Np and Pu are two important actinides of concern for the safe long-term disposal of nuclear waste. Both actinides are, in addition, constituents of global nuclear fallout. Investigation of their environmental behavior requires ultra-sensitive analytical methods, but current methods for a concurrent determination in clay minerals are lacking. In the present study, a Pu isotope was investigated for use as a non-isotopic yield tracer for Np in extraction, purification, and mass spectrometric determination of Np and Pu isotopes in clay materials. Inductively coupled plasma mass spectrometry was used in this developmental study, but the method is intended for future ultra-trace analysis of global-fallout Np and Pu in clay-rich soil materials by the more sensitive accelerator mass spectrometry. Another field of application may be the investigation of diffusion patterns of actinides in compacted clay liners and potential host rocks for radioactive waste disposal. The analytical procedure includes the following steps: (1) extraction of Np and Pu from clay samples; (2) adjustment of Np and Pu to Np(IV) and Pu(III); (3) pre-concentration of Np and Pu by co-precipitation with iron hydroxide; (4) adjustment of Pu to Pu(IV); (5) extraction chromatographic separation of Pu and Np from iron and matrix elements; and (6) determination of Np and Pu by mass spectrometry. The analytical procedure was applied successfully to spiked montmorillonite and illite test portions of up to 1 g. High chemical yields near 90% were obtained for both Np and Pu. The suitability of Pu as a non-isotopic tracer for Np was indicated by Np/Pu chemical yield ratios close to unity. Accurate pH adjustment during the reductive co-precipitation and short processing times are vital to obtain high chemical yields and Np/Pu yield ratios close to unity.

In 1946, in the Southern Urals, construction of the Union of Soviet Socialist Republics first plutonium plant fell to the GULAG-Narodnyi Komissariat Vnutrennikh Del (NKVD). The chief officers in charge of the program – Lavrentii Beria, Sergei Kruglov, and Ivan Tkachenko – had been pivotal figures in the deportation and political and ethnic cleansing of territories retaken from Axis forces during WWII. These men were charged with building a nuclear weapons complex to defend the Soviet Union from the American nuclear monopoly. In part thanks to the criminalization and deportation of ethnic minorities, Gulag territories grew crowded with foreign nationals and ethnic minorities in the postwar years. The NKVD generals were appalled to find that masses of forced laborers employed at the plutonium construction site were members of enemy nations. Beria issued orders to cleanse the ranks of foreign enemies, but construction managers could not spare a single healthy body as they raced to complete their deadlines. To solve this problem, they created two zones: an interior, affluent zone for plutonium workers made up almost exclusively of Russians; and anterior zones of prisoners, soldiers, ex-cons, and local farmers, many of whom were non-Russian. The selective quality of Soviet “nuclearity” meant that many people who were exposed to the plant's secret plutonium disasters were ethnic minorities, people whose exposures went unrecorded or under-recorded because of their invisibility and low social value.

Understanding the environmental and biogeochemical behaviour of radionuclides is essential for managing our nuclear legacy safely. Remediation efforts and the concept of geological disposal of nuclear waste focus on immobilizing radionuclides within the subsurface. Here we review recentdevelopments in the understanding of solid-phase capture processes of Cs, Sr, Tc, U, Pu and Np. Abiotic interactions between minerals and these radionuclides (including sorption, reductive precipitation and co-precipitation) have been studied in various conditions. Microbially driven processesare much less well characterized, for example the effects of microbial reduction on the structure and reactivity of existing minerals, or their role in the formation of new minerals. Metabolites released by bacteria can play a role in both mineral dissolution and formation, and better understandingtheir release and role in mineralization has great potential in the development of solid-phase capture processes for radionuclides.

With the aid of a map of the research landscape covered by this review (created using a cluster-analysis tool, a self-organizing map), we highlight the mostpromising sequestration processes for specific radionuclides. However, radionuclides exhibit highly species-specific behaviour in their interactions with minerals and microorganisms. More research is required to characterize the role mineral surfaces play in bioreductive immobilization ofPu and Np, the reduction products formed, and their relative stability. Further studies should concentrate on more environmentally relevant experiments that include bacteria, minerals and radionuclides.

