Background Information: This is a technical request for information that does not take into account contractual limitations or obligations under the Standard Contract for Disposal of Spent Nuclear Fuel and/or High-Level Radioactive Waste (Standard Contract) (10 CFR Part 961). For example, under the provisions of the Standard Contract, spent nuclear fuel (SNF) in multi-assembly canisters is not an acceptable waste form, absent a mutually agreed to contract amendment. To the extent discussions in this request for information conflict with the provisions of the Standard Contract, the Standard Contract governs the obligations of the parties, and this request for information in no manner supersedes, overrides, or amends the Standard Contract. This request for information, and the research and development activities it describes, reflect technical work which could support future decision making by Department of Energy (DOE). No inferences should be drawn from this request for information regarding future actions by DOE, which are limited both by the terms of the Standard Contract and a lack of Congressional appropriations for the Department to fulfill its obligations under the Nuclear Waste Policy Act including licensing and construction of a spent nuclear fuel repository. Commercial generation of energy by nuclear power plants in the United States (U.S.) has produced thousands of metric tons of SNF, the disposal of which is the responsibility of the U.S. DOE. Utilities typically utilize the practice of storing this SNF in dual-purpose canisters (DPCs). While DPCs are designed, licensed, and loaded to meet Nuclear Regulatory Commission (NRC) requirements and preclude the possibility of a criticality event during SNF storage and transport, they are not designed or loaded to preclude the possibility of a criticality event during the regulated postclosure period following disposal, which could be up to 1,000,000 years. As of March 2019, there are over 2,700 DPCs in storage in the United States that contain SNF. The potential to dispose of commercial SNF in DPCs, rather than repackaging it into purpose-designed disposal canisters (e.g., materials, robustness of design), is a consideration in nuclear fuel management. Direct disposal of DPCs could result in less collective worker radiation dose than would be associated with the repackaging of stored SNF, and considerable cost savings for disposal (billions of dollars). Other benefits may accrue such as simplification of the waste management system, less transport of waste by rail and highway, and so on. Research and development is needed primarily because DPCs were not designed for disposal, so they differ in certain ways from purpose-designed disposal canisters. The performance of DPCs in disposal environments needs to be investigated and technically described, the engineering challenges defined, and the regulatory implications for direct disposal analyzed, to provide a basis for program decisions whether to proceed. The scope of needed R&D combines scientific, engineering, and regulatory investigations. National Technology and Engineering Solutions of Sandia LLC (NTESS), with Department of Energy (DOE) sponsorship, has begun to evaluate potential filler materials as a means to enable direct and long-term disposal of DPCs in a geologic repository. Filling the void space of a DPC that is already loaded and sealed, with an appropriate material injected through drain and vent ports, could limit the possibility of criticality over the post-closure regulatory period. The effectiveness of a filler material to mitigate criticality will ultimately depend on its ability to reduce moderation effectiveness in a DPC, or to provide a vehicle for a neutron poison. To do so will require that the filler exhibit several attributes including: (1) moderator displacement by filling more than 60% of the DPC free volume with non-hydrogeneous material; (2) minimal intrinsic ability to moderate neutrons; (3) capability to emplace and stabilize granular neutron poison materials constituting up to 10% of total volume; and (4) a minimal (10% or less) compaction or volume reduction after emplacement in a DPC. Opportunity Description: NTESS is seeking information and expressions of interest via this Federal Business Opportunity (FBO) for a possible future partnership for the development of potential DPC filler materials. This request for information is a first step in advance of a possible request for proposal (RFP) and collaborative effort to develop a filler product suitable for use to enable the possibility of direct geologic disposal of DPCs. Respondents shall consider the following criteria developed by SNL for potentially viable DPC filler materials: Injectability –Ease of handling, mixing, pumping, and emplacement of filler material is important. Candidate fillers must be injected through one or more ports with inner diameters of roughly 10 to 20 mm. Fillers must be pumpable so that ~6,000 liters can be pumped into a canister and flow into all interstices, before setting as a monolithic pour. The filling rate and temperature conditions for solidification must be readily controllable. Void Filling – Self-leveling, and readily penetrating DPC interstices with apertures as small as ~1 mm. While filling small voids, filler can also act as a carrier and binder for boron carbide powder and/or other chemically inert particulate materials. Long-Term Chemical Stability – Forms a long-lasting solid with expected longevity of thousands of years in ground water, with natural analog and/or experimental evidence. Filler has low hydraulic permeability that can slow its degradation on exposure to ground water. Filler does not interact chemically with, nor contribute to degradation of basket components such as neutron absorber plates. Retrievability/Recoverability – Filler can be safely removed from filled canisters after setting, e.g., for safety reasons or to recover economic value. This may be a second-order concern because if entire waste packages can be retrieved then they can generally be processed by various methods to separate spent fuel constituents. Material Compatibility – Chemically inert or reacts very slowly with DPC internal components, especially Zircaloy cladding and aluminum-based neutron absorber or structural materials. Stable to groundwater and chloride brine (if used in a salt repository) after set and during aging at temperature. Controlled shrinkage/expansion behavior during initial set and subsequent cooling, to limit stress and maintain low permeability. Filler readily bonds to metal surfaces of the fuel and canister internals (promotes void filling and durability). Moderator Displacement – Limits