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The High Voltage Engineering Europa B.V. (HVEE) 1 MV spectrometer at NIPNE-Bucharest was extended to allow highly sensitive Accelerator Mass Spectrometry (AMS) measurements of tritium (3H). The new established analyzing procedure and a complete AMS experiment with tritium are described in detail.

Decommissioning of nuclear reactors requires determination of all remnant long-lived isotopes that were produced during their long functioning time of the respective facilities. Radiocarbon (14C) is such an isotope (T1/2 = 5730 yr), widely produced by neutron reactions in a thermal column of a nuclear reactor. Accelerator mass spectrometry (AMS) uses 14C for precise dating of up to 50,000 years old archaeological artifacts. This study presents a premier AMS measurement of high concentrated 14C samples that are strictly forbidden in laboratories dedicated to perform 14C dating. The determined 14C activities range from the natural level (isotopic ratio 14C/12C = 1.2 × 10–12) up to values of 10,000 times higher. 14C bulk and depth profile concentrations were measured in the thermal column disks of a decommissioned nuclear reactor. Results have shown that the 14C concentration in the thermal column, close the reactor core is about 75 kBq/g and decreases to 0.7 Bq/g and the end of the column. Such AMS measurements are applicable for decommissioning and waste management of nuclear reactors.

The ongoing public concern about the Fukushima nuclear accident’s real consequences determined us to start a new Accelerator Mass Spectrometry study of 129I concentrations in the North Pacific Ocean. Our results show that currently, the radioiodine 129 concentrations from coastal Japanese sea water samples are in the range of (0.9–1.6) × 108 atoms L−1. Higher 129I concentrations of 6.4 × 108 atoms L−1 have been found in the Tadami River, located close to the damaged nuclear reactors. For the North Pacific and all the way into the western shore line we found to have now much lower concentrations, with an average of 2.5 × 107 atoms L−1. Therefore, Fukushima and its vicinities remain an isolated area of nuclear pollution.

Currently, several locations of the North Atlantic Ocean have the 129 I concentration levels 10 4 –10 5 times higher than those of the pre-nuclear era. As a consequence, the southeastern part of Europe, with its rivers and seawaters, should be influenced by the outspread through the atmospheric and hydrospheric transport of iodine-129. This is a long lived fission isotope and a “low beta emitter”. It can be used as long-term tracer for nuclear pollution if the concentration of 129 I is known in the investigated geographical region. This AMS study has determined the 129 I concentrations in the southeast part of Europe, from the Lower Danube River, the Danube Delta and the Black Sea. The 129 I concentrations measured in the Black Sea were in the range of (1–1.4) × 10 8 atoms/L, which equals the range values of the North Atlantic Ocean at latitudes (31°–50°N) of (0.4–1.3) × 10 8 atoms/L. For the Danube Delta, the measured concentration values were very close to those of the Black Sea, due to the small inflow from the sea. For the region of the Lower Danube, 129 I concentrations were (4.1–7.4) × 10 7 atoms/L. The averaged results of 129 I measurements provided the actual baseline of (1.2 ± 0.1) × 10 8 atoms/L valid for the Danube Delta and the Black Sea region and of (6.4 ± 0.1) × 10 7 atoms/L for the Lower Danube.

Accelerator Mass Spectrometry (AMS) and the Full Combustion (FC) method followed by isotope separation and liquid scintillation counting (LSC) have been applied for measuring the produced and accumulated 14C in the thermal column of the decommissioned VVR-S reactor in NIPNE Bucharest. The FC method has also been used to measure the tritium (3H) deposition in the reactor column. The two employed methods are complementary and during this study they were the subjects of a cross comparison exercise.

The need to investigate the behavior of solid state materials on the impact/retention/repulsion/contamination/impregnation with special trace elements or radioactive elements has driven us to develop a modified Accelerator Mass Spectrometry (AMS) analyzing method that is able to perform the measurement of the concentration depth profile of an element in a host material. This upgraded method that we call AMS-depth profiling method (AMS-DP) measures continuously the concentration of a trace element in a given sample material as a function of the depth from the surface (e.g., tritium in carbon, deuterium in tungsten, etc.). However, in order to perform depth profiling, common AMS facilities have to undergo several changes: a new replaceable sample target-holder has to be constructed to accept small plates of solid material as samples; their position has to be adjusted in the focus point of the sputter beam; crater rim effects of the produced hole in the sample have to be avoided or removed from the registered events in the detector; suitable reference samples have to be prepared and used for calibration. All procedures are presented in the paper together with several applications.

Over the last 7–8 years, two quantitative analyzing methods—accelerator mass spectrometry (AMS) and full combustion (FC) followed by scintillation detection have been applied for determining the tritium activity concentrations in JET divertor tiles. These methods have two main differences – the range of detection and the spatial resolution – and are thus complementary. However, these differences can also complicate the comparison of the two techniques for typical JET divertor samples. Therefore a cross comparison exercise for tritium measurements was performed between the two methods using specially produced identical standard samples. The cross comparison measurements were performed firstly on the identical standard samples and were extended then to selected samples from the JET divertor tile (laser treated and non-treated samples from tile 14ING3B exposed in 2001–2004). The results obtained by AMS and FC agreed within an error limit of 10% for the standard samples and of 18% for the JET divertor samples. The results of this comparison study provided also useful information concerning the efficiency of tritium removal from the plasma facing surface of the divertor tiles by means of laser ablation.