Separated stocks of UK civil plutonium are currently held as a zero value asset in storage, as there is no final decision about whether they should be treated as a resource for future use as nuclear fuel or as waste. Irrespective of future UK government strategies regarding plutonium, at least a portion of the UK civil plutonium inventory will be designated for geological disposal. In this context, we performed a high-level review of the performance of potential wasteforms for the disposal of separated civil plutonium. The key issues considered were the durability and chemical reactivity of the wasteforms in aqueous environments and the long-term radionuclide release under conditions relevant to geological disposal. The major findings of the review, relevant not only to the situation in the UK but to plutonium disposal in general, are summarized in this paper. The review showed that, in the event of a decision being taken to declare plutonium as a waste for disposal, more systematic studies would be required to constrain the wasteform performance under repository conditions in order to derive realistic source terms for a safety case.

Understanding the biogeochemical behaviour of actinides in the environment is essential for the longterm stewardship of radionuclide contaminated land. Plutonium is of particular concern due its high radiotoxicity, long half-life and complex chemistry, with these factors contributingto the limited literature available on its environmental behaviour. Here, we investigate the biogeochemistry of Pu in contaminated soil as microbial processes have the potential to mobilize Pu through numerous mechanisms including the reduction of Pu(IV) to the potentially more mobile Pu(III).After the addition of glucose to stimulate microbial activities, there was a substantial shift in the 16S rRNA gene profile of the extant microbial communities between days 0 and 44 with an increase in Clostridium species, known glucose fermenters which have been reported to facilitatethe reduction of Pu(IV) to Pu(III). A minor increase in Pu mobility was observed at day 44, returning to initial levels by day 118. The negligible change in Pu mobility, despite the onset of reducing conditions and changing mineralogy, would suggest the Pu is highly refractory. This informationis important for developing remediation options for Pu-contaminated soils, suggesting that managing legacy Pu in situ may be preferred to mobilization via the stimulation of metal-reducing bacteria.

The effects of ion irradiation in the ABO4-type compounds were compared by performing experiments on four materials that include the most common crystal structures (monazite vs. zircon) and chemical compositions (phosphates vs. silicates) for these phases. Pure synthetic single crystals of ZrSiO4, monoclinic ThSiO4, LaPO4 and ScPO4 were irradiated using 800 keV Kr+ ions. Radiation damage accumulation was monitored as a function of temperature in situ in a transmission electron microscope. The activation energies for recrystallization during irradiation were calculated to be 3.1–3.3 eV for the orthosilicates but only 1.0–1.5 eV for the isostructural orthophosphates. For the ion-beam-irradiated samples, the critical temperature, above which the recrystallization processes are faster than damage accumulation and amorphization cannot be induced, is >700°C for ZrSiO4 but it is only 35°C for LaPO4. At temperatures above 600°C, zircon decomposed during irradiation into its component oxides (i.e. crystalline ZrO2 plus amorphous SiO2). The data are evaluated with respect to the proposed use of the orthophosphates and orthosilicates as host materials for the stabilization and disposal of high-level nuclear waste. The results show that zircon with 10 wt.% Pu would have to be maintained at temperatures in excess of 300°C in order to prevent it from becoming completely amorphous. In contrast, a similar analysis for the orthophosphates implies that monazite-based waste forms would not become amorphous or undergo a phase decomposition.

During the past 70 years, more than 2000 metric tonnes of Pu, and substantial quantities of the ‘minor’ actinides such as Np, Am and Cm, have been generated in nuclear reactors. Some of these transuranium elements can be a source of energy in fission reactions (e.g. 239Pu), a source of fissile material for nuclear weapons (e.g. 239Pu and 2Np), and of environmental concern because of their long half-lives and radiotoxicity (e.g. 239Pu and 237Np). There are two basic strategies for the disposition of these transuranium elements: (1) to ‘burn’ or fission the actinides using nuclear reactors or accelerators; (2) to dispose of the actinides directly as spent nuclear fuel or to ‘sequester’ the actinides in chemically durable, radiation-resistant materials that are also suitable for geological disposal. For the latter strategy, there has been substantial interest in the use of actinide-bearing minerals, especially isometric pyrochlore, A2B2Oi (A = rare earths; B = Ti, Zr, Sn, Hf), for the immobilization of actinides, particularly plutonium, both as inert matrix fuels and nuclear waste forms. Systematic studies of rare-earth pyrochlores have led to the discovery that certain compositions (B = Zr, Hf) are stable to very high doses of α-decay event damage. Recent developments in the understanding of the properties of actinide-bearing solids have opened up new possibilities for the design of advanced nuclear materials that can be used as fuels and waste forms. As an example, the amount of radiation damage that accumulates over time can be controlled by the selection of an appropriate composition for the pyrochlore and a consideration of the thermal environment of disposal. In the case of deep borehole disposal (3—5 km), the natural geothermal gradient may provide enough heat to reduce the amount of accumulated radiation damage by thermal annealing.

