Nuclear power plant operation along with many other industrial plant operations is inextricably linked with a number of environmental issues. These have and are being considered within a global context, e. g. within the UN (Stockholm 1972 and Rio 1992) and also within the EC. National governments are also addressing these issues by charging various government bodies, agencies and commissions to advise on policy and propose discharge consents, etc. to meet national and/or international targets for emissions.

In the UK (Fisk, 1999), a number of enquiries into future nuclear power have addressed environmental issues in their deliberations. For example, within the past few years the House of Lords has conducted an enquiry into nuclear waste, the Environmental Agency has proposed discharge consents for reprocessing at Sellafield and the Royal Commission for Environmental Pollution has considered evidence on energy and the environment. These initiatives have largely been driven to make input to the debate on how the UK can meet greenhouse gas emission targets for the period 2008-2012. This issue has been a consideration in the UK Energy Strategy Review (Performance Innovation Unit, 2002; DTI Energy White Paper, 2003). The greenhouse gas targets are particularly challenging. Figures 2.4 and 2.5 show the dependence on nuclear energy in 2002 with nuclear electricity representing 23% of the total electricity supply. Without new building, the nuclear fraction figure will reduce with the shutting down of all the remaining Magnox stations by 2010, and some of the remaining AGRs by 2020 (Table 2.8).

Fisk (1999) considers environmental issues within the wider context of ‘sustainable development’ to which the UK government is committed. There are a number of definitions of this concept. A common definition is ‘meeting the needs of our generation without compromising the ability of future generations to meet their needs.’ This definition was put forward by the Brundtland at the end of the 1980s. Generally, the term has come to

mean improved welfare for everyone both in the present and the future. The key concept here is ‘improvement for everyone as opposed to improvement for some at the expense of others.’

Sustainable development and nuclear power invoke a number of issues, perhaps the most important is the issue of waste. Nuclear waste can in principle cause harm to future generations, which could certainly result in the future without an adequate waste strategy. Since in most countries at the present time, there is no agreed strategy, the question must be asked whether it is justifiable to continue with nuclear energy power production, thus generating waste in the hope that future generations will be able to solve the problem.

□ Renewable 3%

Different countries may have different levels of acceptability. There are legacies of inadequate waste disposal in some countries that are now posing significant problems (and expense) to resolve. Practices have been adopted that would now not be considered as acceptable, yet were considered so at the time. Thus, levels of acceptability can and do vary from one country to another and will also change with time. Further there may be economic reasons to transport waste from one country to another, perhaps with less stringent environmental standards. Is this acceptable, both from a global environmental standpoint, or indeed from a moral standpoint — clearly the answer should be no.

The liabilities associated with decommissioning nuclear power plants once they have reached end of life are another important issue. These are obviously inescapable for currently operating plant; liabilities are a critical factor with regard to decision-making for the building of new plant. Having adequate decommissioning plans prior to building is now typically a regulatory requirement. In the UK, for example, there must be such a provision. From an economic perspective, there is the issue of whether adequate funds are in place for decommissioning, these may be available through increased price levies, or government underwriting of liabilities.

Aside from the concerns of waste disposal, perhaps the major environmental requirement from the public is that the risk of severe accidents is not only small, but also that if such accidents were to occur they can be effectively managed. This is a particular concern for older currently operating plant, which perhaps (and indeed were) licensed under more tolerant licensing regimes than those of the present day. Such plants may have greater vulnerabilities for severe accidents than some modern plants.

It has been discussed above that an important environmental benefit put forward for continued nuclear power plant operation is that it does not contribute to increased global warming and acid rain. The challenge is how to realise this benefit. National governments may set up infrastructures offering incentives to reduce emissions, which might be achieved either by building of new nuclear plant or through life extension of existing plant. In the latter case though, safety must not be compromised. Pressures to continue operation may be very great where no alternative power producers are available. This may be particularly true in the less developed countries. From an environment perspective, clearly safety considerations and the avoidance of adverse environmental consequences resulting from an accident must be paramount.

