During the operation of a complex system such as a nuclear power plant, it is not unusual to find that one or more components have ceased to operate correctly. Given the fact that plant design incorporates extensive redundancy due to defence in depth and defence in time design and operat­ing procedure, as described earlier in this text, there is a reasonable prob­ability that a single failure still will leave the plant in an operable condition. That condition must be fully understood, however, to be certain that con­tinued operation will remain safe, and will stay within the terms and condi­tions of the plant’s operating licence. The most important benefit of this process is that it can reduce the uncertainty associated with slightly abnormal plant states. In case of uncertainty, of course, the operator is bound to return the plant to a known safe operating state.

Attribution of radiation risks and effects to radiation exposure situations, particularly those involving the low doses registered at NPPs, is a tricky issue. It means regarding actual effects or postulated risk, or both, as being caused by the exposure situation and assigning them to the situation, there­fore transferring to the situation the related responsibilities and liabilities (the term is rooted in the Latin attribuere, from ad — ‘to’ + tribuere ‘assign’).

However, this chapter is not intended to address issues of law involving imputation rather than attribution; e. g., it does not deal with the legal concept of causality that is common in occupational litigations (ILO, 2010). Rather, its aims are to focus on the epistemology of the issue, namely on the current theories of knowledge on health effects of radiation at low doses, especially with regard to the methods, validity and scope of the theo­ries. From this epistemological basis, it endeavours to clarify a conundrum in radiation sciences: whether radiation risks or radiation effects, or both, are attributable to NPP operations.

While the attribution of radiation risk is associated with the concept of probability, the attribution of radiation effects should be based on the concept of provability. These two concepts are subtly distinct: probability is an established quantity, measurable through statistical techniques or assign­able through formal Bayesian approaches, which measure the likelihood that harm might be incurred; conversely, provability appears to be an unquantifiable quality describing the capability to demonstrate by evidence the actual occurrence of radiation effects. Thus, on the basis of the available evidence, attribution notions should be elucidated. These should be appar­ent to experts but are usually not substantiated on epistemology and seem­ingly remain obscure for decision-makers and the general public.

A nuclear emergency could lead to very complex situations that require the

intervention of a number of specialized organizations to implement ade­quate countermeasures.

• Fire and rescue brigades, which are responsible for providing help to make the plant safe and to assist the victims most severely affected by conditions derived from and during the emergency.

• Police organizations, which are responsible for maintaining order if controlling access to the affected areas or evacuation of affected people is needed.

• Medical services, which are responsible for providing medical assistance to victims affected by radiation, contamination or as a consequence of the implementation of countermeasures. Medical services are also responsible for providing specific health care by using prophylaxis with stable iodine, which could be a very effective countermeasure to prevent radiation injuries produced by inhalation of radioiodine that is released in case of severe damage to a nuclear reactor, because of its volatility.

• Social services, which are responsible for providing assistance to victims and providing them with adequate first-aid and relocation settlements when necessary. Psychological care of victims of a nuclear accident could also be an important task of social services because the population is not familiar with radiation risk and this can produce anxiety in some cases.

The radioactive material released in the case of a large nuclear emer­gency comprises mainly gases or aerosols. Liquid releases are easily isolated and it is unlikely that a huge amount of radioactive materials would escape in liquid form. In some cases, gaseous releases could be impelled by the large amount of energy accumulated or produced in the nuclear facility, particularly if the facility is a nuclear reactor. This energy can contribute to spreading the releases into high levels of the atmosphere and reaching long distances. In these circumstances the information provided by meteorologi­cal services is crucial in predicting the scope of the contamination and the areas that can be affected as a consequence of the emergency.

In addition, the response to very large nuclear emergencies affecting large geographical areas could require also the participation of many dif­ferent organizations specialized in topics such as facilities decontamination, radiation environmental surveillance, radio-epidemiology and radio-ecol­ogy. Usually these organizations are national institutions which have many international interfaces with homologous organizations from other coun­tries or international organizations. The experience gained from the long­term response given to the Chernobyl accident shows that this kind of international cooperation is a proper way to share knowledge and optimize resources in responding to nuclear emergencies.

Radioactive waste covers a wide spectrum of material types, physical com­position and radioactivity concentration. Also the composition of radionu­clides included in the waste and their corresponding half-lives differs widely. This means that the methods to take care of the radioactive waste will have to be adapted to the specific waste form. In particular it is important to distinguish between solid, liquid and gaseous waste, as well as to consider the radiation level at the waste package and the half-life of the radionu­clides contained in the waste. The physical form of the waste (solid, liquid or gaseous) determines the treatment, conditioning and packaging methods to be used for the waste. The radiation level determines the handling and storage method for the waste, and the concentration and half-life of the radionuclides determines the way they need to be finally disposed of. Radionuclides with half-lives of 30 years or shorter are considered to be short-lived.

