[en] EdF is planning to install systems at its PWRs for controlled depressurisation of containment through sand filters. The requirements which the filter system must satisfy are outlined, and the filter and system design and operation are described. The depressurisation systems will be fitted from the second half of 1987 onwards. (author)

[en] Published in summary form only

[en] A proposal is described for displays suitable to monitor the status of the safety systems and safety-related systems at the Dukovany NPP. In particular, displays suitable for monitoring the status and performance of the active and passive emergency core cooling systems and of the active and passive pressure reduction system in the hermetic area of the reactor are detailed. (author)

[en] The Ulchin 3 and 4, which are 2825 MWt PWRs, adopted Safety Depressurization System (SDS) to mitigate the beyond design basis event of Total Loss of Feedwater (TLOFW). In this study the results and methodology of the analyses for the determination of SDS bleed capacity are discussed. The SDS design bleed capacity has been determined from the CEFLASH-4AS/REM simulation according to the following design criteria: 1) Each SDS flow path, in conjunction with one of two High Pressure Safety Injection (HPSI) pumps, is designed to have a sufficient capacity to prevent core uncovery if one SDS path is opened simultaneously with the opening of the Pressurizer Safety Valves (PSVs). 2) Both SDS bleed paths are designed to have sufficient total capacity with both HPSI pumps operating to prevent core uncovery if the Feed and Bleed (F and B) initiation is delayed up to thirty minutes from the time of the PSVs lift. To verify the results of CEFLASH-4AS/REM simulation a comparative analysis has also been performed by more sophisticated computer code, RELAP5/MOD3. The TLOFW event without operator recovery and TLOFW event with F and B are analyzed. The predictions by the CEFLASH-4AS/REM of the transient two phase system behavior are in good qualitative and quantitative agreement with those by the RELAP5/MOD3 simulation. Both of the results of analyses by CEFLASH-4AS/REM and RELAP5/MOD3 have demonstrated that decay heat removal and core inventory make-up can be successfully accomplished by F and B operation during TLOFW event for the Ulchin 3 and 4. 18 figs., 2 tabs., 14 refs. (Author)

[en] A nuclear reactor having a reactor vessel disposed in a containment shell is depressurized in stages using depressurizer valves coupled in fluid communication with the coolant circuit. At least one sparger submerged in the in-containment refueling water storage tank which can be drained into the containment sump communicates between one or more of the valves and an inside of the containment shell. The depressurizer valves are opened in stages, preferably at progressively lower coolant levels and for opening progressively larger flowpaths to effect depressurization through a number of the valves in parallel. The valves can be associated with a pressurizer tank in the containment shell, coupled to a coolant outlet of the reactor. At least one depressurization valve stage openable at a lowest pressure is coupled directly between the coolant circuit and the containment shell. The reactor is disposed in the open sump in the containment shell, and a further valve couples the open sump to a conduit coupling the refueling water storage tank to the coolant circuit for adding water to the coolant circuit, whereby water in the containment shell can be added to the reactor from the open sump. 4 figures

No abstract available

[en] This article shows the prediction method of conditions of flange joints depressurization during the assembly of pipelines using technological and standard fasteners. (paper)

[en] Complete text of publication follows. Current stage in the IFE research has passed to a closing stage: creation of the experimental reactor and realization of electric power generation. HiPER is a proposed European High Power laser Energy Research facility dedicated to demonstrating the feasibility of laser driven fusion for IFE reactor. The HiPER facility operation requires the formation and delivery of spherical shock ignition cryogenic targets with a rate of several Hz. The targets must be free-standing, or un-mounted. At the Lebedev Physical Institute (LPI), significant progress has been made in the technology development based on rapid fuel layering inside moving free-standing targets which refers to as FST layering method. It allows one to form cryogenic targets with a required rate. In this report, we present the results of a feasibility study on high rep-rate formation of HiPER-class targets by FST. We consider two types of the baseline target for shock ignition. The first one (BT-2) is a 2.094-mm diameter compact polymer shell with a 3 μm thick wall. The solid layer thickness is 211 μm. The second (BT-2a) consists of a 2.046-mm diameter compact polymer shell (3 μm thick also) having a DT-filled CH foam (70 μm) on its inner surface, and then a 120 μm thick solid layer of pure DT. The work addresses the physical concept, and the modeling results of the major stages of FST technologies for different shell materials: Filling stage optimization (computation): optimal filling of a target batch up to ∼ 1000 atm at 300 K requires minimizing the diffusion fill time due to using the ramp filling method for both BT-2 and BT-2a; Depressurization stage optimization (computation and experiments): it requires providing the shell container leak proofness during the process of its cooling down to a depressurization temperature. This allows one to fulfill the technical requirements on the risks minimization associated with the damage of the HiPER-class targets; Layering stage optimization (computation and experiments): First step requires (a) choosing an optimal temperature of target input into the layering channel, (b) analyzing the 'liquid-vapor' interface behavior at different cooling rates, and (c) computation of the FST layering time; A preliminary concept of the FST-layering module for HiPER-class targets (including the interface unit for target-and-sabot assembly) is presented. The results of the mock-ups testing are discussed, namely: (a) FST layering channels (LC) of different geometry have been created and the time of target residence inside LC has been measured for 2 mm diameter targets of different weight and material, including a HiPER-class surrogate target. This allows determining the requirements on the LC manufacturing. (b) Mock-up of target positioning device has been constructed and tested. It was found that the device ensures a comprehensive look at the target for the time less than 1 sec. Acknowledgements. This work supported by the International Science and Technology Center (ISTC) under contract No. 3927 (partner of the project is Science and Technology Facilities Council (STFC), UK).

[en] Noncondensible gases may become dissolved in boiling water reactor (BWR) water-level instrumentation during normal operations. Any dissolved noncondensible gases inside these water columns may come out of solution during rapid depressurization events and displace water from the reference leg piping, resulting in a false high level. Significant errors in water-level indication are not expected to occur until the reactor pressure vessel (RPV) pressure has dropped below ∼450 psig. These water level errors may cause a delay or failure in emergency core cooling system (ECCS) actuation. The RPV water level is monitored using the pressure of a water column having a varying height (reactor water level) that is compared to the pressure of a water column maintained at a constant height (reference level). The reference legs have small-diameter pipes with varying lengths that provide a constant head of water and are located outside the drywell. The amount of noncondensible gases dissolved in each reference leg is very dependent on the amount of leakage from the reference leg and its geometry and interaction of the reactor coolant system with the containment, i.e., torus or suppression pool, and reactor building. If a rapid depressurization causes an erroneously high water level, preventing automatic ECCS actuation, it becomes important to determine if there would be other adequate indications for operator response. In the postulated inadvertent opening of all seven automatic depressurization system (ADS) valves, the ECCS signal on high drywell pressure would be circumvented because the ADS valves discharge directly into the suppression pool. A best-estimate analysis of such an inadvertent opening of all ADS valves would have to consider the thermal-hydraulic coupling between the pool, drywell, reactor building, and RPV

No abstract available