Simulation codes allow one to reduce the high conservativism in nuclear reactor design improving the reliability and sustainability associated with nuclear power. Full-core coupled reactor physics at the rod level are not provided by most simulation codes. This has led in the UK to the development of a multiscale and multiphysics software development focused on LWRS. In terms of the thermal hydraulics, simulation codes suitable for this multiscale and multiphysics software development include the subchannel code CTF and the thermal hydraulics module FLOCAL of the nodal code DYN3D. In this journal article, CTF and FLOCAL thermal hydraulics validations and verifications within the multiscale and multiphysics software development have been performed to evaluate the accuracy and methodology available to obtain thermal hydraulics at the rod level in both simulation codes. These validations and verifications have proved that CTF is a highly accurate subchannel code for thermal hydraulics. In addition, these verifications have proved that CTF provides a wide range of crossflow and turbulent mixing methods, while FLOCAL in general provides the simplified no-crossflow method as the rest of the methods were only tested during its implementation into DYN3D.

Understanding and optimizing the relation between nuclear reactor components or physical phenomena allows us to improve the economics and safety of nuclear reactors, deliver new nuclear reactor designs, and educate nuclear staff. Such relation in the case of the reactor core is described by coupled reactor physics as heat transfer depends on energy production while energy production depends on heat transfer with almost none of the available codes providing full coupled reactor physics at the fuel pin level. A Multiscale and Multiphysics nuclear software development between NURESIM and CASL for LWRs has been proposed for the UK. Improved coupled reactor physics at the fuel pin level can be simulated through coupling nodal codes such as DYN3D as well as subchannel codes such as CTF. In this journal article, the first part of the DYN3D and CTF coupling within the Multiscale and Multiphysics software development is presented to evaluate all inner iterations within one outer iteration to provide partially verified improved coupled reactor physics at the fuel pin level. Such verification has proven that the DYN3D and CTF coupling provides improved feedback distributions over the DYN3D coupling as crossflow and turbulent mixing are present in the former.

Traditionally, the complex coupled physical phenomena in nuclear reactors has resulted in them being treated separately or, at most, simplistically coupled in between within nuclear codes. Currently, coupling software environments are allowing different types of coupling, modularizing the nuclear codes or multi-physics. Several multiscale and multi-physics software developments for LWR are incorporating these to deliver improved or full coupled reactor physics at the fuel pin level. An alternative multiscale and multi-physics nuclear software development between NURESIM and CASL is being created for the UK. The coupling between DYN3D nodal code and CTF subchannel code can be used to deliver improved coupled reactor physics at the fuel pin level. In the current journal article, the second part of the DYN3D and CTF coupling was carried out to analyse a parallel two-way coupling between these codes and, hence, the outer iterations necessary for convergence to deliver verified improved coupled reactor physics at the fuel pin level. This final verification shows that the DYN3D and CTF coupling delivers improved effective multiplication factors, fission, and feedback distributions due to the presence of crossflow and turbulent mixing.

Almen intensity cannot carry a peening result from one material to another. This paper gives a cavity-based correlation for the depth of compression that can, within a declared domain of materials, media and processes. Johnson’s expanding-cavity model is applied to the shot impact and solved exactly with an energy balance, placing the depth at a fixed multiple of the plastic-zone radius with one fitted depth constant (1.43 on a measured shot-velocity scale), conditional on the constitutive and velocity models; a simpler form, also new, agrees within 8% and is as accurate on every test, so the exact form is preferred for its physics, not its accuracy. On 31 conditions in 15 materials and states, its error on a withheld material is 7.9% (±13% at 90%). Locked, then applied to 30 conditions from seven further laboratories, it predicts depth to 11.4% (9.6% weighting the seven laboratories equally; 22 of the 30 conditions come from one laboratory), against 19.4% for depth proportional to intensity and 12.7% for a four-constant power law in intensity, shot size and strength fitted to the same data. In locked predictions for three more laboratories, steel depths are predicted to 20% weighting laboratories equally, and to 15% for the six profiles measured through the full depth. Nickel alloys need measured velocity. The domain is steel media at 0.125–0.45 mm A and 100–200% coverage in quenched-and-tempered steels and titanium and aluminium alloys; ferrite-dominated mild steels appear to need a higher strain-rate factor. Four propositions explain why intensity fails: among them, under the restricted scaling model a strip record makes shot velocity and size structurally identifiable, with a practical precision that is predicted but not yet demonstrated, and the strip lot only structurally with a dent and metered flow, so shot size must be fixed. Provisional screening factors modelled on B and A basis conventions, not qualified allowables, are 0.74 and 0.61 on the predicted median depth from the strip record alone, rising to about 0.92 with profiles on the part, for use through an AS7045 qualification route once the statistical basis is accepted.