Other initiatives to promote the renewal of competencies are on-going in different fields: nuclear safety courses organized by the Network of Excellence for Severe Accident Research (SARNET), winter and summer schools in the field of actinide science organized by the ACTINET Network of Excellence, the Frederic Joliot and Otto Hahn Summer School on Nuclear Reactors, and the Latin American Network for Education and Training in Nuclear Technology (LANENT), currently in the process of creation, are examples of such initiatives.

Especially active are the European Nuclear Engineering Network (ENEN) and the Asian Network for Education in Nuclear Technology

(anent).

Maintenance of good chemistry of reactor system fluids is essential for minimizing corrosion of reactor system components and generation of acti­vation products that can give rise to high radiation fields on piping and equipment, resulting in increased radiation exposure of plant personnel. Reactor coolant and moderator water chemistry is generally maintained by circulating a part of the coolant flow through ion exchange resin beds. At times neutron poisons such as boron are added to the coolant in the form of boric acid to suppress excess reactivity. In this case the resins used need to be saturated with boron to prevent unwarranted boron removal that can give rise to reactivity gain. For the same reason dilution of borated water in the reactor system by inadvertent addition of unborated water must be prevented. Conversely, boron removal to gain reactivity in a controlled manner can be done by passing the coolant through ion exchange resins that have not been saturated in boron. The moderator system is normally vented to an inert cover gas such as helium in heavy water moderated reac­tors. Build-up of deuterium can take place in the moderator cover gas due to radiolytic decomposition of heavy water. This has to be kept within pre­scribed limits to prevent the concentration reaching explosive limits. For this purpose the cover gas has to be purified by passing over a catalytic recombiner. Similarly, in light water reactors hydrogen build-up in the reactor coolant is vented to catalytic recombiners. From time to time activa­tion products that have deposited on the inner surfaces of system piping need to be removed to bring down radiation fields on piping. This is done by dilute chemical decontamination of the system, ensuring that base metal of the piping and other system components including cladding of fuel assemblies in the core are not subjected to any significant corrosion.

Chemistry of the secondary coolant of the reactor also has to be main­tained within proper limits to ensure good health of the secondary system components such as the steam generators and the steam turbine. Appropriate chemicals are added to the system and the condensate is subjected to pol­ishing by ion exchange resins before being pumped back into the feed water system. Deaeration of feed water is done to maintain dissolved oxygen content at very low values to minimize corrosion of secondary system inner surfaces.

It may be noted that chemistry control of reactor systems plays a vital role in minimizing corrosion and thereby helps in trouble-free operation of the NPP over long periods of time. It also helps in minimizing build-up of radiation fields on system piping and components thereby reducing radia­tion exposures of personnel. Proper maintenance of system chemistry is also necessary from a reactivity safety point of view. A well-trained and competent reactor chemistry group is therefore essential for safe and effi­cient long-term operation of the NPP. The technical competence of this group should be continually enhanced by in-house research as also by keeping abreast with the latest developments in this field worldwide. The chemistry group should also maintain close contact with academic and other relevant institutions in the country having expertise in specific areas such as corrosion and seek their assistance whenever necessary.

Various organizations, including design organizations, utilities, universities, national laboratories, and research institutes, are involved in the develop­ment of advanced nuclear plants. The IAEA ARIS database (IAEA, 2010) summarizes global trends in advanced reactor designs and technology and provides balanced and objective information about all available designs.

Since this chapter focuses on the technology options that are available for newcomer countries, it will concentrate on the evolutionary reactor designs, as these are the most likely candidate technologies for most coun­tries’ first nuclear power plant, particularly in the near to middle term. For completeness, however, there will also be included a brief discussion exam­ining future trends for the development of nuclear reactors in the long term.

Evolutionary reactor designs have concentrated on improving the eco­nomics and the performance of existing nuclear reactors. At the same time, these designs meet even more demanding nuclear safety requirements than those currently in operation. While efforts have also been made in optimiz­ing the use of fissionable materials and minimizing the production of used fuel and nuclear waste, it is expected that the closure of the nuclear fuel cycle will only be achieved once innovative reactor designs come online.

There are many organizations that can and will help an operating organiza­tion build up the necessary skills, recommend their optimal business and professional infrastructure, and assess the performance of the organization over the lifetime of the plant. In addition, current members of some of these organizations, usually who operate similar plants to the one that the new operating organization has built, have formed ‘owners groups’ with the purpose of exchanging detailed operating information and experience. Some have set up arrangements whereby they manage common research and development projects on behalf of their members. These owners’ groups have proven to be very valuable in broadening knowledge as well as in reducing operating costs.

