Abstract. Although ranging among the most expensive gourmet foods, it remains unclear whether Burgundy truffles (Tuber aestivum) accumulate radioactivity at a harmful level comparable to other fungal species. Here, we measure the 137Cs in 82 T. aestivum fruit bodies from Switzerland, Germany, France, Italy, and Hungary. All tested specimens reveal insignificant radiocaesium concentrations, thus providing an all-clear for many truffle hunters and cultivators in large parts of Europe as well as the subsequent chain of dealers and customers from around the world. Our results are particularly relevant in the light of ongoing efforts to cultivate Burgundy truffles, as well as the fact that several forest ecosystems are still highly contaminated with 137Cs, for which mushrooms are one of the main pathways to human diets.

Abstract. Although ranging among the most expensive gourmet foods, it remains unclear if Burgundy truffles (Tuber aestivum) accumulate radioactivity at a harmful level comparable to other fungi. Here, we measure the 137Cs in 82 T. aestivum fruitbodies from Switzerland, Germany, France, Italy and Hungary. All specimens reveal insignificant radiocaesium concentrations, thus providing an all clear for truffle hunters and cultivators in Europe as well as dealers and customers from around the world. Our results are particularly relevant in the light of recent cultivation efforts and the fact that forest ecosystems are still highly contaminated with 137Cs, for which mushrooms are the main pathways to human diets.

We report on gold foil activation measurements performed along a vertical channel along the tank of the ultracold neutron source at the Paul Scherrer Institute. The activities obtained at various distances from the spallation target are in very good agreement with MCNPX simulations which take into account the detailed description of the source as built.

Soil and radioactive slurries were analyzed for the presence of beta emitting 241Pu and 90Sr. The comparison study between two different LSC apparatus, TriCarb 2200/2550 and Hidex 300 SL, shows good agreement for the quench corrected 241Pu activity concentrations. The 90Sr activity concentrations of most soil samples were in agreement, and were confirmed by the recommended IAEA-375 value. The Hidex 300 SL is an excellent apparatus to measure pure β-emitters of routine samples.

An analytical method for determination of 210Pb, 226Ra and 228Ra is presented based on adsorption on 3M Empore RadDiscs, and measurement applying liquid scintillation spectrometry (LSC) after elution. The LSC measurement was performed with optimized α⧸β-discrimination and isotope standardization using the triple to double coincidence ratio (TDCR). The consistency of measurement results between radioactive parent–daughter pairs 210Pb/210Bi, 226Ra/222Rn and 228Ra/228Ac was checked in long-term counting experiments and the influence ofinterference of in-growing daughters from 226Ra into the β-spectrum of 228Ra+228Ac was studied as well. Recommendations for optimized LSC 228Ra measurement besides presence of 226Ra are given.

Abstract In the context of two reactor decommissioning projects, radioactive slurry from concrete cutting was collected in the retention pond (RHB) at the Paul Scherrer Institute, along with radioactive drain outlets. Additionally, there are active residues from former operations. The task was to determine the nuclide vector of the radioactive slurry before final disposal. Due to the slurry from neutron-activated concrete, activation products, like 55Fe, 60Co, 63Ni, 133Ba, 152Eu, 154Eu and 155Eu can be expected. Accumulated drain outlets from laboratories, where work with radioactive substances is being done, were expected to contain 22Na, 60Co, 134Cs, 137Cs, 133Ba, 152Eu, 154Eu, 155Eu, 241Am, 239/240Pu, 241Pu, 244Cm, 234U, 235U, 238U, 230Th, 232Th and 90Sr. For further clarification, 3H and 14C in the water and in the organic phase had to be measured as well. This work gives an overview about the slurry dissolution techniques, the radiochemical separation methods and activity concentrations of the nuclide vector. Further processing of the slurry is also discussed.

241Pu was determined in slurry samples from a nuclear reactor decommissioning project at the Paul Scherrer Institute (Switzerland). To validate the results, the 241Pu activities of five samples were determined by LSC (TriCarb and Quantulus) and ICP-MS, with each instrument at a different laboratory. In lack of certified reference materials for 241Pu, the methods were further validated using the 241Pu information values of two reference sediments (IAEA-300 and IAEA-384). Excellent agreement with the results was found between LSC and ICP-MS in the nuclear waste slurries and the reference sediments.

