UK National Nuclear Laboratory

Seascale, United Kingdom

UK National Nuclear Laboratory

Seascale, United Kingdom
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Arun S.,University of Phayao | Sherry A.H.,UK National Nuclear Laboratory | Smith M.C.,University of Manchester | Sheikh M.,University of Manchester
Engineering Fracture Mechanics | Year: 2017

STYLE or "Structural integrity for lifetime management-non-RPV component" was a EURATOM Framework 7 project which try to develop a new understanding of the combined influence of mechanical loading and residual stresses on the ductile fracture behaviour. The project was divided into two main parts, i.e. experimental part and the simulation part. The work presented in this paper relates to the simulation part of the STYLE project. The paper presents the results of a ductile damage mechanics procedure that was developed to predict ductile crack extension under a combination of primary and weld residual stress in a large-scale four-point bending test performed on a repair welded Esshete 1250 pipe containing a circumferential through-thickness crack. In this work, a finite element model of the test was created in ABAQUS, and the weld residual stress was introduced to the model by an iterative technique. The Rousselier model was calibrated against the ductile fracture behaviour of a test specimen including crack initiation and growth. The prediction of final crack growth in the large-scale test obtained from this analysis is compared with the results obtained from a fracture mechanics analysis based on the J-integral and the large-scale test outcome. The Rousselier model and the fracture mechanics approach predicted a similar amount of ductile tearing to the average amount of crack extension observed in the large-scale test, with any slight differences likely to be an artefact of either non-symmetric loading in the test, or differences between test weld residual stresses or material properties compared with those measured on "sister" specimens. The shape of the crack growth was well predicted by both approaches. © 2017 Elsevier Ltd.


