Small modular nuclear reactor reaches criticality in first test

小型模块化核反应堆在首次测试中实现临界

Just over a year ago, the Trump Administration issued an executive order meant to accelerate the development of nuclear power in the US. While an entire startup ecosystem has developed around the use of different—and typically smaller—reactor designs, only one of them has been fully licensed so far, and there are no plans to actually build any instances of that design.

一年多前，特朗普政府发布了一项行政命令，旨在加速美国核能的发展。尽管围绕使用不同（且通常更小）的反应堆设计已经形成了一个完整的初创企业生态系统，但迄今为止只有其中一个获得了全面许可，且目前尚无建造该设计实例的计划。

The executive order directed the Department of Energy to have three different reactor designs reach criticality in a bit over a year. On Thursday, a startup called Antares announced that a test reactor it had placed at the Idaho National Laboratory had reached criticality, making it the first new design to cross this threshold. Criticality means that the nuclear reactions inside the hardware had become self-sustaining; it does not mean the reactor had started to generate power.

该行政命令指示能源部在一年多一点的时间内，让三种不同的反应堆设计实现临界。周四，一家名为 Antares 的初创公司宣布，其放置在爱达荷国家实验室的测试反应堆已实现临界，成为首个跨越这一门槛的新设计。“临界”意味着硬件内部的核反应已实现自持；但这并不意味着反应堆已经开始发电。

Antares is one of a number of companies that is basing its design on a new fuel system called TRISO that takes some of the complexity and safety out of the reactor design and places them in the fuel design. The fuel design is based on tiny pellets with a uranium oxide core. The pellets are surrounded by several layers of carbon that can moderate the energy of both the neutrons and lighter nuclei that are released by fission reactions. All of that is encased in a hard ceramic shell that’s designed to withstand the highest temperatures that can be produced by the encased uranium.

Antares 是众多基于一种名为 TRISO 的新型燃料系统进行设计的公司之一。该系统将反应堆设计中的部分复杂性和安全性要求转移到了燃料设计中。这种燃料设计基于带有氧化铀核心的微小颗粒。颗粒被几层碳包裹，这些碳可以调节裂变反应释放出的中子和较轻原子核的能量。所有这些都被封装在一个坚硬的陶瓷外壳中，该外壳旨在承受封装铀所能产生的最高温度。

As long as your reactor can keep the TRISO pellets contained, then there should be no risk of meltdown or even the release of the most dangerous isotopes produced from the reactions. There are still some safety concerns, as neutrons will still escape and can potentially convert some of the surrounding material into unstable isotopes. But the Antares design surrounds the TRISO with a graphite sheath, which should slow most of these neutrons down.

只要反应堆能将 TRISO 颗粒保持在受控状态，就不会有堆芯熔毁的风险，甚至不会释放反应产生的最危险的同位素。当然，仍存在一些安全顾虑，因为中子仍会逃逸，并可能将周围的一些材料转化为不稳定的同位素。但 Antares 的设计在 TRISO 周围包裹了一层石墨护套，这应该能减缓大部分中子的速度。

To mitigate non-radioactive risks, the Antares design uses sodium to take heat from the reactor to a heat exchanger. The heat is transferred to pressurized nitrogen, which then drives a turbine in a closed Brayton cycle setup. At the moment, Antares is just testing what it calls a Mark 0 reactor, which is not connected to the power-generation portion. Instead, it’s being used to validate the company’s modeling of the physical conditions in its reactors and generate safety data that can be used during licensing applications.

为了降低非放射性风险，Antares 的设计使用钠将热量从反应堆传导至热交换器。热量随后被传递给加压氮气，进而驱动闭式布雷顿循环装置中的涡轮机。目前，Antares 仅在测试其所谓的“Mark 0”反应堆，该反应堆尚未连接到发电部分。相反，它被用于验证公司对反应堆物理条件的建模，并生成可用于许可申请的安全数据。

Attempts to run the entire system, including electrical generation, are expected to happen next year. While the work was done at a Department of Energy Lab, the company is working with the Department of Defense’s Project Pele program for developing a mobile nuclear reactor. The company has also received support from NASA.

包括发电在内的整个系统的运行测试预计将于明年进行。虽然这项工作是在能源部实验室完成的，但该公司目前正与国防部的“Pele 项目”合作，共同开发移动式核反应堆。此外，该公司还获得了美国国家航空航天局（NASA）的支持。