The experience from nuclear plant operation has shown that effective plant management and organisational structures are essential to support all operations of plant activity including normal operation, maintenance, refuelling, etc. These are also necessary to achieve the economic performance required by the licensee and to meet the environmental and safety standards required by the regulator.

A good description of practices presently adopted by international bodies and the results achieved is given in IAEA Technical Report No. 369. This book is written in the form of a manual describing a number of ways by which interested parties can transfer to their own situation, the experiences of experts from a number of IAEA Member States. Many of these management practices (developed in the remainder of this section) apply across other large industries.

It requires significant managerial skill to achieve the necessary cost reductions and resource allocations against budget limitations without impacting on the operational and safety performance of the plant. To facilitate these, senior managers must define carefully and communicate to their workforce, the objectives, strategies and criteria in order that correct decisions can be made at all levels to achieve balance between the trade-offs of operational excellence and low cost.

To further the implementation of high standards, an approved quality assurance (QA) programme is usually mandatory, which should be periodically reviewed and updated. International standards such as ISO-9000 are required for many plants (or other comparable quality management systems).

To achieve good operational efficiency, it is important to have a positive and well — motivated work-force and this can only achieved via good employee and management relations. Management must be seen to implement its stated programmes in order to command the necessary respect and support from employees. It must also maintain good relationships with contractors.

In cutting costs to improve efficiency, it may be necessary to reduce staffing levels and this situation may impact adversely on staff morale. Technical Support Organisations can also be impacted if the operating companies place less work outside. This situation must be managed to ensure that the resource reduction is achieved via voluntary staff release as far as possible.

Clearly loss of valuable technical expertise may not result in increased efficiency if there is an inadequate quota of technically trained staff remaining. In many instances, it is the more able staff who leave first during uncertainty and times of change. At a later date, there may be increased costs in recruiting and training new staff in the highly specialised and technical nuclear industry.

Efficiency may be improved via new and more innovative management approaches. New management may consider greater empowerment to lower levels of the organisation. Delays in processes (e. g. signing of routine forms) due to the absence of senior management and the burden on senior management in performing such activities are not efficient. A more imaginative management may introduce simpler work processes.

It is important that the consequences of necessary management decisions to improve efficiency are portrayed in a balanced picture. In times of change, employees may dwell on more negative aspects but for example, reduction in work-force and greater empowerment will mean that the remaining employees have greater responsibilities, more rewarding jobs and more opportunities for promotion. Such positive aspects should be recognised in good management teams.

By virtue of the plant operating licence, ageing plant structures must have sufficient integrity to meet all safety requirements during the latter stages of plant life. However, the impact on the structures from decommissioning operations must also be assessed prior to decommissioning. For example, in the case of the containment, there may be a need to erect another structure to meet the required containment safety function.

In the decommissioning of ageing plants, structural integrity of vital components cannot be expected to meet the present day standards. In this case, the adequacy of the components will need to be considered against ALARP principles.

Current plants in Japan are licensed against Japanese regulatory standards, codes and guidelines. The Japanese approach to safety is harmonised with other international activities through participation in IAEA activities. For example, Japanese utilities participate in the US ALWR initiatives.

The requirements for future ALWRs are being established by both regulator and utilities. In parallel, design programmes for future plants are proceeding with improved safety levels. Current Japanese plants such as the APWR and ABWR have core melt frequencies below 1E-6/reactor year, below the International Nuclear Safety Advisory Group (INSAG)-3 target for future plants of 10E-5/reactor year.

6.3.8 Argentina

Regarding the present, there are two PHWRs operating in Argentina. Regarding the future, Argentina is a member of the Generation IV Forum initiative.

6.3.9 Brazil

Brazil has two PWRs operational at the present time. Brazil has also signed two ‘energy’ partnerships with the US which amongst other objectives are to aid research and development in advanced nuclear technology. This relates particularly to the international Generation IV initiative (Foratom e-Bulletin, 2003e).

