With the success of the mediation mission assigned to Christian Bataille, whose objective was to conduct preliminary consultations to propose to the government favourable sites for the implementation of underground labo­ratories, teams from ANDRA returned to fieldwork in 1994. They per­formed geological investigations in four Departments:

• Gard (clay),

• Vienna (granite),

• the Meuse (clay),

• the Haute-Marne (clay).

Through seismic campaigns and core drilling, the geological layers that could accommodate a laboratory were determined. This was done under very different conditions from those existing prior to the moratorium. First, a law now regulated the action of ANDRA. Second, around the sites, local elected officials supported the Agency. There was still some opposition, demonstrations, and some malicious acts, but the work of ANDRA was not hindered.

In 1996, projects for the Meuse and Haute-Marne Departments were combined in a single site located in the town of Bure. ANDRA then filed three applications for installation of underground laboratories. However, in 1997, political difficulties prevented any decision. In the new French govern­ment of Lionel Jospin, the underground laboratory project was no longer unanimously accepted.

1998: ANDRA now has permission to establish a laboratory in clay

ANDRA’s research on the feasibility of an underground facility did not stop. From 1996 to 1998 the Agency joined the ‘Mont Terri’ Swiss project in the Jura, where researchers were using the viewing gallery of a motorway tunnel to conduct experiments on a clay layer with qualities similar to those of the clay at Bure. ANDRA also continued to fund research in many uni­versity laboratories.

In August 1998, a large European anti-nuclear gathering took place at Bure. That day, the mayors of a dozen neighbouring municipalities installed signs ‘Yes to the lab’ to the fronts of their town halls. In December 1998, a political compromise was found and the government announced its decision:

• future storage must be reversible.

• the site of the Gard was discarded.

• the research on the granite site of the Vienne Department was consid­ered inconclusive, but ANDRA should nevertheless continue to study the rock.

Finally, the Meuse/Haute-Marne site was chosen to implement an under­ground laboratory: more than 10 years after its first research (1987), ANDRA had the permission to create a laboratory in clay.

Discharges from Sellafield (see Figs 16.8 and 16.9 , compiled from Gray et al., 1995; Jackson et al., 2000; Environment Agency et al., 1971-2011 and

BNFL, 1976-2004) illustrate the influence of many factors affecting LLW management, including perception of tolerable risk, the design and specifi­cation of new plant and post-operational waste conditioning, and the chang­ing emphasis to reduce discharges to the environment in favour of solid waste disposals.

Peak discharges to air occurred in the 1960s and peak discharges to sea occurred in the 1970s. Over the past decades there has been an increasing emphasis on effluent treatment and containment of radioactivity within solid wastes. At the same time, there has also been an increasing emphasis on reducing waste arisings and on volume reduction for those wastes that cannot be avoided. The rise in discharges to sea during 2001 reflected pri­marily processing of larger quantities of medium active concentrates (with associated increased discharges of Tc-99 and Sr-90). Discharges of C-14 to sea also increased in 2001, mainly due to diversion (by introduction of a gas scrubber) of activity previously discharged to air, recognising that this diversion was made to reduce the overall environmental impact of site discharges (BNFL, 2002).

Reprocessing of fuel from DMTR produced ILW waste liquors called raffi­nates that have been stored in underground tanks housed in stainless steel lined shielded vaults. In the late 1980s and early 1990s, the Dounreay cementation plant (DCP) was constructed. This plant takes the raffinate from the storage tanks in batches and then mixes measured quantities of raffinate and cement powders in 500 litre stainless steel drums to form a monolithic solid wasteform that can be stored for at least 100 years prior to a final end point being identified. This wasteform has a Letter of Compli­ance (LoC) from the Radioactive Waste Management Directorate (RWMD) of NDA accepting its suitability for geological disposal.

A dedicated ILW vault store has been constructed for storing these 500 litre drums. It can also store overpacked 200 litre drums retrieved from the miscellaneous ILW store. It has an import/export facility to allow transfer of the drums in transport flasks to other facilities when the need arises.