In France, the activities carried out by the “small-scaleholders” of nuclear materials are organized by a specific regulatorysystem which defines in a detailed way their obligations and themeans of control of the government. The first part of the articlepresents the legal framework relating to the use of nuclear materialsby small-scale holders in civilian fields. The importance of thedeclaration of the nuclear material inventory is clearly emphasizedand must be prepared and transmitted to the Institute for RadiologicalProtection and Nuclear Safety (IRSN) every year. The second partdescribes how this declaration is used to provide basic informationfor the competent Ministry and the inspectors to check the correct applicationof the regulatory requirements relating to physical protection andto the control of nuclear materials. Finally, the last part presentsthe on-site inspections carried out by sworn and accredited inspectorsunder the authority of the competent Authority, which provide anoverall picture and allow an evaluation of the risks of theft, lossor diversion of these materials.

Due to α radioactive decay Pu is vulnerable to aging. The behavior of He in Pu is the foundation for understanding Pu self-radiation damage aging. Molecular dynamics technique is performed to investigate the behavior of defects, the interaction between He and defects, the processes of initial nucleation and growth of He bubble and the dependence of He bubble on the macroscopical properties of Pu. Modified embedded atom method, Morse pair potential and the Lennard-Jones pair potential are used for describing the interactions of Pu-Pu, Pu-He and He-He, respectively. The main calculated results show that He atoms can combine with vacancies to form Hevacancy cluster (i.e., the precursor of He bubble) during the process of self-radiation as a result of high binding energy of an interstitial He atom to vacancy; He bubble’s growth can be dominated by the mechanism of punching out of dislocation loop; the swelling induced by He bubble is very small; grain boundaries give rise to an energetically more favorable zone for the interstitial He atom and self-interstitial atom accumulation than for vacancy accumulation; the process of He release can be identified as the formation of release channel induced by the cracking of He bubble and surface structure.

To minimize waste, improve process safety, and reduce costs, modifications were implemented to a method for quantifying gallium in plutonium metal using wavelength dispersive X-ray fluorescence. These changes included reducing sample sizes, reducing ion exchange process volumes, using cheaper reagent grade acids, eliminating the use of HF acid, and using more robust containment films for sample analysis. Relative precision and accuracy achieved from analyzing multiple aliquots from a single parent sample were approximately 0.2 and 0.1%, respectively. The same precision was obtained from analyzing a total of four parent materials, and the average relative accuracy from all the samples was 0.4%, which is within programmatic uncertainty requirements.

A novel method for preparing thin films was investigated for quantifying gallium and iron in plutonium solutions using WDXRF. This technique was developed to eliminate the potential for radioactive liquid to leak into the spectrometer, decrease specimen preparation time, and minimize waste. Samples were cast in μL quantities onto Kapton, and a surfactant was added to disperse the solution uniformly across the Kapton. After drying the specimens, they were sealed in a cell for analysis. Results to date indicate the method can provide a relative precision of ∼0.5% for gallium and ∼2% for iron, which is more than sufficient for routine sample analyses.

En vue d’optimiser la protection des travailleurs vis-à-vis des rayonnements ionisants, la réglementation française impose des limites de dose et une démarche de réduction progressive de l’exposition, dans la continuité des recommandations de la Commission internationale de protection radiologique (CIPR). Afin de vérifier le respect des limites et contraintes de dose lorsqu’un risque significatif de contamination interne existe, des programmes de surveillance sont mis en place, comprenant des mesures radiotoxicologiques périodiques. Cependant, des incertitudes dans l’interprétation dosimétrique de ces mesures sont introduites par leurs variabilités propres et par la connaissance incomplète des circonstances de l’exposition. Ces incertitudes ont été prises en compte par des techniques statistiques bayésiennes. La méthodologie développée a été appliquée à l’analyse du programme de surveillance des travailleurs des ateliers de purification du plutonium du site AREVA NC de La Hague. À partir du seuil de décision du comptage nucléaire, une dose minimale détectable (DMD) par ce programme de routine avec un niveau de confiance donné peut être calculée à l’aide du logiciel « Optimisation des programmes de surveillance de la contamination interne » (OPSCI). Cette méthodologie s’avère un support utile à l’optimisation des programmes de surveillance systématique par la recherche du meilleur compromis entre leur sensibilité et leur coût