Earlier classification schemes distinguished between exempt waste, short­lived low — and intermediate-level waste, long lived low — and intermediate — level waste and high-level waste. Exempt waste had no radiological restrictions. Low-level waste could be handled without extra shielding, while intermediate and high-level waste required shielding for handling and high-level waste also required cooling.[81] Short-lived waste could be disposed of at or near the surface, while long-lived waste and high-level waste would require deep geological disposal. This and similar classification schemes are still being used in many countries.

More recently the IAEA has introduced a new classification scheme that is based on the way the waste will be finally disposed of (IAEA, 2009a). It has the following six classes of radioactive waste:

• Exempt waste (EW): Waste that meets the criteria for clearance, i. e. it has been cleared from regulatory control, and is not considered radioac­tive waste.

• Very short-lived waste (VSLW): Waste that can be stored for decay over a limited period of up to a few years and subsequently cleared for uncontrolled disposal, use or discharge.

• Very low-level waste (VLLW): Waste that does not necessarily meet the criteria of EW, but that does not need a high level of containment and isolation and, therefore, is suitable for disposal in near-surface landfill — type facilities with limited regulatory control.

• Low-level waste (LLW): Radioactive waste with only limited amounts of long-lived radionuclides. Such waste requires robust isolation and containment for periods of up to a few hundred years and is suitable for disposal in engineered near-surface facilities.

• Intermediate-level waste (ILW): Waste that, because of its content, par­ticularly of long-lived radionuclides, requires disposal at greater depths, of the order of tens of metres to a few hundred metres.

• High-level waste (HLW): Waste with levels of activity concentration high enough to generate significant quantities of heat, or waste with large amounts of long-lived radionuclides. Disposal in deep, stable geo­logical formations usually several hundred metres or more below the surface is the generally recognized option for disposal of HLW.

14.1.2 Radioactive waste from nuclear power production

Several kinds of radioactive waste are generated from nuclear power pro­duction. The most hazardous is the spent nuclear fuel (if considered as waste), or the high-level waste from chemical reprocessing of the fuel. Intermediate-level waste is mainly irradiated core components and some long-lived waste from reprocessing. Low-level waste comes from the treat­ment of the water in and off-gases from the reactor primary circuit and fuel handling facilities and from components and material that have been in contact with such water or gases. Some of this waste could even qualify as very low-level waste. LLW and VLLW are generated both during the opera­tion and maintenance of the nuclear power plants (and possible reprocess­ing plants) and during their final decommissioning and dismantling after power production has ceased. In particular, large volumes of VLLW are generated during dismantling.

Some minor amounts of radioactive substances are released from nuclear power plants during normal operation through the cooling water or with the off-gases. These amounts are strictly controlled and in compliance with regulatory limits. Such limits are set very low to ensure a very small radio­logical impact on the people and environment in the vicinity of the power plant. Different processes, e. g. filtration, ion exchange and evaporation, are used to minimize the releases. The normal operational releases from a power plant are not further dealt with in this chapter (see Chapters 11 and 17 for further details), which is dedicated to waste that will be further taken care of.

While OC are important for vendors for preparing their cost calculations and bids, it is the sum of OC and IDC that utilities must arrange financing for. The investment decision, however, is usually guided by a comparison of the total estimated generating costs, i. e. OC plus IDC plus estimated future fuel, operating and maintenance costs, of nuclear power to the same sum for alternative electricity generating options.

Four factors determine the IDC of a construction project: (a) OC, (b) the construction period, (c) the distribution of the OC over the construction period, and (d) the return on equity to shareholders and the interest rate, or rates, to be paid for loans (different rates may apply to different plant components or construction stages). IDC adds an extra layer of uncertainty to the final investment costs of a nuclear power plant. While interest rates can usually be fixed before construction begins or, if they are variable, hedged through various financial instruments, the largest uncertainty in IDC arises from possible construction delays. When cost overruns occur, the largest portion is generally due to construction delays. To the extent that regulatory intervention during plant construction causes delays, it will also increase IDC.

Table 15.1 shows that an increase in the construction period from four years to six or 10 years can increase IDC’s share of total investment costs

from 28% to 41% or 75%, assuming OC of $2000/kW(e), a uniform distri­bution of OC over the construction period and a 10% real interest rate. If the interest rate were only 5%, IDC would be 13%, 19% and 32%, respec­tively, of total investment costs.