The separation methods for soil samples applied at PSI are based on extraction chromatography and ion exchange. After sample leaching, the actinides are pre-concentrated via precipitation using oxalic acid. Besides the classical separation methods applying the extraction chromatographic resins U/TEVA (for U, Th), TRU (Pu, Am), new methods were recently implemented to increase the radiochemical recovery of particularly trivalent Am and Cm. These methods do not require initial reduction of Pu(IV) to Pu(III) but stabilize Pu on the tetravalent oxidation state using a mixture of NaNO(2)/H(2)O(2) in strong acidic medium. The Pu-fraction is then fixed along with Th onto Dowex AG 1-X2 anion exchanger resin. Th is eluted via complexation with 10M HCl, Pu via reduction with HI. The fractions of Am+Cm and U are loaded onto DGA resin. This resin shows extraordinary high distribution coefficients (k'-values) exceeding 10(4) (for Am) in strong nitric acid medium. The separation between U and Am is obtained quantitatively by decreasing the HNO(3) concentration from 3 to 0.25 M (stripping of the U-fraction) while Am can be easily eluted thereafter using 0.25 M HCl as complexation compound.

The radionuclide inventory of a copper beam dump from the 590 MeV proton accelerator of the Paul Scherrer Institute in Switzerland was determined, focusing on radioisotopes with half-lives of more than 60 d, and in particular, of long-lived isotopes with T(1/2) = 10(4) - 10(7) years, which are important regarding radioactive waste management. The measurements were carried out using high resolution gamma-measurement without sample destruction, as well as liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) after chemical separation. For the first time, a beam dump from a high power accelerator facility was completely characterized concerning the depth and radical distribution profile of the most hazardous and/or long-lived radionuclides. Moreover, it turned out that some of the investigated radionuclides, like for instance (26)Al, (44)Ti or (60)Fe represent valuable material for application in several scientific field like nuclear astrophysics, basic nuclear physics research, radiopharmacy and many others. therefore, based on the analytical results, a special research and development program has been started at PSI objecting on specific preparative extraction of long-lived radioisotopes (ERAWAST - exotic radionuclides from accelerator waste for science and technology).

Radioactive waste (slurry) from a detention pond deriving from two research reactors and several inactive and active drain outlets at the Paul Scherrer Institute are the basis for the current 90Sr investigation. For decomposition, a microwave method was applied, where 1 g of dry-ashed slurry was partially dissolved (HNO3 (65%)/H2O2 (30%); v:v=8:2). In this slurry we obtained an 90Sr activity of 5.3±0.2 Bq/g in solution. In a second run, we applied a borate-fusion (Li metaborate/Li tetraborate (80:20 w/w%) dissolving 1 g of dry-ashed "Si-free" slurry at 1100 °C in a muffle furnace. We achieved an 90Sr activity of (7.8±0.3) Bq/g, yet observing BaSO4 precipitation during the chromatographical separation of Sr. An alkali fusion using Na2CO3 was done using the Bunsen burner and the muffle furnace for 20 min at 1000 °C, in combination. During formation of the hot glass, the surplus of Na2CO3, produced Na2SO4 and BaCO3 in solid form. The hot glass was dissolved in deionised water, removing thus the SO42− ions. Dissolving the residue directly in HNO3, solves Ba as Ba(NO3)2 and thus we achieved over 80% of the 133Ba activity in the solution, as measured by γ-spectrometry. 85Sr tracer of 88.0%±3.3% was recovered, yielding on average in (7.4±0.3) Bq/g of 90Sr activity. The increase of 2.1–2.5 Bq/g of 90Sr activity achieved with the alkali fusion, and the Li metaborate/Li tetraborate 80:20 w/w% fusion, respectively, clearly shows that some Sr must have been present as SrSO4 in the slurry.

