1The terms ‘spent fuel’ and ‘spent nuclear fuel’ are used throughout this publication in the same meaning.

2INTERNATIONAL ATOMIC ENERGY AGENCY, Storage of Spent Nuclear Fuel, IAEA Safety Standards Series No. SSG-15, IAEA, Vienna (2012).

3The terms ‘degraded fuel’ or ‘failed fuel’ can cover a broad range of conditions, from minor pinholes to cracked cladding to broken fuel pins.

4There might be one or a number of regulatory authorities with responsibility for facilities or activities in the State (see para. 3.15).

5The safety case is a collection of arguments and evidence in support of the safety of a facility or activity. This collection of arguments and evidence may be known by different names (e.g. safety report, safety dossier, safety file) in different States and might be presented in a single document or a series of documents (see Section 5).

6The operating organization is assumed to be the licensee. If the facility is operated under contract, the interface between responsibilities of the licensee and those of the contracted operational management need to be clearly defined, agreed upon and documented.

7Safeguards agreements between the IAEA and non-nuclear-weapon States party to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) contain the obligation of the State to establish and maintain a national system of accountancy for and control of nuclear material. The IAEA document describing the structure and content of such NPT safeguards agreements, INFCIRC/153(Corrected) [27], also known as the ‘Blue Book’, sets out the basic requirement for a State’s system of accounting for and control of nuclear material.

8After inclusion of uncertainties in the calculations and data, in many States a margin to criticality of 5% is applied for operational states and a smaller margin to criticality (2% or 3%) is applied for credible abnormal conditions.

9The infinite multiplication factor is the ratio of the number of neutrons produced by fission in one generation to the number of neutrons lost through absorption in the preceding generation.

10Design extension conditions are postulated accident conditions that are not considered for design basis accidents, but that are considered in the design process for the facility in accordance with best estimate methodology, and for which releases of radioactive material are kept within acceptable limits [3].

11Only safety aspects as consequences of potential human induced events are addressed here.

12Only inadvertent intrusion events that can potentially compromise safety are addressed here.