This article elaborates the evolution of code and standards for nuclear power plants. In the 1950s, need was felt for a revised set of design and fabrication rules to facilitate the development of safe, economically competitive water-cooled reactors contained in pressure vessels. These rules were codified in the first edition of the ASME Boiler and Pressure Vessel Code Section III, which was completed in 1963 and published in 1964. From the outset, both regulators and industry realized that the best way to develop many of the needed rules for the design, construction, and operation of nuclear facilities was the national standards consensus process. This process, followed by the American National Standards Institute and other recognized standards-issuing bodies such as ASME, brings together the expertise of individuals from government, industry, academia, and other stakeholders. In the years following the first publication of Section III, the coverage of the Code expanded to incorporate piping requirements, pressure-retaining components for pumps and valves, equipment and piping supports, reactor vessel internal structures, and other features of nuclear power plants.
But from the beginning, that unprecedented power was also seen by engineers and researchers as having the potential to be harnessed for constructive ends. Controlled fission reactions could be the heat source for large-scale thermal plants that could power cities. That vision was in the minds of the engineers who designed and built the first commercial nuclear power plant in the United States, which went on line at Shippingport, Pa., in 1957.
Nuclear power began out of military necessity. The first— uncontrolled—uses were the blasts that devastated Hiroshima and Nagasaki. A decade later, the military used nuclear power for propulsion in the USS Nautilus.
It was no coincidence that the civilian use of nuclear power grew hand in hand with ASME Codes and Standards. The engineers who designed the pressurized water-cooled reactors at the heart of the Nautilus and Shippingport power plant, which is now an ASME Historic Mechanical Engineering Landmark, recognized that they were essentially pressure vessels. As a result, they designed those reactors in a way consistent with the existing ASME Boiler and Pressure Vessel Code rules.
That approach worked, but it was clear from the outset that it wouldn’t work indefinitely. The Shippingport reactor had an output of 60 megawatts of electricity, and its pressure vessel was the largest ever built at the time. Sam Cerni, a design engineer who worked on the Shippingport core, recalls that the reactor operated at 2,000 psia and was designed for 2,500 psi.
The vessel, designed and fabricated by Babcock and Wilcox, weighed 153 tons, had an inside height of 32 feet, an inside diameter of 109 inches and the wall was about 8 inches thick.
To be economically competitive, the output of nuclear reactors would need to be substantially increased beyond Shippingport's nameplate capacity of 60 MW. But the fabrication capabilities of the ASME Code at the time put limits on the potential size of pressure vessels and plants using the existing Code rules. There also were thermal stress conditions and radiation effects unique to nuclear plants, and they were not adequately treated by the Code as it existed in the 1950s.
Thus there was a need for a revised set of design and fabrication rules to facilitate the development of safe, economically competitive water-cooled reactors contained in pressure vessels. These rules were codified in the first edition of the ASME Boiler and Pressure Vessel Code Section III, which was completed in 1963 and published 50 years ago this year, in 1964.
From the outset, both regulators and industry realized that the best way to develop many of the needed rules for the design, construction, and operation of nuclear facilities was the national standards consensus process. This process, followed by the American National Standards Institute and other recognized standards-issuing bodies such as ASME, brings together the expertise of individuals from government, industry, academia, and other stakeholders. The general public is invited to read and comment on the proposed drafts of standards.
By the 1950s this process had a long history of assuring public safety and was encouraged as a way to assure that the best expertise was applied to the development of practical and necessary rules.
Frank Williams was an engineer who was involved in the Section III process from the start. In a 1990 book, The Code, author Wilbur Cross quotes Williams at length. Williams recalled how ASME's interest in conventional pressure vessel equipment led to an interest in developing nuclear codes and standards.
“In the early days of nuclear involvement,” Williams said, “we at Taylor Forge, along with several other companies, such as Kellogg and Westinghouse, made a lot of equipment in the form of pipe fittings, piping, nozzles, and the like for an experimental plant and for the very first nuclear power plant at Shippingport. At first we talked informally about this subject, and then proposed the course of action we felt we should take. The result was the formation of a study committee.”
A meeting in Tulsa led to the formation of a separate ASME Boiler and Pressure Vessel Code subcommittee in 1955, and Williams, because of his knowledge of the codes, was its first chairman. The nuclear Code, Williams wrote, took the name Section III, because that had once designated a section of the Code for locomotive boilers, and as he put it, that section “had become defunct.”
Another volunteer who served on the Subcommittee on Nuclear Power when Section III was approved in the 1960s is Keith Wichman, now a retired engineer who still participates in the activities of the nuclear Code.
“The ASME Subcommittee on Nuclear Power was formed to develop rules for the construction of nuclear vessels,” Wichman wrote in an e-mail. “The first edition of Section III drew heavily upon the Navy document, ‘Tentative Structural Design Basis for Reactor Pressure Vessels and Directly Associated Components,’ which was issued in a revised version in 1958. The contents of that document were instrumental in the design and construction of the components that powered the first nuclear submarines.”
Several key figures in the development of the Navy rules were subsequently important to the development of Section III. They included Bernard Langer of Bettis Atomic Power Laboratory (for whom the ASME Bernard F. Langer Nuclear Codes and Standards Award is named), William Cooper of the Knolls Atomic Power Laboratory, and James Mershon of the Navy Bureau of Ships, who was Wichman's boss and would later join the Atomic Energy Commission.
Nuclear code provisions have reached beyond power plants and even to other industries.
