changed, and many features had to be mandated as retrofits. Thus the light water reactors under construction and in operation today do not represent an optimized LWR design.

Utilities' experience with the LWR range from excellent to poor. Some reactors have operated at up to an 80-percent capacity factor for years with no significant problems, while others have been plagued with continual hardware problems that lead to low-capacity utilization. While the safety record to date is very good, the accident at Three Mile Island (TMI) and other potentially severe incidents raise concerns about the ability of all utilities to maintain that record.

Many of the concerns over safety and reliability have been fueled by the seemingly constant stream of hardware problems and backfits associated with LWRS. Many of those in the nuclear industry feel that such problems reflect normal progress along the learning curve of a very complex technology, and they assert that the reactors are nearing a plateau on that curve. Nuclear critics observe that there are still many unresolved safety issues associated with LWRs, and the technology must continue to change until these are addressed adequately.

The design and operation of LWRS has unquestionably improved over time. The training of operators has been upgraded, human factors considerations have been incorporated into control room design, information on operating experience is shared, and numerous retrofits have been made to existing reactors.

Whether these steps have made LWRS safe enough cannot be demonstrated unambiguously, however. There is no consensus on how to determine the present level of safety, nor on the magnitude of risk represented by particular problems or the cost-benefit criteria for assessing possible solutions. In some cases, retrofits in one area can possibly reduce safety in other areas, either because of unanticipated system interactions, or simply because the additional hardware makes it difficult to get into part of the plant for maintenance or repairs. Even if all the parties to the debate could agree that the risks are acceptably small, the public still might not perceive nuclear power as safe.

It is clear that, before they order new nuclear plants, utilities will want assurances that the plants will operate reliably and will not require expensive retrofits or repairs due to unanticipated design problems or new Nuclear Regulatory Commission (NRC) regulations which may be needed to solve such problems, and that they will not run an unacceptable risk of a TMI-type accident that could bankrupt them.

Many of the nuclear industry's concerns about the current generation of LWRs are being addressed in designs for advanced reactors. An advanced pressurized water reactor is being designed to be safer and easier to operate than the present generation, and to have improved fuel burnup and higher availability (90 percent is the goal) through resolution of some of the more critical hardware problems. An advanced boiling water reactor is being designed to operate at a relatively high capacity factor and to incorporate advanced safety features that will reduce the risk of core-melting even if the primary cooling system fails.

If the utilities and the public cannot be convinced that new LWRS would be acceptably safe and reliable, however, renewed interest may develop in using alternative reactor technologies. Among the more promising near-term possibilities are high temperature gas-cooled reactors, LWRs with inherently safe features, and the heavy

water reactor.

The high temperature gas-cooled reactor (HTGR) has attracted considerable interest because of its high thermal efficiency (nearly 40 percent-compared to 33 percent for an LWR) and its inherent safety features. The core of the HTGR is slow to heat up even if coolant flow is interrupted; this reduces the urgency of the actions that must be taken to respond to an accident. In addition, the entire core and the primary cooling loops are enclosed by a vessel which would prevent the release of radioactive materials even after an accident. Lessons learned on the only U.S. operating HTGR are being applied to the design of a 900-megawatt (MW) prototype. Small, modular versions (fig. 1) also have been proposed that might have very attractive safety characteristics and be especially suitable as a

source of process heat. While HTGRs appear to be potentially safer than LWRs, there are still many questions concerning HTGR reliability and economics. Continued research and development (R&D) of the HTGR is necessary if these questions are to be resolved.

The heavy water reactor (HWR) has attractive safety and reliability features, but there are several roadblocks to its adoption in this country. The HWR has performed well in Canada, but the process of adapting it to the American environment might introduce modifications which would lower its performance. In addition, much of its good performance may be the result of skillful management and not a consequence of the reactor design. Without significant evidence that the reactor is inherently superior to other options, the HWR is not a strong candidate for the U.S.

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SOURCE: Office of Technology Assessment.

Steel reactor

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market, unless the Canadian technology can be easily adapted, or the U.S. experience with HWRs in the weapons program can be utilized.

The process inherent ultimately safe (PIUS) reactor, a new LWR concept being developed in Sweden, is designed with safety as the primary objective. Protective against large releases of radioactivity would be provided by passive means that are independent of operator intervention and

mechanical or electrical components. Because the PIUS is designed so that a meltdown is virtually impossible, it might be the reactor most suited to restoring public confidence in nuclear power. The PIUS reactor is still in the initial design phase, however, and has not yet been tested, although computer simulations have been initiated to address questions about operational stability. Extensive R&D is needed to narrow the uncertainties about cost, operation, and maintenance. This R&D and eventual deployment of the PIUS, would be expedited by its similarity, in some respects, to conventional LWRs.

Features that might be applied to any reactor technology include smaller sizes and standardized designs. Smaller nuclear plants would provide greater flexibility in utility planningespecially in times of uncertain demand growth -and less extreme economic consequences from an unscheduled outage. The shorter construction periods and lower interest costs during construction would reduce the utilities' financial exposure. The ability to build more of the subsystems in the factory rather than onsite might reduce some construction costs, offsetting the lost economies of scale. Moreover, smaller reactors might be easier to understand, more manageable to construct, and safer to operate. Federal R&D

would probably be required to achieve designs that exploit the favorable characteristics of small reactors.