The MEGAwatt PIlot Experiment (MEGAPIE) project was started in 2000 to design, build and operate a liquid metal spallation neutron target at the power level of 1 MW. The project is an important step in the roadmap towards the demonstration of the Accelerator-Driven System (ADS) concept and for high power molten metal targets in general. In an ADS the spallation target is placed inside a sub-critical reactor core. The role of the spallation target is to provide the extra neutrons needed by the sub-critical core to keep the reactor working. Since an ADS is a fast neutron system, there is no moderation and the spallation neutron spectrum is therefore a typical fast spectrum. For a sub-critical core with k{sub eff} = 0.95, a strong neutron source is needed, and in the roadmap an accelerator current higher than 10 mA is indicated as baseline parameter for the experimental ADS. The choice of the accelerator current and energy depends primarily on the number of neutrons that need to be generated, and that are used to drive the reactor. With the 590 MeV cyclotron delivering a continuous beam on target with a current up to 1.8 mA, SINQ was chosen for the MEGAPIE experiment as the most powerful spallation neutron source in the world, with a proton beam power on target that can reach 1 MW. Up to MEGAPIE all SINQ targets were based on a bundle of heavy material rods (full zircaloy, steel rods filled with Pb, zircaloy rods filled with Pb) cooled by a flow of heavy water. For the MEGAPIE target a loop of about 82 litres of lead-bismuth eutectic (LBE) circulates enclosed by a steel structure. The target is about 5 m long and the LBE is made circulating by means of a main electromagnetic pump. The neutronic performance was deduced from flux measurements done at different positions and distances from the spallation target, because the neutron yield (number of neutrons per incoming proton) cannot be directly measured. The presence of the heavy water moderator in the SINQ facility changes the spectrum, from a fast one to a prevalently thermal one, in most of the measurement points (with the exception of measurements performed near the centre of the target). The neutronic performance of a liquid target is compared to the standard solid targets used in SINQ. In the MEGAPIE experiment the neutron flux is measured in the close proximity of the spallation zone by means of innovative micro fission chambers which give a current proportional to the neutron yield. Coupled with very detailed Monte Carlo simulations, these integral measurements provide accurate data on the neutron generation. Spallation residues accumulation or temperature influence the neutron balance and the neutron energy spectrum. Overall, the results obtained with the 3 codes FLUKA 2006.3b, MCNPX 2.5.0 and SNT are consistent. The comparison was performed for the LBE, where the results compare well, and for the structure of the target for which the discrepancies are larger. The reason is related to the different origin of the activation: residual nuclei in LBE are mainly due to spallation reactions, while target structure activation is mainly due to low-energy neutron capture. The latter is sensitive to the simulated thermalization process and to the capture cross sections data used. By comparing measurements and calculations of the neutron flux, differences of 20% were found for thermal fluxes. For epithermal flux the 'background' of neutrons with E 1 MeV) a disagreement of a factor 2-3 (depending on the chamber position) was found. It seems that the calculation of the fission rates is not correct due to the inherent difficulty of reproducing the mixed neutron spectrum, with strong thermal, epithermal and fast components at the detector locations. MEGAPIE has a neutronic performance higher than the solid targets of SINQ. The performance change between the two different solid targets and MEGAPIE has been correctly reproduced. To achieve a good accuracy in the calculation of the neutronic performance of an ADS system, an accurate definition of the geometrical model taking into account the influence of structural materials is of primary importance. The results depend also on the beam profile used in the simulations, at least for the flux calculations close to the target interaction point. Radioactive nuclides produced in liquid metal targets are transported into hot cells, pumps or close to electronics with radiation sensitive components. Besides the considerable amount of decay {gamma} activity in the irradiated liquid metal, a significant amount of the Delayed Neutron (DN) precursor activity accumulates in the target fluid. The transit time of a liquid metal target being as short as a few seconds, DNs may contribute significantly to the activation and dose rates. The importance of the DN issues in liquid metal targets is confirmed. Another problem is the gas production and release in an ADS target, the proton beam generating a large amount of gas by spallation reactions. A large amount of Po isotopes, volatile at relatively high temperatures, are produced in the LBE. The gas production was measured by {gamma} spectroscopy. The release rates of noble gases in MEGAPIE are at the % level after 1-2 days of operation, while the release becomes almost complete weeks after the beginning of operation. Pressure increase in the cover gas could be reproduced with calculations within a factor of 2. The effect of the impurities in the radionuclide inventory of the LBE, using the actual chemical composition of the LBE used in MEGAPIE, is minimal.

