Analysis of the source term formation in a severe accident initiated by end fitting failure in CANDU type reactors

CANDU type reactors have some peculiarities in initiation and progression of severe accidents. In the present paper one of the specificities – the End Fitting Failure accident – is analysed from the point of view of source term formation. The accident is initiated by a failure of the re-fueling machine. Fuel bundles are ejected in the re-fuelling machine room and fuel elements suffer a significant fragmentation by mechanical impact and by the rapid increase of the temperature. A direct transfer of the fission products occurs directly to the containment. The source term in the containment and also the source term to the environment is calculated supposing an open venting communication to the external atmosphere. The simulation is performed by using the ASTEC code in coupled calculation CPA-IODE-ISODOPE-DOSE option. The evolution of the distributions for the most important released fission products is presented for different regions and for different hosts. The most important factors of influence on the source term formation are identified and discussed.

Biological therapies in moderate and severe psoriasis: perspectives and certainties

An inflammatory, proliferative condition with chronic evolution and systemic response, psoriasis, is positioned today among the most common inflammatory skin diseases affecting the Caucasian population worldwide. With a significant incidence, psoriasis has been increasingly defined as a disease with a major impact on the patient's life and the society to which he/she belongs. This paper conducts an analysis of the currently available therapies for the treatment of moderate and severe psoriasis, therapies with biological agents obtained through sophisticated genetic engineering technologies. Recent research and the increasing interest in therapeutic methods as complete and efficient as possible make us optimistic and confident in the future.

Chemistry aspects of the source term formation for a severe accident in a CANDU type reactor

The progression of a severe accident in a CANDU type reactor is slow because the core is surrounded by a large quantity of heavy and light water which acts as a heat sink to remove the decay heat. Therefore, the source term formation is a complex and long process involving fission products transport and releasing in the fuel matrix, thermal hydraulics of the transport fluid in the primary heat system and containment, deposition and transport of fission products, chemistry including the interaction with the dousing system, structural materials and paints, etc. The source term is strongly dependent on initial conditions and accident type. The paper presents chemistry aspects for a severe accident in a CANDU type reactor, in terms of the retention in the primary heat system. After releasing from the fuel elements, the fission products suffer a multitude of phenomena before they are partly transferred into the containment region. The most important species involved in the deposition were identified. At the same time, the influence of the break position in the transfer fractions from the primary heat system to the containment was investigated.

Uncertainty analysis for fission products transport in CANDU primary heat transport during a severe accident

The work realized under the Severe Accident Research Network of excellence (SARNET) project has shown that the SOPHAEROS module, part of Accident Source Term Evaluation Code (ASTEC) can be fully used to simulate the fission products transport and deposition phenomena in the CANDU Primary Heat Transport (PHT) system. This paper presents an uncertainty analysis for the fission products transport in the CANDU PHT system during a severe accident to obtain the domains of the output parameters, for this study masses of Caesium, Strontium and Iodine deposited in the PHT system and its nodes, taking into account the associated input parameters uncertainties. Five uncertain parameters, the starting time for the releasing process, the duration of the releasing process, the releasing fractions for Cs, Sr and I have been chosen. To generate aleatory values for the uncertain parameters, a method and software have been developed and Monte Carlo simulations to determine uncertainties propagation through the SOPHAEROS module has been carried out.

SU-E-T-499: Validation of the Varian Generic Phase Space Files for Monte Carlo Calculations of Dose Distributions for the TrueBeam Linac Head

PURPOSE

To validate the generic phase space files for Varian TrueBeam linac head simulations.

METHODS

The generic phase space files include the simulation results of 6MV, 10MV, 6MV FFF, and 10MV FFF (flattening-filter free) operating modes of TrueBeam for patient-independent linac head components. Using the generic phase space files as the radiation sources, the BEAMnrc Monte Carlo codes are used to simulate the patient-dependent parts of the TrueBeam linac and the resulting phase space files are generated at a plane just before entering a water phantom for 4 different field sizes (5×5, 10×10, 20×20, and 40×40 cm² ). Dose distributions are calculated by DOSXYZnrc in the water phantom of size 50×50×40 cm³ . The percentage-depth-dose (PDD) curves and lateral dose profiles at three different depths (dmax, 10cm, 20cm) are obtained. Comprehensive comparisons have been made for a total of 64 dose profiles (including PDDs) between the Monte Carlo calculations and the measured data. The gamma index analysis is performed for all the comparisons.

RESULTS

The matching of the calculated dose distributions to the measured ones is analyzed by the gamma index method with a criterion of 2% dose tolerance and 2 mm distance-to-agreement. Of the 64 comparisons, the minimum gamma index passing rate is at least 92%, after taking into account the statistical nature of the Monte Carlo calculated dose values. Despite the existence of latent variance of phase space files, the phantom dose calculation uncertainty can be less than 1% for field sizes as small as 5×5 cm² . The computing time saved by using phase space files could be a factor of 5-10.

CONCLUSIONS

The Varian generic phase space files are accurate and efficient radiation sources for Monte Carlo calculations of radiation dose distributions for TrueBeam linac head. This work was supported in part by Varian Medical Systems and the NIH (1R01 CA104205 and 1R21 CA153587).

Glatiramer acetate in combination with minocycline in patients with relapsing--remitting multiple sclerosis: results of a Canadian, multicenter, double-blind, placebo-controlled trial

Minocycline is proposed as an add-on therapy to improve the efficacy of glatiramer acetate in relapsing-remitting multiple sclerosis. The effect of minocycline plus glatiramer acetate was evaluated in this double-blind, placebo-controlled study by determining the total number of T1 gadolinium-enhanced lesions at months 8 and 9 in patients who were starting glatiramer acetate and had at least one T1 gadolinium-enhanced lesion on screening magnetic resonance imaging. Forty-four participants were randomized to either minocycline 100 mg twice daily or matching placebo for 9 months as add-on therapy. They were assessed at screening and months 1, 3, 6, 8 and 9. Forty participants completed the study. Compared with glatiramer acetate/placebo, glatiramer acetate/minocycline reduced the total number of T1 gadolinium-enhanced lesions by 63% (mean 1.47 versus 2.95; p = 0.08), the total number of new and enlarging T2 lesions by 65% (mean 1.84 versus 5.14; p = 0.06), and the total T2 disease burden (p = 0.10). A higher number of gadolinium-enhanced lesions were present in the glatiramer acetate/minocycline group at baseline; this was incorporated into the analysis of the primary endpoint but makes interpretation of the data more challenging. The risk of relapse tended to be lower in the combination group (0.19 versus 0.41; p = NS). Treatment was safe and well tolerated. We conclude that efficacy endpoints showed a consistent trend favoring combination treatment. As minocycline is a relatively safe oral therapy, further study of this combination is warranted in relapsing-remitting multiple sclerosis.

New multifunctional textile biomaterials for the treatment of leg venous insufficiency

Acryloyl monomers have been synthesized by reaction of beta-cyclodextrin and troxerutin with acryloyl chloride and grafted on a knitted material obtained from polyamide 6.6 and polyurethane fibers. Polyamide grafted with beta-cyclodextrin derivative binds troxerutin as a physical complex. The obtained biomaterials have been tested in vivo on rats for their ability to deliver troxerutin (a flebotonic drug) to different skin areas (epidermis, dermis and vascular wall). The results showed that the new synthesized materials can act as multifunctional bioactive textiles that can display both compression (given by the textile material) and sustained venotonic and haemostatic properties (given by the troxerutin delivered from biomaterial to the skin).