| NEWS


United Kingdom NNL investigates graphite oxidation New research from the UK National Nuclear Laboratory and the University of Liverpool uses a novel technique to investigate how thermal oxidation affects the structure of nuclear graphite so that nuclear reactors can be engineered to operate for longer. The researchers examined the porosity of superfine-grained nuclear graphite and linked this to a chemical change known as thermal oxidation. They focussed on the very high temperatures some advanced reactors, known as High Temperature Reactors (HTR), will produce. The findings can be used to design efficient nuclear reactors that can last for much longer than the original fleet. Nassia Tzelepi, Senior Fellow at NNL


explained that thermal oxidation is one of the two mechanisms in HTR graphite components that can affect the performance of the reactors. “Good understanding of its evolution and the effect on the graphite properties is required to qualify a graphite for use in an HTR.” In a high temperature gas reactor (HTGR) helium gas is used as a coolant, reaching temperatures of more than 700 °C. Helium, even after being purified, contains substances such as air or moisture. These impurities, combined with the high temperatures, can cause the graphite to oxidise over the 40 to 60-year life of a reactor. Oxidation can change the porosity of the


graphite, a key characteristic that affects its performance. The process is complex. As with many other composite materials, both the manufacturing process and the type of materials play a role in the properties of the final product. According to Tzelepi, “Every graphite is


different depending on the raw materials and how it’s manufactured. We wanted to know what makes grades of graphite with seemingly the same attributes behave differently under thermal oxidation.” Tzelepi’s team focussed their study on superfine grained graphite with an average grain size of 10-120 micrometres. The overall depth of oxidation was linked to the presence of relatively large, interconnected pores but at the surface of the graphite block a fine network of narrow, open pores enhanced the oxidation near the surface. The team also found that the oxidation


rate appeared to be lower in graphite where some parts of the microstructure had clumped together to form small agglomerates. “The UK has been operating graphite


moderated reactors that are subjected to high levels of radiolytic oxidation for over 50 years,” Tzelepi noted. Although the mechanism of radiolytic oxidation is different, a lot of experience can be drawn on to understand not only the effect of oxidation on the graphite properties but also to develop the methods to study it.”


The insight gained supports the development


of future reactors, ensuring that they operate in optimal condition.


Russia BN-1200 preliminary work completed All research work at the site of the future BN- 1200 reactor at Russia’s Beloyarsk NPP has been completed. The BN-1200 sodium-cooled fast reactor is planned to be built as unit 5 of the Beloyarsk NPP in the Sverdlovsk Region. Two units are currently operating at the plant – unit 3 with the BN-600 fast reactor and unit 4 with the BN-800 fast reactor. Their total installed capacity is 1,485 MWe. These are the world’s only power units with fast neutron reactors. “All planned types of surveys have been


carried out at the BN-1200 site – engineering and geodetic, engineering and environmental, engineering and hydrometeorological, engineering and geotechnical – now reports are being prepared on the work undertaken. These must be completed in August and we will soon receive reports on all the surveys. These will then be analysed and sent by us as part of the investment feasibility study to make a decision on the suitability of the site for construction,” said Chief Engineer Yury Nosov. Rosatom plans to obtain a licence for the


construction for the BN-1200 in 2027. It will be the world’s largest fast reactor, breaking the record held by Beloyark unit 4. Complete construction of Beloyarsk 5 is scheduled for 2035. Earlier Valery Shamansky, Deputy Chief Engineer for Safety & Reliability at Beloyarsk NPP said Rosatom’s roadmap for the construction the unit had been approved. “In 2024, we plan to develop design of the structure. Public discussions and a positive environmental review are planned for 2025,” he added. All design work should be completed in 2025, and construction will begin at the end of 2026-2027.


United States NRC issues final EIS for Hermes The US Nuclear Regulatory Commission has completed its final environmental impact statement (FEIS) on Kairos Power’s application for a permit to build a test version of the company’s Hermes advanced reactor design in Oak Ridge, Tennessee. NRC staff recommended that the permit should be issued. Following hearings, expected to take place later this year, the Commission will vote whether to authorise the staff to issue the permit. Kairos filed the application in September


2021, seeking a permit to build a 35 MWt molten salt coolant reactor intended to support the development of a larger version for commercial power production. Kairos Power will have to submit a separate application for an operating licence and obtain approval from the NRC before operating the Hermes reactor. TRISO fuel pebbles will be produced at the


Los Alamos National Laboratory’s Low Enriched Fuel Fabrication Facility under an agreement reached in late 2022. The company has also commissioned a plant in partnership with Materion Corporation to produce high-purity fluoride salt coolant – known as Flibe – using lithium fluoride and beryllium fluoride. ■


round up


RADWASTE IAEA IS LAUNCHING a new Coordinated Research Project (CRP) to increase international knowledge and drive progress towards testing deep borehole disposal (DBD) for intermediate and high-level radioactive waste. The CRP was launched in response to interest expressed by several countries in further exploring whether DBD might be a suitable option for disposal of their specific inventory of radioactive waste.


THE HANFORD SITE Waste Treatment & Immobilisation Plant (WTP) team has poured the first batches of glass forming beads, called frit, into a melter which recently achieved its operating temperature of 2,100 degrees Fahrenheit. The US Department of Energy’s Office of Environmental Management (EM) said the accomplishment represents a positive step toward waste treatment operations as part of EM’s Direct-Feed Low-Activity Waste Program at Hanford.


D&D


GERMANY’S FEDERAL ASSOCIATION for Final Storage (BGE – Bundesgesellschaft für Endlagerung) has awarded a contract to dismantle the Gorleben mine and to backfill it using the salt previously removed. After the mine building has been filled, the two shafts will be filled under another construction contract (Phase 2) that is still to be tendered. In Phase 3, the site will be restored for use.


CLEAN-UP US POWER UTILITY Xcel Energy announced that it will build an underground metal barrier at the Monticello NPP in Minnesota to contain a leak of water containing tritium and prevent it entering contaminated groundwater from entering the nearby Mississippi River.


ADVANCED REACTORS US-BASED MIRION Technologies has been awarded a strategic design contract with X-Energy Reactor Company to provide detailed design support for the Burn Up Measurement System (BUMS for the fuel cycle of the Xe-100 high-temperature gas-cooled reactor (HTGR).


THE US DEPARTMENT of Energy (DOE) has released the final environmental assessment and a proposed “finding of no significant impact” (FONSI) for the design, construction, and operation of the Molten Chloride Reactor Experiment (MCRE) at Idaho National Laboratory (INL). DOE has determined that the construction and operation of MCRE will have no significant environmental or human health impact.


www.neimagazine.com | September 2023 | 13


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49