The migration of radioactive and chemical contaminants in clay materials and argillaceous host rocks is characterised by diffusion and retention processes. Valuable information on such processes can be gained by combining diffusion studies at laboratory scale with field migration tests. In this work, the outcome of a multi-tracer in situ migration test performed in the Opalinus Clay formation in the Mont Terri underground rock laboratory (Switzerland) is presented. Thus, 1.16 x 10(5) Bq/L of HTO, 3.96 x 10(3) Bq/L of Sr-85, 6.29 x 10(2) Bq/L of Co-60, 2.01 x 10(-3) mol/L Cs, 9.10 x 10(-4) mol/L I and 1.04 x 10(-3) mol/L Br were injected into the borehole. The decrease of the radioisotope concentrations in the borehole was monitored using in situ gamma-spectrometry. The other tracers were analyzed with state-of-the-art laboratory procedures after sampling of small water aliquots from the reservoir. The diffusion experiment was carried out over a period of one year after which the interval section was overcored and analyzed. Based on the experimental data from the tracer evolution in the borehole and the tracer profiles in the rock, the diffusion of tracers was modelled with the numerical code CRUNCH.The results obtained for HTO (H-3), I- and Br- confirm previous lab and in situ diffusion data. Anionic fluxes into the formation were smaller compared to HTO because of anion exclusion effects. The migration of the cations Sr-85(2+), Cs+ and Co-60(2+) was found to be governed by both diffusion and sorption processes. For Sr-85(2+), the slightly higher diffusivity relative to HTO and the low sorption value are consistent with laboratory diffusion measurements on small-scale samples. In the case of Cs+, the numerically deduced high diffusivity and the Freundlich-type sorption behaviour is also supported by ongoing laboratory data. For Co, no laboratory diffusion data were yet available for comparison; however, the modelled data suggests that Co-60(2+) sorption was weaker than would be expected from available batch sorption data. Overall, the results demonstrate the feasibility of the experimental setup for obtaining high-quality diffusion data for conservative and sorbing tracers. (C) 2007 Elsevier Ltd. All rights reserved.

The megawatt pilot experiment (MEGAPIE) has been launched by six European institutions (PSI, FZK, CEA, SCK-CEN, ENEA and CNRS), JAEA (Japan), DOE (US) and KAERI (Korea) with the aim to carry out an experiment, in the SINQ target location at PSI (Switzerland), to demonstrate the safe operation of a liquid metal (lead–bismuth eutectic, LBE) spallation target hit by a ∼1MW proton beam. The European Commission has joined the MEGAPIE project through the 5-year (2001–2006) project named MEGAPIE-TEST. This project has been formally concluded with an International Workshop, where the results and the lessons learned during the project have been summarised. This work presents a review of the outcome of that Workshop.

Soils have been sampled in the vicinity of the Tomsk-Seversk facility (Siberia, Russia) that allows us to measure radioactive contaminations due to atmospheric and aquatic releases. Indeed soils exhibit large inventories of man-made fission products including Cs-137 (ranging from 33,000 to 68,500 Bq m(-2)) and actinides such as plutonium (i.e. Pu131+210 from 420 to 5900 Bq m(-2)) or Am-241 (160-1220 Bq m(-2)). Among all sampling sites, the bank of the Romashka channel exhibits the highest radioisotope concentrations. At this site, some short half-life gamma emitters were detected as well indicating recent aquatic discharge in the channel. In comparison, soils that underwent atmospheric depositions like peat and forest soils exhibit lower activities of actinides and Cs-137.Soil activities are too high to be related solely to global fallout and thus the source of plutonium must be discharges from the Siberian Chemical Combine (SCC) plant. This is confirmed by plutonium isotopic ratios measured by ICP-MS; the low Pu-241/Pu-239 and Pu-240/Pu-219 atomic ratios with respect to global fallout ratio or civil nuclear fuel are consistent with weapons grade signatures.Up to now, the influence of Tomsk-Seversk plutonium discharges was speculated in the Ob River and its estuary. Isotopic data from the present study show that plutonium measured in SCC probably constitutes a significant source of plutonium in the aquatic environment, together with plutonium from global fallout and other contaminated sites including Tomsk, Mayak (Russia) and Semipalatinsk (Republic of Kazakhstan). It is estimated that the proportion of plutonium from SCC source can reach 45% for Pu-239 and 60% for Pu-241 in the sediments. (C) 2007 Elsevier Ltd. All fights reserved.