There are a number of issues impacting the choice of ADS neutronic parameters, in particular the ADS reactivity, keff. The degree of sub-criticality (keff) must be a balance between safety and acceptable economics. Here keff represents the sum of the initial reactivity and all other possible effects, e. g. burn-up reactivity swing including Np or Pa effects, power and void reactivity, etc.

ADS can be used for minimising the sources of long-term radiotoxicity, e. g. reactor fuel inventories, fuel wastes from reprocessing, and long-lived radioactive fission products (Slessarev, 1997). According to Salvatores et al. (1995), the latter two of these sources are the most important in terms of the accumulation of radiotoxicity.

For example, consider the neutronic potential of a representative ADS within a uranium fuel cycle complex (Slessarev, 1997) in the following system. A slightly sub-critical lead — cooled fast breeder reactor with nitride fuel and proton beam source with a keff of 0.98 would exhibit a neutron surplus of about 0.4 neutrons per fission (zero breeding gain in the fuel) plus 0.05 neutrons/fission due to spallation in the lead target. The lead is used as a liquid and target. This gives a total neutron surplus of 0.45 neutrons/fission, sufficient to burnout all dangerous fission products and/or reproduce new fuels for further nuclear power utilisation.

In this system, there is no need for control rods; it is a dual circuit, and a relatively inert coolant from the point of view of safety, e. g. fire hazard. The neutronics are sub-critical plus a stabilised reactivity increment. This system provides an apparently good balance

with regard to economics, reduction of fuel waste potential and safety for the uranium fuel cycle.

The thorium fuel cycle has a much lower waste toxicity level for both thermal and fast reactors than does the uranium fuel cycle. This is because of its smaller production of trans-plutonium (Carminati et al., 1994; Rubbia et al., 1995) and, therefore lower minor actinide concentrations (at least for about 1000 years before some build up of long-term toxic U, U, Pa). From a neutronic perspective, however, every fission of Th produces fewer neutrons than does 238U. There are other disadvantages in relation to achieving sub-criticality at economic cost and a protactinium effect, which implies a low keff value. Thus for the thorium cycle, it is necessary to have a compromise between the economics, sub-criticality level and safety margin. This is difficult because a low keff can only be achieved at more expense; reduced cost would be at the expense of higher keff and less safety margin.

The SVBR-75 reactor module is designed by EDB Gidropress and SSC RFIPPE for steam production to replace VVER-440 reactors that are being decommissioned (SSC RF-IPPE, EDB, 1996; Stepanov et al., 1998) (Figure 14.3). Specifically it has been designed for application in the Novovoronezh power plant facilities as units 2, 3 and 4 are decommissioned. The concept is flexible and can be applied for combined generation of heat and electricity. The SVBR-75 concept exhibits the important features of lead — bismuth coolant systems (Gromov et al., 1996).

14.6.1 ANSTREM

The ANGSTREM project (Stepanov et al., 1998) is based on the concept of a modular, transportable nuclear power and heating station, utilising fast reactor technology with lead-bismuth eutectic cooling. The main design organisation is EDB ‘Gidropress’ together with IPPE, Obninsk providing scientific consultancy. The ANGSTREM technology is envisaged for a number of applications including electricity generation, heat supply, freshwater and possibly hydrogen production.

Separate effects tests were carried out for the AP600 design to demonstrate the feasibility of using a passive core cooling system to mitigate all design basis accidents. There were also confirmatory tests to verify the performance of the various system components. These included: passive residual heat exchanger, automatic depressurisation, passive core cooling system check valve and core make-up tank tests.

In addition to separate effects tests, there were also passive core cooling system tests to demonstrate the overall system performance for both pressurised and de-pressurised conditions. The test facility for this programme was the Oregon State University APEX facility, and the programme was carried out within a Westinghouse/USDOE collaboration.

