GDA Assessment Process & Nuclear Site Licensing (Nov 2021)

Simon Stuttaford & Andrew Renton

What is the link between the Generic Design Assessment process and Nuclear Site Licensing?

With the increasing interest in Small Modular Reactor (SMR) and Advanced Modular Reactor (AMR) technologies, a question that is frequently raised is whether a developer has to go through the Office for Nuclear Regulation (ONR)’s Generic Design Assessment (GDA) process before making an application for nuclear site licensing. In legal terms the question may be put: Is there a specific requirement to obtain approval under the GDA in order for a new nuclear technology to obtain a nuclear site licence and proceed to commercial deployment as a nuclear power station.

We have frequently heard it said that there is no legal requirement to go through the GDA process and in our view whilst that is technically true that is also an oversimplification of a complex and robust system of checks and balances which ONR are obliged to undertake as part of their statutory role.

In order to fully answer this question, it is important to consider: the genesis of the GDA process and precisely what it covers; the key requirements of the UK’s Nuclear Installations Act 1965 as amended; the Site Licence application process; and the function, powers and remit of the Office for Nuclear Regulation (the ONR).


The Generic Design Assessment process was developed by the ONR and the Environment Agency (EA) following a UK Government request as a result of the 2006 Energy Review.

As was stated in the Joint ONR/EA 2013 Guide to the Regulatory process:

“Generic Design Assessment (GDA) enables the safety, security and environmental implications of new nuclear power station designs to be assessed before applications are made for the permissions required to build that design at a particular site.”

Part of the concept of a GDA is that a generic design can be assessed in advance which will provide some sort of assurance for developers/designers that their design will meet the necessary safety requirements prior to committing money to buying a site, setting up a Site Licence Company etc. The ONR does not say that the GDA process only applies in relation to pre-licensing applications. The role of the ONR is to ensure the safety of the design at whatever stage the assessment is to be made.

Note the following extract from the ONR’s own website:

“We will not issue permits for new nuclear power stations unless the design and its potential operators meet the high safety, security, environmental and waste management standards that we require.”

Site Licence Application:

The principal “permit” to which the ONR refers is the Nuclear Site Licence application. At this juncture the ONR will be considering the application of the safety case to a specific site (and in this respect will be reviewing a site specific safety case). The ONR states in its 2019 guide “Licensing Nuclear Installations” that it is examining three main themes when it assesses a nuclear site licence application:

• the capability, organisation and resources of the applicant

• the nature of the prescribed activities and the relevant safety

• the nature and location of the site

The Nuclear Installations Act 1965 as amended is the primary UK piece of legislation for nuclear regulation and amongst other topics covers the regime that applies to nuclear site licensing.

Section 4 deals with the application of conditions that apply to nuclear site licences. We have highlighted the most relevant points.

4 Attachment of conditions to licences

(1) The appropriate national authority—

(a) must, when it grants a nuclear site licence, attach to it such conditions as the authority considers necessary or desirable in the interests of safety, and

(b) may attach such conditions to it at any other time.

(2) For the purposes of subsection (1), “safety” in relation to a nuclear site includes—

(a) safety in normal circumstances, and

(b) safety in the event of any accident or other emergency on the site.

(3) Conditions that may be attached to a licence by virtue of subsection (1) may in particular include provision—

(a) for securing that an efficient system is maintained for detecting and recording the presence and intensity of any ionising radiations from time to time emitted from anything on the site or from anything discharged on or from the site;

(b) with respect to the design, siting, construction, installation, operation, modification and maintenance of any plant or other installation on, or to be installed on, the site;

(c) with respect to preparations for dealing with, and measures to be taken on the happening of, any accident or other emergency on the site;

(d) without prejudice to sections 13 and 16 of the Radioactive Substances Act 1993 or to the Environmental Permitting (England and Wales) Regulations 2016 (S.I. 2016/1154), or to the Environmental Authorisations (Scotland) Regulations 2018 with respect to the discharge of any substance on or from the site.

(4) The appropriate national authority may at any time attach to a nuclear site licence such conditions as the appropriate national authority may consider appropriate with respect to the handling, treatment and disposal of nuclear matter.

This section sets out the role that the ONR has in relation to nuclear site licensing and makes it clear that the ONR is the principal consultee (along with the Environment Agency).

For the avoidance of any doubt, the national authority is the ONR as set out in section 26 of the Act:

26 Interpretation

(1) In this Act, except where the context otherwise requires, the following expressions have the following meanings respectively, that is to say— “the Act of 1959” means the Nuclear Installations (Licensing and Insurance) Act 1959;

[ F227 “the appropriate environment authority” means—

(a) in the case of a site in England, the Environment Agency;

(b) in the case of a site in Scotland, the Scottish Environment Protection Agency;

(c) in the case of a site in Northern Ireland, the Department of Environment in Northern Ireland;

(d) in the case of a site in Wales, the Natural Resources Body for Wales.

