19.5.1 Whiteshell laboratories decommissioning

As discussed above, the Whiteshell Laboratories decommissioning project to date has focused on decontaminating and modifying nuclear facilities, laboratories and the associated service systems and removing redundant buildings to reduce risk and operating costs. The lessons learned associated with the management of the waste already stored on the site and produced during the decommissioning activities arise from three main activities: job planning, physical decommissioning, and maintaining safety through the decommissioning project timeline.

The waste management strategy must be developed in advance, with the flow of waste materials and the required resources identified to ensure that ‘waste material flow’ does not become the critical path, and limit the progress of the physical decommissioning. The process used involved radio­logically screening and segregating the waste at the source. This task can be long and repetitive; therefore, it was found beneficial to rotate workers to enhance training of staff and mitigate human error. To enhance waste mate­rial flow in some situations, a best practice ‘lean manufacturing’ philosophy was applied to the development of the material handling and monitoring process. This planning philosophy had the added benefit of reducing overall costs for the activity, as well as maintaining a high level of worker morale as there were limited bottlenecks in the activity. There is a requirement to ensure the safety of the physical structures within the WL waste manage­ment areas from a variety of perspectives, including upkeep to today’s standards and the development of plans for waste removal and transfer to a long-term waste management facility. Key lessons from the work to date include the importance of records, the need for ongoing geotechnical assess­ment of the area and in-ground structures, and the need for technology for assessment and characterization prior to developing and executing work plans to ensure worker safety throughout any planned waste retrieval. This latter work is in its early stages and interaction with other international groups is assisting with the development of safe work plans.

Similar to nuclear programmes worldwide, the uranium conversion and enrichment research and production projects in South Africa were termi­nated in the early 1990s. During this time, the decommissioning strategy was aimed at returning the Necsa site to greenfield. To achieve this, the final disposal of waste, demolition of all buildings and the remediation of a site to conditions prior to any development was considered. Currently, demoli­tion is no longer considered as a final decommissioning phase and, as the demand for nuclear facilities increases (nuclear renaissance), redevelop­ment and re-use (R/R) after decommissioning are currently envisaged for the buildings on the Necsa site. This will ensure a holistic approach based on current and projected future redevelopment demands. The new redevel­opment and re-use plan aims to allocate previously licensed buildings to similar or the same nuclear projects as housed originally in the specific building, thus meeting most of the design requirements. There are various buildings on the Necsa site that are currently in a decommissioning or a care and maintenance phase that will now be evaluated to ensure the opti­mization of decommissioning costs and waste minimization. The possible reutilization of process equipment could prevent unnecessary generation of waste and the implementation of additional radiological protective meas­ures resulting in decommissioning costs.

Currently, conceptual decommissioning plans exist for most nuclear facil­ities and these plans will be explored to include possible redevelopment options. Emphasis shall be on the preservation of buildings and infrastruc­ture, to keep them structurally sound and operable. For example, the decom­missioning, decontamination and possible reutilisation of the uranium conversion facility at Necsa (Fig. 20.14) could have a major influence on the new Necsa nuclear fuel cycle initiative ’s business strategy and plan and waste management. Decommissioning projects aim at waste minimization by ensuring effective equipment and technology are used and proper seg­regation of waste is applied.

Requirements on surveillance control of disposal facilities after closure have been laid down in China. The Regulations on Radioactive Waste Safety (HAF401) require that, after closure of a disposal site, institutional surveillance and control should be maintained to:

• prevent inadvertent public intrusion onto the site,

• prevent movement and disturbance of disposed radioactive materials,

• monitor the performance of the disposal site against design basis stand­ards, and

• implement necessary remedial actions.

The period following closure of a disposal facility generally includes closed, semi-closed and open phases. Closed phase means a period when the dis­posal facility that has just been closed is kept under closed condition and that no one can access it unless for the purposes of a supervisory task. Semi-closed phase means a period when waste is covered with well — structured cover and associated hazards has proven very small, and people are allowed access but without any activities relevant to drilling and excava­tions. Open phase means a period when radioactivity of waste has reduced to the level at which radiation protection is no longer needed following expiration of the required control period and the site can be fully open to the outside.

Post-closure surveillance of the localities where a disposal facility is located are the duty of the local government. Costs required for carrying out post-closure maintenance, monitoring and emergency measures are estimated before the operation of such a disposal facility and collected in an appropriate amount from the associated waste disposal fees. Re-estimation, and necessary adjustment, can be made for such costs to meet the changing circumstances. Post-closure supervision, such as environmental monitoring, access restriction, installation maintenance, file preservation and possible emergency actions, should be carried out under the auspices of the envi­ronmental protection agencies at both the national and the provincial levels. Both the Guangdong Beilong and the Northwest China LILW disposal sites are in operation, and far from closure.