Radioactive wastes are treated primarily to produce a structurally stable, final waste form and minimize the release of radioactive and hazard­ous components. The United States does not commonly make a distinction between the terms ‘treatment’ and ‘conditioning.’ Conditioning is defined in the international community as an operation producing a waste form suitable for handling, such as conversion of a liquid to a solid, enclosure of the waste in containers, or overpacking. Treatment is defined as those opera­tions intended to improve the safety and/or economy by changing the characteristics of the waste through volume reduction, removal of radionu­clides, and change in composition. US terminology covering both condition­ing and treatment is generally referred to as treatment or processing. Treatment is used in this broader context in this chapter.

18.1.5 High-level waste

HLW from commercial reprocessing activities has been vitrified and is stored at the former reprocessing plant in West Valley, New York. Defense HLW is stored, managed, and treated at three DOE sites: Savannah River Site (SRS) in South Carolina, Hanford Site in Washington, and Idaho National Laboratory (INL) in Idaho.

19.1.2 Used fuel

The selected and approved NWMO ’s APM approach for long-term man­agement of Canada’ s used fuel comprises both a technical method and a management approach (NWMO, 2005). The technical method is based on centralized containment and isolation of the used fuel in a deep geological repository in a suitable rock formation (Fig. 19.2). It provides for continu­ous monitoring of the used fuel and the potential for retrievability for an extended period of time. Consistent with adaptive management, there is provision for contingencies, such as the optional step of shallow storage at the selected central site if circumstances favour early centralization of the used fuel before the repository is ready.

The management system is based on phased and adaptive decision making. Flexibility in the pace and manner of implementation allows for phased decision making, with each step supported by continuous learning,

К-1.2 m>|

19.2Conceptual deep geological repository for nuclear fuel waste (NWMO, 2005).

research and development, and public engagement. An informed, willing community will be sought to host the centralized facilities. Sustained engagement with people and communities is a key element of the plan, as the NWMO continues to work with all stakeholders (i. e., citizens, communi­ties, municipalities, all levels of government, Aboriginal organizations, industry and others).

NWMO ’s implementation activities within its initial five-year plan are focusing on seven key areas:

1. building a relationship with key stakeholders,

2. site selection,

3. design and safety case for APM deep geological repository,

4. financial surety,

5. adapting plans,

6. accountability and governance, and

7. building the organization.

The maximum permitted surface dose rate for each package for storage (drums, concrete containers, ISO containers and ingots) shall not exceed 1 mSv/h at 0.5 m and 2 mSv/h for contact dose rate. The maximum permitted removable surface contamination on waste containers shall not exceed

0. 04.Bq/cm2 for a contamination and 0.4 Bq/cm2 for в contamination.

The following information shall be clearly indicated on the drum or on

a label affixed to the drum:

• unique container number traceable to the information/documentation accompanying the package

• gross mass

• date when filled

• type of waste

• maximum contact dose rate

• dose rate at 0.5 m.

If containers are used with any other specific additional liner/coating to protect the surface of the drum, details describing these liner/coatings shall be provided in the facility-specific waste management programme.

The mass of any waste package shall not exceed the manufacturer’s loading limit as specified for each drum type/design. Should the waste gen­erator have to exceed this limit, prior approval from the manager PDO is required. A report justifying the use, giving evidence of compliance to IAEA transport regulations [13] and metal drums specification [14] shall be prepared and submitted to PDO. An example of current waste packaging is shown in Fig. 20.11.

The following waste containers will not be accepted:

• waste containers coated in an attempt to cover cracks or corroded surfaces

• double packed drums (waste placed inside a drum and again inside another drum).

As specified in the Law of the People’s Republic of China on Prevention and Control of Radioactive Pollution [9], RAW is defined as material, which contains or is contaminated with radionuclides at concentrations or radio­activity levels greater than the clearance level as established by the regula­tory body without foreseen further use. In China, RAW arises principally from NPP, research reactors, the nuclear fuel cycle, nuclear technology applications, the exploitation and utilization of uranium and thorium resources, as well as clean-up activities of contaminated sites and/or facili­ties such as that shown in Fig. 22.2: some nuclear facilities in the Gobi Desert in the west part of China (Qinghai Province), which were used during the 1950s and 1960s, need to be cleaned up.

