Search

The Small Modular Reactor (SMR) concept is designed such that it will solve some of the construction problems of large reactors. SMRs are designed to be “shop fabricated and then transported as modules to the sites for installation” (IAEA, 2018). As a consequence they theoretically have shorter build schedules and require less capital investment (Locatelli et al., 2014). Factory built modules can also increase safety and productivity, due to higher quality tools and inspection available. A literature review has highlighted substantial work has been undertaken in the research, development and construction of different types of reactors and reactor modules but the design of balance of plant modules has not been extensively researched (Wrigley et al., 2018). The focus of this paper is a case study for balance of plant modules in a light water reactor which also could have applications to other reactor types. Modules that are designed for factory build and transport may be built in a standardized module approach. By maximizing module size for transport, this maximizes work offsite, to achieve the cost and schedule savings associated. A design method needs to be developed to help support this approach. To enable this, a three step method is proposed: group components into modules, layout the modules and arrange components inside the modules. The Shearon Harris nuclear power plant was chosen for its publically available data. A previous study on this plant used matrix reordering techniques to group components and heuristically assign them to large modules, built for construction in an assembly area on site, highlighting a potential capital cost savings of 15%. This paper utilizes the same allocation of components to modules as the previous study but aims to undertake the challenge of how balance of plant modules should be arranged. The literature review highlighted that although the facility and plant layout problem has been extensively researched, mathematical layout optimization has not been applied to nuclear power plants. Many techniques for layout optimization have been developed for facilities and process plants however. The work in this paper develops an optimization model using a genetic algorithm for module layout and allocation within a nuclear power plant. This paper analysed two configurations of modules, where balance of plant modules are located on either one or two sides of the nuclear island. The objective function was to minimise pipe length. In the original research, where the plant was configured for assembly on site, the balance of plant modules are located around three sides of the nuclear island. The objective function was calculated at 14,914. As the distances are calculated rectilinearly, this number would be higher in reality as pipework has to be routed around containment. The optimization reduced the objective function by 33.9% and 37.8% for the three and four floor layouts respectively when balance of plant modules are located on two sides of the nuclear island. Furthermore, when modules are located on one side of the nuclear island, the objective function was reduced by 45.4% and 46.1% for three and four floor layouts respectively. This will reduce materials used, reduce build time and hence reduce the cost of a nuclear power plant. This method will also save design time when developing the layout of modules around the plant.

A heat sink module has been developed for high-heat flux applications in the divertor region of a near term DEMO divertor. The concept employs water jet impingement, in a cascading flow path, together with CuCrZr as the structural material. This fluid-flow architecture maximises the heat transfer coefficient obtained for a given coolant flow rate. Combined with high operational pressures, it facilitates increased coolant outlet temperatures. A conjugate CFD study was performed to compare its performance to the ITER divertor under a representative heat flux boundary condition of 10 MW/m2. A transient thermochromic liquid crystal technique was used to experimentally validate the CFD heat transfer data, using air as the working fluid at matched Reynolds numbers. These results showed that area averaged heat transfer coefficients could be accurately predicted by the CFD to within ∼12%.

The influence of high-energy (1.6 MeV) Ar2+ irradiation on the interfacial interaction between cerium oxide thin films (∼15 nm) with a SiO2/Si substrate is investigated using transmission electron microscopy, ultrahigh vacuum x-ray photoelectron spectroscopy (XPS), and a carbon monoxide (CO) oxidation catalytic reaction using ambient pressure XPS. The combination of these methods allows probing the dynamics of vacancy generation and its relation to chemical interactions at the CeO2/SiO2/Si interface. The results suggest that irradiation causes amorphization of some portion of CeO2 at the CeO2/SiO2/Si interface and creates oxygen vacancies due to the formation of Ce2O3 at room temperature. The subsequent ultra-high-vacuum annealing of irradiated films increases the concentration of Ce2O3 with the simultaneous growth of the SiO2 layer. Interactions with CO molecules result in an additional reduction of cerium and promote the transition of Ce2O3 to a silicate compound. Thermal annealing of thin films exposed to oxygen or carbon monoxide shows that the silicate phase is highly stabile even at 450 °C.

