The CAREM Project is under the development of the Detail Engineering needed to start the construction A technical revision was made by the owner of the project (CNEA) in 1992 and a cost estimation following TRF 269 was finished in 1993

During the present year the main tasks were devoted to work on those subjects with lack of experience and were research and development were needed as RPV Containment, Internals, Thermal hydraulics of different Systems (RPV, Secondary, Primary, Containment etc) lay-out This in depth studies encourage the Project Personnel to study different solutions for the containment and RPV From the left to the nght in the next picture we have the previous design and the one in which studies are done at present The “old” design has a containment made totally with steel and the RPV with a conical shape The design was originally aimed to have a modular containment which could be transported in big pieces in order to reduce the on site works However, the solution suggested for the fixation of the containment was a difficult one from the point of view of civil engineers Because of the reduced containment size it was necessary to have the conical shape (small space for the RPV head) The latest design made from concrete m its lower part allow to have bigger available spaces so the RPV is of the straight type This solution increases the maintainability of the NPP, mainly the SG are more available for repairs, one of the weak points in the “old’ The more available space allow us to change the SG feeding pipes from a downwards type to a horizontal which permits an easier manufacturing solution Up to today the only drawback of the latest design is the corresponding to the drive mechanisms support which now is positioned in a bigger cylinder

In the following sections a short description of the activities in process except for those related to the SG in the CAREM Project are mentioned In relation with the SG, a Special Program is been conducted That Program has started with the construction of a mini SG to be tested in a high pressure loop Studies are underway to define the whole scope of data that should be obtained from a 1 1 model The studies include the qualification process and the search of a facility for testing the SG

2. CAPCN (Circuito de Alta Presion у Conveccion Natural): High Pressure Loop.

2.1. Description and Similarities with CAREM-25

The High Pressure Natural Convection Loop is part of the Thermal Hydraulics Laboratory Designed, Constructed and operated by INVAP for the CNEA Its purposes are to verify the thermal hydraulic engineering of CAREM NPP mainly on two subjects dynamic response and critical heat flux These are accomplished by the validation of the calculation procedures and codes for the rig working in states corresponding (by similarity criteria) to the operating states of CAREM reactor

CAPCN resembles CAREM in the primary loop, while the secondary loop is designed just to produce adequate boundary conditions for the heat exchanger Operational parameters are reproduced approximately for intensive magnitudes (Pressures, temperatures, void fractions heat flux etc) and scaled for extensive magnitudes (flow, heating power, size, etc) Height was kept in a I I scale

CAPCN was constructed according ASME for the following parameters I SO bar, 340°C for the primary and 60 bar 340°C for the secondary (pump exception T<240°C) The level difference between center points of core and steam generator is ~ 5 7 m Primary loop may operate in saturated regime (self — pressurized), or subcooled (dome pressure increased with nitrogen injection), with heating power up to 300 kW and different hydraulic resistance

The nuclear core is reproduced by electric heaters operated by a feedback control loop of dome pressure (primary self pressurized) For the dynamic tests the heaters are 1 2 meters long

The heaters bundle that will be used for the CHF tests differs from the one used for the dynamic ones, in order to have a configuration that allows to reach heat fluxes high enough to be sure to obtain departure from nucleate boiling for the complete range of pressures, flows and subcoolings. The heated length is 400 mm. The seven rods bundle has two of the rods which allow an overpower of 20% These rods have six thermocouples each in order to ensure the measurement of the exact location of CHF The rest of the rods only have two thermocouples that guarantee CHF detection if it takes place on One of these rods. AJ1 the thermocouples are located near the upper end of the heated zone because the axial power distribution is uniform in the CHF heaters bundle

The group of states foreseen for these tests include the following range of main parameters’

Natural circulation flow may be regulated by a valve m the cold leg and a by pass to the bottom of riser. A gamma densitometer is available for void fraction measurements The heat exchanger (SG) has two coils, once through, secondary inside For the CHF tests the steam generator is useful only as a cold source, so the secondary loop operating parameters are not relevant as long as they can be controlled

The secondary loop pressures and cold leg temperatures are controlled through feedback loops operating valves. The pump allows the regulation the flow The condenser is an air cooled type with flow control

Both loops allow automatic control and can be pressurized by nitrogen injection

The present configuration of CAPCN allows the study of a stationary state similar to the CAREM conditions of

pressure, specific flow and enthalpy

The combination of primary and secondary states is limited only by conditions attainable with the heat transfer capacity of the heat exchanger As a consequence this loop will permit to validate the calculation tools used on the CAREM Project (RETRAN and ESCAREM) in those conditions.

The inclusion of a SG (IS tubes) with a design similar to the CAREM will allow to have a full 1-D thermalhydraulics analogy, allowing the extrapolation of results directly to the CAREM-2S

The thermal-hydraulic design of CAREM reactor core has been performed using a version of 3-D, two fluid model THERM ІГ code In order to take into account the strong coupling of the thermal-hydraulics and neutronics of the core, THERMIT was linked with an improved version of CITATION code (developed in FNVAP, and called CITVAP) This coupled model allows to obtain a 3-D map of power and thermal-hydraulic parameters at any stage of the bumup cycle.

The thermal limits were calculated using the 1986 AECL-UO Critical Heat Flux Lookup Table, validated till now with all the available measurements in the operational range in order to ensure a 9S/9S reliability/confidence in the thermal limit. The CAPCN CHF test results will be used to improve these calculations by increasing the experimental data in the operating range and fuel element geometry of the CAREM core.