There were a number of thermal-hydraulic facilities commissioned and operated during the 1980s and 90s in support of the needs of currently operating plant. Many of these facilities have been dismantled but others remain either in standby or in operation to service the needs of evolutionary water reactors. Facilities include PKL, SPES for PWR, PIPER-ONE for BWR, PACTEL and PMK for VVER and PANDA for BWR (Addabbo et al., 2001).

The SPES facility (Bacchiani et al., 1994) at the SIET facilities in Piacenza, Italy was modified to include a passive core cooling system and used for high-pressure system loop thermal -hydraulic tests in support of AP600. All the safety systems were simulated and a series of tests addressed LOCA, steam generator tube rupture (SGTR) and SLB thermal — hydraulic issues. PKL is currently in use to simulate boron mixing effects, in connection with a present day reactor transient issue involving boron dilution during reflux condensation in a LOCA.

Although configured for VVER geometry, PACTEL tests (Kervinen et al., 1990), have been carried out to simulate passive injection during a LOCA, which is of relevance to the AP600 safety system function.

15.10.1 Containment Tests

Many of the confirmatory tests for AP600 were in justifying the passive containment cooling system. Separate-effects tests to characterise the decay heat removal character­istics of the containment design were carried out. These tests included the investigation of heat removal from wetted steel plates simulating the containment surface. Also containment external cooling air flow path pressure drop tests were carried out to characterise the frictional losses. Steam condensation tests on surfaces at different angles were performed to simulate condensation inside the containment in the presence on non­condensable gases.

Composite containments, including a steel inner liner and an outer concrete shell, have been considered to meet potential European requirements for licensing. The outer concrete shell provides greater strength to mitigate the consequences of some severe accidents. Experiments to establish passive containment cooling for such containments were carried out in the PASCO facility at FZK, Germany (Erbacher et al., 1995).

Passive systems are a feature of a number of advanced evolutionary LWRs, both for primary coolant system heat removal and for containment cooling. Tests are in progress in the PANDA facility in Switzerland in the EC TEMPEST programme (Wichers et al., to be published), to resolve outstanding issues of the effects of light gases for confirming the long-term LOCA response of the passive containment cooling systems for SWR100 and ESBWR.

Although much progress has been made on the technical issues associated with waste disposal, the public has considerable concerns over the issues of waste management and the management of spent nuclear fuel (Ryhanen, 1996). As a consequence, these concerns are still some of the important reasons put forward against the building of new power plants and the sustainability of nuclear energy. Perhaps the major concerns of the public relate to the legacy of long-term radioactive waste and our obligations to future generations.

Research carried out by Duncan (2003) for the UK, Switzerland and Japan indicates that when considering the environment and family about 60% of the populations sampled considered timescales of 50 years or less and about 85% selected 100 years or less. These are much shorter timescales than are required for the isolation of hazardous wastes before their radiotoxicity is reduced, as illustrated in Figure 2.7.

The issues and status of present day approaches to waste management are considered in detail in Chapter 6.

5.1. INTRODUCTION/OBJECTIVES

Within present day generation plants, there is a continuous drive to improve all aspects of performance and safety in nuclear fuel cycle technology and practices. The approach is to optimise fuel cycles as a whole, taking into account all components from mining to disposal. This will include the various options for fuel supply, fabrication, generation, fuel storage, reprocessing, recycling, waste management, disposal and decommissioning. It will be necessary to simplify the fuel cycle to reduce costs, while still minimising the environmental impact, maintaining the safety of and retaining public confidence in fuel cycle facilities. Particular goals are to improve fuel performance for longer life in the reactor and the development of advanced fuels, including mixed oxide (MOX) fuel. This chapter reviews these issues and practices in turn.

There are many drivers for advanced fuels development. For current and evolutionary plant optimised uranium-based fuels are being considered to enable higher power, longer life and longer fuel cycles. The utilisation of MOX fuels in thermal reactors is one method of burning unwanted plutonium from weapons programmes. Other fuels such as thorium offer advantages of reduced actinide inventory in waste. Future reactor systems offer a means of managing actinides and reducing the radiotoxicity of waste.