News Article | February 4, 2016
Site: www.theenergycollective.com

In addition to its plans for building four huge nuclear power stations, the UK government has also announced it wants to become a global Centre for the development and manufacturing of small modular reactors (SMRs). This blog post assesses the UK’s plans and concludes that it could succeed, but only if the UK is able to scale up its efforts sufficiently and if the government provides active policy support. While NuScale and Westinghouse are targeting construction of their first-of-a-kind units in the UK by 2025, the real challenge will be to book enough orders to bring investors to the table to build factories to turn out SMRs on a cost effective production line basis. There isn’t enough of a market within the UK itself to generate these orders. This means both firms likely see the UK as a launch pad to gain market share in Europe and the Middle East. Replacement of aging coal fired power plants in places like Poland and elsewhere in eastern Europe represent possible market opportunities. The primary reason is that a 50 MW, or even a 225 MW, SMR is still orders of magnitude cheaper than a 1000 MW unit. Plus, the first unit can, with its revenue, pay for the second, and so on. The advantage for the UK is that it could develop a major export market for SMRs which will also generate jobs not only for direct manufacturing of the units, but also stimulate a second round of employment and growth with the supply chain for the production of reactors by the primary vendors. Everything depends on both NuScale and Westinghouse passing through the gauntlet of the UK’s notoriously complicated and expensive generic design review process to certify the safety of their reactors. Both firms have made optimistic estimates of how long this will take. However, like the famous line from the movie “Princess Bride,” they may have to be prepared to be disappointed. Breaking ground by 2025 for either vendor may still be feasible, but new land speed records for bureaucratic action may have to be set in the process. One Size Does Not Fit All In congressional testimony in June 2009, then U.S. VP Al Gore said famously that nuclear reactors only come in one size “extra large.”  Gore’s comment was intended to dismiss nuclear energy because of the size of projects and their costs. With a major effort now underway to build 19 GWe of large nuclear reactors over the next two decades, the UK appears to be headed towards doubling down on its atomic energy bet with a push to open up opportunities for small modular reactors (SMRs). UK Energy Secretary Amber Rudd told Parliament in November 2015 that SMRs have “excellent” potential and that the current government of UK Prime Minister David Cameron “is doing as much as it can” to support the technology. To that end the UK government announced £250m ($378m) funding over the next five years for nuclear research and development including a competition to identify the “best value small modular reactor design for the UK.” The UK is doubling funding for the Department of Energy and Climate Change’s (DECC’s) energy innovation program to £500m over five years, including research into SMRs. The competition will be launched in 2016, which will “pave the way towards building one of the world’s first small modular reactors in the UK in the 2020s”, the Treasury said. Mike Tynan, Director of the UK Nuclear Advanced Manufacturing Research Center, has been quoted in industry trade literature as saying he expects the first SMRs to be operational in the UK sometime between 2027 and 2030. The UK National Nuclear Laboratory (NNL) estimates the value of the SMR market in the UK could be worth £250-400 billion. While the cost of building an SMR currently runs about the same per Kw as their larger cousins, their smaller size makes them affordable to utilities that cannot take on the “bet the company” risk of a 1000 MW plant. A report from the NNL released in December 2014 indicates “there is a very significant market” for SMRs to meet the needs of up to 7 Gwe of generating capacity by 2035. Keep in mind that SMRs come in sizes of 50-300 MW. An installed fleet of 7 GWe would represent as few as 20 SMRs and as many as over 100 depending on their size. These numbers are important because the tally of customer orders will make or break conversion of production of these reactors from being built one-at-a-time to being mass produced in cost efficient factories. A factory that cranks out SMRs on a production line like so many washing machines can dramatically lower the cost per kilowatt compared to 1000 MW units. Both Westinghouse and NuScale are looking closely at supply chain partners to pursue this objective. Tom Mundy, EVP at NuScale, told the Financial Times on 19 January 2016 the economics for SMRs only work if operators order a whole fleet of smaller plants, helping drive down the overall cost per unit. “We are not talking about economies of scale here but economies of multiples.” So how many orders for new SMRs does an SMR vendor need to go the financial markets to get funding to build a factory to make lots of them? The answer, according to David Orr, head of nuclear business development for Rolls-Royce in the UK, which has been making small reactors for the UK’s Royal Navy submarine fleet for decades, is a minimum of about four dozen units and six dozen would be better. Those are high numbers which make some proponents of SMRs unhappy. The reason is this estimate means that turning out the first 50 or so SMRs for any firm in the business could be a high wire act. Former US Energy Secretary Steven Chu is more optimistic. He thinks the 10th unit of the same design is the tipping point where real cost savings start to appear. The real test will be the number of commitments for orders that will convince investors to open their checkbooks to fund a factory. This chicken and egg conundrum hasn’t dampened interest in pursuit of the market. The idea in the UK is that it could establish itself as a global center of manufacturing SMRs for export even supporting multiple vendors and their supply chains, all of which would add thousands of high paying jobs to the economy. However, the UK must do more than just hold a competition for a design and facilitate access to the generic design review process. To be successful, it will need to take pages from the US playbook. This means funding cost sharing with SMR developers for technical design and licensing costs. Export credits would help make inroads into global markets. Real leverage for domestic deployment would include rate guarantees to bring investors to the table. The UK is keen on deploying SMRs in the North of England including Sheffield, Manchester, and Cumbria. The question is whether it will have the capacity and political will to link its economic development initiatives to SMR manufacturing and deployment of the first units in these places. While the US based firm Westinghouse put its SMR effort with Ameren in Missouri on ice in winter 2014, in October 2015 it submitted an unsolicited proposal to partner with the UK government to license and deploy its 225 MW light water reactor (LWR) which has a design that puts all the components inside the reactor pressure vessel (RPV). The design (right) uses a passive safety system to address emergency cooling. The entire facility is built underground. The heart of the Westinghouse proposal is a “shared design development model” that would engage the UK government