The objective of this section is to highlight selected test facilities where ongoing R&D and testing is underway for some of the LW-SMR concepts underdevelopment in the US. Since these LW-SMRs are essentially based on conventional LWR technology, the R&D is more applied than for the A-SMRs. Typically, in the development of a reactor concept one of the key testing facilities in demonstrating new concepts is a thermal hydraulics test facility or loop where essentially all of the non-nuclear testing can be performed in an integrated fashion to examine prototypical thermal hydraulic conditions such as operating flows, temperatures, pressures, pump performance, material performance, etc., where the heat is supplied via electrically heated fuel assemblies or some other means. This type of facility is summarized for each of the three following LW-SMR vendors: NuScale, m-Power, and Westinghouse.

In order to provide a consistent direction to long-term R&D activities the KAEC approved a long-term development plan in December 2008 for future nuclear reactor systems which include SFR, pyroprocess and VHTR. This long-term plan is implemented through nuclear R&D programs of the National Research Foundation, with funds from the Ministry of Education Science and Technology (MEST). The Korea Atomic Energy Promotion Commission (KAEPC) approved the modification of the plan in November 2011, reflecting the maturity of technology achieved hitherto and the budget condition. The modified plan includes a design development of the prototype SFR by 2017, its design approval and construction by 2020 and 2028, respectively as shown in Figure 15.3. The SFR Development Agency (SFRA) was organized in May 2012 to secure the budget and efficiently manage the SFR development project. According to the plan, KAERI, the main body responsible for the fast reactor development in Korea, is developing a conceptual design of the prototype SFR for completion developed in 2012. The prototype SFR development will be extended to the commercialization phase with its initialization around 2050.

For the development of pyroprocess, KAERI has established a PyRoprocess Integrated inactive DEmonstration (PRIDE) facility to produce the engineering data. The pyroprocessing technology capitalizes on the recovery of actinide elements from spent fuel for recycling and fissioning in SFRs for the purpose of burning long-lived radionuclides. The overriding goal of this R&D plan for pyroprocessing technology combined with SFRs is to develop a closed nuclear fuel cycle that is economically viable, resistant to diversion of nuclear materials for a nuclear weapons program, and that minimizes the generation of waste products, thereby efficiently increasing the capacity of a final spent fuel repository by approximately 100 times. In this fuel cycle, plutonium remains with other isotopes and impurities throughout the processes and cannot be chemically separated in a pure form, which reduces the risk of nuclear proliferation. Confining the final product in a hot cell also makes it far less open to misuse.

Figure 4.5 is a flow diagram that summarizes the various stages in establishing an optimized nuclear core design that have been described above. This is an involved and rigorous process that typically takes several weeks of man effort and iteration. The overall timescales are heavily dependent on the experience of the designers, the tools at their disposal (including consideration of set-up time, run time, ease of iteration perhaps using graphical interfaces), the experience-base of previous core analysis of the same reactor design, and the nuances of the reactor design itself.

NuScale/SMR-160 Westinghouse SMR

37 fuel assemblies 89 fuel assemblies

Figure 4.4 Comparison of core size for a range of iPWRs and a modern large PWR.

It should be noted that this is not the end of the design and analysis phase for this reactor. From here, interfaces with other elements of the design team begin (e. g., transient analysis, thermal hydraulics, mechanical design and fuel performance), and additional iterations may be required prior to initiating the go-ahead to start manufacturing the fuel (usually approximately 12 to 18 months prior to refueling).

NSSS temperature instrumentation is an open field for both new tech and older devices. The typical NSSS temperature measurements in large PWRs are:

• boric acid tank temperature;

• let-down heat exchanger outlet temperature;

• let-down orifice safety valve temperature;

• residual heat removal (RHR) loop return temperature;

• pressurizer liquid temperature;

• pressurizer vapor temperature;

• pressurizer surge line temperature;

• pressurizer spray line temperature;

• volume control tank temperature;

• seal water injection temperature;

• chiller related temperatures;

• charging temperature;

• pressurizer relief tank temperature;

• reactor vessel flange leak-off temperature.

Depending on design, iPWRs may require some of the same measurements. Some of these temperature measurements will originate inside the reactor vessel and will need to have a very reliable and verified temperature device pedigree. This need would tend to indicate the traditional RTD and thermocouple devices, although new technology solutions should not be abandoned, even for the harsher environments.

Some of the temperature measurements will be made away from the harsh environment that exists in or near the reactor vessel, and could be an application for new technologies such as MEMs and/or fiber technology. These technologies may offer additional benefits such as easy maintainability, use-and-throw-away devices, better accuracy, more and distributed measurements, and diagnostic capabilities. The new technology is likely to be cheaper, easier to purchase, and more accurate. These economic and engineering benefits may outweigh the pedigree of the traditional

RTD, but will have to be evaluated on a case-by-case basis. Section 6.2.4 identifies some of the new technology options for temperature measurements.

