In some cases the SMR designs can be simplified compared to large reactors belonging to the same technology line, by incorporating certain design features that are peculiar to smaller reactors.

As an example, a PWR SMR with integral design of the primary circuit[48] eliminates large break LOCA by design and also reduces the effect of other LOCA-type accidents, resulting in fewer and simpler safety systems (as discussed in section 4.2.1).

Other examples include the Russian marine derivative reactors that achieve a significant economy of construction materials because of a compact modular design of the nuclear steam supply system (see section 4.2.1).

Fewer safety systems and materials are considered for the boiling water reactor with compact containment, CCR, see the discussion in Section 4.2.2.

Reference [6.5] gives an evaluation of the design simplification factor for the 335 MWe IRIS — a PWR with the integral primary circuit design being developed by the Westinghouse Electric Company (United States). The factor is conservatively estimated by the designer as:

[Design simplification factor for integral design PWR] = 0.85 (6.4)

Factor (6.4) is a correction factor for the overnight cost increase resulting from the application of scaling law (6.3).

The Annex 7 of reference [6.8] contains the comparative economic data pointing to a very similar design simplification factor for the Russian marine derivative design VBER-300 of 325 MWe:

[Design simplification factor for the Russian marine derivative PWR] = 0.84 (6.5)

In both cases, the estimated design simplification factors allow a reduction in the SMR overnight capital costs by ~15%.