To meet the needs for its nuclear power expansion, China has developed uranium enrichment and fuel element manufacture capability. At present, two uranium enrichment plants are in operation, with annual total centrifu­gal enrichment capacity of 1,100 tons of separation work. The first nuclear fuel assembly production line was established in 1988 in Sichuan province, supplying most of the nuclear fuel elements to the Qinshan NPP (Fig. 22.3). Subsequently, the technologies for designing and manufacturing nuclear fuel elements have been imported on a step-by-step basis, to which a techni­cal adaptation was later made. This means that China’s PWR fuel element manufacture can meet the requirements of the international generic stand­ards, so as to ensure that the supply of nuclear fuel elements meets the demands of the current PWR plants in China. Through introducing technol­ogy from Canada, a high pressure reactor fuel element production line, with

a capacity of 200 tonnes per year, was built in Inner Mongolia, Northern China, where it provides HWR fuel elements for Qinshan NPP III.

China ’s RAW categorization system is based on pre-disposal manage­ment and disposal of RAW. In pre-disposal management, the RAW catego­rization system accounts for the nuclear facility operational experience in waste treatment and conditioning requirements, which includes a quantitative categorization system for radioactive gaseous, liquid and solid wastes. The disposal-based RAW categorization system focuses on the final disposal of RAW, in conjunction with the origin of the waste and the planned disposal approach.

The pre-disposal management-based waste categorization system is used to manage gaseous, liquid and solid RAW generated at nuclear facilities, with a detailed categorization for different forms of wastes according to their radioactive characteristics as shown in Table 22.3 . This is consistent with the basic requirements of waste treatment but puts more emphasis on

the cleaning index, shielding design, and other field protection require­ments. These requirements are implemented in the waste treatment and conditioning processes for various systems. It is noticeable that most Chinese standards on nuclear or radioactive waste management are coherent with the current IAEA classification scheme. For example, both the IAEA and Chinese standards specify that management of decay heat should be con­sidered if the thermal power of waste packages reaches several watts per cubic metre [10,11].

The disposal-based radioactive waste categorization system divides solid radioactive waste into solid LLW, solid ILW, solid HLW, solid alpha waste and the waste arising from mining and milling of uranium and thorium, and naturally occurring radioactive materials (NORM) waste. Disposal options considered include centralized deep geological disposal, regional near­surface disposal, and centralized landfill, and others, as shown in Table 22.4. Solid LLW containing only short-lived radionuclides can be released from regulatory control when the radioactivity contained is below the regulatory clearance levels. However, management of cleared waste should be in com­pliance with other relevant environmental requirements.

The uranium enrichment demonstration plant (UEDP) in Ningyo-toge was used to demonstrate uranium enrichment by the gas centrifuge (GCF) method, and was operating continuously from 1988 to 2001. As a result, significant uranium was deposited in the equipment mainly as intermediate uranium fluorides. System chemical decontamination using IF7 gas was proposed as an efficient decontamination method. The secondary waste characteristic of IF7 treatment is IF5 and minor adsorbent. In addition, IF5 is easy to convert to IF7 and re-use for system decontamination. The IF7 treatment technique is performed at room temperature and very low pres­sures such as 10-45 hPa. Secondary reaction is insignificant in IF7 treatment except for the reaction between IF7 gas and the intermediate uranium fluo­ride. The weights of uranium deposited in the cascades were approximately 700 kgU per cascade before IF7 treatment. The IF7 treatment period for each cascade is 60 days applying the near-optimal processing conditions. More than 96% of uranium was recovered from the cascade system. As a result, the U radioactivity of the main parts of the GCF fell to 1.0 Bq/g and below.

