Participation in Development of European Calculation Environment (ECE)).46

46

experiments demonstrated the strong diminishing effect that even small quantities of non-condensable gas can have on dynamic unsteady loadings experienced by submerged pool structures.

• A new two-compartment test facility withstanding prototypical BWR containment pressures was designed and constructed. Main component of the facility is a ~31 m

cylindrical vessel, 7.45 m high and 2.4 m in diameter. It can be operated up to 190 °C and 0.4 MPa overpressure or down to 0.05 MPa underpressure. The vessel sections modeling dry well and wet well are volumetrically scaled according to the corresponding volumes at the plant. An intermediate floor separates the upper drywell compartment from the lower wet well compartment. The number, diameter and location of the blowdown pipes can be varied from one experiment series to another. A possibility for experiments at atmospheric pressure remains since the vessel head of the new facility can be removed.

• Measurement results of the experiments in 2006 can be found from the experiment database maintained by the research group.

• Information related to the progress of the OECD/SETH Programme was distributed.

2.3.6 Participation in Development of European Calculation

47

NEPTUNE is installed in a Linux system, and is fully functional. Validation case documents and theory manual of NEPTUNE have been received. An initial version of the calculation grid has been developed and tested in NEPTUNE. A number of initial water/steam-simulations have been calculated using experimental data. 2D-axisymmetric and full 3D grids have been used. Simulation in 3D geometry has started. Air as 3rd phase has caused problems in simulation. Simulations with STB-31 values indicate very rapid condensation if Hughes-Duffey model has been used and air effects have not been taken into account. Researcher visit of two months in CEA Grenoble started in November 2006.

In “Delivery of experiment data” subproject the experiment results from the SAFIR/

POOLEX project have been converted and delivered. The data processing of the POOLEX test for NURESIM validation (STB-31) has been performed and a test report has been written. In POOLEX test STB-31 the thickness of gas layer in the pipe exit has been checked using temperature data and a report has been written.

Figure 20. Simulation results of POOLEX test. Steam velocity is an order of magnitude higher than in the experiment.

Deliverables in 2006

NEPTUNE condensation models have been validated using 2D and 3D grid for POOLEX test STB-31. Results have been reported to NURESIM project.

Amount of air present in the steam/water interface close to the blowdown pipe outlet in test

STB-31 has been studied and reported.

48 2.3B CONTAINMENT

The Containment group includes the following projects: Wall response to soft impact (WARSI), Impact Tests (IMPACT), Cavity phenomena and hydrogen burn (CAPHORN) and Behaviour of fission products in air-atmosphere (FIKA).

2.3.7 Wall response to soft impact (WARSI) Objectives

The main aim of the project is to develop and take in use methods for predicting response of reinforced concrete structures subjected to impacts of deformable projectiles that may contain combustible liquid, such as jet fuel. Also release and spreading of liquid from fragmented missiles will be dealt with. This project also assists the IMPACT project in planning the tests besides assessing and analysing the test results.

Specific Goals in 2006

The work will be prioritised and planned in detail together with the Technical Advisory Group.

1 Pre-calculations for tests

Pre-calculations needed in planning the tests were continued and the work was carried out in co-operation with the experts of IRSN. Especially, tests for determining the penetration depth of deformable soft missiles needed to be carefully planned.

2 Post-calculations for tests

First, the post-calculations for the tests carried out in the end of 2005 were be finalised.

This information was needed in planning the tests for 2006.

So far, the test missiles in the IMPACT project were constructed using easily available thin walled steel pipes stiffened with For the sake of comparison, tests with thin walled aluminium missiles were needed in order to assess the effect of material properties on the impact behaviour of the projectiles. Numerical methods were applied in planning the tests with aluminium model missiles and in assessing the impact test results.

Numerical simulation work was focused on some selected wall tests and several sensitivity studies were carried out.

Jet fuel release and spreading

The task supported the planning of the IMPACT test arrangement in order to quantify how liquid is released and spread from ruptured projectiles. For example, the liquid release velocity in the vicinity of impact location, wet pool area on floor, spread of liquid spray far-away from the impact location, and droplet size are possible measured variables. Other measurement arrangements were also considered.

Primary objective of Task 3 is to analyse and report the main results of the IMPACT tests

relating to liquid release and dispersal. If some resources remain, analytical and/or

49

numerical methods will be applied in assessing the liquid spreading, and the calculation results will be compared against the IMPACT test data.

Deliverables

The results of this work, methods and calculation tools can be applied in predicting structural behaviour of impact loaded structures and in assessment of pressure loads caused by deformable missiles filled with fluid. Also the know-how and calculation methods developed during the project can be applied in assessing the fuel spreading and combustion phenomena under impact conditions.

Figure 21. Missile after test and the calculated deformation by ABAQUS/Explicit FE-code.

m = 45.4 kg, v = 122 m/s

0.0E+00 5.0E+05 1.0E+06 1.5E+06 2.0E+06 2.5E+06 3.0E+06

0 0.002 0.004 0.006 0.008 0.01 0.012

time [s]

reaction force [N]

axisymmetric analysis

3D analysis

Riera (D = 6800, q = 4)

Riera (D = 40, q = 5)

40 per. Mov. Avg. (axisymmetric analysis)

Figure 22. Reaction force in the 3D and axisymmetric analyses and in viscoplastic Riera calculations with two different parameter sets.

Tools, models and methods have been developed for determining impact force-time

functions for different types of missiles. Nonlinear reinforced concrete wall analysis tools

were developed. Numerical results were verified against experimental data.

50 Fuel dispersion in impact

Fuel release and dispersal from impacting projectiles was studied. Drop size, liquid front velocity and extent of dispersal were predicted based on impact tests. Simulation of fuel dispersal was carried out with Fire Dynamic Simulator (FDS) code

Figure 23. Extract from the simulation of fuel dispersal with Fire Dynamic Simulator

(FDS) code.