Radioactive Waste

Challenge. Conduct review and provide input to national agency responsible for issuing a general license to construct and operate a spent nuclear fuel (SNF) repository in Sweden

Solution. INTERA personnel serve as key consultants, in the area of engineered barrier systems (EBS), for the review of the post-closure radiological safety analysis report (SR-Site) produced by the Swedish Nuclear Fuel and Waste Management Company (SKB) to obtain a license for the construction and operation of a deep geological repository located in Forsmark for the permanent disposal of SNF. As part of the Initial Review Phase, consisting of a broad review of the main SR-Site and supporting references, we completed a preliminary assessment of the scientific and technical quality of the licensing documentation, identified the need for complementary information and clarifications to be delivered by SKB, and helped develop a task report that incorporates review comments from the entire team of international technical experts. After completing the Initial Review Phase, we worked with SSM and determined that the quality and comprehensiveness of the safety assessment is sufficient to warrant the in-depth assessment (Main Phase of the review) required to receive a construction license for the repository. Previously, INTERA personnel served on the Barriers for Radioactive Waste Isolation and Technical Evaluation (BRITE) advisory panel responsible for conducting an independent evaluation of the technical and performance assessment issues related to SNF disposal in the Forsmark repository. Specific analyses focused on the corrosion of copper canisters under expected repository conditions, potential erosion of clay buffer during construction and future glacial periods, and overall release behavior of radionuclides from the EBS. The BRITE provided independent technical support to SSM in preparation for receiving and reviewing the formal general Construction License Application discussed above.

Challenge. Perform studies of hydrogeologic characterization and modeling methods in preparation for siting deep geologic repository for radioactive wastes

Solution. In support of NDA’s development of a geosphere characterization program, INTERA has provided expertise and services in a number of technical areas including hydrogeology, hydrogeochemistry, transport of radionuclides, and site investigation techniques. We completed a study to develop an understanding of approaches that can be adopted for evaluating the geological aspects of candidate sites. The study examined the nature and content of geoscientific information available as input to the studies of candidate sites; the various means by which geoscientific information can be presented to non-geoscientific audiences; and the approaches that can be adopted for evaluating and presenting geoscientific information and site investigation issues. INTERA updated a previously conducted review of available instrumentation systems for the monitoring of groundwater pressure, with an emphasis on use in low-permeability environments. This study reviewed and documented issues such as the benefits and constraints of each system; the accuracy and resolution of data collected, commercial availability of each technique, and anticipated design life of the equipment; borehole design requirements associated with each system; and approaches to data transmission and management. We completed a comprehensive study to define the information requirements for developing a hydrogeology site descriptive model, including the interpretation of fluid logging tests to delineate flowing and non-flowing strata or features, the interpretation of borehole fluid density surveys, the interpretation of hydrogeologic tests in fractured and unfractured media to determine hydraulic conductivity and storativity, the development of discrete and spatially varying input parameters (e.g., transmissivity), and the modeling of near- and far-field state variables (e.g., groundwater pressures or heads, groundwater velocities, and travel times) to assess the performance of the geosphere system. INTERA also participated in an evaluation of the long-term stability of materials that can be used as components in sealing systems for investigation boreholes. The review included an assessment of the plans and experience of radioactive waste management programs worldwide, most notably Nagra and SKB/Posiva, as well as on other geoscientific sectors concerned with long-term isolation of resources and/or wastes. In the area of hydrogeochemistry, we have reviewed and evaluated sampling, testing, and modeling techniques for developing the conceptual understanding of undisturbed hydrochemical conditions and how site-specific hydrogeochemistry supports and interacts with the design and the safety case development.

Challenge. Provide technical reviews and assistance for licensing and regulatory oversight of deep geological disposal of radioactive wastes

Solution. For more than a decade, INTERA personnel have served on a number of independent technical review teams and committees to support STUK in evaluating the performance and safety of the proposed spent nuclear fuel disposal repository at Olkiluoto. We coordinated all technical reviews regarding the design, fabrication, installation, and long-term performance and safety of the engineered barrier system (EBS) as presented in Posiva’s Construction License Application for the Olkiluoto repository. As part of the Safety Assessment for Radioactive Waste Isolation (SAFARI) advisory group, we provided STUK with advice on interactions and interrelationships among engineered, natural, and radiological factors affecting long-term isolation of nuclear waste in geological repositories. The group also developed independent containment, release, and transport models incorporated into the Ecolego code to assess long-term waste isolation. Our personnel led the Assessment of Engineered Geological Isolation Systems (AEGIS) interdisciplinary team of academic and industry experts in the review of issues related to materials selection, testing, fabrication, and emplacement and safety assessment on EBS for the Olkiluoto repository. We have also led the Nuclear Waste Safety Committee (NWSC) responsible for advising STUK on technical issues associated with regulatory oversight of nuclear waste management and disposal in Finland. These issues include development of regulations, decommissioning of reactors, storage of wastes, transportation, monitoring, and disposal, as well as licensing and stakeholder communication related to these activities.

Challenge. Provide input and advice on state-of-the-science approaches and methods for the deep geologic disposal of radioactive wastes

Solution. For NUMO, the agency responsible for siting, developing, and operating deep geological repositories for both high-level waste (HLW) and transuranic (TRU) wastes in Japan, INTERA staff served as the technical representative from the U.S. on an international Technical Advisory Committee (ITAC). The process of locating and evaluating sites is expected to take at least 15 years to reach the point of initial repository construction. During the period before construction, NUMO is identifying sites as well as repository concepts that are compatible with these sites. To expedite this process and ensure that state-of-the-science knowledge and technology is incorporated into the Japanese program, NUMO convened a special program, composed of internationally recognized experts from the U.S., U.K., Switzerland, Sweden, Finland, and France. As the selected expert from the U.S. HLW program, INTERA’s Dr. Michael ‘Mick’ Apted provided summaries of plans, results, and lessons learned from the U.S. on topics including siting, public communication, repository concepts, and safety assessment methodologies. The ITAC also reviewed NUMO’s own plans, conducted workshops with a Japanese Domestic Technical Advisory Committee (DTAC), and held open public hearings with both ITAC and DTAC representatives to respond to questions from the general public on technical issues related to geological disposal. To meet one of the key challenges facing the Japanese radioactive waste disposal program—ensuring safe isolation of the waste for 10,000 years or more within a very active tectonic environment—INTERA also participated in a multi-year series of International Tectonics Meetings (ITM/TOPAZ) to evaluate the volcano-tectonic hazards across the Japanese archipelago. INTERA staff organized and conducted expert elicitation of international and Japanese geosciences experts on possible long-term evolution of the volcano-tectonic setting of Japan. The results of this elicitation were then used to develop impact scenarios arising from credible natural-event scenarios that could affect repository safety and isolation performance for time periods up to several million years after waste emplacement. For a recent assignment with JAEA, INTERA has complied and assessed a wide variety of international concepts pertaining to direct disposal of spent nuclear fuel into deep geological repositories.