In 2018, nuclear energy generated 55% of United States’ and one third of the world’s carbon free electricity, making nuclear energy a key tool in efforts to mitigate climate change before 2050. However, the current nuclear technology, light water reactors (LWRs), is limited to 300°C, so it cannot be used to decarbonize industrial process heat which accounts for 12% of US greenhouse gas emissions. High temperature gas reactors (HTGRs) can meet the high temperature demand with carbon free nuclear heat. The estimated cost of HTGRs, such as the Next Generation Nuclear Plant (NGNP), are even higher than state-of-the-art LWRs. In this paper, we expanded our nuclear cost estimating tool to include HTGRs and find that the NGNP overnight capital costs were 32% higher than an advanced LWR per unit capacity. The higher cost will naturally result in larger risk to cost overrun as recently experienced by larger LWRs in western nations. With a design-to-build mindset to minimize cost and construction risk, we introduce the horizontal, compact HTGR (HC-HTGR). The reactor core and steam generator are mounted horizontally on rails and in-line with one another, decreasing the size of the reactor building relative to the power capacity four times when compared to traditional HTGRs. The HC-HTGR reduced overnight civil structure costs by 42%, indirect costs by 38%, and total capital costs by 20% from NGNP. We discussed the required engineering of new systems for the HC-HTGR including vessel supports, the reactor cavity cooling system, and steam generator design. Finally, we estimated the fuel and operations costs of the HC-HTGR, and a survey of low-carbon industrial process heat technology showed the HC-HTGR can deliver a highly competitive levelized cost of heat in the range of $6.13–12.48/GJ.

2018 年，核能产生了美国 55% 和世界三分之一的无碳电力，使核能成为 2050 年之前减缓气候变化的关键工具。 然而，目前的核技术，轻水反应堆 (LWR) , 限制在 300°C，因此它不能用于对占美国温室气体排放量 12% 的工业过程热量进行脱碳。高温气体反应堆（HTGRs）可以通过无碳核热满足高温需求。HTGR 的估计成本，例如下一代核电站 (NGNP)，甚至高于最先进的 LWR。在本文中，我们扩展了我们的核成本估算工具以包括 HTGR，并发现 NGNP 隔夜资本成本比每单位容量的先进 LWR 高 32%。更高的成本自然会导致更大的成本超支风险，正如西方国家大型轻水堆最近所经历的那样。本着从设计到建造的理念，最大限度地降低成本和施工风险，我们推出了卧式紧凑型 HTGR (HC-HTGR)。反应堆堆芯和蒸汽发生器水平安装在轨道上并相互成一直线，与传统的高温气冷堆相比，反应堆建筑的尺寸相对于功率容量减少了四倍。HC-HTGR 将 NGNP 的隔夜土木结构成本降低了 42%，间接成本降低了 38%，总资本成本降低了 20%。我们讨论了 HC-HTGR 新系统所需的工程设计，包括容器支架、反应堆腔体冷却系统和蒸汽发生器设计。最后，我们估算了 HC-HTGR 的燃料和运行成本，