Comparing two concepts of the OECD-NEA RK&M Initiative (2011–2019): The Set of Essential Records and the Key Information File

In the last decade, the Nuclear Energy Agency (NEA) of the OECD​​​​​​​ co-ordinated an international initiative to develop understanding and guidelines related to the longer-term preservation of records, knowledge and memory (RK&M) regarding radioactive waste repositories, the so-called “RK&M Initiative”. Their final report (NEA, 2019) can be read as a general guide to the RK&M preservation topic. In terms of practical support, the group prepared an RK&M preservation toolbox, comprising 35 different preservation mechanisms. Amongst those are classical, much discussed tools such as “archives”, “surface markers” or “land use control”, hitherto less discussed tools such as “international regulations”, “small time capsules” or “clear and planned responsibilities”, and two entirely new concepts: the Set of Essential Records (SER) and the Key Information File (KIF). In the current contribution, I present these two concepts, pointing out their role both in the wider RK&M preservation context (i.e. in the toolbox as a whole) and in the narrower “documents” context. My main focus is a comparative approach, addressing the peculiarities of the KIF and the SER concepts by working out the differences between the two. It becomes apparent that the KIF is far from being a condensation of the SER, but in fact KIF and SER are independent concepts: in terms of their authors/creators, their target audiences, and first and foremost their functioning, i.e. “how” they contribute to RK&M preservation.

Swelling Characteristics of Compacted Claystone-Bentonite Mixtures

High-density claystone mixtures have been suggested as liners in radioactive waste repositories. However, this material can also be used as a liner in landfills. This study focuses on swelling characteristics of compacted claystone-bentonite at a low density for landfill applications. Claystone was taken from the Banjarbakula landfill project in Banjarbaru. The bentonite used is a commercially available bentonite from Indonesia. Claystone was mixed with 5, 10, 15, and 20% of bentonite on a dry weight basis. The mixture was statically compacted with moisture contents of 10, 15, and 20% to achieve a dry density of 16 kN/m3. A swell-load test was carried out using conventional oedometer equipment to obtain the swelling potential and swelling pressure of the samples. The results show that the swelling potential and swelling pressure increased with an increase in bentonite contents. At a bentonite content of more than 10%, both increased significantly. This research also revealed a linear relationship between swelling potential and swelling pressure.

Thermally Induced Bentonite Alterations in the SKB ABM5 Hot Bentonite Experiment

Pilot sites are currently used to test the performance of bentonite barriers for sealing high-level radioactive waste repositories, but the degree of mineral stability under enhanced thermal conditions remains a topic of debate. This study focuses on the SKB ABM5 experiment, which ran for 5 years (2012 to 2017) and locally reached a maximum temperature of 250 °C. Five bentonites were investigated using XRD with Rietveld refinement, SEM-EDX and by measuring pH, CEC and EC. Samples extracted from bentonite blocks at 0.1, 1, 4 and 7 cm away from the heating pipe showed various stages of alteration related to the horizontal thermal gradient. Bentonites close to the contact with lower CEC values showed smectite alterations in the form of tetrahedral substitution of Si4+ by Al3+ and some octahedral metal substitutions, probably related to ferric/ferrous iron derived from corrosion of the heater during oxidative boiling, with pyrite dissolution and acidity occurring in some bentonite layers. This alteration was furthermore associated with higher amounts of hematite and minor calcite dissolution. However, as none of the bentonites showed any smectite loss and only displayed stronger alterations at the heater–bentonite contact, the sealants are considered to have remained largely intact.

Overview of Validation Experiments Focused on Silicon in LR-0

Silicon dioxide is a common material in nature and is also often used in the nuclear industry (concrete, radioactive waste repositories in bedrocks), therefore, properly characterizing neutronic properties is very important for nuclear energy and criticality safety applications. The criticality worth was measured for several core arrangements containing silica sand both inside the core and/or as a reflector by measuring the moderator level. The core arrangements used sand as both lateral and central reflectors in different combinations. The results showed that the new thermal scattering law matrix for silicon dioxide available in ENDF/B-VIII.0 may have a problem for backward neutron scattering.

The structure and composition of solid complexes comprising of Nd(III), Ca(II) and D-gluconate isolated from solutions relevant to radioactive waste disposal

Certain complexing agents (such as D-gluconate, D-isosaccharinate, etc.) as well as actinides and lanthanides are simultaneously present in cementitious radioactive waste repositories and (in the presence of water) are capable of forming complex compounds. Such processes may immobilize radionuclides and are of importance in the thermodynamic modelling of the aqueous chemistry of waste repositories. Nd(III) is considered to be a suitable model for trivalent lanthanides and actinides, due to the similarity of their ionic radii. In the current work, solid complexes isolated from aqueous solution containing Nd(III), Ca(II) and D-gluconate (Gluc−) were investigated. In an aqueous solution containing Nd(III) and Gluc−, the formation of a precipitate was observed at pH ≥ 8. This precipitate was found to redissolve around pH ~ 11, but reprecipitated when Ca(II) ions were added to the solution. In order to gain an insight in binary and ternary aqueous systems, in the present work we report the structure of these solid complexes obtained from XRD, FT-IR, Raman, SEM-EDAX and UV-DRS measurements. The structure of these solids, where possible, was compared with those identified in solution. The compositions of these complexes are suggested to be NdGlucH−1(OH) · 2H2O and CaNdGlucH−1(OH)3 · 2H2O, respectively. In these, the chemical environment of the Nd(III) was found to be the same as that in the NdGlucH−1(OH)0(aq) solution species.