Westinghouse Electric Company is simultaneously building eight passively safe nuclear power plants based on a single first-of-a-kind and first-to-be-licensed in the US, standard design. It is a new and enormous undertaking, and interested people from around the world are watching. What they are witnessing is how the company is applying lessons learned to successfully turn the first of these massive new-build projects into a finely honed process to drive Nth-of-kind delivery for future AP1000® nuclear power plant owners. By Joni Falascino, vice president of project delivery, Jerod Parkinson, director of module delivery, Mike Valore, director of materials and equipment delivery, Westinghouse Electric Company
The Westinghouse model for AP1000 plant project delivery is the key. It is a vertical, integrated team approach led by Westinghouse’s delivery organisation, which includes quality, engineering and supplier sourcing. This vertical integration streamlines the many activities required to design, manufacture and deliver the plants. It provides a single point of accountability, including responsibility to incorporate lessons learned into project execution so that the benefits of the lessons can be realised by current and future plant owners.
The Westinghouse AP1000 nuclear power plant underwent many first-of-a-kind challenges through design and construction, beginning with the first two of these plants being constructed at the Sanmen site in Zhejiang Province in China. The six additional AP1000 plants under construction include two at the Haiyang site in Shandong Province, China; two at the Vogtle site in Waynesboro, Georgia, USA; and two at the V C Summer site in Jenkinsville, South Carolina, USA.
Through its integrated delivery model, Westinghouse has been turning first-of- a-kind challenges into valuable lessons learned and applying them to create a growing rolling benefit effect for subsequent plants. In this manner, the company is reducing construction time and increasing delivery certainty.
The full benefits of lessons learned from constructing these first eight AP1000 plants will be available for the next, which Westinghouse expects to be at the Moorside site in the United Kingdom. The UK’s Office for Nuclear Regulation and Environment Agency are conducting the generic design acceptance review of the Westinghouse AP1000 nuclear reactor design. Issuance of the Design Acceptance Confirmation and Statement of Design Acceptance Confirmation is expected in March 2017.
Focus on safety and economics
The Westinghouse AP1000 plant is a Generation III+ nuclear power plant design. Its creation was the result of several drivers in the industry: increased understanding by regulators and industry following Three Mile Island and Chernobyl; the need for regulatory and licensing certainty; and recognition of the practicality, from an efficiency, economic and safety viewpoint, of a standard design that takes advantage of new modular construction techniques. One could say that the AP1000 plant itself is the fruition of decades of lessons learned through plant construction and operation experience.
Licensed by the US Nuclear Regulatory Commission (NRC) in 2006 and considered to be the most scrutinised nuclear power plant design licensed to date, the AP1000 plant underwent further examination following the 9/11 attack and the tsunami and earthquake that overtook the backup emergency generators at the Fukushima Daiichi nuclear power plant in March 2011.
Following 9/11 it became necessary to demonstrate, for new build projects, including those approved prior to the new ruling, the ability to withstand an impact by commercial aircraft, leading to a change to the design of the already approved AP1000 plant.
The repercussions of Fukushima were wider reaching, prompting governments, regulatory agencies and utilities to re- examine procedures and practices in place for existing nuclear power plants and to carry out further safety design verifications for plants under construction. Those examinations increased appreciation of passive safety systems such as those used in the AP1000 plant.
Optimising delivery through experience
Westinghouse began refining its module procurement, fabrication and assembly processes eight years ago with the construction of the first AP1000 plants in China, allowing more than 14 000 module-related improvements to be realised by the US AP1000 plant projects, which began later. Additionally, these improvements have provided flexibility to fabricators and construction personnel at the US sites, resulting in further benefits in process and equipment efficiencies. This has equated to 30 to 70% labour-hour reductions at supplier facilities and in the site assembly areas for module fabrication and construction for the current US AP1000 plant projects. Westinghouse expects continued benefits for future projects.