Although the particulars will vary considerably between jurisdictions, the decision to build a new nuclear plant will invariably involve a consideration of the anticipated environmental impacts, and whether they can be miti­gated, or even tolerated, to a level whereby the benefits of the development will sufficiently outweigh them. This is not a trivial consideration and history has demonstrated the role that environmental considerations can play in shaping development decisions. There are a variety of different stakehold­ers involved that can influence the decision-making process in favour of the environment such as concerned local residents, nongovernmental organisa­tions and the environmental and planning authorities. All of these inter­ested groups have the potential to ensure that the environmental impacts of a proposed development, taking into account the information available, including that generated from environmental assessments, are factored into the decision on whether or not to proceed. These considerations will also have an effect on the resulting site licensing conditions if the authorities ultimately do provide consent for a proposed installation.

In most civil nuclear States, the planning system is employed to manage the process and help ensure that there has been adequate scrutiny of envi­ronmental impacts. Environmental considerations play a pervasive role in the planning debate and there is therefore a need to understand its proc­esses and the key authorities involved. Although there are common features which unite the legal processes of individual States, this is an area where they have retained considerable autonomy. There are, therefore, a number of permutations and no approach to draw from which will be generally applicable.

For example, many of the relevant provisions that govern the nuclear planning regime in the US are contained in Part 51 of the United States Regulatory Commission’s NRC Regulations (10 CFR Part 51). In addition, IAEA documentation such as the Fundamental Safety Principles (IAEA, no. SF-1), Milestones in the Development of a National Infrastructure for Nuclear Power (IAEA, no. NG-G-3.1) and Stakeholder Involvement in Nuclear Issues (IAEA, INSAG-20) are all important starting points from which most civil nuclear States have developed their domestic legal systems. Although there is no common approach, the UK experience serves as an instructive model with respect to land-use planning. The Planning Act 2008 (PA 2008) has introduced significant changes which will alter the content and procedure of the planning process (albeit subject to further change following the election of the coalition government in the UK in May 2010). Added to this is the considerable international interest in the UK market relating to its commitment to a new generation of nuclear power stations. There is significant common ground between the planning system in the UK and other civil nuclear jurisdictions, and a general understanding of its key features will be beneficial to a variety of different stakeholders.

The potential impacts that an operating NPP may bring to the site are related to the atmospheric, surface and ground water dispersion of radioac­tive material affecting the population and the use of land and water in the affected region. Specific requirements and corresponding safety guides follow.

Atmospheric dispersion of radioactive materials

During NPP operation small amounts of radioactive nuclides are released to the atmosphere under strict control. Those nuclides include some noble gases which cannot be retained by any treatment process, as well as some volatile elements and particulate matter which may not be completely retained in the high-efficiency radioactive waste treatment system.

In pressurized water reactors (PWRs) fission and activation gases in the coolant are separated and stored for decay and finally vented to the atmos­phere before refuelling outages; most of these gases have short lives and disappear during the storage period with the exception of krypton-85 (half­life 10.6 years) which becomes the larger contributor of gaseous releases. Iodine-131 (half-life 8.06 days) and hot particles — radioactive particles including fission and activation generated radioactive nuclides — could also be found in the containment atmosphere from coolant leakages. Small amounts of such materials can also be released to the atmosphere after being filtered by activated carbon filters, to retain iodine, and high-efficiency particle air filters. In boiling water reactors (BWRs) radioactive gases gen­erated in the coolant are carried by the steam, separated in the condenser and released to the atmosphere continuously after passing for a few days through a delay system composed of a large activated carbon bed main­tained at low temperature; short-life nuclides decay during transit through the bed with the exception of krypton-85 and xenon-137 (half-life 5.27 days), while most of the iodine nuclides are retained in the activated carbon bed.

The behaviour of the released radioactive nuclides has to be predicted to measure the potential effects of such releases on the health and safety of the affected people and on the environment. Meteorological dispersion parameters have to be measured by dedicated meteorological towers to determine wind speed and direction, air temperature, precipitation, humid­ity and atmospheric stability parameters. With all these data sophisticated dispersion models are developed which also take into account the topogra­phy of the place and the effects that buildings may have on the dispersion of the released materials. These studies are conducted at least one year before starting plant construction and meteorological towers and data gath­ering are maintained during the whole operating life of the NPP.

The availability of meteorological data at the time and during an acci­dental release of radioactive products is essential to emergency manage­ment. In these cases the site dispersion data have to be supplemented with the data and dispersion models of the country’s central meteorological agency.