The potential benefit of a standardized design appears to be especially high in view of the prob- ! lems of today's nuclear industry. Many of the problems with construction and operation stem from mismanagement and inexperience, and a standardized plant would help all utilities learn from those who have been successful. France and Canada seem to have done well with building many plants of one basic design. Still, the implementation of standardized plants in the United States faces many obstacles. Reactor system designs differ from vendor to vendor and grow further apart when coupled with the different balance of plant designs supplied by the numerous AEs. They are additionally modified by the requirements of NRC, the utilities, and the specific sites. Despite these obstacles, the industry may be motivated to converge on one or two standardized designs if that path seemed to offer streamlined licensing, stabilized regulation, faster construction, and better management. The help of the Federal Government may be required to develop and approve of a common design, especially if it is significantly different from the LWR.

The management of commercial nuclear powerplants has proven to be a more difficult task than originally anticipated by the early proponents of nuclear technology. While the overall safety record of U.S. plants is very good, there has been great variability in construction times and capacity factors (see table 2). Some utilities have demonstrated that nuclear power can be well managed, but many utilities have encountered difficulties. Some of these problems have been serious enough to have safety and financial implications. Since the entire industry is often judged by the worst cases, it is important that all nuclear utilities be able to demonstrate the capability to manage their powerplants safely and reliably.

There are many special problems associated with managing a nuclear powerplant. Nuclear reactors are typically half again as large and considerably more complex than coal plants. The job of building and operating a nuclear powerplant has been further complicated by the rapid pace of development. As new lessons were learned from the maturing technology, they had to be incorporated as retrofits rather than integrated into the original design. The regulatory structure was evolving along with the plants, and the additional engineering associated with changing NRC regulations and with retrofits strained the already scarce resources of many utilities. Some utilities have also had difficulty coordinating the various participants in a construction project.

Reliabilityb

Both technical and institutional changes are needed to improve the management of the nuclear enterprise. Technical modifications would be useful insofar as they reduce the complexity and sophistication of nuclear plants and their sensitivity to system interactions and human error. More substantial design changes, such as the PIUS reactor concept, might be considered as an option since they have the potential to additionally decrease the sensitivity of nuclear plants to variations in management ability.

Technological changes, by themselves, however, cannot eliminate all the difficulties involved in building and operating nuclear units since they cannot replace commitment to quality and safety. It is important that design changes be supplemented with institutional measures to improve the management of the nuclear enterprise. One example is the Institute of Nuclear Power Operations (INPO),* which is attempting to improve the quality of nuclear powerplant operation, and to enhance communication among the various segments of the industry.

*The Institute for Nuclear Power Operations is a self-regulatory nonprofit organization organized by the electric utilities to establish industrywide standards for the operation of nuclear powerplants, including personnel and training standards, and to ensure that utilities meet those standards.

The most important improvement required is in the internal management of nuclear utilities. Top utility executives must become aware of the unique demands of nuclear technology. They not only must develop the commitment and skills to meet those demands, but they must become directly involved in their nuclear projects and they must impress on their project managers and contractors a commitment to safety that goes beyond the need to meet regulatory requirements. They also need to establish clear lines of authority and specific responsibilities to ensure that their objectives will be met. INPO could be instrumental in stimulating an awareness of the unique management needs of nuclear power and in providing guidance to the utilities.

It is also important that utilities be evaluated objectively to assure that they are performing well. Both NRC and INPO have recognized the need for such evaluations, and currently are engaged in assessment activities. INPO attempts to assess the performance of utility management in order to identify the root causes of the problems as well as their consequences. The NRC conducts several inspection programs with the purpose of identifying severe or recurrent deficiencies. NRC's program is more fragmented than INPO's,

and the relationships among its various inspection activities appear to be uncoordinated.

Enforcement activities also can be important in encouraging better management. Both NRC and INPO can take actions to encourage utilities to make changes or penalize them if their performance is below standard. If measures taken by NRC and INPO prove to be ineffective in promoting quality construction and safe operation of nuclear powerplants, however, more aggressive action might be required. A future for nuclear power could depend on institutional changes that demonstrate the ability of all utilities with nuclear powerplants to operate them safely and reliably. It is not yet clear whether these efforts will prove adequate.

Another approach might be for the NRC to require that a utility be certified as to its fitness to build and operate nuclear powerplants. Certification could force the poor performers to either improve their management capabilities, obtain the expertise from outside, or choose other types of generating capacity.

Many of the current management problems can also be traced to the overlapping and conflicting authority of the the utility, the reactor vendor, the AE, and the constructor. Centralized responsibility for overall design and, in some

cases, actual construction could alleviate this problem. Increased vendor responsibility might encourage fixed-price contracts for nuclear plants, but it could detract from utilities' ability to manage the plant if they are not involved actively in all stages of construction.

A second means of centralizing responsibility is through nuclear service companies, which already offer a broad range of regulatory, engineering, and other services to utilities. Nuclear service companies could help strengthen the capabilities of the weaker utilities by providing all the services needed to build and/or operate a nuclear plant. However, utilities may be reluctant to forego their responsibility for safety and quality while retaining financial liability. Also, without some mechanism that required weaker utilities to hire service companies, their existence might have little effect on the overall quality of nuclear management.

Privately owned regional or national nuclear power companies would extend the service company concept into the actual ownership of nuclear powerplants. Such companies could be owned by a consortium of utilities, vendors, AES, and/or constructors and would be created expressly to build and operate nuclear powerplants.