and UK companies in the reactor supply chain like Sheffield Forgemasters International Ltd. The firm is one of a handful of British companies which can fabricate safety-critical cast and forged components within nuclear power stations. In 2010 the two firms tried to convince the UK government, without success, to provide a major loan to the firm to allow it to build a capability to forge the extremely large components needed for full size nuclear reactors. It may be that the two firms are planning to make another run at the concept now that the current government is so enthusiastic about SMRs. Since SMRs are much smaller, the forging capabilities needed to build reactor pressure vessels for them are similarly downsized, and less costly, in terms of manufacturing requirements. This makes the possibility of new financing more likely though so far the UK government hasn’t formally responded to the Westinghouse proposal. Westinghouse would have to take its SMR reactor through the UK’s notoriously complicated and costly generic design review to get a license to build them. However, the company says that since its SMR borrows many design features from the AP1000, which has mostly completed the process, it could shave a year off the process for the SMR. This confidence may be misplaced as the firm has just encountered new headwinds with the AP1000 and the design review. The Office of Nuclear Regulation (ONR) is calling for the firm to “re-baseline” the entire effort. ONR said it hopes the effort would support making decisions about the AP1000 in January 2017. US-based NuScale, which is rapidly making progress toward submitting its design to the Nuclear Regulatory Commission (NRC), the US regulator, for safety review in late 2016, is looking for partners to deploy its 50 MW SMR in the UK. NuScale Chairman and CEO John Hopkins told World Nuclear News in October 2015 that it wants to develop an aggressive timetable to deploy its SMRs across the pond. He said the firm is scouting for appropriate sites and seeking partners for investment and to help develop its supply chain. NuScale has opened an office in London. In 2013 Rolls-Royce joined Fluor Corporation in supporting NuScale’s efforts to progress towards deployment and commercialization. According to NuScale, UK based Rolls-Royce supported NuScale Power in its submission to the United States Department of Energy’s Funding Opportunity Announcement (FOA) to bring innovative SMR technology to market. NuScale is planning to leverage a relationship it has with the UK National Nuclear Laboratory (NNL) through its major investor the Fluor Corp. That company has worked on nuclear fuel design with the NNL. With an eye toward a supply chain, the firm is partnered with the Nuclear Advanced Manufacturing Research Center. The UK is the most attractive overseas market for NuScale as it has the most robust and practical commitment to nuclear energy outside of China and Russia. India is fading as a market for new nuclear reactors due to its continued commitment to a draconian nuclear supplier liability law and the immense political and financial influence of its existing coal mine operators. According to NuScale a nuclear power plant based on its technology is comprised of individual NuScale Power Modules™, each producing 50 megawatts of electricity (gross) with its own factory-built combined containment vessel and reactor vessel, and its own packaged turbine-generator set. A power plant can include as many as 12 NuScale Power Modules to produce as much as 600 MWe. The reactor coolant is driven by natural circulation and can be shut down safely with no operator action, no AC or DC power, and no external water supply. NuScale power plants are scalable – additional modules are added as customer demand for electricity increases. NuScale’s technology also is intended for customers who want to supply energy for district heating, desalination, and other applications. Westinghouse to produce SMR fuel in the UK The US firm announced Jan 7, 2016 that its UK nucler fuel fabrication center is ready to manufacture nuclear fuel assemblies for SMRs. The issues for these fuel assemblies is that they are expected to be in the reactor longer than conventional fuel assemblies for larger reactors. This means they will have a slightly higher level of enrichment, but not more than 5% U235. According to a press statement, Westinghouse is positioning its UK SMR nuclear fuel plant as a “strategic national asset” for the industry. NuScale announced on December 2, 2015, that it has signed a contract with Areva for the French state-owned nuclear firm to manufacture fuel assemblies at its Richland, WA, plant for SMRs. Areva will supply the initial cores for NuScale’s 50 MW SMRs as well as fuel reloads. Areva has designed nuclear fuel assemblies specifically for SMRs. Mechanical and hydraulic testing is underway as part of NuScale’s development of a submission in late 2016 to the NRC for a safety design review. NuScale to offer 100% MOX fuel option for its SMR NuScale Power announced the completion of a study commissioned from the UK National Nuclear Laboratory (NNL) supporting the suitability of NuScale’s world-leading Small Modular Reactor technology for the effective disposition of plutonium. It is the second proposal for use of reactor technology to dispose of surplus plutonium in the UK. The first is the GE-Hitachi PRISM reactor which is based on the design of the Argonne West Integral Fast Reactor. The NNL study in the UK evaluated scenarios with partial and full-core loading of mixed uranium-plutonium oxide (MOX) fuel and confirmed that MOX could be used in the NuScale core with minimal effect on the reactor’s design and operation. The study also demonstrated that a 12-module NuScale plant with 100% MOX cores could consume a 100 metric-ton stockpile of discharged plutonium in roughly 40 years, during which time it would generate approximately 200 million megawatt-hours of carbon free electricity. The world of advanced reactor development efforts is full of R&D sandboxes, but one proposal stands out. GE-Hitachi (GEH) is developing a 311 MW liquid metal (sodium) cooled reactor based on the Integral Fast Reactor design. The firm has submitted an unsolicited proposal to the UK Nuclear Decomissioning Authority (NDA) to burn surplus plutonium as a way to dispose of it. The GEH plan calls for two units each with its own turbine. According to GEH the facility could be built in as little as three years. However, like all other new reactor projects, it would have to pass through the UK Generic Design Review. It is unclear whether the government’s regulators have the means to assess the safety of the new design. The GEH reactors are intended not only to provide electrical power, but also to solve a major problem for the NDA. It has a large inventory of plutonium from spent fuel and also UK defense sources. Burning it in the PRISM reactors would be a path to safe disposition and would remove the need for a large, permanent geologic repository for it. GE Hitachi is designing an Advanced Recycling Centre (ARC) which integrates electrometallurgical processing with its PRISM fast reactors. The main feed is used fuel from light water reactors. The three products are fission products, uranium, and transuranics, which become fuel for the fast reactors (with some of the uranium). A full commercial-scale ARC would comprise an electrometallurgical plant and three power blocks of 622 MWe each (six 311 MWe reactor modules).