The half-life of the neutron-rich nuclide $^{60}\mathrm{Fe}$ has been in dispute in recent years. A measurement in 2009 published a value of $(2.62\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ years, almost twice that of the previously accepted value from 1984 of $(1.49\ifmmode\pm\else\textpm\fi{}0.27)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of $(2.50\ifmmode\pm\else\textpm\fi{}0.12)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr. All three half-life measurements used the grow-in of the $\ensuremath{\gamma}$-ray lines in $^{60}\mathrm{Ni}$ from the decay of the ground state of $^{60}\mathrm{Co}$ (${t}_{1/2}=5.27$ yr) to determine the activity of a sample with a known number of $^{60}\mathrm{Fe}$ atoms. In contrast, the work presented here measured the $^{60}\mathrm{Fe}$ activity directly via the 58.6 keV $\ensuremath{\gamma}$-ray line from the short-lived isomeric state of $^{60}\mathrm{Co}$ (${t}_{1/2}=10.5$ min), thus being independent of any possible contamination from long-lived $^{60\mathrm{g}}\mathrm{Co}$. A fraction of the material from the 2015 experiment with a known number of $^{60}\mathrm{Fe}$ atoms was used for the activity measurement, resulting in a half-life value of $(2.72\ifmmode\pm\else\textpm\fi{}0.16)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr, confirming again the longer half-life. In addition, $^{60}\mathrm{Fe}/^{56}\mathrm{Fe}$ isotopic ratios of samples with two different dilutions of this material were measured with accelerator mass spectrometry to determine the number of $^{60}\mathrm{Fe}$ atoms. Combining this with our activity measurement resulted in a half-life value of $(2.69\ifmmode\pm\else\textpm\fi{}0.28)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ yr, again agreeing with the longer half-life.

The necessity to handle heat loads in the MW/m2 range has become increasingly prevalent in a number of industries. Termed high-heat flux cooling, some of the most challenging conditions in this field occur at the first wall and divertor regions of a fusion tokamak. Steady-state heat fluxes here may reach values in excess of 10 MW/m2 in some areas for a first stage DEMO. The situation is exasperated further by the environment within the machine, which severely alters material properties with time. Even coolant choice itself can have an impact beyond thermal considerations through tritium inventory and neutron activation. Successfully addressing these issues is of critical importance to the development of commercial fusion power. A number of heat sink modules utilising jet impingement in a flat plate geometry were manufactured using diffusion bonding. Each sample produced was subject to leak and hydrostatic pressure measurements, together with further non-destructive analyses. Thermo-fluid measurements were performed on the components in a purpose built facility employing water as the coolant at pressures of up to 200 bar. To replicate the thermal boundary conditions a resistive thin-film heater technique was utilised. This allowed heat fluxes in the MW/m2 range to be applied to the modules. The results indicate that the concept may be a viable alternative heat sink candidate for first wall or divertor applications in a DEMO, but that further research is required to optimise certain aspects of the design.

A multiscale investigation was pursued in order to obtain the strain distribution and evolution during tensile testing both at the macro- and micro-scale for a diffusion bonded 316L stainless steel. The samples were designed for the purpose to demonstrate that the bond line properties were equal or better than the parent material in a sample geometry that was extracted from a larger component. The macroscopic stress-strain curves were coupled to the strain distributions using a camera-based 2D – Digital Image Correlation system. Results showed significant amount of plastic deformation predominantly concentrated in shear bands which were extended over a large region, crossing through the joint area. Yet it was not possible to be certain whether the joint has shown significant plastic deformation. In order to obtain the joints’ mechanical response in more detail, in situ micromechanical testing was conducted in the SEM chamber that allowed areas of 1x1 mm2 and 50x50 mm2 to be investigated.\ud \ud The size of the welded region was rather small to be accurately captured from the camera based DIC system. Therefore a microscale investigation was pursued where the samples were tested within an SEM chamber. Low magnification SEM imaging was utilised in order to cover a viewing area of 1 mm×1 mm while high magnification SEM imaging was employed to provide evidence of the occurrence of plastic deformation within the joint, at an area of just 50 μm×50 μm. The strain evolution over the microstructural level, within the joint and at the base material was obtained. The local strains were highly non-homogeneous through the whole test. Final failure occurred approximately 0.2 mm away from the joint. Large local strains were measured within the joint region, while SEM imaging showed that plastic deformation occurs via the formation of strong slip bands, followed by the activation of additional slip systems upon further plastic deformation which end up in additional slip bands to form on the surface. Plastic deformation occurred by slip and twinning mechanisms. Upon necking, significant out of plane deformations and slip deformation mechanisms were observed which suggested that plastic deformation was also happening at the last stages of damage evolution for the specific alloy. This was also evident from the large difference between the 600 MPa UTS stress value and the low stress values before final failure (which in many cases was below 30 MPa).

