Plutonium in the environment: key factors related to impact assessment in case of an accidental atmospheric release

International audienceThis paper deals with plutonium and key factors related to impact assessment. It is based on recent work performed by CEA which summarize the main features of plutonium behaviour from sources inside installations to the environment and man, and to report current knowledge on the different parameters used in models for environmental and radiological impact assessment. These key factors are illustrated through a case study based on an accidental atmospheric release of Pu in a nuclear facility

Evolution of the UV LF from z~15 to z~8 Using New JWST NIRCam Medium-Band Observations over the HUDF/XDF

Here we present the first constraints on the prevalence of z>10 galaxies in the Hubble Ultra Deep Field (HUDF) leveraging new NIRCam medium-band observations taken with JWST. These NIRCam observations probe redward of 1.6microns, beyond the wavelength limit of HST, allowing us to search for galaxies to z>10. These observations indicate that the highest redshift candidate identified over the HUDF with HST, UDFj-39546284, has a redshift of z=12.0+/-0.1, as had been suggested in multiple analyses of the HUDF12/XDF data. This source thus appears to be the most distant galaxy discovered by HST in its more than 30 years of operation. Additionally, we identify nine other z~8-13 candidate galaxies over the HUDF, two of which are entirely new discoveries and appear to lie at z~11 and z~12. We use these results to characterize the evolution of the UV luminosity function (LF) from z~15 to z~8.7. While our LF results at z~8.7 and z~10.5 are consistent with previous findings over the HUDF, our new LF estimates at z~12.6 are substantially higher than other results in the literature, potentially pointing to a milder evolution in the UV luminosity density from z~12.6. We emphasize that our LF results are uncertain given the small number of sources in our z~12.6 selection and limited volume probed. The new NIRCam data also indicate that the faint z~8-13 galaxies in the HUDF/XDF show very blue UV-continuum slopes beta~-2.7, high specific star formation rates ~24.5 Gyr$^{-1}$, and high EW (~1300A) [OIII]+Hbeta emission, with two z~8.5 sources showing [OIII]+Hbeta EWs of ~2300 Angstroms.Comment: 19 pages, 14 figures, 7 tables, submitted to MNRAS, with some minor typos correcte

Mapping dusty galaxy growth at z>5z>5 with FRESCO: Detection of Hα\alpha in submm galaxy HDF850.1 and the surrounding overdense structures

We report the detection of a 13$\sigma$ H$\alpha$ emission line from HDF850.1 at $z=5.188\pm0.001$ using the FRESCO NIRCam F444W grism observations. Detection of H$\alpha$ in HDF850.1 is noteworthy, given its high far-IR luminosity, substantial dust obscuration, and the historical challenges in deriving its redshift. HDF850.1 shows a clear detection in the F444W imaging data, distributed between a northern and southern component, mirroring that seen in [CII] from the Plateau de Bure Interferometer. Modeling the SED of each component separately, we find that the northern component has a higher mass, star formation rate (SFR), and dust extinction than the southern component. The observed H$\alpha$ emission appears to arise entirely from the less-obscured southern component and shows a similar $\Delta$v$\sim$+130 km/s velocity offset to that seen for [CII] relative to the source systemic redshift. Leveraging H$\alpha$-derived redshifts from FRESCO observations, we find that HDF850.1 is forming in one of the richest environments identified to date at $z>5$, with 100 $z=5.17-5.20$ galaxies distributed across 10 structures and a $\sim$(15 cMpc)$^3$ volume. Based on the evolution of analogous structures in cosmological simulations, the $z=5.17-5.20$ structures seem likely to collapse into a single $>$10$^{14}$ $M_{\odot}$ cluster by $z\sim0$. Comparing galaxy properties forming within this overdensity with those outside, we find the masses, SFRs, and $UV$ luminosities inside the overdensity to be clearly higher. The prominence of H$\alpha$ line emission from HDF850.1 and other known highly-obscured $z>5$ galaxies illustrates the potential of NIRCam-grism programs to map both the early build-up of IR-luminous galaxies and overdense structures.Comment: Submitted to MNRAS. 20 pages, 10 figures and 8 tables (including appendices

The JWST FRESCO Survey: Legacy NIRCam/Grism Spectroscopy and Imaging in the two GOODS Fields

