SG-TAST-GD-001 (Issue 4) January 2026 Safeguards
SG-TAST-GD-002 (Issue 2) January 2025 Nuclear Material Accountancy