Jones A.E.,University of Liverpool | Turner P.,Atomic Weapons Establishment | Zimmerman C.,UK National Nuclear Laboratory | Goulermas J.Y.,University of Liverpool
Analytical Chemistry | Year: 2014

In this paper we demonstrate the use of pattern recognition and machine learning techniques to determine the reactor type from which spent reactor fuel has originated. This has been done using the isotopic and elemental measurements of the sample and proves to be very useful in the field of nuclear forensics. Nuclear materials contain many variables (impurities and isotopes) that are very difficult to consider individually. A method that considers all material parameters simultaneously is advantageous. Currently the field of nuclear forensics focuses on the analysis of key material properties to determine details about the materials processing history, for example, utilizing known half-lives of isotopes can determine when the material was last processed (Stanley, F. E. J. Anal. At. Spectrom. 2012, 27, 1821; Varga, Z.; Wallenius, M.; Mayer, K.; Keegan, E.; Millet, S. Anal. Chem. 2009, 81, 8327-8334). However, it has been demonstrated that multivariate statistical analysis of isotopic concentrations can complement these method and are able to make use of a greater level of information through dimensionality reduction techniques (Robel, M.; Kristo, M. J. J. Environ. Radioact. 2008, 99, 1789-1797; Robel, M.; Kristo, M. J.; Heller, M. A. Nuclear Forensic Inferences Using Iterative Multidimensional Statistics. In Proceedings of the Institute of Nuclear Materials Management 50th Annual Meeting, Tucson, AZ, July 2009; 12 pages; Nicolaou, G. J. Environ. Radioact. 2006, 86, 313-318; Pajo, L.; Mayer, K.; Koch, L. Fresenius' J. Anal. Chem. 2001, 371, 348-352). There has been some success in using such multidimensional statistical methods to determine details about the history of spent reactor fuel (Robel, M.; Kristo, M. J. J. Environ. Radioact. 2008, 99, 1789-1797). Here, we aim to expand on these findings by pursuing more robust dimensionality reduction techniques based on manifold embedding which are able to better capture the intrinsic data set information. Furthermore, we demonstrate the use of a number of classification algorithms to reliably determine the reactor type in which a spent fuel material has been irradiated. A number of these classification techniques are novel applications in nuclear forensics and expand on the existing knowledge in this field by creating a reliable and robust classification model. The results from this analysis show that our techniques have been very successful and further ascertain the excellent potential of these techniques in the field of nuclear forensics at least with regard to spent reactor fuel. © 2014 American Chemical Society.