The drive of low-energy nuclear astrophysics laboratories is to study the reactions of importance to stellar burning processes and elemental production through stellar nucleosynthesis, over the energy range of astrophysical interest. As laboratory measurements approach the stellar burning window, the rapid drop off of cross-sections is a significant barrier and drives the need to lower background interference. The natural background suppression of underground accelerator facilities enables the extension of current experimental data to lower energies. An example of such reactions of interest are those thought to be sources of neutrons for the s-process, the major production mechanism for elements above the iron peak. The reactions 13 C(α,n)16 O and 22 Ne(α,n)25 Mg are the proposed initial focus of the new nuclear astrophysics accelerator laboratory (CASPAR) currently under construction at the Sanford Underground Research Facility, Lead, South Dakota

We report on the first measurement of 39Ar in argon from underground natural gas reservoirs. The gas stored in the US National Helium Reserve was found to contain a low level of 39Ar. The ratio of 39Ar to stable argon was found to be, 6 pages, 2 figures, 2 tables

Cross section measurements of the reactions ${}^{90,92}$Zr($p$,$\ensuremath{\gamma}$)${}^{91,93}$Nb were performed using the National Superconducting Cyclotron Laboratory Summing NaI(Tl) detector at the University of Notre Dame. These reactions are part of the nuclear reaction flow for the synthesis of the light $p$ nuclei. For the ${}^{90}$Zr($p$,$\ensuremath{\gamma}$)${}^{91}$Nb reaction the new measurement resolves the disagreement between previous results. For the ${}^{92}$Zr($p$,$\ensuremath{\gamma}$)${}^{93}$Nb reaction the present work reports the first measurement of this reaction cross section. Both reaction cross sections are compared to theoretical calculations and a very good agreement with the standard non-smoker model is observed.

A systematic study of the radiative proton capture reaction for all stable nickel isotopes is presented. The results were obtained using 2.0 - 6.0 MeV protons from the 11 MV tandem Van de Graaff accelerator at the University of Notre Dame. The \gamma-rays were detected by the NSCL SuN detector utilising the \gamma-summing technique. The results are compared to a compilation of earlier measurements and discrepancies between the previous data are resolved. The experimental results are also compared to the theoretical predictions obtained using the NON-SMOKER and SMARAGD codes. Based on these comparisons an improved set of astrophysical reaction rates is proposed for the (p,\gamma) reactions on the stable nickel isotopes as well as for the 56Ni(p,\gamma)57Cu reaction.

Neutrons produced by the carbon fusion reaction (12)C((12)C,n)(23)Mg play an important role in stellar nucleosynthesis. However, past studies have shown large discrepancies between experimental data and theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the first direct measurement that extends deep into the astrophysical energy range along with a new and improved extrapolation technique based on experimental data from the mirror reaction (12)C((12)C,p)(23)Na. The new reaction rate has been determined with a well-defined uncertainty that exceeds the precision required by astrophysics models. Using our constrained rate, we find that (12)C((12)C,n)(23)Mg is crucial to the production of Na and Al in pop-III pair instability supernovae. It also plays a nonnegligible role in the production of weak s-process elements, as well as in the production of the important galactic γ-ray emitter (60)Fe.