A 1 MV AMS machine was recently installed in the National Institute for Physics and Nuclear Engineering IFIN-HH, Bucharest Romania. It is the second AMS facility at IFIN-HH having the goal not only to continue but mainly to enlarge the research area of this highly sensitive analyzing method. The multi-element AMS was developed by HVEE to measure 14C, 10Be, and 26Al, and 129I. The results of an acceptance test are presented and demonstrate that this machine is capable of routine 14C age dating and of measurements of other radioisotopes in terms of accuracy and precision as well as a low background level.

The Accelerator mass spectrometry (AMS) analysing method is described with applications for the detection of tritium leaks, detection of pollution and for research in the fusion experiments. The special requirements for an experiment of AMS with tritium are also presented. This paper concludes by showing the possibilities for each AMS facility to perform applications for detecting and preventing the environment pollution with tritium.

Accelerator mass spectrometry (AMS) and the full combustion method (FCM) followed by liquid scintillation counting were applied to quantitatively determine the tritium retention in the tungsten-coated carbon fibre composites (CFC), in comparison to uncoated CFC tiles from the JET divertor. The tiles were adjacent and exposed to plasma operations between 2007 and 2009. The tritium depth profiles are showing that the tritium retention on the W-coated tile was reduced by a factor of 13.5 in comparison to the uncoated tile whereas the bulk tritium concentration is approximately the same for both tiles.

The neutron capture cross section 209Bi(n, γ) 210mBi was measured by means of accelerator mass spectrometry (AMS). An absolute measuring procedure based on calibrated ion beam attenuators was applied to overcome the lack of standard samples. Experimental aspects of absolute AMS analyses are described. The capture cross section of 209Bi is important in the construction of accelerator-driven transmutation (ADT) devices that are based on the Pb–Bi eutectic complex as the spallation target to produce very intense neutron fluxes.

Accelerator mass spectrometry measures the depth profiles of material concentration in solid samples. Crater edge effects affect the experimental data when the secondary ions are sputtered from the sidewalls of the produced crater. We present a simple mathematical unfolding procedure that removes the perturbing contribution from the measured depth profile data. Application of this procedure to experimental data is also presented.

International audience; This paper presents the results of an experimental study we performed by using the Accelerator Mass Spectrometry (AMS) method with iodine 129 (T1/2 = 15.7 My), to determine the increase of the radionuclide content in the USA West Pacific Coast waters, two years after the March 2011 Fukushima Daiichi nuclear power plant accident. The collection of the water samples took place between April and July 2013 at regular intervals of time, from the Pacific Ocean, at the cove of La Jolla, San Diego, USA. The results of the experiments showed a significant increase of the radionuclide concentration during the late spring of 2013. Compared to the isotopic ratio 129I/127I, measured at a 40 km distance, offshore of Fukushima and immediately after the accident, our results show an increase on the USA West Coast that was more than a 2.5 factor higher. Also, compared with the pre-Fukushima background values, our results show an isotopic ratio of about two orders of magnitude higher. A distinct feature of the reconstructed radioactive plume was that it traveled with a speed of 12 cm s-1, which we estimated and is consistent with the zonal speed in the Pacific. We coupled our 129I results with the measurements from the June 2011 KOK cruise and we derived the levels of activity for 3H and 137Cs. On the USA West Coast, they did not exceed the international regulatory limits.

At the Accelerator Laboratory of Ludwig Maximilian University (LMU) and Technical University Munich (TUM) Garching, Germany, the ultra-clean injector of the accelerator mass spectrometry facility was upgraded in order to permit depth profiling of sample materials. The facility was tested and then routinely used in measurements of depth profiles of tritium and deuterium in vessel wall samples from the fusion experiments Joint European Torus (JET) in Culham, Great Britain and from the Axial Symmetric Divertor Experiment (ASDEX-Upgrade) in Garching, Germany.

To investigate the cosmogenic production of 36 Cl from atmospheric argon, cross sections of the reactions 40 Ar(p,αn) 36 Cl and 40 Ar(p,2p3n) 36 Cl were measured using accelerator mass spectrometry. For this purpose, natural 40 Ar gas targets were irradiated with protons in the energy interval 17–1000 MeV. The experimental data were compared with calculations according to the semi-empirical formalisms for spallation reactions of Rudstam and of Silberberg and Tsao. For energies below 40 MeV multi-step statistical model calculations were performed using the code STAPRE-H.

The accelerator mass spectrometry analyzing method has been applied to measure low boron concentrations in graphite for nuclear reactors. The detection limits were found to be between 5 × 10−6 (upper limit) and 3 × 10−12 (lower limit) for the B/C mass ratio.