Lessons learned during module construction
Westinghouse designed the AP1000 plant to be built using modern modular construction techniques to make use of the significant advantages this approach offers. Constructing the plant in modules – or prefabricated structural shapes, rooms and floors – allows work to be done in parallel in multiple supplier shops rather than in sequence on the job sites. This reduces the construction schedule and number of field workers required on-site. Since off-site fabrication requires shipping the prefabricated items to sites, each AP1000 unit is made up of 714 submodules that are designed to be transported by ship, truck or rail. Many of these form the key structural elements within the plant’s main buildings and once on-site, are further assembled and/ or outfitted before being set into a unit’s nuclear island. This entirely new approach to nuclear unit construction has provided numerous opportunities for improvement.
Some of these improvements can be found within the Module Assembly Building where, on each AP1000 construction site, certain submodules are received and assembled into larger structures, mostly through welding. For example, from 29 September to 22 October 2016, an average 798 linear feet of welding occurred per day on one module being assembled within the building. Optimising weld sequencing has provided Westinghouse many opportunities to produce significant savings in the schedule.
For the CA20 module, a critical multi-level infrastructure module weighing more than 2 million pounds and standing nearly 70 feet tall, with eight mechanical submodules and 21 rooms, the improvements are particularly notable. Based on the collective lessons learned from the first Vogtle unit submodule procurement and CA20 module assembly, Westinghouse decreased the CA20 module’s assembly duration from 24 months for the first Vogtle unit to 18 months for the second Vogtle unit, a significant amount of the savings being credited to optimisation of welding sequencing.
Expanding the supply chain
Due to the 30-year lapse in new nuclear power plant construction in the USA, the original US project model for sub-module fabrication was based on there being a limited number of suppliers. However, Westinghouse worked to expand the international supplier base capable of meeting the stringent quality requirements of the commercial nuclear power industry in terms of products and documentation. The undertaking included vetting numerous bidders and visiting supplier sites to closely examine and match each supplier to the most appropriate product. In this way, Westinghouse has expanded the supplier base for sub-module fabricators to some ten companies to meet demand and provide supply flexibility, and has in turn expanded the qualified supplier base for the commercial nuclear power industry as a whole.
The company achieved this by creating strategic relationships with suppliers. Rather than being simply transactional, these relationships are rooted in sharing lessons learned across the entire supply base. Westinghouse facilitates this relationship- building by hosting supplier summits where Westinghouse and suppliers discuss the appropriate support level suppliers need from Westinghouse, and suppliers help one another by sharing techniques, lessons learned and improvements they’ve discovered through experience. This sourcing model will be employed for future AP1000 plants to benefit new suppliers and to help achieve customer-specific localisation requirements.
Documentation, less is more
Quality documentation is a critical aspect of supplier success. Westinghouse documentation requirements for suppliers are based on regulatory stipulations that are grounded in safety classifications and other information needed for plant construction or plant operation. Suppliers must provide the necessary documentation that proves how each of those requirements has been met.
In the early AP1000 construction stages, Westinghouse found that data received from suppliers for simple equipment often equalled 100 pages, for medium-sized equipment and sub-modules perhaps 3000-4000 pages and for complex equipment and sub-modules up to 10 000 pages. Westinghouse quality inspectors must evaluate all of the data and it quickly became clear that some of the information being received wasn’t necessary; reviewing such volumes of information was also delaying shipments since each data item requires scrutiny.
Westinghouse conducted a study to reach more uniform and succinct documentation delivery by evaluating the value of each type of information being received, working with suppliers to eliminate extraneous information and consolidating the remaining required information. This effort included overhauling supplier data collection and report generation systems to facilitate data capture and reporting.
Applying rigorous control and discipline throughout the process, Westinghouse achieved a 75% reduction in the number of quality records that were required to be prepared, reviewed and maintained, without any loss of quality in the data packages.
Driving efficiencies in equipment delivery
Safe, efficient and timely delivery of equipment is imperative to maintaining construction schedules and to containing costs. Because many pieces of equipment for the first-of-a-kind AP1000 plant are fabricated away from construction sites, their size and weight require a significant amount of logistical planning to achieve the best shipping method, which is dictated by site-specific needs.
For example, delivering the steam generators for the AP1000 plants under construction at the Vogtle and V C Summer sites in the USA presented a number of unique challenges, and opportunities for implementing best practices.