Support groups in operating organizations have established so-called ‘living PSA’ analysis systems with responsibility for daily updating of the plant operating and maintenance state, forward planning of scheduled mainte­nance operations, and contingency planning programs to predict the correct course of action for shift management personnel in the event of anticipated abnormal operating states. These incremental risk estimates are based on the latest updated version of the plant safety assessment.

A good example of this application to power plant operation is the soft­ware package named EOOS (Equipment Out Of Service), the risk and reliability workstation (EOOS Demo 3.5, 2008) produced by the Electric Power Research Institute (EPRI). EOOS is independent of other EPRI reliability analysis software such as the Cutset and Fault Tree Analysis (CAFTA) system (CAFTA, 2009) but uses many of the same conventions.

EOOS uses a safety or risk model of the plant, based on fault tress and minimal cutsets, such as those developed in a Probabilistic Risk Assessment (PRA). EOOS wraps a user-friendly interface around these reliability analysis tools to make them accessible to non-PSA experts.

EOOS communicates in the language of its users — using the familiar termi­nology of components, trains, systems, tests, and clearances. Using the current plant configuration, EOOS can propagate information through the model and quantify risk measures. EOOS translates fault tree results into color-coded status panels, timelines, and lists of relevant and risk-significant activities. Within seconds, an EOOS user can identify a safety problem, and the specific work activities that cause it. The EOOS user will then have the information to decide whether the problem is significant enough to warrant special contin­gency actions.

The software offers various benefits and values for the user. EOOS can help reduce Operation and Maintenance (O&M) costs by: (a) reducing the chance of a costly operational mistake. As unplanned events creep into a well-planned work schedule, you run the risk of unexpected reductions in plant safety. EOOS detects these safety problems that routinely escape the scrutiny of safety reviews based on train-level work windows, (b) by reducing the labor needed to perform safety reviews. An EOOS model integrates the safety impact of all work tasks affecting all risk significant safety functions into concise screen presentations and printed reports, (c) by providing credible, risk-based insights that minimize unnecessarily conservative requirements. EOOS results can become the basis for eliminating requirements that increase outage dura­tion, without a commensurate safety benefit.

Conversely, malignant or hereditary effects cannot be unequivocally attrib­uted to radiation exposure on individual bases for reasons of counterfactual conditionality. This is because radiation exposure is not the only possible cause of these types of effects and, at present, no biomarkers are available for these effects that are specific to radiation exposure.

However, while the occurrence of malignant effects (or of hereditable effects in the descendants of those exposed) cannot be unequivocally attrib­utable to radiation on an individual basis, an increased incidence of these effects in a population can theoretically be attributed to radiation on a col­lective basis. Collective attribution can be established through epidemio­logical analysis, under the following conditions:

• The number of cases of the effect in the exposed population should be sufficient to overcome the inherent aleatory uncertainties of epidemio­logical analyses.

• In addition, the increase in the collective prevalence of the effect in the exposed population is properly attested by a qualified radio-epidemio­logical procedure.

In situations of chronic exposures at levels similar to those arising from normal operations of NPPs, the expected number of additional cases of malignancies in a commensurate population for an epidemiological study would be so low that attribution is unattainable either individually or collectively.

Thus, while increased incidences of malignancies and hereditary effects might theoretically occur in populations exposed to NPPs, since it is not feasible to obtain unequivocal scientific evidence of their occurrence, they therefore should neither be deemed attributable nor be used prospectively in notional projections of radiation harm. Moreover, hereditary effects cannot at present be attributed to radiation exposure, even at high doses, because the fluctuation in the normal incidence of these effects is likely to be so much larger than any expected radiation-related increase in the incidence.

It is to be noted, however, that occasionally individual attribution can nevertheless be ostensible, namely, apparently factual, even if not necessar­ily so; this may be the case when:

• the ‘background’ incidence of the effect is low, and

• the radio-sensitivity of the effect is high.

A typical example of ostensible individual attributibility is the case of fol­licular thyroid cancer in children exposed to relatively high thyroid doses such as those incurred after the Chernobyl accident.

