| Nuclear power Design evolution
Another striking feature of the U-Battery illustrated by the mock-up is the innovative design of the cross vessel duct, which is in the form of a U-tube, similar to an umbrella handle, rather than the straight pipe normally found in small modular high temperature reactor designs. The cross vessel duct is a co-axial contraflow pipe that connects the reactor pressure vessel module with the intermediate heat exchanger module, transferring hot helium from the reactor to the heat exchanger and returning cooled helium to the reactor. Onerous operating conditions, including the high temperatures, mean that the duct needs to be replaceable, perhaps at the mid-life of the U-Battery plant.
“The U-shaped duct, although simplistic and unconventional at first glance, actually yields significant advantages over more conventional straight designs”, notes Tom Arnold, technical lead for Cavendish Nuclear’s delivery of the U-Battery AMM project. “The main benefit of this profile is that it can be installed from a single side, without needing to move the two vessels or their supporting modules, thus simplifying and enabling a modular installation approach. Other benefits include the fact that thermal expansion and the resulting stresses will be in a single orientation and separation forces between the vessels under thermal or seismic loading will be reduced significantly compared to the more traditional straight pipe connection.” In addition to the Advanced Manufacturing and Materials programme, U-Battery is participating in Phase 2 of the UK government’s Advanced Modular Reactor competition. In July 2020, it was one of three vendors to progress from Phase 1 to Phase 2 of the competition (the others being Tokamak Energy (compact fusion employing spherical tokamak with high-temperature- superconductor magnets) and Westinghouse (450 MWe lead cooled fast reactor) and was awarded £10 million of funding to initiate design and development work.
A key future milestone for U-Battery is finalisation of work funded via this AMR competition award, with a target date of end June 2022. This will provide U-Battery with a proven conceptual design and means it will be ready to start front-end engineering design. And, in the UK, depending on advice from ONR/EA, the hope is it will be able to enter the Generic Design Assessment process.
The design is continuing to evolve. For example, an option now under consideration is to employ helium in the secondary circuit (in a Brayton cycle, directly driving a Rolls-Royce designed gas turbine). The current design envisages helium in the primary circuit and nitrogen in the secondary.
Markets envisaged
With its high output temperature, over 700°C, the U-Battery is potentially a useful source of decarbonised process heat and one important potential market envisaged for the technology by its developers is the decarbonisation of hard- to-abate industries, the “foundation industries”, eg, cement, metal and paper. “We think this is a
www.modernpowersystems.com | November/December 2021 | 49
Right: Primary circuit circulator, intermediate heat exchanger and cross vessel duct, seen through viewing window in the simulated operating floor
sweet spot for us”, says Steve Threlfall. “Sizable prospective markets” have been identified in both the UK, where U-Battery can be used to power heavy industrial sites, and in Canada, where it can be deployed at extractive industries/mining sites and in off-grid remote communities.
The potential applications envisaged in the UK and Canada also exist elsewhere around the world, and other focus areas for U-Battery include Japan, Poland and India, for example. High temperature reactors promise an efficient route to low-carbon hydrogen production and this is attracting increasing interest.
Size comparisons
U-Battery focus areas
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