Deposition of tellurium-129m was determined from soil samples taken during the period from June 6 to July 8 over an area of 100 km radius around the Fukushima Daiichi NPP. Tellurium-129m, which is a fission product with 33.6 days half-life is as volatile as, and shows similar behaviour to iodine. The highest concentration found was 2.66 m Bq/m2 , 2 km from the plant in the empty town of Okuma. It was pointed out that the observed ratio of tellu — rium-129m to cesium-137 varies with the location of the deposition. The average ratio obtained for the deposition in the north region from the NPP is about 0.19, while it was 0.88 for the coastal area in the south. In southern inland areas, it was 0.23. They may suggest that, between tellurium and cesium, there is a different mechanism or source term, different environ­mental behavior, as well as a different timing of the release. The amount of tellurium-129m released is a few tenths that of iodine-131 (Table 24.3), and its radiological significance was not high compared to iodine and cesium.

Regional groundwater flow in the eastern NNSS is southward through the carbonate aquifer beneath the basins and testing areas of Yucca and French­man Flats (Fig. 26.2). Groundwater flow directions change to the southwest in southern Frenchman Flat influenced by increased underflow from east of the NNSS, and following en echelon faults of the southwest trending, right slip Rock Valley fault system (USDOE, 1997; O’Leary, 2000; Belcher et al., 2004). The eastern carbonate flow system of the NNSS drains either into the Alkali Flat-Furnace Creek Ranch or Ash Meadows discharge areas of the southern Amargosa Valley and Death Valley located to the southwest of the NNSS (Winograd and Thordarson, 1975; Fenelon et al., 2010; Belcher and Sweetkind, 2010).

Radionuclides from underground testing in Yucca Flat, as noted previ­ously, remain mostly in the alluvial and volcanic rocks. Where local condi­tions allow migration through these rocks, radionuclides are expected to move vertically downward and feed into the carbonate aquifer in the central and southern part of the basin, most likely along sets of north-south trend­ing faults. Particle track studies for selected test locations in Yucca Flat show flow south beneath Yucca Flat, CP Basin and southwestward along the Rock Valley fault system, discharging into the Alkali Flat-Furnace Creek Ranch system (USDOE, 1997). Alternatively, flow may diverge southward across the Rock Valley fault system and terminate in the Ash Meadows discharge area (Fenelon et al., 2010; see Fig. 26.2). For either case, groundwater from Yucca Flat is expected to travel a minimum of 40 km from sites of underground testing before crossing the southern boundary of the NNSS.

Modeling studies of radionuclide transport in Frenchman Flat show that significant quantities of radionuclides are unlikely to reach the regional carbonate aquifer within 1,000 years. Two underground tests in the north part of the basin are located near the eastern edge of the NNSS (Fig. 26.4); radionuclide transport in the fractured volcanic aquifers from these two tests may cross the southeast boundary into Federally controlled land adja­cent to the NNSS within 1,000 years (NNES, 2010a).

Preliminary estimates of the travel times through the unsaturated zone to the regional groundwater table for radionuclides from the underground

tests in the tunnel beds of Rainier Mesa and Shoshone Mountain exceed hundreds of years; radionuclide concentrations in groundwater beneath the Mesa are expected to be low. Travel time estimates to the regional ground­water table for the two tests conducted in vertical shafts in southwest Rainier Mesa are much shorter than for the tunnel bed detonations. There are multiple permissive directions of groundwater flow from Rainier Mesa: northward, southwestward beneath Pahute Mesa, or southward (Fenelon et al., 2008). Southward migration of radionuclides from the Mesa areas is toward and beneath Fortymile Canyon and Jackass Flat entering into the Alkali Flat-Furnace Creek flow system (Fig. 26.2). Minimum distances of radionuclide migration from the Rainier Mesa and Shoshone Mountain underground tests to the south boundary of the NNSS are greater than 45 km for Shoshone Mountain and greater than 60 km for underground testing at Rainier Mesa.

Regional groundwater flow from testing areas of western and central Pahute Mesa is dominantly off the mesa highlands moving generally south — westward off the NNSS toward surface springs in Oasis Valley of the Oasis Valley flow system (Figs 26.2 and 26.7). Analysis of groundwater from an exploratory well located immediately outside of the NNSS boundary south of Pahute Mesa show small concentrations of tritium from underground testing, the only confirmed occurrence of local test-produced radionuclides outside of the boundaries of the NNSS.

Heat-generating wastes are placed in interim storage for decaying and cooling at a total of 15 separate facilities in Germany pending their final disposal in a future geological repository. Germany maintains three central­ized storage facilities at Gorleben, Ahaus, and the Interim Storage North (Zwischenlager Nord, ZLN) facility on the site of the former NPP Greif — swald. Twelve additional decentralized facilities are located adjacent to the various nuclear power stations. These facilities are subject to the regulatory authority of both the federal government as well as the local state governments.