In designing a nuclear facility a comprehensive safety analysis is carried out to identify all sources of exposure and to evaluate radiation doses that could be received by workers and the public, as well as the potential impact the facility can have on the environment. Every event sequence, including those originated by extreme external phenomena, that may lead to an accident is examined in the safety analysis, and the results are used as the basis for designing emergency arrangements, which include:

• Designing and ensuring full operability of the safety system installed to mitigate accidental sequences leading to uncontrolled releases of radio­active material to the environment or producing damage to the plant and the unwanted exposure of its personnel

• Implementing adequate operational procedures to lead the plant to safe conditions after any accident or malicious acts that can seriously damage reactivity control systems, cooling systems or confinement of radioactive material systems

• Implementing a training programme to ensure that all personnel have adequate skills to manage any crisis generated by any situation that can lead to an emergency situation.

During plant operation emergency preparedness activities are focused on maintaining and improving the capacity to manage any emergency situ­ation. These include: [9]

• Conducting an adequate drill and exercise programme to validate, train and enhance the emergency plans and procedures.

Over the years an international regime has developed for the safe manage­ment of spent fuel and radioactive waste. Three components can be distin­guished: (1) the Joint Convention on the Safety of Spent Fuel Management and the Safety of Radioactive Waste Management, (2) the IAEA Safety Standards Series and (3) the National Regulatory Control Systems.

The objectives of the Joint Convention (IAEA, 2006a) are to achieve and maintain a high degree of safety worldwide, to ensure that there are effec­tive defences in place against potential hazards and to prevent accidents and mitigate their consequences. The Joint Convention is the first interna­tional legally binding agreement in the area of radioactive waste manage­ment. The technical basis for the Convention is provided by the IAEA Safety Fundamentals (IAEA, 2006b). It is an ‘incentive’ convention, which means that there are no fixed penalties and that improvements in safety are stimulated through the review process. The articles of the Joint Convention set targets. Issues covered by the Joint Convention include provisions on how to ensure safety through proper legal and regulatory systems and proper siting, design, operation and decommissioning of the necessary facilities.

The Joint Convention applies to spent fuel and radioactive waste result­ing from civilian nuclear reactors and applications or handled in a civilian programme. It also includes spent sealed sources, planned and controlled releases into the environment from regulated nuclear facilities and waste from mining and processing of uranium.

The important tools of the Joint Convention are given by the review meetings that are held every three years. At the review meetings the national reports are reviewed and commented on by the parties to the Joint

Convention. The national reports give a good overview of the management of spent fuel and radioactive waste in the country. The review process pro­vides a good opportunity for exchange of lessons learned and also encour­ages the countries to develop their activities. At the end of 2009 the Joint Convention had 52 contracting parties, including 26 of the 30 countries with nuclear power plants.

The term nuclear fuel costs often refers to nuclear fuel cycle costs which in many cases includes the costs for the front end and back end of the fuel cycle. The front-end or fuel input costs of the nuclear fuel cycle are deter­mined by the prices of uranium mining and milling, conversion to UF6, enrichment, if applicable, fuel assembly fabrication and interest on fuel in inventory. Back-end costs include those for reprocessing, if applicable, and disposal of high-level radioactive waste or spent fuel and for plant decom­missioning (after final closure of the plant) and site rehabilitation.

Historically, nuclear fuel costs have varied between 10% and 20% of total generating cost (see Fig. 15.8) depending on prevailing uranium resource and enrichment costs, interest rates and whether or not back-end costs are included in fuel costs or treated as part of the variable O&M costs. Although generating costs are location — and design-specific, Fig. 15.8 indicates the relative shares of the cost components of nuclear electricity generation.

Source: NEA

15.6 Nuclear power life-cycle generating costs (NEA, 2003). Fuel costs for nuclear comprise the costs of the full nuclear fuel cycle including spent fuel reprocessing or disposal.

Uranium metal and the price of enrichment services are the cost compo­nents most susceptible to fluctuation and supply and demand imbalances.

The IAEA document entitled Milestones in the Development of a National Infrastructure for Nuclear Power (IAEA, no. NG-G-3.1) sets out a frame­work of milestones in the development of a national nuclear infrastructure. The three core milestones are: (1) ready to make a knowledgeable commit­ment to a nuclear programme; (2) ready to invite bids for the first nuclear power plant; and (3) ready to commission and operate the first nuclear power plant. The first of these milestones is of paramount importance whether a State is deciding to embark on its first nuclear power plant or, as in the UK, deciding to commission a new fleet of nuclear power plants. If there is no desire on the part of the legislature or national authorities in a given State, installations will not generate enough interest to survive to the planning stages of a development. In the UK, after many years of indeci­sion, milestone 1 was achieved when government energy policy, enshrined in legislative White Papers, made an express commitment to a new genera­tion of nuclear plants.