Chapter 4 of reference [9.14] explains “license-by-test” approach as follows:

A reactor prototype could be built and subjected to a pre-agreed set of anticipated transient without scram (ATWS) and other accident initiators. By demonstrating safety based on passive response, on the prototype, the licensing authority might be able to certify the design, permitting the manufacture of many tens (or hundreds) of replicate plants to the set of prints and design specifications used for the prototype. In order to assure that aging effects do not degrade the passive safety features of deployed plants, the licensing authority could prescribe the performance of periodic in-situ tests on the plant to confirm continued presence of reactivity feedbacks in the required range and of passive decay heat removal continuously operating at the required rate.

Application of such approach may be useful for licensing of the small reactors with long operation cycle, for which:

• it would be difficult to obtain the immediate licence for a long (15-30 years) operation cycle;

• mass production of standardised reactor modules is foreseen.

An example of the regulatory framework for the license-by-test approach is provided by the US NRC regulation 10 CFR Part 52 “Early site permits; standard design certifications; and combined licenses for nuclear power plants” [9.15]. Part B of this document refers to “…acceptable testing of an appropriately sited, full-size prototype of the design over a sufficient range of normal operating conditions, transient conditions, and specified accident sequences, including equilibrium core conditions.”. So far, there have been no applications proposing license-by-test under 10 CFR Part 52. However, very similar approach has been used in licensing of the non-commercial Experimental Breeder Reactor — II (EBR-II) built and operated in the Argonne National Laboratory (ANL, United States) in the 70-90s [9.16].