Office for Nuclear Regulation

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Office for Nuclear Regulation (ONR) 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 principles presented in the SAPs 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. However,they also contain guidance relevant to principles underlining the enforcement of licence condition compliance which supplements the Technical Inspection Guides. Thus the Technical Assessment Guides have relevance to all inspectors within ONR, regardless of function. The technical assessment guides also provide information to licensees regarding ONR's expectations of the nature and content of relevant technical elements of licensees safety cases.

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 Regulatory Assurance programme

The guides available below are the latest issues. As revised versions are produced they will replace the older versions.

Should an earlier issue be required, please request it via

Document ID Review date Title
NS-TAST-GD-002 (Rev 5) May 2019 Radiation Shielding
NS-TAST-GD-003 (Rev 7) December 2017 Safety Systems
NS-TAST-GD-004 (Rev 5) April 2019 Fundamental principles
NS-TAST-GD-005 (Rev 7) September 2018 Guidance on the Demonstration of ALARP (As Low As Reasonably Practicable)
NS-TAST-GD-006 (Rev 4) April 2018 Deterministic Safety Analysis and The Use of Engineering Principles in Safety Assessment
NS-TAST-GD-007 (Rev 2) April 2018 Selection of Standards and Criteria for Assessment
T/AST/008 - Withdrawn
NS-TAST-GD-009 (Rev 3) November 2018 Examination, Inspection, Maintenance and Testing of Items Important to Safety
NS-TAST-GD-010 (Rev 4) May 2017 Early initiation of safety systems
NS-TAST-GD-011 (Rev 2) May 2018 The single failure criterion
NS-TAST-GD-013 (Rev 5) September 2017 External hazards
NS-TAST-GD-014 (Rev 4) September 2019 Internal Hazards
NS-TAST-GD-015 (Rev 2) April 2018 Electromagnetic compatibility
NS-TAST-GD-016 (Rev 4) March 2017 Integrity of Metal Components and Structures
NS-TAST-GD-017 (Rev 3) May 2018 Civil Engineering
NS-TAST-GD-018 (Rev 5) May 2019 Criticality Warning Systems
NS-TAST-GD-019 (Rev 3) July 2019 Essential Services
NS-TAST-GD-020 (Rev 3) November 2017 Containment for Reactor Plant
NS-TAST-GD-021 (Rev 3) June 2019 Containment Chemical Plants
NS-TAST-GD-022 (Rev 3) June 2017 Ventilation
NS-TAST-GD-023 (Rev 4) August 2019 Control of Processes Involving Nuclear Matter (SAP - ENM. 1 to 8)
NS-TAST-GD-024 (Rev 5) August 2019 Management of radioactive materials and radioactive waste on nuclear licensed sites
NS-TAST-GD-026 (Rev 4) September 2019 Decommissioning
NS-TAST-GD-027 (Rev 4) November 2017 Training and assuring personnel competence
NS-TAST-GD-028 (Rev 4) September 2019 Control and Instrumentation Aspects of Nuclear Commissioning
NS-TAST-GD-029 (Rev 3) July 2018 Graphite reactor cores
NS-TAST-GD-030 (Rev 5) June 2019 Probabilistic Safety Analysis
NS-TAST-GD-031 (Rev 4) July 2017 Safety related instrumentation
NS-TAST-GD-033 (Rev 4) March 2019 Licensee management of records
NS-TAST-GD-034 (Rev 3) July 2019 Transient Analysis for DBAs in Nuclear Reactors
NS-TAST-GD-035 (Rev 4) August 2017 The Limits and Conditions for Nuclear Plant Safety
NS-TAST-GD-036 (Rev 3) April 2017 Diversity, redundancy, segregation and layout of mechanical plant
NS-TAST-GD-037 (Rev 2) May 2018 Heat Transport Systems
NS-TAST-GD-038 (Rev 6) November 2017 Radiological protection
NS-TAST-GD-041 (Rev 4) May 2019 Criticality safety
NS-TAST-GD-042 (Rev 3) July 2019 Validation of Computer Codes and Calculation Methods
