[en] Bentonite pellets are planned to be used as a part of the backfill in the Swedish spent nuclear fuel deep repository concept KBS-3. This report describes testing and evaluation of different backfill pellet candidates. The work completed included testing of both pellet material and pellet type. The materials tested were sourced from India (ASHA), Greece (IBECO, 2 products) and Wyoming USA (MX-80 clay). The majority of the tests were completed on the ASHA clay as well as the IBECO-RWC-BF products, with only limited testing of the others. The pellets tested were manufactured using both extrusion and roller compaction techniques and had different sizes and geometries. The following tests have been performed and are presented in this report: 1. General tests. Water content, bulk density and dry density have been determined for both the pellet filling and the individual pellets. The compressibility of the pellet filling was tested with CRS-tests and the strength of the individual pellets was tested with a special compression test. The water content varied from 11.3% to 18.7% and was highest for the extruded pellets. The dry density was somewhat higher for the roller-compacted pellets and their compressibility was lower. The strength of the individual pellets was generally higher for the extruded pellets. 2. Erosion. The pellet filling will be exposed to groundwater inflow when installed in the tunnel. This flow could possibly cause significant erosion on the pellet filling. Erosion tests have been performed with comparisons in erosion resistance made on the various material- and pellet-types. The influence of variations in water salinity and flow rates was also tested. The IBECO extruded 6- and 10- mm diameter rods and the compacted Posiva spec.-A pellet filling seem to have the lowest tendency to erode. It is also the IBECO extruded pellet filling that withstands variations in water salinity and flow rates best. 3. Water storing capacity. The pellet filling's ability to buffer the inflowing groundwater during the installation phase was investigated in two types of tests. In the first test the wetting behavior was observed at small scale in a Plexiglas tube. The second test was performed in an artificial pellet slot with Plexiglas sides. The ASHA extruded 6 mm pellet seem to be the superior in water storing capacity, though it is suggested that this result may be more related to the presence of a fine grained material within the pellet mass than the pellets themselves. 4. Installation test. The pellets will most likely be installed with a shotcrete machine blowing them into place. This method was tested at full scale in order to investigate how much of the pellet filling that would be crushed into fine grained material if there is no water used during their placement. ASHA extruded 6 mm was the most durable pellet type with 5% of the material being crushed. 7 - 8% of the IBECO extruded pellet types (6 and 10 mm) were crushed into finer grains. The least durable pellets were the ASHA compacted pellets (pillow and almond shaped) with a crushing ratio of 53 to 61%. These results may have significance in terms of subsequent water uptake behavior. Large scale tests at repository-scale still need to be done utilizing shotcrete equipment so that more experience is obtained in how to control the installation of the pellet filling and identify the key influences on its composition and as-placed condition