[en] Design and tests of equipments for the dismantling of fuel assemblies for LWR or FBR in fuel reprocessing plants are studied for reliability. Three examples are given: 1. Qualitative analysis with fault trees and FMEA for a full equipment. This study enabled to propose preventive actions in order to reduce the severity or the probability of a failure. 2. Calculation of the probability of a failure for a part of a mechanical device. This study enabled to show that this part has a very high probability at failure and then, that it is necessary to foresee the possibility of repair. 3. Estimation of the availability of on equipment. Calculations were performed from test results on various prototypes allowing comparisons between them and allowing to verify if expected availability was reached

[en] This paper deals with the description of the experimental device, the study programme and the physical model developed for the final interpretation of the experiments. Some experimental results are given as an example. The experimental device enables one side of a concrete cylinder of 1 m³ (section 1 m², height 1 m), fitted with temperature and pressure measurement instrument in the mass, to be heated. The water is collected continuously on each of the 2 sides. Several experiments have been carried out on reinforced and non reinforced concrete samples, for hot face maximum temperatures in the 300 to 600⁰C range. The duration of an experiment varies from 2 days to one week. The physical model developed for interpreting the experiments allows for all thermal exchanges and various types of water transport in the porosity of the concrete (gaseous or liquid phase, towards the hot side or the cold side)

[en] Forty-five dairy farms were randomly chose among those with average to good management practices. Each of the total of 1265 cows was followed from calving to pregnancy. The herd health programme consisted of systematic examination of the key periods of the sexual cycle: at about 30 days post-partum to monitor uterine involution and to detect and treat uterine infection; at about 60 days post-partum to examine and treat anestrous animals, and following insemination, to test for pregnancy by assaying progesterone levels in milk samples collected on day 22 post-insemination and to examine and treat cows inseminated more than three times and still not pregnant (repeat breeders). Pregnancy diagnosis by examination per rectum was carried out at about 60 days post insemination. Manual recording of the age of animal, the number of the lactation, and conditions at calving (dystocia and retention of placenta) was done. Data from 1265 calvings were analysed. Reproductive performance before and after the application of the programme, as well as effects of extrinsic and intrinsic factors on pathology and reproductive performance, were also investigated. The results show the effectiveness of such programmes in improving productivity and the importance of matching genotypes to the local environment. (author). 30 refs, 4 tabs

[en] Short communication

[en] The PWR reactor vessel is supported by a steel ring laying on the reactor pit. This support has to ensure a good behaviour of the vessel in the event of accidental conditions (earthquake and pipe rupture). A new evolution of the evaluation methods of the applied forces has shown a significant increase in the design loads used until now. In order to take into account these new forces, we carried out a test on a representative mock-up of the vessel support (scale 1/6). This test was performed by CEA, EDF and FRAMATOME. Several static equivalent forces were applied on the experimental mock-up. Displacements and strains were simultaneously recorded. The results of the test have enabled to justify the design of the pit and the ring, to show up a wide safety margin until the collapse of the structures and to check our hypothesis about the transmission of the forces between the ring and the pit

[en] A study was carried out in order to investigate the validity of a concrete model including tensile fracture and strain-softening under compressive loading. Triaxial tests were performed on micro-concrete specimens, and the post-peak behaviour of the material was characterized. The parameters required by the model were therefore obtained. The case of a circular slab loaded up to failure was then considered, in order to compare the numerical results obtained by a finite elements analysis including the concrete model, to the experimental data. (orig.)

[en] The GAREC group has performed an analysis of Ex-Vessel Corium Recovery capability for some actual and future PWR designs. This analysis includes : scenario analyses for core meltdown and corium transfer to the lower head, corium behaviour in the lower head (debris and corium pools), vessel failure, risk of vapour explosion, corium-concrete interaction and coolability, corium spreading, corium accumulation, corium-ceramic interaction, residual power distribution, long term stabilisation. This analysis is based on available and most recent experimental results (ACE, MACE, VULCANO, CIRMAT, PHYTHER, etc.), on advanced calculation tools (TOLBIAC, THEMA, CORAN, CASTEM) and on engineer evaluations. Coolability during MCCI cannot be demonstrated with the present state of scientific knowledge even if there is a great potential that it can be achieved. The paper outlines the specific aspects of the approach developed by GAREC. These aspects are based on a better knowledge of the behaviour of the corium melt. This analysis leads to the conclusion that the liquid melt in a corium pool may have rather low viscosity which in turn favours melt ejection in presence of a floating crust. The R and D program engaged by CEA in France on this subject will be outlined. For the EPR concept, the main uncertainties are related to (1)- the melt-through of the gate, (2)- the effects of late water injections. The progress performed on the spreading problem (THEMA, VULCANO) are summarised. The efforts made in support of the comprehension of corium-ceramic interactions are described. These efforts involve: basic understanding of corium-ceramic interaction, model developments, CIRMAT tests, Test for the analysis of effect related to oxygen diffusion through a metal layer. It is concluded that the attack of the ceramic may be stabilised provided that the heat extracted from below the ceramic is sufficient. Some aspects concerning consequences of vapour explosion in the reactor pit are also outlined. (orig.)

[en] The authors describe the analyses of the in-vessel retention capability which the GAREC group has performed for present and future French PWR designs. They present the reactor characteristics which are considered, describe the physical situations which are analysed and the relocation processes initiated by a corium flow, discuss the jet impacts, the debris formation and behaviour in the vessel lower head in a dry situation with absence of cooling, in wet situations in absence of external cooling, in wet situation with external cooling, in dry situation with external cooling. In this last case, they discuss the power dissipated in the corium, the molten salt behaviour, the heat flux distribution from the pool, the residual wall thickness, the heat flux distribution from the metal layer, the thermal-hydraulic aspects of water injection in the pool, the effects of crust instabilities, the external cooling, and the vessel mechanical behaviour. Then, they address the vapour explosion which may occur: mechanical loads leading to vessel failure in the cases of an eroded or non-eroded vessel, corium masses participating to the interaction (corium jets to the lower head, reflooding of corium pools with water). They finally briefly discuss the possible design improvements for in-vessel retention