In the past it was easy to classify HSIs as either input (keyboards, switches, mice, etc.) or output devices (displays, gauges or printers). With the convergence of modern HSIs it is no longer that simple — many devices are now combining input and output on the same device (tablets, smartphones, etc.). Even distinguishing between hardware and software is becoming increasingly difficult because many devices have embedded software and the device is rather considered in terms of the functions that the user can perform with it. It is now more sensible to classify HSIs in terms of the mode of interaction, or ‘interaction modality’.

Interaction modality can be described as a means of communication between the human and the system or device. The term ‘communication’ implies the process of exchanging information between the human and the system primarily through the visual, auditory, speech and touch senses. All HSI technologies can be categorised according to the human sense for which the device is designed. Most devices rely on only two or three of the most common senses used to obtain information from the environment: vision, hearing and touch. Some technologies can combine these senses into one device; more advanced devices can also enable interaction through other senses, such as speech, smell, motion or event kinaesthesia or proprioception. (Kinesthesia is the subliminal awareness of the position and movement of parts of the body by means of proprioceptory organs in the muscles and joints; Hale, 2006.) When multiple modalities are available, that is, when more than one sense can be used for some tasks or parts of tasks, the system is said to offer multimodal interaction functions. A system that is based on only one modality is called uni-modal.

When technology types are categorised in terms of the human sense for which they are designed, it is possible to classify interaction modality as either:

• input — perceiving information produced by the system through a device that allows a human to observe it by means of one or more senses, such as visual, auditory, or tactile; or

• output — performing an action with a specific device that would cause the system to perform a function. This output in turn becomes the input to the system in the form of discrete actuations (for example, key presses) or continuous actions (using a mouse or similar device to select or manipulate objects on a display).

Based upon primary senses used in interacting with a device, HSIs can now be divided into three categories: visual, auditory and mechanical motion. Devices associated with these modalities would be either input or output devices (that is, devices accepting user input or providing output to the user), or hybrid devices where both input and output are combined in the same device.

In the control room and any of the operational domains described earlier, a multimodal interface acts as a facilitator of HSI via two or more modes of input that go beyond the traditional keyboard and mouse. Multimodal HSIs can incorporate different combinations of speech, gesture, gaze, touch and other non-conventional modes of input. Touch and gesture have become the most commonly supported combinations of input methods, as seen in the rapid development of tablets and smartphone devices (Oviatt, 2003). These are already making an appearance in control rooms for non-control applications, like procedure following and calculations, but they are likely to become much more prominent in future NPPs, provided that they can be proven reliable.

These combined modalities open up a vast world of possibilities to interact with the work environment. It is already possible, for example, to interact with displays, not only with both hands, but also with all fingers simultaneously or by various combinations of ‘hand waving’.

Based on the description above, it is now possible to define four classes of technology: visual technologies for visual perception, audio technologies for audio perceptions, mechanical control devices for providing input to a system, and hybrid devices for multimodal interaction.

9.2.1 The basic evaluation approach

The basic evaluation approach developed by the Generation IV International Forum’s (GIF) Working Group on Proliferation Resistance and Physical Protection comprises definition of a set of threats or challenges, evaluation of the system’s response to these challenges, and expression of outcomes in terms of measures.

A progressive approach permits broad application of the PR&PP evaluation to SMRs. SMRs assessed for PR&PP can range from systems under development to fully designed and operating systems. The scope and complexity of the assessment should be appropriate to the level of detailed design information available and the level of detail with which the threats can be specified.

The main steps to be performed in each component of the approach are illustrated in Figure 9.2 and discussed in the following sections.

Figure 9.2 Framework for the PR&PP evaluation methodology.

On account of the investment modularization, multiple SMRs offer greater stability in their financial performance, faced with unfavourable boundary conditions: lower average invested capital accounts for lower interest capitalization and lower risk of financial default. All these features are particularly valuable in the so-called ‘merchant’ scenarios, based on the rules of competition in liberalized electricity and capital markets, and characterized by the high cost of financing. Analysis and simulations in these conditions show that the gap in cost-effectiveness becomes narrower. With a high cost of equity and increasing cost of debt, there is a point where economic performance of SMRs overtakes that of LRs (Figure 10.18), on account of SMRs’ capability to limit IDC escalation.

When deterministic and predictable scenarios are considered, assuming the construction schedule is respected, LRs normally show better economic performance based on economy of scale and lower overnight construction costs: PI and IRR are higher and, accordingly, generation cost is lower. But when scenario conditions become stochastic and uncertainties are included in the analysis, multiple SMRs may record higher mean profitability than LRs. In particular, assuming the possibility of a stochastic delay event affecting the construction schedule of both LR and multiple SMR projects, the calculated profitability distribution shows more favourable data dispersion for SMRs toward positive values, meaning that SMRs have a greater chance of performing better in terms of profitability than LRs (Figure 10.19; Boarin and Ricotti, 2011a). A sensitivity analysis on the main economic and financial parameters shows that SMRs have a better capability to perform in changed scenario conditions (Figure 10.20).