Each AP1000 plant steam generator is more than 80 feet long and weighs more than 1.3 million pounds. A unique aspect of the AP1000 design is that the reactor coolant pump casings are welded to the steam generators, adding 150 000 pounds to the weight and six feet to the length. This posed new challenges for delivering these components to the two US construction sites, which require transport from port to site by railcar, unlike the sites in China, to which components could be delivered by barge.
The size and weight of the steam generator with the casings already welded in place would require modifications to even the largest railcar in the world, the Westinghouse Schnabel car. Knowing this, the team had originally decided to ship and deliver the steam generators and casings separately and have them welded together on-site. However, this approach would result in significant additional cost and work scope. Also, the weld to attach the casings is intricate as it crosses four code jurisdictional boundaries to complete; a process that is better controlled in the shop rather than the plant site.
The Westinghouse team charged with the delivery implemented an initiative to determine best practice, challenging their assumptions about what would be possible, to arrive at the best shipping method in terms of schedule, quality and delivery certainty. They re-examined their original plan, developing a new schedule, conducting a feasibility analysis and evaluating: welding the casings in the shop versus on-site; shipping the steam generators with casings attached; modifying the railcar; and potential port and rail route options. The results showed that while this approach required renegotiation of the supplier contract for welding of the casings on-site and many modifications to accommodate the greater weight and larger size, it provided better product quality control and was optimal in terms of reduced schedule and cost.
Their assessment was correct. Westinghouse achieved significant quality and schedule improvements as a result of the effort. The steam-generator-to-casing weld was successfully completed in a controlled shop environment, with the necessary level of quality, and one month ahead of the estimated schedule for welding on-site. This approach also freed up field resources to work on other tasks rather than having to focus on a large amount of welding. The benefits continued during the delivery of the remaining steam generators to the US construction sites.
Fabrication and installation improvements
Westinghouse has also applied best practices and lessons learned to shorten fabrication and installation schedules for major AP1000 plant components such as the steam generators and reactor coolant pumps.
The AP1000 steam generator is one of the largest components within the plant and requires substantial lead time to manufacture. For the Sanmen 1 and Haiyang 1 sites, it took an average of 56 months to procure materials and fabricate, test and release the steam generators for shipment. Lessons learned were implemented to gain improvements in all aspects of the process, reducing the average duration for the same work volume to 48 months – an average eight-month reduction in total lead time – for the Vogtle and VC Summer sites.
Westinghouse made similar gains in the complex reactor coolant pump installation process, which requires substantial manpower and co-ordination to meet the intricate fit-up requirements necessary for acceptable pump performance during plant operation. A total of eight reactor coolant pumps were installed at Sanmen unit 1 and Haiyang unit 1 from January to April 2016. The first was completed within the original baseline schedule of 30 days. Westinghouse documented many lessons learned based on the initial installation and used them to make improvements for future installations, which included eliminating equipment delays, and modifying the installation process, with changes to tooling by both Westinghouse and the manufacturer, among other specific installation process improvements. By the time the last reactor coolant pump was installed in Haiyang unit 1 in April, the installation schedule had been reduced by 37% to just 19 days. Further optimisation opportunities exist that may condense the installation schedule to just 15 days for subsequent plants.
Shield Building panel fabrication
To address the US NRC amendment of its regulations in June 2009 that required applicants for new nuclear power plants to perform a design-specific assessment of the effects of the impact of large commercial aircraft, Westinghouse needed to design and fabricate eight first-of-a-kind reinforced concrete-filled steel panels weighing more than 10 tons each. The new panels were fabricated for the AP1000 Shield Building, which structurally supports the containment cooling water supply and protects the containment vessel and is comprised of more than 160 individual panels.
The US projects were the first to have these panels installed. From a steep learning curve that took about two years to climb, Westinghouse applied lessons learned and created a sustainable fabrication model for global delivery of the panels that achieves a 70% reduction in fabrication duration.
Success of single point accountability
In summary, the single point of accountability that is key to the Westinghouse model for AP1000 project delivery, including responsibility to incorporate lessons learned into project execution, has proved to be successful. This model is driving efficiencies and taking the AP1000 plant construction from first-of-a-kind learning to a refined and effective delivery model that the company will continue to apply and improve for future AP1000 plant owners.