The 2002 amendment to the Atomic Energy Act committed NPP opera­tors to establish interim decentralized storage facilities for SNF resulting from plant operations. As a result, current wastes being generated are stored at the 12 decentralized locations. The facilities became operational and began accepting waste in 2006 and 2007. A thirteenth facility is cur­rently in the licensing process. Spent fuel from earlier NPP operations is stored at the centralized interim storage facilities. HLW returned from reprocessing in France and the United Kingdom is stored at Gorleben. The decentralized interim storage facilities generally consist of surface struc­tures made of reinforced concrete (at the Neckarwestheim site storage tunnels are used). SNF is stored at these locations in CASTOR®-type trans­portation and storage casks.

Wastes classified as RAW with negligible heat generation are produced in association with research institutions, the nuclear energy industry, decom­missioned nuclear facilities, the former reprocessing plant at Karlsruhe, and various other state and industrial activities. These wastes are in the form of LLW and ILW and are stored at numerous interim storage facilities in Germany. The facilities are subject to the regulatory control of the Federal States where they are located. Upon completion of the Konrad repository for wastes with negligible heat generation, these wastes will be transported and permanently disposed of at the licensed facility.

Radioactive wastes in the UK are categorised into low level waste (LLW), intermediate level waste (ILW) and high level waste (HLW) (Defra et al., 2007). In addition, some materials and wastes are defined as out of scope or exempt from the requirements of EPR10 (as amended) in England and Wales (Defra et al. , 2011) even though they contain some radioisotopes. Effectively, ‘out of scope’ equates to ‘not radioactive’ for the purposes of the legislation. Radioactive substances that are ‘out of scope’ are not subject to any regulatory requirement under this legislation. Other substances, which are considered to be radioactive by definition, may be exempt from the need for a permit if the level of radioactivity is below the level specified in the exemption order; however, specified conditions must be met. The levels of radioactivity that are defined as ‘out of scope’ are taken from EC guidance and are expressed as radionuclide specific activity concentrations.

For naturally occurring radioactive substances or articles used in ‘indus­trial activities’, the numerical values are based on a radiation dose of 300 pSv/year to a member of the public. For artificial radionuclides, and for naturally occurring radioactive substances or articles used for their radioac­tive, fissile or fertile properties (a ‘practice’), the values are based on a radiation dose of 10 pSv/year to a member of the public (IAEA, 1988). In effect, this recognises that naturally occurring radioactive materials (NORM) are universal and that it is not practicable to regulate such that the radiation dose criterion of 10 pSv/year to a member of the public is met (IAEA, 2004). Other media and radionuclide specific activity concentra­tions or total site activity holdings have been established for the exemption order, using the same radiological criteria.

In the case of exemption for disposal, the radiological impact assessments do not assume uncontrolled disposal of waste to the environment. The exemption levels therefore apply to specific types of substance or article (e. g., a waste sealed source), to the disposal route (e. g., to a sewer, or to a landfill), or to the management of waste (e. g., disposed of with considerable quantities of non-radioactive waste), etc. Out of scope and exempt wastes are not considered further here.

Of the radioactive wastes for which a permit is required, LLW is volu — metrically the largest component of the UK’s radioactive inventory and is classified as waste not exceeding four GBq per tonne of alpha or 12 GBq per tonne of beta/gamma activity (Defra et al., 2007). (The definition of LLW was originally set out in the Government White Paper, Command 2919 (1995) but was superseded by Defra et al., 2007.) Figure 16.3 provides

a breakdown of current and projected RAW arisings in the UK over the next century or so, by waste category. The UK now recognises high and low volume very low level waste (VLLW) as sub-categories of LLW (Defra et al, 2007). This offers more flexible, sustainable approaches to long-term management of wastes as alternatives to disposal to the LLW repository (LLWR) at Drigg, Cumbria.

Low volume VLLW is defined by Defra et al. (2007) as radioactive waste containing no more than 400 kBq of beta/gamma activity for each 0.1 m3 and is mostly comprised of small volumes from hospitals and universities. For carbon-14 and tritium-containing wastes, the activity limit is 4,000 kBq for each 0.1 m3 in total. High volume VLLW is defined by Defra et al. (2007) as radioactive waste with an upper limit of 4 MBq per tonne (not including tritium) that can be disposed to specified landfill sites. For tritium contain­ing wastes, the upper limit is 40 MBq per tonne.

ILW is classified on the basis of radioactivity exceeding the upper bound­aries for LLW and which does not require heating to be taken into account during storage or disposal. ILW may be sub-categorised as shorter-lived ILW or less radiotoxic ILW. These are not formally defined terms but have been used in a regulatory context to identify wastes that may be suitable for specific waste management options (e. g., Environment Agency et al., 2009; Environment Agency and Northern Ireland Environment Agency, 2009).