In the years following the first publication of Section III, the coverage of the Code expanded to incorporate piping requirements (which were originally developed separately by the ASME B31 Committee as B31.7), pressure retaining components for pumps and valves, equipment and piping supports, reactor vessel internal structures, and other features of nuclear power plants.
Subsequent editions added requirements for steel and concrete containment structures, high-temperature reactors, containments for spent fuel and radioactive waste, use of materials such as graphite, and other components for advanced reactor designs.
Since 1963, ASME has developed many additional codes and standards to maintain the safety of operating nuclear power plants and those planned for the future. These codes and standards were extended to cover other nuclear facilities, such as spent fuel storage, and they have been implemented by national and local government agencies and other regulatory bodies worldwide.
Several of them, such as spent fuel storage, nuclear fuel and waste processing, waste management, and equipment and fuel fabrication, have been extended beyond nuclear power plants to other nuclear facilities. Some, such as the special requirements for air and gas treatment and for cranes handling special equipment, have been adopted for use in other industries.
The original concept of nuclear power plant designers was that the higher standards adopted for design and fabrication would make in-service examinations unnecessary, and little attention was given to provisions for access.
By 1966 the Atomic Energy Commission recognized that a planned program of periodic inspections would be needed. They began to develop criteria, and in 1968 a joint AEC-industry Code development program began under the auspices of the ANSI N-45 Committee. A draft Code was published by ASME in 1968, and Section XI of the Boiler and Pressure Vessel Code, Rules for Inservice Inspection of Nuclear Power Plant Components, was published in 1970.
Section XI is directed toward the owners of nuclear power plants. The owners’ needs proved to be significantly different from the Section III rules for construction of the nuclear components. Section XI responded by providing new requirements appropriate for operating plants. These rules have addressed repair methods, analytical evaluation techniques, non-destructive evaluation methods, and acceptance standards appropriate for ultrasonic examination.
The first commercial reactors were fabricated from stainless steel and low-alloy ferritic steel. To enhance the corrosion resistance to chloride environments (which could result from condenser leakage) plants implemented a new high-nickel alloy. This material proved susceptible to corrosion in a pure water environment, and Section XI addressed this situation with enhanced inspection requirements, and new mitigation and repair techniques.
Over the years the number of nuclear plants worldwide and their individual power levels have increased substantially, the largest operating units have output in excess of 1,300 MW. Units with power output in excess of 1,500 MW are under construction. Essentially all of them have safely and reliably produced a significant portion of the world's electrical power with minimal environmental pollution.
Modern plants require partial refueling every year or two and run annually at full power over 90 percent of the time. Nuclear power plants typically have the lowest operating costs. When operating at full capacity, they have lower power costs than all other options except existing hydroelectric installations.
Not only has the Code grown in scope over the past 50 years, it has become international. It was the origin for the French nuclear code and for those of Japan, Russia, and Korea. Many countries, including Canada and Spain, have adopted the ASME Code. Out of the current 1,000 ASME Section III Nuclear Certificates, over half are international.
The evolution of the Code will require greater participation from the global engineering community.
As the Code has become international, so has its governing process. The Section III Committee has recently met in Japan and Korea. In addition, International Working Groups have formed in Korea, India, Germany, and China, which is building four AP1000 reactors.
International Working Groups permit non-U.S. technical experts to participate in the development of the Code in the same manner as members of other working groups within the committee hierarchy. The evolution of the Code will require greater participation and contribution from the global nuclear engineering community.
As we look to the future of nuclear power we see dynamic events, some global and others focused regionally. Future plant designs promise to be as safe as current designs, or safer. They will be less costly to construct and more efficient to operate. There are also discussions about further extending the life of the current fleet of reactors in the United States. The current Code will be required to change to reflect these new designs and circumstances.
The Code is developed and maintained by consensus committees. Within the consensus committee hierarchy of standards committee, subgroups, and working groups, hundreds of technical experts participate as volunteers, representing the best and brightest engineers from industry, academia, and government. Meetings are open to the public.
It has always been a project of many hands and minds. Section III has been developed, maintained, and expanded over these 50 years by countless engineers who have volunteered their time and effort with support from ASME staff. We also recognize the corporate sponsorship of volunteers provided by utilities, architect engineers, manufacturers, as well as government agencies.
The current Code will be required to change to reflect new designs and circumstances.
There are about 500 volunteers working today to maintain and improve the Section III Code. Nearly 1,300 volunteers serve ASME Nuclear Codes and Standards groups. Volunteers in Code development are participating in addition to meeting the demands of their full-time jobs. They make the effort to assure continuing safety and to resolve daily issues requiring their knowledge and experience.
Long-time member and past Section III committee chair Richard Barnes aptly describes the influence of the volunteers: “These folks work tirelessly and quietly, but their influence extends throughout the Code like yeast does in bread.”
Barnes tells an anecdote, which conveys the sense of teamwork among consensus committees, involving longtime volunteer Doug Cooper of Atomic Energy of Canada Ltd., and Don Landers of Teledyne Brown Engineering, who was considered a legend among those who worked on the Code:
“I will never forget the night that Doug Cooper received the ASME Dedicated Service Award at the National Board Banquet,” Barnes said. “Don Landers presented it to him, and when Don said the recipient was Doug Cooper, Doug was shocked; he was speechless in fact. He came to the stage to receive his award and when he went to the microphone to speak the only thing he said, and he repeated it twice, ‘I don’t deserve this; there are so many others.’ ”