“the appropriate national authority” means—

(a) in relation to England and Wales and Scotland, the ONR;

(b) in relation to Northern Ireland, the Secretary of State; ] [ F228“appropriate permit” has the meaning given by section 7B;] “atomic energy” has the meaning assigned by the M8Atomic Energy Act 1946; “the Authority” means the United Kingdom Atomic Energy Authority; [ F228“continental shelf”,

in relation to a country or territory, means—

(a) in the case of the United Kingdom, areas designated under section 1(7) of the Continental Shelf Act 1964;

(b) in the case of a country or territory outside the United Kingdom, an area outside its territorial sea within which rights are exercisable in relation to the sea bed and subsoil and their natural resources by that country or territory;] “contravention”, in relation to any enactment or to any condition imposed or direction given thereunder, includes a failure to comply with that enactment, condition or direction, and cognate expressions shall be construed accordingly; “costs” in the application of this Act to Scotland, means expenses;

It is clear in our view that determination and satisfaction of nuclear site licence conditions cannot be satisfied other than by reference to the ONR.

In this respect we also refer to the Licensing Condition Handbook:

Licence Condition 14: Safety Documentation

1 “Without prejudice to any other requirements of the conditions attached to this licence the licensee shall make and implement adequate arrangements for the production and assessment of safety cases consisting of documentation to justify safety during the design, construction, manufacture, commissioning, operation and decommissioning phases of the installation.”

Licence Condition 16: Site plans, designs and specifications

4 The licensee shall furnish to ONR such plans, designs, specifications or other information relating to such buildings, plant and operations as ONR may specify.

Licence Condition 21: Commissioning

7 The licensee shall ensure that no plant or process which may affect safety is operated (except for the purpose of commissioning) until:

b) a safety case or cases as appropriate, which shall include the safety implications of modifications made since the commencement of construction of the plant and those arising from the commissioning of the plant, and any matters whereby the operation of the plant may be affected by such modifications or commissioning, has been considered in accordance with the arrangements referred to in paragraph 1 of this condition.

The conclusion to be drawn is that a number of the Site Licence Conditions on the face of it are only likely to be satisfied following direct outputs of GDA or a process that resembles GDA.

The ONR’s role:

It is also interesting to consider the genesis of the ONR which was established as a statutory Public body on 1 April 2014 under the Energy Act 2013. The ONR was formally established under Part 3 of the Energy Act.

See in this respect sections 67 and 68 and again we have highlighted the most relevant points.

67 The ONR’s purposes

In this Part, “the ONR’s purposes” means—

(a) the nuclear safety purposes (see section 68),

(b) the nuclear site health and safety purposes (see section 69),

(c) the nuclear security purposes (see section 70),

(d) the nuclear safeguards purposes (see section 72), and

(e) the transport purposes (see section 73).

68 Nuclear safety purposes

(1) In this Part, the “nuclear safety purposes” means the purposes of protecting persons against risks of harm from ionising radiations from GB nuclear sites, including through—

(a) the design and construction of relevant nuclear installations and their associated sites,

(b) arrangements for the operation and decommissioning of, and other processes connected with, relevant nuclear installations,

(c) arrangements for the storage and use of nuclear matter on GB nuclear sites, and

(d) arrangements to minimise those risks in the event of an escape or release of such ionising radiations.

(2) For this purpose, ionising radiations from GB nuclear sites are ionising radiations from—

(a) relevant nuclear installations, or

(b) nuclear matter stored or used on a GB nuclear site; and an escape or release of ionising radiations from a GB nuclear site includes ionising radiations from

nuclear matter that has escaped or been released on or from a GB nuclear site.

(3) In this section—

• “GB nuclear site” means a nuclear site in England, Wales or Scotland;

• “nuclear installation” has the same meaning as in the Nuclear Installations Act 1965 (see section 26 of that Act);

• “nuclear matter” has the same meaning as in that Act (see section 26 of that Act);

• “relevant nuclear installation” means a nuclear installation on a site (its “associated site”) in England, Wales or Scotland for which a nuclear site licence is required by virtue of the installation (and includes a proposed or former nuclear installation in respect of which such a licence would be or has ever been so required).

See also an extract from the ONR Primary Impact legislation Impact Assessment, dated 27/10/2011:

“A prime role of ONR is to enable the safe, secure, effective use and control of nuclear technology and material for the overall benefit of society. This is effected through prescriptive activities aligned to the nuclear operators’ arrangements agreed within the legal Site Licence framework, and through regulator identified (non-prescriptive) activities to maintain confidence and drive continuous improvement in the UK nuclear industry. All such regulator activities have been reinforced following the events at Fukushima in early 2011 and are recognised in the Chief Inspector’s report on this event.”

GDA/Licensing Approach:

In the ONR/EA 2013 Guide, two points are highlighted:

• the GDA process is not mandatory;

• the GDA process and Site Licensing are two distinct phases:

Para 3:

“Although GDA is not a mandatory process, because of its advantages for reactor vendors and developers, it is expected that it will form Phase 1 of regulatory assessment for new nuclear power stations in the UK. Phase 2 will be the regulatory assessment of a site-specific proposal to construct and operate a power station based on a design which had been through GDA.”