Rossiter G.,UK National Nuclear Laboratory
Nuclear Engineering and Technology | Year: 2011

UK National Nuclear Laboratory's (NNL's) version of the ENIGMA fuel performance code is described, including details of the development history, the system modelled, the key assumptions, the thermo-mechanical solution scheme, and the various incorporated models. The recent development of ENIGMA in the areas of whole core analysis and dry storage applications is then discussed. With respect to the former, the NEXUS code has been developed by NNL to automate whole core fuel performance modelling for an LWR core, using ENIGMA as the underlying fuel performance engine. NEXUS runs on NNL's GEMSTONE high performance computing cluster and utilises 3-D core power distribution data obtained from the output of Studsvik Scandpower's SIMULATE code. With respect to the latter, ENIGMA has been developed such that it can model the thermo-mechanical behaviour of a given LWR fuel rod during irradiation, pond cooling, drying, and dry storage - this involved: (a) incorporating an out-of-pile clad creep model for irradiated Zircaloy-4; (b) including the ability to simulate annealing out of the clad irradiation damage; (c) writing of additional post-irradiation output; (d) several other minor modifications to allow modelling of post-irradiation conditions.


Whillock G.O.H.,UK National Nuclear Laboratory | Worthington S.E.,UK National Nuclear Laboratory | Donohoe C.J.,UK National Nuclear Laboratory
Corrosion | Year: 2012

Parts of a nuclear waste cooling water system, constructed from an austenitic stainless steel, are known to be susceptible to localized corrosion. This is attributed to the presence of chloride ions in the water, albeit only at low concentrations (<10 mg/L), and oxidants produced by water radiolysis. Experiments were carried out using an engineered crevice connected to a large passive stainless steel surface to demonstrate the viability of crevice corrosion. Similar tests were undertaken to investigate the efficacy of nitrate as an inhibitor. In irradiated water containing up to 300 mg/L Cl- and at temperatures of up to 60°C, crevice corrosion of UNS 30403 and 18Cr° 13Ni 1Nb was inhibited by nitrate added at molar ratios of approximately 2.9 to 5.7 with respect to chloride. Once corrosion is inhibited, the nitrate/chloride ratio can be reduced to maintain passivity, but a nitrate: chloride ratio of approximately 0.6 or lower is unlikely to be effective. © 2012, NACE International.


Whillock G.O.H.,UK National Nuclear Laboratory | Binks T.J.,UK National Nuclear Laboratory | Donohoe C.J.,UK National Nuclear Laboratory
Corrosion | Year: 2012

A nuclear waste cooling water system, constructed from an austenitic stainless steel, is known to be susceptible to localized corrosion because of the combined presence of low concentrations of chloride (Cl -) ions in the water (<10 mg/L) and oxidants produced by water radiolysis. Corrosion propagates in the system as pitting corrosion, and inspections of accessible components indicated that large pit cavities could form. To investigate possible inhibition options, an artificial pit, termed the wire-electrode artificial pit, was developed and shown to be capable of sustaining corrosion under representative conditions. Tests carried out using this artificial pit to investigate the effect of sodium nitrate (NaNO 3) added to the bulk water are reported here. The results showed that nitrate (NO 3 -) was capable of affecting inhibition at 60°C, although large concentrations and long times were required, e.g., inhibition took up to 20 days at 60,000 mg/L NO 3 -. Complimentary polarization tests were also carried out in a range of artificial pit solutions as a function of nitrate concentration to aid interpretation of the wire-electrode tests. The existence of a threshold molar NO 3 -/Cl - ratio for passivation to occur was identified but not clearly defined. © 2012, NACE International.