the amount of ground water or other liquid neutron moderator that can flow into the canister after waste package breach, such that spent fuel criticality is prevented. Gas Generation – Gas generation by chemical reactions or as a result of radiolysis, is limited or can be controlled while the DPC is intact and sealed, so as to avoid initiating canister rupture. Filler has low porosity and low water content, and otherwise resists gas generation from gamma and neutron radiolysis, especially for the first few hundred years after disposal when the radiation field is maximal. Solidification Temperature – The conditions of emplacement, particularly temperature, are consistent with maintaining the integrity of both the filler and the spent fuel. Solidifies in a temperature environment of approximately 150°C to 200°C (a nominal temperature for spent fuel in dry storage after some aging). Controllable heat of fusion or reaction (e.g., not more than about 10 W per liter during set) to limit the peak temperature and prevent thermal runaway (if exothermic and thermally setting). Thermal conductivity before and after set is sufficient to dissipate heat of fusion and waste heat, so the filled canister temperature stabilizes at an acceptable and predictable level. Toxicity – Filler material does not include large amounts of constituents that are known toxins (e.g., regulated metals). Radionuclide Sequestration – Solidified filler and its weathering products have certain chemical affinities after exposure to ground water that enhance sequestration of long-lived radionuclides that are important to repository performance assessment (PA). Material Cost – Filler material cost is reasonable (e.g., favorable to selection of filling vs. other approaches to fuel preparation such as re-packaging). Sandia National Laboratories (SNL) has performed an assessment of potential filler materials that could meet these criteria. As a result, materials currently under consideration as DPC fillers include low-melting point metals and cements that are primarily phosphate-based. Oak Ridge National Laboratory (ORNL) is currently researching metals and SNL is researching cement materials. The focus of the current request is for information and expressions of interest on the collaborative development of cements, including phosphate-based cements, that meet the criteria listed above. However, SNL will consider any material alternatives proposed by respondents that can be demonstrated to meet the criteria above. What SNL Brings to the Partnership: SNL brings a wide array of capabilities to the assessment of potential options for the direct disposal of DPCs including concept development leading to potential solutions, and evaluation of engineering alternatives and their associated costing. Specific SNL capabilities include: (1) analysis of postclosure criticality and its consequences in a repository; (2) development of regulatory strategies that accommodate criticality events in a repository and their consequences to waste isolation performance; (3) multi-physics simulation of degradation processes for SNF and packaging, and how they influence the likelihood of criticality events, and are affected by the occurrence of criticality events; (4) fundamental and applied materials research and development of potential filler materials; (5) chemical and mechanical testing to assess the viability of potential filler materials; and (6) assessments of the effects of gamma radiation on the integrity and stability of potential filler materials. Information Sought: Responses to this request are anticipated to be brief (up to 10 pages). The following information is requested. Interested parties may provide additional relevant information as needed. Description of potential filler materials and their ability to meet the criteria described above. Limited information on the design details of commercially available DPCs for which the filler could be used. Specifically, such details will include the flow path length, inner diameter, wall thickness, material of construction, location of seals, and pressure rating of the DPC system. Description of the relevant experience, expertise, and capabilities of the interested party. Description of any past experience partnering with Federally Funded Research and Development Centers (FFRDC), National Laboratories, or Government Laboratories. More detailed information may be requested during the review process. In addition, if required, an NDA can be put in place should the respondent desire to share proprietary information beyond the publicly available information provided in the initial response to this request. Instructions to Responders: Interested parties that meet the Mandatory Requirements provided below are invited to respond to this request for information. Any and all responses are voluntary. Sandia will not pay for any information submitted in response to this opportunity RFI. Responses should be emailed to Mark J. Rigali (
[email protected]). Responses should include the Opportunity title and the submitting organization’s name in the subject line. Any attachments should not exceed 5MB; only document formats with a .docx, .doc, or .pdf suffix will be accepted. Questions may be submitted to the same email. Evaluation Criteria: In addition to evaluating the information for their technical content and viability, SNL will evaluate all responses and select prospective parties to engage in further discussions based on the following criteria: Mandatory Firms willing and able to enter into a partnership agreement with SNL, such as a Non-Disclosure Agreement (NDA), cooperative research and development agreement (CRADA), strategic partnership project (SPP), etc. Compliance with Federal Export Control requirements per the U.S. Department of State. Ability to provide in-kind support and collaborate on specific activities as defined within potential future Statements of Work developed jointly with the interested party and SNL. Desired Demonstrated successful partnering and teaming relationships with R&D organizations. Demonstrated experience, expertise, and capabilities in the design, development, and manufacturing of materials that can potentially serve as DPC filler materials. Discussion with organizations of interest may begin soon after the application is received and may be ongoing while the FBO is open. These conversations do not indicate a commitment from SNL. In addition, we will consider teaming arrangements where two or more companies may form a team to satisfy the Desired Requirements. Keywords: Dual Purpose Canister, Filler Material, Cement, Low-Melting Point Metal, Spent Nuclear Fuel, Criticality Mitigation, Long-Term Geologic Disposal