2.0

1.5

о

1.0

0.5

0

Shaped metal deposition (SMD) is a wire-based additive manufacturing process based on a three-dimensional tungsten-inert gas (TIG) welding system. SMD can produce components in nuclear-grade materials, without the need for special tooling, in a relatively short lead-time when compared to forging or casting routes. The SMD process was developed and patented by Rolls-Royce and was subsequently licensed for use and further development by the University of Sheffield.

The SMD system employs cold wire TIG deposition, using a tungsten cathode to weld the selected material in an inert argon atmosphere to prevent the substrate, electrode and part from reacting with atmospheric gasses. This is a very stable process, chosen for the maturity of process control. The TIG welding head is attached to a six-axis robot and produces weld on to a rotating turntable base. Weld material is built up in an additive way and the construction is monitored throughout the entire process to ensure that the weld parameters are maintained and a robust final component is produced.

Because SMD is a weld-based technique, accuracy in fabrication of the component depends on the thermal stresses induced during the welding process. Control of the thermal transfer during weld deposition can allow reduction in the final component residual stress and hence the distortion. Simulation modelling tools can be employed to predict the distortion levels and this can be fed back in to the SMD process during the deposition phase.

The wall thickness of the component is controlled by the current, travel speed and wire feed rate and also to some extent by the wire thickness. The travel speed is the product of the rotation rate on the turntable, and the rate of movement of the robotic head — the faster the travel speed, the thinner the wall thickness, but the limiting factor is the ability to maintain a robust arc at the weld head.

Cylindrical components are easily produced on the turntable but with the multi­axis robotic head, there is opportunity to produce more complex forms. One such form is shown in Figure 12.6 where two cylindrical components were formed as a prototype exercise.

The complete component is essentially a 100% weld and unlike the previous additive manufacturing systems which use metal powder to produce the component, SMD components do require post-processing heat treatment and final machining to attain the design-intent form. The SMD process is also well positioned to provide

Figure 12.6 Picture of SMD trial piece.

a route for adding material to an existing component such as a large vessel with a boss or nozzle. As a deployable SMD system, this solution could allow for the fabrication of more simple cylindrical forms through the traditional forging route and adding on the external features through an SMD-type technique.

Synthetic diesel may be produced from coal or natural gas through the Fischer Tropsch process. The Fischer Tropsch reaction converts syngas, hydrogen, and carbon dioxide to a liquid fuel by using iron or cobalt-based catalysts. The processes for coal-to-diesel and natural gas-to-diesel differ both in syngas production and diesel production.

For the nuclear integrated cases, nuclear-generated heat and electricity are applied to the HTSE process to produce hydrogen for the coal case. Nuclear heat is applied to the reforming, CO2 and sulfur removal, hydrotreating, and product upgrading processes for the natural gas case. Nuclear integration provides significant reduction in coal consumption and CO2 emissions and modest decreases in natural gas consumption [3, 21].

15.3.1 SFR system

15.3.1.1 Phase 1

It has been recognized nationwide that a fast reactor system is one of the most promising nuclear options for electricity generation with an efficient utilization of uranium resources and a reduction of the radioactive waste from NPPs. In response to this recognition, the SFR technology development efforts in Korea commenced in June 1992 with the Korea Atomic Energy Commission’s approval of a national mid — and long-term nuclear R&D program on an SFR with the objective of developing basic key technologies for fast reactors which can meet the goals of a sustainability, safety and economic competitiveness.

At the early stages of its development, the research efforts focused on basic R&D on core neutronics, thermal hydraulics and sodium technology, with the aim to enhance the basic liquid metal-cooled reactor (LMR) technology capabilities. Since 1977, the basic key technology development for an SFR has been continued, and the design concepts of KALIMER-150 and KALIMER-600 have been successfully achieved. In 2008, the Korea Atomic Energy Commission (KAEC) approved a long­term advanced SFR R&D plan which aims at the construction of an advanced SFR prototype plant by 2028 in association with the pyroprocess technology development. The SFR R&D program is shown in Figure 15.3. To support this R&D plan, KAERI has been focusing on the development of an advanced design concept of a burner reactor that satisfies the future goals of safety, economics, sustainability and proliferation resistance. In addition, R&D activities have been developed to achieve a safe and reliable advanced SFR design, such as large-scale sodium thermal-hydraulic test facilities, a supercritical CO2 Brayton cycle system, an under-sodium viewing technique, metal fuel and a safety analysis code.