G. RUSKAUFF and B. CROWE, Navarro-Intera, LLC, USA and S. DRELLACK, National Security

Technologies, LLC, USA

DOI: 10.1533/9780857097446.3.801

Abstract: This chapter outlines the hydrogeological setting of the Nevada National Security Site (NNSS) and the expected pathways of groundwater flow and radionuclide transport. It describes the evolving strategy developed cooperatively between the National Nuclear Security Administration Nevada Site Office (NNSA/NSO) and the Nevada Division of Environment Protection (NDEP) to assess groundwater contamination from underground testing of nuclear weapons and to protect the health and safety of the public. The modeling challenges and progress in the Underground Test Area Project (UGTA) are also discussed.

Key words: radionuclide contamination, groundwater, flow and transport model, regulatory strategy.

26.1 Introduction

The Underground Test Area Project (UGTA) of the US Department of Energy (DOE), National Nuclear Security Administration Nevada Site Office (NNSA/NSO) is implementing remediation strategies for protecting the health and safety of the public and the environment from radioactive contamination of groundwater produced during past underground testing of nuclear weapons at the Nevada National Security Site (NNSS; formerly called the Nevada Test Site). The NNSS was chosen as the continental site for testing nuclear weapons in 1950 because of the sparse population in the arid southwest region of the United States, the availability of nearby facili­ties for operational support, and to reduce the cost and logistical difficulties of testing in the western Pacific (US Department of Energy (DOE), 2000a). The first atmospheric tests were conducted in 1951 and the NNSS subse­quently became the primary site for testing nuclear weapons. Following the Limited Test Ban Treaty of 1963, atmospheric testing ceased, and nearly 90 percent of the underground weapons tests by the United States were deto­nated at the NNSS (USDOE, 2000a). Congress imposed a moratorium on

801

testing of nuclear weapons, and in September of 1992, underground testing ceased.

The NNSS continues to be used for national defense activities and is a major remediation site for the DOE Environmental Management mission of cleanup of the environmental legacy from nuclear weapons and nuclear energy research. The Environmental Restoration Project was established in 1989 for evaluating and remediating contaminated sites on the NNSS and other areas of the state of Nevada. The UGTA under the Environmental Restoration Project is tasked with assessing contaminated groundwater from underground testing. The NNSA/NSO also operates and maintains two facilities located in alluvial basins of the NNSS that dispose of low-level radioactive waste (RAW) and mixed low-level radioactive waste. The RAW is from cleanup activities on the NNSS and from cleanup activities at multiple remediation sites across the DOE complex (nationwide). The RAW is buried in shallow trenches, pits, subsidence craters created by underground testing of nuclear weapons and large-diameter boreholes (greater confinement boreholes) (Shott et al., 1998, 2000; Crowe et al., 2002,2005; USDOE, 2005).

The UGTA is evaluating 907 underground nuclear detonations that were conducted at the NNSS; all underground tests are listed in a compendium of weapons tests conducted by the United States from July 1945 through September 1992 (USDOE, 2000b). The NNSS tests were conducted above, near and below the groundwater table in alluvial basins, in volcanic high­lands, in shafts and tunnels of zeolitized volcanic rocks, and in tunnels mined in granitic rock.

The phenomenology of underground nuclear explosions is summarized in Borg et al. (1976), US Congress Office of Technology Assessment (1989), and the International Atomic Energy Agency (IAEA, 1998). An under­ground test produces a spherical cavity from combined vaporization, melting and shock compression of the host rock. As the detonation pressure subsides, the rocks above the cavity typically collapse (timeframe of seconds to days after the test) and the cavity is filled with rubble consisting of col­lapsed rock, and solidified rock melt (melt glass). The collapse void can propagate upward variable distances forming a chimney that may or may not extend to the surface forming a subsidence crater. The temperature and pressure history of an explosion and response of the surrounding host rock control the distribution of radionuclides around the test. Radionuclides produced underground include tritium, fission products, actinides and acti­vation products. Refractory radionuclides (higher boiling points) are trapped primarily in the melt glass, and in cavity rubble and compressed rock around the cavity (up to 1.5 cavity radii from the test point); volatile species circulate outward and condense in cracks and void spaces for dis­tances of 1-3 cavity radii from the test point (Tompson et al., 1999;Tompson, 2008 ; Pawloski et al., 2008 ).