An IAEA safety guide has been developed to indicate the ways and means to obtain such data and develop the site dispersion models (IAEA, 2002b). The guide describes how to select and display a meteorological data gathering system appropriate to the topography and physical characteristics of the region where the plant is located. The guide also describes methods to develop an ad hoc dispersion models which will also include the con­tamination of soil and the potential resuspension of radioactive aerosols and hot particles, as well as contamination of vegetables and other food products. Such models are essential parts of the theoretical estimation of the potential radiation doses that the affected population may receive from atmospheric radioactive releases by direct exposure to the radioactive cloud and other pathways. The model is also essential in the epidemiological studies generally conducted around nuclear sites.

This section is dedicated to laying out the owner’s requirements for com­munications among project participants. The main topics to be addressed are requirements for written communications, correspondence filing and coding system, correspondence distribution criteria, record keeping, quality assurance requirements for the transmission of quality-related design data, and record of correspondence pending answer.

19.4 Technical data sheets

The technical data sheets (DS) document consists of a set of data sheets summarising the following information in a table:

• The main technical requirements specified in the TR, NF and PI documents

• The main technical data for plant structures, systems and components.

The table format usually presents the information in the following manner: in the left-hand column, the owner briefly sums up the key technical require­ments for which a summary answer is requested from the bidder (to be included in the right-side column, left blank). This table is to be completed by the bidder directly and included in his bid.

It should be noted that data sheets are only a summary of technical features and data presented in an organised and systematic manner, for the purpose of obtaining, in addition to the bids: (a) answers from all the bidders organised in the same fashion; (b) a quick understanding of the compliance of each bidder with key requirements; and (c) a consistent tabu­lation of plant data to facilitate bid evaluation. Thus it is understood that more detailed information regarding plant design and features is to be found in the technical descriptions, drawings and data included by the bidder in other parts of the bid.

It is advisable for the technical data sheets to be organised into three sets, as follows:

1. Data sheets covering the main data at the overall plant level, to provide a quick overview of plant design parameters and features.

2. Data sheets addressing compliance with the main top-level design objectives as they are specified in the BIS and organised by project discipline (e. g. licensing and regulations; nuclear safety; civil-structural; NSSS; systems and equipment; turbine-generator and steam cycle; rad — waste systems; electrical systems; I&C; BOP; project implementation).

3. Data sheets listing the main technical data (i. e. performance, design conditions, operating conditions, materials, quality classification, codes and standards, etc.) of main plant structures, systems and components. This third set of technical data sheets can be organised as follows: NSSS systems and components (e. g. reactor pressure vessel, steam generators, main coolant pumps); emergency core cooling systems (ECCS); reactor auxiliary systems, containment systems, nuclear fuel supply and han­dling; radwaste systems; plant auxiliary systems; electrical systems; I&C systems; turbine-generator and auxiliaries; steam-cycle systems (main steam, feedwater, condensate, etc.); and cooling water system.

The RB must verify compliance with applicable regulatory requirements and with the license terms and conditions during each phase in the life of the NPP. Such verifications are achieved through regulatory inspections, oversight procedures, and analysis of the multiple progress and evaluation reports provided by the licensee.

20.6.1 Regulatory inspections

Regulatory inspections are carried out during each phase in the life of the NPP with the aim of checking the safety compliance of the NPP, through physical verification of the condition of its SSCs and by auditing of opera­tional records. In many countries, the RB keeps resident inspectors in a given plant or clusters of plants to continually oversee the safety of the installation. The RB should specify the frequency, lay down formal procedures and authorize appropriate staff for carrying out these inspec­tions. However, special inspections can be conducted when considered necessary.

The inspection findings should be discussed with senior managers of the NPP to resolve any anomalies and thereafter the inspection report should be submitted for review by the appropriate safety committees. RBs have established formal procedures on how to write inspection reports and how to formally include in such reports the licensee observations and claims to be considered before any regulatory action is taken.

The recommendations arising from the inspections and from a review of the inspection reports should be categorized according to their importance to safety following the criteria specified by the RB. Implementation of the recommendations should be done according to the schedule agreed upon between the RB and the operating organization, and the RB staff should follow this up.

For a country with nuclear interests the development of a national nuclear education programme involving government agencies, laboratories and research facilities, helping to attract and develop initial experience and knowledge in nuclear technology, is highly recommended.

Nevertheless, and while the national academy system is mature enough and some nuclear programmes have been developed at the university level, it is possible to rely on other countries to offer and maintain these types of educational programmes.

What is, without any doubt, necessary from the beginning is to have a good general engineering (electrical, mechanical, control and process) and physics education infrastructure, producing high-quality graduates, who can then be trained in appropriate nuclear subjects, either within the industry, in cooperation with other training or academic providers, or even as part of the turnkey contract by the vendor.