Un nouvel outil a été développé pour optimiser l’efficacité des traitements par le DTPA après blessure, sur la base d’une réduction de la dose efficace engagée. Les simulations montrent, notamment, que pour du 239Pu modérément soluble (type M), des traitements précoces (24 i.v.) étalées sur 4 mois permettent une réduction d’un tiers de la dose, alors que leur prolongement sur 5 ans, avec un intervalle de 2 semaines, peut diminuer la dose d’un facteur 5. En revanche, pour des composés peu solubles (type S), l’efficacité des traitements précoces est négligeable et un gain dosimétrique d’un facteur 3 n’est atteint que pour des traitements effectués 2 fois par mois durant 50 ans. Certaines des hypothèses retenues pour la modélisation ont été validées par les résultats d’expérimentations animales récemment publiés. Enfin, la structure d’un nouveau modèle applicable à la fois au Pu et à l’Am est rapportée, structure tenant compte de la décorporation urinaire et fécale de ces actinides et qui pourrait être adapté à différentes posologies et formes galéniques de DTPA.

Le service de santé au travail du CEA/CADARACHE est un service médical de site chargé de la surveillance radiologique de l'exposition interne de l'ensemble du personnel travaillant sur le centre de Cadarache. Dans notre activité spécifique de surveillance du risque radiologique prédomine la gestion des expositions aux actinides, plutonium et américium principalement, avec environ 600 agents concernés. Nous présentons les protocoles de prise en charge des incidents de contamination que nous avons élaborés et mis en place en 1996 ainsi que le retour d'expérience sur plus de 1 500 évènements gérés jusqu'à fin 2002.

Le cas rapporté concerne une plaie contaminée par du plutonium. La prise en charge de cet accident amène le médecin du travail de l'INB à résoudre un certain nombre de questions dans le domaine de la dosimétrie, de la communication et des aspects réglementaires. Les notions de dosimétrie et l'interprétation du risque sont complexes en matière de contamination interne. Les limites réglementaires de dose sont des limites annuelles et il est difficile d'expliquer aux victimes d'un incident de contamination que la réglementation détermine les conséquences sur le maintien de l'aptitude au travail en fonction d'une dose engagée sur cinquante ans. Par ailleurs, les déclarations obligatoires à l'employeur, à l'inspection du travail et à l'organisme national de contrôle en radioprotection provoquent de multiples interventions dans le domaine de l'information. Cette observation permet d'évoquer différents aspects pratiques de gestion médicale et de dosimétrie. Dans le cas présenté, le suivi radiotoxicologique et la thérapeutique sont documentés sur une période de plus de cinq ans.

L'étude de la distribution spatiale et de l'évolution temporelle des isotopes du plutonium (238Pu, $^{239{-}240}$Pu) chez des espèces indicatrices (Fucus serratus, Patella sp., Mytilus edulis) a été réalisée le long des côtes de la Manche. Plusieurs époques ont été considérées, 1982-1983, 1990-1993 et 1996. Les concentrations des différents isotopes sont inférieures à 1 Bq kg-1 sec pour les années les plus récentes. Une diminution de ces concentrations depuis plusieurs années est observée et elle est associée à la diminution desquantités de plutonium rejetées par l'usine de la Hague. Des gradients de distribution des isotopes le long des côtes apparaissent pour les fucus. La différence entre les rapports isotopiques des espèces et des rejets conduit à discuter des diverses sources de radioactivité influençant les niveaux de plutonium. Enfin, les facteurs de concentration sont définis.

Nous avons mesuré la survie de macrophages alvéolaires de rat après une irradiation alpha réalisée in vitro à l'aide de sources électrodéposées de 239-Pu. La survie a été évaluée en mesurant,par puits de culture, le nombre de cellules adhérentes par unité de surface comparée àdes puits non irradiés. La relation dose-effet obtenue suit une fonction exponentielle de la fluence alphaémise par la source. Après mesure des surfaces projetées des cellules entières et de leurs noyaux par microscopie optique, et détermination de la forme cellulaire par microscopie confocale, uncalcul dosimétrique a été effectué. Environ 550 alpha/cellule et 150 alpha/noyau induisent une létalité de 63 % des macrophages alvéolaires, soit une Do de l'ordre de 90 Gy pour la cellule ou lenoyau. Ces résultats permettent d'évaluer la survie des macrophages in vivo après phagocytose d'oxydes d'actinides, en fonction de la taille et de l'activité alpha spécifique de la particule. Aprèsinhalation, une létalité significative des macrophages alvéolaires serait induite pour des particules d'oxydes d'actinides de diamètre aérodynamique supérieur à 1 micron et d'activité spécifiquesupérieure à celle du 239-PuO2.