Donohoe C.J.,UK National Nuclear Laboratory | Whillock G.O.H.,UK National Nuclear Laboratory
Corrosion | Year: 2012

Parts of a nuclear waste cooling water system, constructed from an austenitic stainless steel, are known to be susceptible to localized corrosion. To enable the investigation of corrosion inhibitors for potential application to that system, an artificial corrosion pit cell made from stainless steel was developed to simulate corrosion of large pits. A number of inhibition treatments were tested using these pit specimens, including substitution of chloride-containing water with demineralized water, sodium hydroxide dosing, and molybdate dosing. Corrosion was monitored by measuring the current flowing between the pit specimens and a large piece of non-corroding stainless steel wire mesh using a "zero-resistance" ammeter. The corrosion persisted despite long-term purging with high-quality demineralized water or sodium hydroxide dosing to pH 11. Sodium molybdate dosing to a molybdate concentration of 50 mg/L was ineffective, though it did have a strong effect of catalytically decomposing hydrogen peroxide (included to simulate the effects of water radiolysis). Two distinctly different internal morphologies were found consistent with salt-filming and the etch-type mechanisms of pitting. © 2012, NACE International.


Donohoe C.J.,UK National Nuclear Laboratory | Whillock G.O.H.,UK National Nuclear Laboratory | Apps P.J.,UK National Nuclear Laboratory
Corrosion | Year: 2012

Parts of a nuclear waste cooling water system, constructed from an austenitic stainless steel, are known to be susceptible to localized corrosion. This is attributed to the presence of chloride ions in the water, albeit only at low concentration (<10 mg/L), and oxidants produced by water radiolysis. Plate samples were cut and taken for examination from downstream tanks located in man-access areas out of the radiation field. Large pits were found. The largest were highly elongated but had failed to form through-wall penetrations. Smaller pits that were spheroidal in shape were found that had formed through-wall penetrations. The pits were sectioned and their internal morphologies examined by scanning electron microscopy. The elongated pits were found to have a crystalline internal morphology associated with the mechanism of etchtype pitting. The spheroidal pits had a smoother interior morphology but it was not bright or distinctive-like classic pits formed by a salt-filming mechanism. Formation of the spheroidal pits is attributed to corrosion by a quasi-salt-filming mechanism. © 2012, NACE International.


Whillock G.O.H.,UK National Nuclear Laboratory | Binks T.J.,UK National Nuclear Laboratory | Donohoe C.J.,UK National Nuclear Laboratory
Corrosion | Year: 2012

To enable testing of candidate inhibitors for chloride-induced pitting of austenitic stainless steel in a radiation field, an artificial pit cell was required that was capable of sustaining corrosion at rates in the range revealed by plant inspections. Two designs of artificial pit cells are described. These allowed measurement of the internal and external cathodic contributions to the corrosion rate and changes in the composition of the artificial pit solution as time progressed. The number of electrolytic holes and the type and quantity of ferruginous sludge used were found to exert significant effects. The final design adopted on the basis of empirical testing demonstrated stable corrosion at a high rate (5 mm/y to 6 mm/y) in nominally 15 mg/L Cl - bulk solution containing 5 mg/L hydrogen peroxide (H 2O 2) at 60°C and stable pit solution composition for 20 days to 25 days at least. The initial strength of pit solution used was found to be unimportant, since the composition quickly gravitated toward 10 g/L to 20 g/L Cl- with a pH in the range of 1.5 to 2. For this composition, the corrosion reaction was driven almost exclusively by the external cathode, the internal hydrogen evolution ceasing to make a significant contribution. © 2012, NACE International.


Whillock G.O.H.,UK National Nuclear Laboratory | Donohoe C.J.,UK National Nuclear Laboratory
Corrosion | Year: 2013

To investigate possible inhibition options for large corrosion pits in 18Cr-13Ni-1Nb stainless steel, various designs of artificial pits were developed previously and shown to be capable of sustaining corrosion for long periods. Nitrate added to the bulk water in large concentrations was found previously to be capable of affecting inhibition, but there were indications of deleterious effects in the form of increased corrosion, and it also was speculated that stress corrosion cracking might result in some circumstances. To provide the means of investigating any tendency for a transition from pitting to stress corrosion cracking, work is reported here to incorporate tensile stress into the artificial pit specimen, consequently rendering it capable of detecting stress corrosion cracking if the environmental conditions are conducive. Tensile stress was incorporated by including a notch ahead of the pit cavity, which was compressively loaded. The developed specimen, termed the stressed all-metal pit, is shown to be capable of undergoing stress corrosion cracking initiated from the pit cavity. © 2013, NACE International.

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