The design of the Isolation Condenser in the Dodewaard Reactor is shown in Fig. 9. Some operational tests have been performed as well as some sequences occurred where the isolation condenser was used to cope with transients.

Because the operational instrumentation did not completely cover the phenomena needed for a detailed analysis and because some manual operation (not documented in detail) was used to cope with the transient a detailed evaluation of the operational data is not possible. Therefore, in Fig. 10 calculated values for the Dodewaard Isolation Condenser is given. One power level could be compared with a TRAC calculation; the agreement is good.

FIG. 7. Arrangement of the PANDA-IC in the pool.

FIG. 8. Power levels of the PANDA-IC calculated with ATHLET as a function ofpressure for the pure steam tests.

FIG. 9. Arrangement of the isolation condenser in the condenser tank of the Dodewaard nuclear power plant.

3. DISCUSSION AND CONCLUSIONS

The requirements from licensing bodies for the acceptance of experimental and analytical data in a licensing process are quite higher now than 10 or 20 years ago.

To the extend possible original geometries and materials should be used; if this is not possible, reliable scaling rules should exist.

For the Emergency Condenser (EC) and the Dodewaard Isolation Condenser (IC) original geometries and materials were used. The Isolation Condenser in PANDA is a scaled-down test section. However, the components with original geometries and materials have been tested in the PANTHERS facility; the data are not publicly available except for the licensing bodies.

The equivalent thermal-hydraulic initial and boundary conditions should be used.

This is the case for the EC and the Dodewaard IC. The PANDA IC was limited to 1 MPa, but the full pressure has been used in PANTHERS.

To the extend possible the components should be tested also with beyond-design thermal — hydraulic conditions and for low-power or shutdown situations.

The EC and PANDA IC have also been tested with non-condensables in the inlet flow. The EC has been tested with shutdown situations.

The data and procedures should be documented; an uncertainty analysis should be available.

With the exception of the Dodewaard IC those requirements could be met.

The sequences tested should be simulated with at least one computer code and the results compared with the experimental data.

This has been extensively done for the EC and PANDA IC test series.

In conclusion, tests as well as related calculations with several computer codes have been performed for passive decay heat removal systems. The spectrum tested and the quality should allow its use in a licensing process.

The NOKO test facility located at the Institute for Safety Research and Reactor Technology of the Research Center Jiilich is a thermal hydraulic test rig, which was constructed within the framework of a research task in a joint project of the Research Center Jiilich (FZJ) and SIEMENS AG, Power Generation Division (KWU), with support from the German Federal Ministry of Education, Science, Research and Technology and German utilities. The facility is suited for a broad spectrum of experiments in the field of thermodynamics and fluid dynamics of water, water vapor and non-condensable gases. Different passive safety systems can be investigated with only minor modifications.

The parameter limits given by the design are:

• maximum primary pressure: 7 MPa;

• maximum secondary pressure: 1 MPa;

• maximum power: 4 MW.

The maximum temperatures are the corresponding saturation temperatures.

The NOKO facility is composed of three sections. The first section is the primary circuit with the pressure vessel, the bundle of the emergency condenser and the associated connecting lines. The second section is the secondary side with condenser tank, relief lines and relief tank. The system of steam generation with electric boiler, separator and the associated lines forms the third section. The arrangement and linkage of the individual sections can be seen from Figure Al.

The steam-water mixture produced in the electric boiler is passed into the water — steam separator where the steam is separated from the water. The water is pumped back into the electric boiler. The separated steam is either passed into the pressure vessel or — if more steam was produced than is needed — the excess steam blown off into the relief tank. The steam is condensed in the relief tank which is cooled by an external cooling circuit. The components are made of austenitic steel. An exception is the condenser tank, which consists of ferritic steel and is internally coated with XYVADUR 569 for reasons of corrosion protection. This coating is resistant up to 200°C.

The PANDA test facility was erected in the early 1990s within the framework of the so-called ALPHA Program (Advanced Light Water Reactor Passive Heat Removal and Aerosol Retention Program) at the Paul Scherrer Institute. The PANDA test facility is a large-scale thermal hydraulic low-pressure test facility for investigating passive decay heat removal systems for the next generation of Light Water Reactors. In the first instance, PANDA is used to examine the integral long-term performance of the Passive Containment Cooling System for the Simplified Boiling Water Reactor (SBWR). The facility is an approximately 1:25 volumetric, full-scale height simulation of the SBWR containment system.

Within the project here, experiments with newly developed components were carried out in the PANDA test facility. This included the PANDA isolation condenser, the SWR-1000 building condenser and a plate condenser. All three components serve for heat removal from the containment after a serious accident.

The PANDA test facility is of modular design. It consists of a pressure vessel simulating the reactor pressure vessel, two dry-well and two wet-well containers as well as a Gravity Driven Cooling System (GDCS) pool. The facility has two separated water pools. In a water pool two passive containment coolers (PCC) are installed. In the other pool one PCC which was also used as an isolation condenser (IC) was placed. The condensers are full-scale mock-ups which only differ from those projected for the SBWR by the number of tubes. The setup of the facility is shown in Figure B1 comprising also the connections between the containers, which are not described here in detail.

The PANDA-PCC consists of 20 vertically arranged tubes connected at their ends with drum — type headers. The upper header has a connection for steam supply, the bottom header has a drain for the condensate produced and a drain for non-condensable gases. The tubes of the PCC have an outside diameter of 50.8 mm and a wall thickness of 1.65 mm. They are made of austenitic steel.

The PCC as well as the IC are passively acting components. They are heat exchangers serving to condense steam. The gas flows to the condensers without the use of pumps. It enters into the upper drum and most of the steam is condensed in the vertical tubes. The condenser pool has a ground surface of 1.5 m x 2 m and a height of 5 m. The water level is approx. 4.50 m.