[en] The calculation of pressure vessel wall thickness is made with formulae usually imposed by national codes. Although the Lame's formulae give actual stresses and leave the decision on the safety factor to the designer, these codes impose certain safety factors in the calculation of allowable stresses, or even include the safety factor in the wall thickness calculation formula. If we take as an example a pressure made of 316 SS with 125 mm ID, and designed for 400 bar, the methods of calculation which are most commonly used are: Lame, Stroomwezen (Dutch Code), AD merkblatt (German Code), CODAP (French Code), ASME Code Section VIII, Division 1 or 2 (USA). Obviously, the thicker the wall, the lower the stresses due to the pressure. However, some other factors need to be considered, the most important of them probably being thermal stresses. The thicker the wall, the higher the thermal stresses, all other parameters being equal. When such vessel is heated from the outside, a temperature gradient is created across the wall and the temperature is higher on the outside than the inside. Consequently, the thermal stresses are in compression on the outside, and in tension on the inside, and come in addition to the pressure stresses. Consequently, the designer must choose the wall thickness so as to minimize the total of pressure and thermal stresses. (orig.)

[en] Since the start of the French electronuclear program, the three partners Fermate, EDF and Cea (DRN and IPSN) have devoted considerable effort to research and development for safety issues. In particular an important program on thermal hydraulics was initiated at the beginning of the seventies. It is illustrated by the development of the CATHARE thermalhydraulic safety code which includes physical models derived from a large experimental support program and the construction of the BETHSY integral facility which is aimed to assess both the CATHARE code and the physical relevance of the accident management procedures to be applied on reactors. The state of the art on this program is described with particular emphasis on the capabilities and the assessment of the last version of CATHARE and the lessons drawn from 50 BETHSY tests performed so far. The future plans for safety research cover the following strategy: - to solve the few problems identified on present computing tools and extend the assessment - to solve the few problems identified on present computing tools and extend the assessment - to perform safety studies on the basis of plant operation feedback - to contribute to treating the safety issues related to the future reactors and in particular the case of severe accidents which have to be taken into account from the design stage. The program on severe accidents is aimed to support the design studies performed by the industrial partners and to provide computing tools which model the various phases of severe accidents and will be validated on experiments performed with real and simulating materials. The main lines of the program are: - the development of the TOLBIAC 3D code for the thermal hydraulics of core melt pools, which will be validated against the Bali experiment presently under construction - the Sultan experiment, to study the capability of cooling by external flooding of the reactor vessel - the development of the MC-3D code for core melt-coolant interaction, which will be validated against the BILLEAU experiment intended to characterize the pre-mixing phase - the CORINE experiment, to study core melt spreading under various conditions and which will be used to validate the EPRI MELTSPREAD code and the THEMA code which is under development - the COPAIN experiment for modelling wall condensation in the presence of non-condensable gas. down of the long term CATHARE-BETHSY program which will be compensated by a substantial effort on severe accident studies

[en] In the general frame of Cathare assessment this operation is aimed to qualify the set of constitutive laws by reconstitution of experimental tests. The experimental tests are selected following 2 objectives: to be able to qualify separately (as far as possible) the constitutive laws, and, to cover the entire parameter range which is of interest for safety studies. This selection has led to a set of 135 separate effect tests taken from 15 experimental facilities and which can be arranged in 3 main categories: Adiabatic flow tests, without significant external heat exchange; non adiabatic flow tests, in which external heating or cooling is applied to the test section but not being driven by wall heat exchange; and, heat transfer tests, in which wall heat transfer plays the dominant role

[en] Purpose: Interindividual heterogeneity of the radiobiological characteristics of malignant and normal tissues hampers the derivation of radiobiological parameters from clinical data. Focusing on the ratio Dprolif, i.e., the dose to compensate 1 day of treatment interruption, this article investigates the hypothesis that ratios of parameters might be less sensitive to interpatient heterogeneity and may constitute a more reliable description of the radiobiological properties of tissues than the parameters themselves. Methods and Materials: Analytic calculations were performed in an idealized example in which the only source of heterogeneity was the number of clonogenic cells. Computer simulations were used to assess the effects of heterogeneity in radiosensitivity and in proliferative capacity. Treatment outcome was simulated in pseudopatients with increasing dose-time correlation. Results: Interindividual heterogeneity in clonogenic cell number, radiosensitivity, or proliferative ability results in a marked underestimation of the response parameters describing these processes. In contrast, the estimates of the ratio Dprolif were more stable. The coefficients of variation increased with increasing heterogeneity. However, this only became unacceptable when heterogeneity in radiosensitivity was marked, or when total dose and treatment time were closely correlated. Conclusion: Parameter ratios may provide more robust radiobiological information than single parameters estimated from clinical data except when interindividual heterogeneity is very large or when the treatment modalities are too highly correlated. As usual, caution is advised in the presence of patient selection, a correlation between treatment prescription and expected outcome, or limited ranges of dose-time treatment patterns

No abstract available

[en] The aim of this report is to bring up the conclusions of the conceptual study of the J.E.T. plasma heating by lower hybrid waves. While giving an overall view of potential use for lower hybrid heating (LHH) in the J.E.T. plasma, this study deals more specificaly with the following concerns: up-to-date status of LHH theory and experiment; the physics of LHH on J.E.T.: RF requirements and expected results from numerical computations; the J.E.T. LHH coupling structure; the 10 MW RF generator; the associated RF diagnostics; the time schedule and the cost estimates

[en] For the purpose of T.T.M.P. (transit time magnetic pumping) heating experiment, a new vacuum vessel has been built which is mostly alumina. The energy confinement time and Zsub(eff) are compared to those obtained with the previous stainless steel liner. Using gas injection during the discharge, high density (n approximately 4.10¹³ e/cm³) and low Z (<2) are obtained. The reproducibility of the discharges, impeded by oxygen release, may be improved by various wall treatment procedures

[en] In connection with the construction of an alumina vacuum vessel on the PETULA Tokamak, measurements of the outgassing properties of alumina and studies of alumina-plasma interaction have been undertaken. Outgassing rates of 10^-11 to 10^-12 Torr l/scm² are achieved for baking temperature ranging between 150⁰ and 200⁰ C. Two categories of results have been obtained from the studies of alumina-plasma interaction depending on the plasma interacting with the alumina. For dense and cold plasma 10¹³e/cm³ a few eV, impurity concentrations lower than 1% are measured -ELISA experiment. For dense and hot plasmas, comparison between discharges produced with tungsten and alumina limiters shows an improvement of plasma characteristics in the case of alumina: ohmic power and oxygen contamination are significantly reduced

No abstract available

No abstract available