Small Modular Reactor Vessel Manufacture/Fabrication Using PM-HIP and Electron Beam Welding Technologies

Abstract

Many of the same manufacturing/fabrication technologies that were employed for light water reactors (LWR) plants built 30-50 years ago are also being employed today to build advanced light water reactors (ALWRs). Manufacturing technologies have not changed dramatically for the nuclear industry even though higher quality production processes are available which could be used to significantly reduce overall component manufacturing/fabrication costs. New manufacturing/fabrication technologies that can accelerate production and reduce costs are vital for the next generation of plants (Small Modular Reactors (SMR) and GEN IV plants) to assure they can be competitive in today’s and tomorrow’s market. This project has been assembled to demonstrate and test several of these new manufacturing/ fabrication technologies with a goal of producing critical assemblies of a 2/3rds scale demonstration SMR reactor pressure vessel (RPV). Through use of technologies including: powder metallurgy-hot isostatic pressing, (PM-HIP), electron beam welding, diode laser cladding, bulk additive manufacturing, advanced machining, and elimination of dissimilar metal welds (DMWs), EPRI, the US Department of Energy, and the UK-based Nuclear-Advanced Manufacturing Research Centre (Nuclear-AMRC) (together with a number of other industrial team members) will seek to demonstrate the hypothesis that critical sections of an SMR reactor can be manufactured/fabricated in a timeframe of less than 12 months and at an overall cost savings of >40% (versus today’s technologies). Major components that will be fabricated from PM-HIP include: the lower reactor head, upper reactor head, steam plenum, steam plenum access covers, and upper transition shell. The project aims to demonstrate and test the impact that each of these technologies would have on future production of SMRs, and explore the relevance of the technologies to the production of ALWRs, SMRs, GEN IV, Ultra-supercritical fossil, and supercritical CO2 plants. The project, if successful, may accelerate deployment of SMRs in both the USA and UK, and ultimately throughout the world for power production. Introduction Over the past decade, EPRI, DOE, Nuclear-AMRC, and various OEMs and vendors have investigated a number of advanced technologies to support the manufacture of small modular reactors (SMRs). Advanced technologies including: electron beam welding for thick sections, powder metallurgy-HIP, diode laser cladding, dissimilar metal joining, and cryogenic machining Hot Isostatic Pressing – HIP‘17 Materials Research Forum LLC Materials Research Proceedings 10 (2019) 224-234 doi: http://dx.doi.org/10.21741/9781644900031-29 225 are just a few of the examples technologies. Many of these technologies are now mature and can be readily demonstrated from production of SMRs. In early 2016, EPRI and Nuclear-AMRC began assembly of a large project wherein the two organizations planned to demonstrate several of these advanced technologies aimed at the manufacture and fabrication of a 2/3rds scale SMR vessel. Their efforts were met with tremendous interest from industry and with co-sponsorship by the US Department of Energy (DOE) through its Advanced Methods for Manufacturing (AMM) program. The collaborative project began in earnest in early 2017 and is focused on developing/demonstrating three key advanced manufacturing technologies: electron beam welding for thick section components, powder metallurgy-HIP, and diode laser cladding, among a number of other manufacturing/fabrication technologies. The technologies are being demonstrated using NuScale Power’s 50MWe (160MWth) SMR design. The project aims to demonstrate and test the impact that each of these technologies would have on future production of SMRs, and explore the relevance of the technologies to the production of ALWRs, SMRs, GEN IV, Ultra-supercritical fossil, and supercritical CO2 plants. The project, if successful, may accelerate deployment of SMRs in both the USA and UK, and ultimately throughout the world for power production. Project Objectives Three key objectives were identified for this project. These include:  Develop and demonstrate advanced manufacturing and fabrication technologies to rapidly accelerate the deployment of SMRs  Develop/demonstrate new methods for manufacture/fabrication of a Reactor Pressure Vessel (RPV) which could lead to production of a vessel in under 12 months.  Eliminate 40% of the costs of production of an SMR RPV, while reducing the overall schedule by up to 18 months. These three objectives formed the basis formed for the entire project. Large Component Manufacture As described above, the NuScale Power reactor pressure vessel design, a 50MWe (160MWth), was selected for demonstration of various advanced manufacturing technologies at a 2/3rds scale. The NuScale Power RPV design was selected based upon its size and on the basis that it appears to be very near production. The RPV is shown in Figure 1 and consists of 8 major sections. In the current project, two assemblies, upper and lower (Figures 2 and 3), will be demonstrated. These two assemblies were selected based on the premise that the two assemblies would demonstrate many of the advanced manufacturing/fabrication technologies required for construction of an SMR and that assembly of the middle section would simply be redundant with regards to demonstrating these technologies. Manufacture of the key components for the reactor vessel includes both conventional forging and PM-HIP. The breakdown of the key A508 low alloy steel components are as follows: PM-HIP (A508, Grade 3, Class 1) • Lower reactor head • Upper reactor head