There are actually dozens of small modular reactor (SMR) and microreactor designs being developed by totally different firms all over the world, and among the work has been happening for many years. But, solely two designs have truly been constructed and put into business operation. POWER takes a better have a look at each of them.
Many nuclear energy supporters have lengthy thought small modular reactors (SMRs) would revolutionize the trade. Advocates count on SMRs to shorten building schedules and produce prices down via modularization and manufacturing unit building. They usually cite quite a few different advantages that make SMRs appear to be no-brainers, and but, solely two SMR designs have ever been constructed and positioned in business operation.
The Worldwide Atomic Vitality Company (IAEA) publishes booklets biennially on the standing of SMR expertise. Within the IAEA’s most up-to-date booklet, it notes 25 land-based water-cooled SMRs and one other eight marine-based water-cooled designs are underneath growth globally. It additionally lists 17 high-temperature gas-cooled SMRs, eight liquid-metal-cooled fast-neutron-spectrum SMRs, 13 molten-salt SMRs, and 12 microreactors. When you do the maths, that’s 83 SMR designs underneath growth, however solely the KLT-40S and HTR-PM are literally operational.
KLT-40S
The KLT-40S is a pressurized water reactor (PWR) that was developed in Russia. It’s a sophisticated model of the KLT-40 reactor, which has been utilized in nuclear-powered icebreakers. The primary KLT-40S models, and, to this point, the one two of those models to enter business operation, had been deployed within the Akademik Lomonosov—the world’s first purpose-built floating nuclear energy plant (FNPP, Determine 1).
1. The floating nuclear energy plant (FNPP) Akademik Lomonosov is provided with two KLT-40S reactors. The FNPP’s energy capability is 70 MW, whereas the warmth capability is 50 Gcal/hr. The plant’s size is 140 meters, width is 30 meters, and displacement is 21,500 tons. Courtesy: Rosatom
Primary Design Options. The KLT-40S has a capability of 150 MWth or 35 MWe per module. Its nuclear steam provide system working stress is 12.7 MPa (1,842 psig). The reactor core inlet and outlet coolant temperatures are 280C and 316 C (536F and 601F), respectively. The unit makes use of uranium dioxide (UO2) pellets in silumin matrix for gasoline with an enrichment of 18.6%. The core comprises 121 gasoline assemblies and operates on a 30- to 36-month refueling cycle. The design life is 40 years.
The reactor has a modular design with the core, steam mills (SGs), and predominant circulation pumps linked with brief nozzles. The reactor has a four-loop system with pressured and pure circulation, a pressurized main circuit with canned motor-pumps and leak-tight bellow-type valves, a once-through coiled SG, and passive security programs.
The KLT-40S’s thermal-hydraulic connections embody an exterior pressurizer, accumulators, and separation warmth exchanger. The pressurizer just isn’t an integral a part of the reactor system, and on this design, it’s fashioned by a number of separate tanks, designed to accommodate modifications in coolant quantity, particularly throughout reactor startup.
The core is cooled by water flowing from the core backside to the highest, in accordance with typical PWR core movement patterns. Nonetheless, movement patterns between the core shroud and the reactor stress vessel (RPV) inside partitions differ considerably from typical exterior loop PWR configurations. As soon as scorching coolant exits the highest of the core and enters any of the a number of SGs, it makes use of coaxial hydraulic paths whereby the hot and cold legs are basically surrounding each other. As scorching coolant enters the SG, it begins to switch thermal power with the fluid circulating within the secondary loop (secondary facet of the SGs).
Deployment Particulars. The development of a FNPP was first broached in 1998. The Russian Federation Ministry of Pure Sources authorised the environmental influence evaluation for the undertaking in 2002. After a number of delays, the undertaking was revived in 2006, however nonetheless moved at a reasonably gradual tempo. It wasn’t till 2012 that Pevek, Chukotka, in Russia’s Far East, was chosen as the positioning for remaining set up and Baltiysky Zavod JSC took cost of the development, set up, testing, and commissioning for the primary floating energy unit (FPU).
Building and testing of the FPU was accomplished in 2017 on the Baltic shipyard. In Could 2018, the vessel was towed 4,000 kilometers (km), round Finland and Sweden, to Murmansk, finishing the primary leg of its journey to Pevek. Gas loading was accomplished in Murmansk in October 2018. First criticality was achieved in November 2018, then in August 2019, the vessel launched into the second leg of its journey—a distance of 4,700 km—towed by two tugboats to the Arctic port city of Pevek, the place it was linked to the grid on Dec. 19, 2019. Akademik Lomonosov was absolutely commissioned on Could 22, 2020, and it at present offers warmth to the city of Pevek and provides electrical energy to the regional Chaun-Bilibino energy system.
HTR-PM
On Dec. 6, 2023, China Nationwide Nuclear Corp. introduced it had commenced business operation of the high-temperature gas-cooled modular pebble mattress (HTR-PM) reactor demonstrator. The HTR-PM undertaking was constructed at a web site in Rongcheng, Shandong Province, roughly halfway between Beijing and Shanghai in jap China. Touted because the world’s first commercially operational modular nuclear energy plant with fourth-generation nuclear expertise, the achievement marked an essential milestone, transitioning the expertise from experiments to the business market.