We present the JWST Cycle 1 53.8hr medium program FRESCO, short for "First Reionization Epoch Spectroscopically Complete Observations". FRESCO covers 62 arcmin$^2$ in each of the two GOODS/CANDELS fields for a total area of 124 arcmin$^2$ exploiting JWST's powerful new grism spectroscopic capabilities at near-infrared wavelengths. By obtaining ~2 hr deep NIRCam/grism observations with the F444W filter, FRESCO yields unprecedented spectra at R~1600 covering 3.8 to 5.0 $\mu$m for most galaxies in the NIRCam field-of-view. This setup enables emission line measurements over most of cosmic history, from strong PAH lines at z~0.2-0.5, to Pa$\alpha$ and Pa$\beta$ at z~1-3, HeI and [SIII] at z~2.5-4.5, H$\alpha$ and [NII] at z~5-6.5, up to [OIII] and H$\beta$ for z~7-9 galaxies, and possibly even [OII] at z~10-12. FRESCO's grism observations provide total line fluxes for accurately estimating galaxy stellar masses and calibrating slit-loss corrections of NIRSpec/MSA spectra in the same field. Additionally, FRESCO results in a mosaic of F182M, F210M, and F444W imaging in the same fields to a depth of ~28.2 mag (5 $\sigma$ in 0.32" diameter apertures). Together with this publication, the v1 imaging mosaics are released as high-level science products via MAST. Here, we describe the overall survey design and the key science goals that can be addressed with FRESCO. We also highlight several, early science results, including: spectroscopic redshifts of Lyman break galaxies that were identified almost 20 years ago, the discovery of broad-line active galactic nuclei at z>4, and resolved Pa$\alpha$ maps of galaxies at z~1.4. These results demonstrate the enormous power for serendipitous discovery of NIRCam/grism observations. Given the wealth of ancillary data available in these fields, the zero-proprietary time FRESCO data is poised to enable a large amount of legacy science by the community.Comment: 11 pages, 11 figures; submitted to MNRAS; for more information on the survey and data releases, see http://jwst-fresco.astro.unige.ch

The JWST FRESCO Survey:Legacy NIRCam/Grism Spectroscopy and Imaging in the two GOODS Fields

We present the JWST cycle 1 53.8 h medium program FRESCO, short for 'First Reionization Epoch Spectroscopically Complete Observations'. FRESCO covers 62 arcmin2 in each of the two GOODS/CANDELS fields for a total area of 124 arcmin2 exploiting JWST's powerful new grism spectroscopic capabilities at near-infrared wavelengths. By obtaining ∼2 h deep NIRCam/grism observations with the F444W filter, FRESCO yields unprecedented spectra at R ∼1600 covering 3.8-5.0 μm for most galaxies in the NIRCam field of view. This setup enables emission line measurements over most of cosmic history, from strong PAH lines at z ∼0.2-0.5, to Pa α and Pa β at z ∼1-3, He i and [S iii] at z ∼2.5-4.5, H α and [N ii] at z ∼5-6.5, up to [O iii] and H β for z ∼7-9 galaxies. FRESCO's grism observations provide total line fluxes for accurately estimating galaxy stellar masses and calibrating slit-loss corrections of NIRSpec/MSA spectra in the same field. Additionally, FRESCO results in a mosaic of F182M, F210M, and F444W imaging in the same fields to a depth of ∼28.2 mag (5σ in 032 diameter apertures). Here, we describe the overall survey design and the key science goals that can be addressed with FRESCO. We also highlight several, early science results, including: spectroscopic redshifts of Lyman break galaxies that were identified almost 20 yr ago, the discovery of broad-line active galactic nuclei at z &gt; 4, and resolved Pa α maps of galaxies at z ∼1.4. These results demonstrate the enormous power for serendipitous discovery of NIRCam/grism observations.</p

The JWST FRESCO Survey: Legacy NIRCam/Grism Spectroscopy and Imaging in the two GOODS Fields

We present the JWST Cycle 1 53.8hr medium program FRESCO, short for “First Reionization Epoch Spectroscopically Complete Observations”. FRESCO covers 62 arcmin2 in each of the two GOODS/CANDELS fields for a total area of 124 arcmin2 exploiting JWST’s powerful new grism spectroscopic capabilities at near-infrared wavelengths. By obtaining ∼2hr deep NIRCam/grism observations with the F444W filter, FRESCO yields unprecedented spectra at R ∼ 1600 covering 3.8 to 5.0 μm for most galaxies in the NIRCam field-of-view. This setup enables emission line measurements over most of cosmic history, from strong PAH lines at z ∼ 0.2 − 0.5, to Paα and Paβ at z ∼ 1 − 3, HeI and [SIII] at z ∼ 2.5 − 4.5, Hα and [NII] at z ∼ 5 − 6.5, up to [OIII] and Hβ for z∼7-9 galaxies. FRESCO’s grism observations provide total line fluxes for accurately estimating galaxy stellar masses and calibrating slit-loss corrections of NIRSpec/MSA spectra in the same field. Additionally, FRESCO results in a mosaic of F182M, F210M, and F444W imaging in the same fields to a depth of ∼28.2 mag (5 σ in 0${_{.}^{\prime\prime}}$32 diameter apertures). Here, we describe the overall survey design and the key science goals that can be addressed with FRESCO. We also highlight several, early science results, including: spectroscopic redshifts of Lyman break galaxies that were identified almost 20 years ago, the discovery of broad-line active galactic nuclei at z &amp;gt; 4, and resolved Paα maps of galaxies at z ∼ 1.4. These results demonstrate the enormous power for serendipitous discovery of NIRCam/grism observations

The JWST FRESCO survey: legacy NIRCam/grism spectroscopy and imaging in the two GOODS fields