The radionuclides deposited underground from detonation of a nuclear device are referred to as the radiological source term; the portion of the inventory that is migrating in groundwater is the hydrological source term, a subset of the radiological source term. Underground testing on the NNSS deposited an estimated 132 million curies of radioactivity below ground, decay corrected to 1992 (the radiological source of Bowen et al, 2001). Unclassified estimates of this radiological inventory are apportioned among 43 radionuclides and these radionuclides define the source term used in the modeling studies.

Important features of the NNSS with respect to radionuclide contamina­tion of groundwater are the considerable depth from the surface to ground­water throughout most of the site and the absence of natural springs or surface areas of groundwater discharge on the NNSS which would allow radioactive contaminants to be released in the environment. Accordingly, there are no immediate hazards to workers or the public from exposure to contaminated groundwater. The challenges facing the UGTA are to under­stand the physical and chemical processes of migration of radionuclides within and adjacent to the NNSS, to forecast migration of radionuclides over 1,000 years, and to support regulatory decisions to protect the public. The approach used to address these challenges is a combination of data collection and development of numerical models of groundwater flow and radionuclide transport, model evaluation to test and build confidence in model results sufficient to design a long-term monitoring network, and identification of institutional control policies to restrict public access to contaminated groundwater.

The goals for this chapter are:

• to describe the hydrogeological setting of the NNSS and the expected pathways of groundwater flow and radionuclide transport,

• to describe the evolving strategy developed cooperatively between the NNSA/NSO and the Nevada Division of Environment Protection (NDEP) to assess groundwater contamination from underground testing of nuclear weapons and to protect the health and safety of the public,

• to describe the modeling challenges and progress in UGTA.

Germany is a contracting party to the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive

Waste Management. Waste management legislation in Germany is based on European law, German federal law, and regional state laws. In accord­ance with the AtG, waste producers are committed to avoid or reduce the generation of radioactive waste to the greatest extent possible. Ownership of the waste is retained by the producer until such time as it has been accepted for final disposal in an approved geological repository (AtG §9a).

As previously discussed, all radioactive waste in Germany, subject to the controls of the AtG will, in accordance with federal policy, be disposed of in a suitable deep geological repository. The specific requirements that a repository must meet are determined based on the heat-generating capacity of the waste destined for disposal and the isolation requirements associated with the waste. These requirements are specified in the site licensing docu­ments as required by the pertinent German laws. Pending disposal, waste related to power generation is managed in secure on-site or near-site interim storage facilities at the expense of the waste producer. For all other wastes, particularly those originating from radioisotope applications in industry, universities and medicine, the Federal States are responsible for construct­ing and operating regional interim storage facilities (AtG §9a(3)).

Germany was one of the first nations to initiate serious efforts in develop­ing strategies and techniques for deep geological disposal of RAW. The German government policy on deep geological disposal for all radioactive wastes can be traced back to 1960 when the former German Atomic Com­mission unilaterally rejected the idea of surface disposal for these wastes. In 1967, Germany initiated a pilot test-bed geological disposal facility for low and intermediate level wastes (LLW and ILW) at the former Asse salt mine. The facility was the first attempt at developing a prototype repository for the storage of nuclear wastes by any nation (Fisher, 1978). In 1971, the former GDR (East Germany) began disposing of LLW and ILW wastes in the rock salt mine Bartensleben near Morsleben, Saxony-Anhalt. Waste storage practices at Asse ceased in 1978, while waste disposal practices at Morsleben continued uninterrupted until 1991 and again from 1994 until 1998. Currently the only facility licensed in accordance with the AtG for the disposal of negligible heat-generating wastes in Germany is being con­structed in the former iron-ore mine at Konrad.

With respect to the geological disposal of heat-generating wastes, i. e., HLW and SNF, Germany was one of the first nations to initiate serious efforts in developing a permanent deep geological repository for heat­generating wastes, and by 1977 had selected the salt dome at Gorleben for investigation regarding the suitability of the formation for hosting a poten­tial repository for HLW and SNF.