2. Gas loading on the Shidaowan high-temperature gas-cooled modular pebble mattress (HTR-PM) in China started within the spring of 2021. It concerned placing 870,000 spherical tri-structural isotropic (TRISO) particle gasoline parts into the 2 small reactors that may drive a single 210-MWe turbine. Courtesy: China Nationwide Nuclear Corp.
Primary Design Options. The HTR-PM has a capability of two x 250 MWth or 210 MWe. Every reactor is loaded (Determine 2) with greater than 400,000 spherical gasoline parts, or pebbles, every 60 millimeters in diameter, which is roughly the scale of a tennis ball. Every pebble comprises about seven grams of uranium gasoline enriched to eight.5%.
Every HTR-PM module contains an RPV, graphite, carbon, and metallic reactor internals; a steam generator; a predominant helium blower; and a scorching gasoline duct. The first helium coolant works at a stress of seven.0 MPa (1,015 psig) with a rated mass flowrate of 96 kilograms/second (761,918 lbm/hr). Helium coolant enters the reactor within the backside space contained in the RPV with an inlet temperature of 250C (482F). Helium coolant flows upward within the facet reflector channels to the highest reflector degree the place it reverses movement course and flows into the pebble mattress in a downward movement sample.
Bypass flows are launched into the gasoline discharge tubes to chill the gasoline parts and into the management rod channels for management rod cooling. Helium is heated within the lively reactor core, then blended to a mean outlet temperature of 750C (1,382F). It then flows to the steam generator. The secondary steam regular working stress is 13.25 MPa (1,922 psig) and temperature is 567C (1,053F) on the steam turbine entrance.
The HTR-PM makes use of a steady gasoline loading and discharging system. The gasoline parts drop into the reactor core from the central fuel-loading tube and are discharged via a gasoline extraction pipe on the core backside. Subsequently, the discharged gasoline parts move a burnup measurement gadget one after the other. If a gasoline sphere reaches the goal burnup, it’s discharged to the spent gasoline storage tank, in any other case, it’s re-inserted into the reactor to move via the core once more.
Deployment Particulars. The HTR-PM design has a protracted historical past, which started in 1992 when the Chinese language authorities authorised the development of the 10-MWth pebble-bed high-temperature gas-cooled check reactor (HTR-10) at Tsinghua College’s Institute of Nuclear and New Vitality Know-how (INET). Because the HTR-10 unit neared completion in 2001, the HTR-PM undertaking was launched. HTR-10 finally achieved full energy operation in 2003, and INET subsequently accomplished many experiments on the unit to confirm essential security options and validate the design.
In the meantime, the primary concrete for the HTR-PM demonstration energy plant was poured on Dec. 9, 2012. To help first-of-a-kind (FOAK) gear manufacturing and design licensing, large-scale engineering check amenities had been constructed. Gas plant building began in 2013. The next yr, qualification irradiation checks of gasoline parts had been accomplished.
The civil work for the nuclear island buildings was accomplished in 2016 with the primary of two reactor stress vessels put in in March that yr. The gasoline plant reached its anticipated manufacturing capability in 2017. Startup commissioning and testing of the first circuit had been completed by the top of 2020. The HTR-PM achieved first criticality in September 2021, and was finally grid linked on Dec. 20, 2021.
Spotty Outcomes at Finest
Whereas it’s laudable that these SMRs—the KLT-40S and HTR-PM—have been positioned in business operation, their efficiency since coming into service has come underneath hearth. In The World Nuclear Trade Standing Report 2023 (WNISR), a Mycle Schneider Consulting Mission, co-funded by the German Federal Ministry for the Surroundings, Nature Conservation, Nuclear Security, and Shopper Safety, it says each designs have operated at low capability components not too long ago.
In regards to the Chinese language HTR-PM, the WNISR says, “Between January and December 2022, the reactors operated for less than 27 hours out of a potential most of 8,760 hours. Within the subsequent three months, they appear to have operated at a load issue of round 10 %.” The Russian models’ efficiency has been practically as dismal. “The working data of the 2 KLT-40S reactors have been fairly poor. In line with the IAEA’s PRIS [Power Reactor Information System] database, the 2 reactors had load components of simply 26.4 and 30.5 % respectively in 2022, and lifelong load components of simply 34 and 22.4 %. The explanations for the mediocre power-generation efficiency stay unclear,” the report says.
In the meantime, the guarantees of shortened timelines and decrease prices weren’t borne out by these initiatives. “The expertise to this point in establishing these two SMRs in addition to estimates for reactor designs like NuScale’s SMR present that these designs are additionally topic to the historic sample of value escalations and time overruns. These value escalations do make it even much less probably that SMRs will turn into commercialized, because the collapse of the Carbon Free Energy Mission involving NuScale reactors in the US illustrated,” the WNISR says.
With that stated, it must be famous that these had been FOAK initiatives, and people not often progress with out hitches. If the teachings realized from these two accomplished dual-unit SMRs will be parlayed into future successes, the initiatives might but show to be extremely beneficial.
—Aaron Larson is POWER’s government editor.