Whilst logically one might think that the appropriate order would be GDA followed by the Site Licence application process, that is not necessarily the case and indeed the ONR’s 2019 guidance “New Nuclear Power Plants: Generic Design Assessment Guidance to Requesting Parties” (ONR-GDA-GD-006 Revision 0 October 2019), at para 1, states as follows:

“This document provides guidance on the Office for Nuclear Regulation’s (ONR) Generic Design Assessment (GDA) process for the safety and security assessment of new Nuclear Power Plants (NPP). This process will be applied where ONR is asked to assess a proposed design in advance, or in parallel to an application for a nuclear site licence.”

Again, this guidance document confirms that the GDA is not a mandatory process (at para 6):

“Although GDA is not a mandatory process, because of its inherent benefits, it is expected that it will usually be requested for new NPPs intended for construction in GB.”

So what exactly does a developer/designer achieve by going through GDA?

Essentially, a certain assurance that the safety and security of the design proposed meets ONR standards, typically by means of a “Design Acceptance Confirmation” (or DAC) (and in the case of the EA a “Statement of Design Acceptability” (SODA).)

As is stated at para 47:

“The output from a GDA represents ONR’s expert judgement on the adequacy of the safety and security of the proposed design at the time it is provided.”

The outputs from a GDA are not in themselves legally binding. See in this respect para 47:

“None of the outputs from GDA have a binding legal status and are not a formal requirement of the GB nuclear licensing regime;”

It is also acknowledged that potentially a developer or designer is at liberty to proceed directly to a site licence application without going through the GDA process (para 47):

“since it is possible to apply directly to ONR for a site licence based on a design which has not been subject to GDA.”

Although there is a strong presumption from ONR that the GDA process will be followed, with some tangible advantages:

Para 48:

“However, ONR anticipates that future licensees are likely to want the design they are proposing to construct and operate to have undertaken a GDA, as this will demonstrate some regulatory certainty and thereby reduce the project risk.”

Para 50:

“Clearly the generic safety and security cases used as the basis for GDA, and as defined within the output from that GDA, are not in themselves sufficient for a future licensee to seek a regulatory permission. However, in line with the objective of GDA (para. 8), the intent is that these would form the foundation for the site-specific safety case which is a requirement to commence nuclear safety related construction.”

Para 61:

“If, at the end of Step 3, ONR provides a DAC to a RP it will mean it is confident that, based on the generic safety and security cases, the design is capable of being built and operated on a site bounded by the generic site envelope, in a way that is acceptably safe and secure. This is of course subject to site-specific assessment and licensing.”

Para 62:

“ONR would take a valid DAC into consideration in assessing the adequacy of a licensee’s case for starting nuclear safety related construction, if the GDA outputs form part of that case. ONR will not further assess, at the site-specific stage, those aspects of the safety and security cases already assessed during GDA.”

Para 112:

“By the end of GDA, ONR will expect the generic safety and security cases to be fit for use by a future licensee. In any subsequent site-specific licensing phase, ONR will assess the degree to which the prospective site licensee understands and takes responsibility for the safety and security cases.”


It seems clear that ONR envisaged a GDA process to assess the design and safety case followed by a site-specific Licensing process. Conducting these two processes simultaneously or at least with some degree of overlap is not ruled out.
Whilst there is no legal requirement to go to GDA, the Site Licence Application process does have a mandatory requirement to refer the technology to be deployed to the national authority (the ONR) to ensure the safety of the design.
In our view if a developer/designer takes the route of going straight to Site Licence application it will have to prepare a strong case on safety and security. Without offering a solution for the ONR to the safety scrutiny requirement it seems the ONR may choose to use the GDA process or its equivalent in the course of the licensing process. Indeed, one of the first questions the ONR raises in relation to the GDA is where the technology is going to be deployed.
Going straight for licensing in our view will only save time and money if there is a clear and agreed process with the ONR. The ONR is unlikely to be persuaded purely by a developer’s need for speed or ability to pay. It’s overriding mandate is safety.
At present we are not aware that any SMR technology developer has agreed a process other than a GDA approach. Indeed, we are aware that Rolls-Royce have been engaging ONR in pre-GDA discussions for some time and have now “booked” a GDA slot.
In our view engaging with the ONR to discuss the option of a more efficient and cost-effective way of dealing with design and safety requirements with a well-prepared safety case briefing on the applicable technology is an essential first step in understanding the BEIS and ONR view. We note in this respect that nowhere does the ONR set out a process for technology safety or design approval and pre-licensing which is not the GDA process. That is not to say that ONR might not consider an alternative but what does that look like? Our understanding is that BEIS is open to discussion with developers, and we suggest it would be a sensible and commercially efficient course of action to enter into a dialogue with BEIS and ONR. The ONR may well be persuaded to modify or abridge the GDA process if doing so does not undermine the paramount safety considerations.

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