NS-TAST-GD-043 (Rev 3) June 2019 Radiological Analysis Normal Operation
NS-TAST-GD-044 (Rev 0) N/A Selection of Standards and Criteria for Assessment [NS-TAST-GD-044]
NS-TAST-GD-045 (Rev 3) July 2019 Radiological analysis Fault conditions
NS-TAST-GD-046 (Rev 4) February 2020 Computer Based Safety Systems
NS-TAST-GD-048 (Rev 4) March 2018 Organisational capability
NS-TAST-GD-049 (Rev 5) April 2019 Licensee use of contractors and intelligent customer capability
NS-TAST-GD-050 (Rev 4) April 2017 Periodic safety reviews (PSRs) [NS-TAST-GD-050]
NS-TAST-GD-051 (Rev 4) July 2019 The purpose, scope and content of nuclear safety cases
NS-TAST-GD-056 (Rev 3) November 2017 Nuclear Lifting Operations
NS-TAST-GD-057 (Rev 3) November 2017 Design Safety Assurance
NS-TAST-GD-058 (Rev 3) February 2017 Human factors integration
NS-TAST-GD-059 (Rev 3) November 2019 Human Machine Interface
NS-TAST-GD-060 (Rev 2) November 2017 Procedure Design and Administrative Controls
NS-TAST-GD-061 (Rev 3) February 2017 Staffing levels and task organisation
NS-TAST-GD-062 (Rev 2) February 2017 Workplaces and work environment
NS-TAST-GD-063 (Rev 3) May 2018 Human Reliability Analysis
NS-TAST-GD-064 (Rev 2) November 2017 Allocation of function between human and engineered systems
NS-TAST-GD-065 (Rev 2) May 2018 Function and content of the Nuclear Baseline
NS-TAST-GD-067 (Rev 0) November 2017 Pressure Systems Safety
NS-TAST-GD-072 (Rev 2) April 2018 Function and content of a safety management prospectus
NS-TAST-GD-075 (Rev 0) September 2017 Safety aspects specific to Nuclear fuel in Power Reactors
NS-TAST-GD-076 (Rev 2) September 2018 Construction Assurance
NS-TAST-GD-077 (Rev 3) February 2018 Supply Chain Management Arrangements for the Procurement of Nuclear Safety Related Items or Services
NS-TAST-GD-079 (Rev 3) April 2019 Licensee design authority capability
NS-TAST-GD-080 (Rev 2) May 2018 Challenge Culture, Independent Challenge Capability (including an Internal Regulation function) and the Provision of Nuclear Safety Advice
NS-TAST-GD-081 (Rev 2) March 2019 Safety aspects specific to storage of spent nuclear fuel
NS-TAST-GD-082 (Rev 3) December 2018 The Technical Assessment of REPPIR Submissions
NS-TAST-GD-083 (Rev 0) November 2018 Land Quality Management
NS-TAST-GD-087 (Rev 0) March 2017 Control of Property Transactions on Licensed Sites
NS-TAST-GD-088 (Rev 1) March 2020 Chemistry of Operating Civil Nuclear Reactors
NS-TAST-GD-093 (Rev 2) September 2019 Guidance for Undertaking Leadership and Management for Safety Reviews
NS-TAST-GD-094 (Rev 0) November 2018 Categorisation of Safety Functions and Classification of Structures and Components
NS-TAST-GD-098 (Rev 0) October 2019 Asset Management
CNS-TAST-GD-001 (Rev 1) March 2019 Guidance on the purpose , scope and quality of nuclear site security plan (NSSP)
CNS-TAST-GD-002 (Rev 1) April 2019 Guidance on the assessment of nuclear security culture within a company/organisation
CNS-TAST-GD-003 (Rev 0) January 2019 Guidance on the Assessment of the Commissioning of Security Systems and Infrastructure
CNS-TAST-GD-005 (Rev 1) August 2019 Guidance on how to assess the adequacy of a vital area identification submission
CNS-TAST-GD-007 (Rev 0) May 2017 Guidance on the Security Assessment of Generic New Nuclear Reactor Designs
CNS-TAST-GD-010 (Rev 0) October 2017 Guidance on the purpose, scope and quality of a transport security statement
CNS-TAST-GD-015 (Rev 0) August 2017 Guidance on the Assessment of a Dutyholder's Security Performance
CNS-TAST-GD-016 (Rev 1) January 2019 Counter Terrorist Contingency Plans