We present the JWST cycle 1 53.8 h medium program FRESCO, short for 'First Reionization Epoch Spectroscopically Complete Observations'. FRESCO covers 62 arcmin2 in each of the two GOODS/CANDELS fields for a total area of 124 arcmin2 exploiting JWST's powerful new grism spectroscopic capabilities at near-infrared wavelengths. By obtaining ∼2 h deep NIRCam/grism observations with the F444W filter, FRESCO yields unprecedented spectra at R ∼1600 covering 3.8-5.0 μm for most galaxies in the NIRCam field of view. This setup enables emission line measurements over most of cosmic history, from strong PAH lines at z ∼0.2-0.5, to Pa α and Pa β at z ∼1-3, He i and [S iii] at z ∼2.5-4.5, H α and [N ii] at z ∼5-6.5, up to [O iii] and H β for z ∼7-9 galaxies. FRESCO's grism observations provide total line fluxes for accurately estimating galaxy stellar masses and calibrating slit-loss corrections of NIRSpec/MSA spectra in the same field. Additionally, FRESCO results in a mosaic of F182M, F210M, and F444W imaging in the same fields to a depth of ∼28.2 mag (5σ in 032 diameter apertures). Here, we describe the overall survey design and the key science goals that can be addressed with FRESCO. We also highlight several, early science results, including: spectroscopic redshifts of Lyman break galaxies that were identified almost 20 yr ago, the discovery of broad-line active galactic nuclei at z > 4, and resolved Pa α maps of galaxies at z ∼1.4. These results demonstrate the enormous power for serendipitous discovery of NIRCam/grism observations

Les méthodes et les limites de la dosimétrie après contamination interne

The assessment of absorbed, equivalent and effective doses after internal exposure is based on activity measurement by in vivo counting or bioassay. A dose value is derived from this measurement by means of biokinetic and dosimetric models which describe the behaviour of radionuclides in the body of a reference man and the subsequent deposition of energy. To enforce regulatory dose limits, monitoring programs are designed. The doses can be estimated from the measurement data according to a standard procedure as proposed by the IDEAS group. However, a significant uncertainty is associated with the dose estimate, due to the uncertainties of measurement, to the incomplete knowledge of the conditions of exposure and to the imperfect realism of the models. In addition to this uncertainty, the extrapolation to low dose of biological effects observed at higher dose, the chemical toxicity of radionuclides and the heterogeneous energy deposition make the estimation of the risk following an internal exposure very difficult. As a conclusion, it should be reminded that the effective dose is a tool for the management of radiological protection but not a quantitative indicator of the individual risk. © 2007 EDP Sciences.Protéger l’environnement est aujourd’hui une problématique globale qui concerne toutes les activités de l’homme. Il s’agit donc d’être capable de démontrer la compatibilité de ces activités avec la protection des milieux naturels, mais aussi si nécessaire d’agir pour pallier à un risque potentiel ou avéré, et ce généralement dans le cadre d’une réglementation de plus en plus stricte. Dans le domaine chimique, la prise en compte de cette problématique se traduit par l’existence de méthodes dédiées à l’évaluation du risque environnemental. Dans le domaine radiologique, la nécessité de disposer de tels outils s’est accentuée récemment, afin de pouvoir justifier aux yeux du public et en toute transparence le rejet de substances radioactives dans l’environnement, de répondre aux exigences des nouvelles réglementations en matière de protection de l’environnement et enfin d’harmoniser les approches entre radioprotection humaine et radioprotection de l’environnement, mais aussi entre polluants chimiques et radioactifs, simultanément présents par exemple dans les rejets de routine des centres nucléaires de production d’électricité. Dans cette optique d’harmonisation, les démarches d’évaluation du risque à l’environnement lié à la présence de radionucléides ou de substances chimiques sont présentées depuis les concepts théoriques jusqu’à leur mise en œuvre comparative, approche nouvelle en cours de développement dont les premiers résultats sont présentés

Évaluation de la toxicité chimique des radionucléides à vie longue sur la base des directives de qualité pour l'eau de boisson fixées par l'OMS

L'estimation qui est faite actuellement des risques sanitaires liés à la gestion des déchets nucléaires à vie longue est incomplète si elle ne tient compte que des aspects radiotoxiques. Bien que cette approche soit justifiée à l'égard d'un grand nombre de radionucléides inventoriés, elle ne peut cependant être exclusive et généralisée : la toxicité chimique doit être considérée notamment lorsque la période radioactive d'un radionucléide excède 105 ans. Pour évaluer la toxicité chimique ou radiologique d'un radionucléide, on peut confronter une dose de référence appliquée à la consommation d'eau de boisson (0,1 mSv/an) avec les informations toxicologiques existantes. L'organisation mondiale de la Santé l'a fait pour l'uranium naturel et recommande une valeur guide pour l'eau de boisson, fondée sur sa toxicité chimique (2 μg/l). La démarche adoptée par l'OMS est reprise ici en vue de montrer que la toxicité chimique potentielle d'un élément est une donnée à intégrer dans l'estimation du risque sanitaire des radionucléides à vie longue