HLW is waste in which the temperature may rise as a result of radioactive decay and HLW may be referred to as ‘heat-generating radioactive waste’ (e. g., Defra et al;, 2008; Command 2919, 1995), although this does not dis­tinguish between types of HLW. HLW in the UK typically arises as a liquid by-product of spent fuel reprocessing. Historical stocks of liquid HLW, together with current arisings, are being conditioned through the Sellafield waste vitrification plant to form a solid material, making it passively safe and suitable for disposal. It is anticipated that by 2015, the UK’s HLW will have been converted to vitrified product and will be stored for 50 years to allow further time for radioactive decay.

The term higher activity waste (HAW) has no formal definition and should not be confused with HLW. In Scotland, HAW is used to describe wastes which would otherwise be classified as ILW but which do not gener­ate enough heat for this to need to be taken into account in the design of treatment, storage or disposal facilities (e. g., Scottish Government, 2011) but may also be taken to include LLW which, for one reason or another, is considered unsuitable for disposal as LLW (e. g., Defra and NDA, 2008). The definition of HAW in Scotland is a reflection of the fact that Scotland does not currently possess HLW. The definition of HAW in England and Wales is generally considered to encompass both ILW and HLW in addition to some LLW not suitable for disposal in the LLW repository. Other radioactive materials may be considered for disposal but are not currently classified as waste. These include spent nuclear fuel and the plutonium and uranium obtained from reprocessing spent fuel (Defra et al., 2008).

17.1.2 Operating civil nuclear power stations

There are two operating nuclear power stations in Scotland, Hunterston B and Torness. Both are of the advanced gas-cooled reactor (AGR) type with

two reactors each, and both are currently owned and operated by EDF Energy. Together they produce around 30% of electricity generated in Scotland (Scottish Government, 2012). They both have water-filled ponds for storing spent fuel from their reactors to allow cooling of the fuel before it is transported to Sellafield for storage and reprocessing, or long-term storage. The NDA’s strategy for management of spent AGR fuel is currently under review.

The EPA has regulatory responsibilities for a variety of other man-made and naturally occurring radioactive wastes:

• developing general radiation protection guidance to the federal government

• limiting airborne emissions of radionuclides

• setting drinking water regulations, under the Safe Drinking Water Act (as amended), including standards for radionuclides in community water systems

• coordinating with state radiation protection agencies to protect the environment, workers, and the public from naturally occurring radioac­tive materials exposed or concentrated by mining or processing

• coordinating with the DOE, NRC, and states on orphaned sources, recycled materials, and controlling imports and exports to prevent radio­actively contaminated scrap from entering the United States. The US Coast Guard and the US Department of Homeland Security Customs and Border Protection have the lead in detecting and taking steps to prevent the illegal entry of such materials. They have the authority to take enforcement actions and, depending on the circumstances, may seize or have a shipment returned to the point of origination.

18.9.1 Background

In 1977, the DOE identified Yucca Mountain, Nevada, as a potential reposi­tory site for future investigation to host the nation ’s first deep geological repository for the disposal of SNF and HLW (Fig. 18.3). Other potential sites included bedded salts in Texas and Utah, salt domes in Louisiana and Mississippi, and basalt in the State of Washington. In 1982, Congress passed the NWPA, which established an office within the DOE with the responsi­bility of providing for the permanent disposal of SNF and HLW, and laid out the process for siting, developing, licensing, and constructing a geologic repository. In 1987, the NWPA was amended and directed the DOE to

investigate only one potential repository site, at Yucca Mountain. The period from 1987 to 2002 was devoted to site characterization of the Yucca Mountain site for a geologic repository, and the following years were dedi­cated to engineering studies and license application (LA) activities. In February 2002, the Secretary of Energy recommended the site to the Presi­dent, and the President recommended the site to Congress. In July 2002, Congress granted the authority to the DOE to prepare and submit a LA for constructing a repository at Yucca Mountain. The LA was submitted to the NRC in June 2008, and it was subsequently accepted for review by the NRC.

In early 2009, the Obama Administration determined that a repository at Yucca Mountain was not a workable option and that the project should be terminated. On March 3, 2010, the DOE filed a motion with an NRC Atomic Safety and Licensing Board (ASLB), seeking permission to with­draw the license application for a HLW repository at Yucca Mountain. On June 29, 2010, the ASLB issued an Order denying the DOE ’s motion to withdraw. This decision was appealed to the NRC. In October 2010, the NRC commenced and continued with the orderly closure of Yucca Moun­tain LA review activities. In September 2011, the Commission announced that the commissioners were evenly divided on the question of whether the ASLB Order should be overturned but, for budgetary reasons, ordered the ASLB to complete all pending case management matters. The ASLB sus­pended the licensing proceeding and, as of April 2012, the proceeding remains suspended.