Nuclear Energy for New Europe 2009

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No: 209

Conference: Nuclear Energy for New Europe 2009

Title: Simulation of Containment Thermal-Hydraulics in the Marviken Blowdown Experiment with ASTEC and CONTAIN Codes

Theme: Thermal Hydraulics

Author(s): Ivo Kljenak, Borut Mavko

Contact : Ivo Kljenak

E-mail: ivo.kljenak@ijs.si

Address: Institut "Jožef Stefan" R4
1001 Ljubljana

Country: Slovenia

The Marviken Boiling Heavy Water Reactor (BHWR) nuclear power plant in Sweden was completed in 1971 up to light water commissioning tests, but the reactor never operated. The BHWR reactor and containment were used to perform experiments of containment behaviour at accident conditions. In the period 1972-1973, 16 blowdown experiments were performed.
In the proposed work, the simulation of the test Blowdown 16 is presented. The pressure vessel, which is situated in a pressure suppression containment, was filled with 3 times the normal quantity of water. The initial pressure in the containment was 1.1 bar, and the initial relative humidity 100% in all compartments. The test simulated a large water line break in the lower drywell of the containment: about 200 tons of water were discharged from the steam line (from time 0 s to 83 s) and from the feedwater line (from time 10 s to 283 s). The pressure in the containment increased up to 2.9 bar.
In an earlier work (Kljenak and Mavko, 2008), a simulation of the thermal-hydraulic phenomena in the Marviken containment during the Blowdown 16 test with the lumped-parameter code CONTAIN was presented. In the present work, a simulation performed with the ASTEC V1.3 code is also included. On one hand, simulations with different codes provide opportunities to compare the adequacy of the codes for simulating specific transients. On the other hand, a relatively good agreement of the results obtained by both codes with experimental results increases the trust in future theoretical predictions by either code.
Separate input models consisting of 18 cells (representing 15 rooms in the actual containment) and 31 flowpaths between cells were developed for both codes. The connection between the header and the wetwell pool was modelled separately, using adequate models that are included in both codes. The discharge from the pressure vessel was modelled by prescribing measured water mass flow rates from the steam and feedwater lines as sources in the input model. The simulation reproduced the first 500 s of the test (including the blowdown phase, which lasted about 290 s). The simulated thermal-hydraulic conditions (pressure and atmosphere temperature) in different rooms of the containment, as well as the conditions of the water pool in the wetwell, are compared with experimental results.

Reference: I.Kljenak, B.Mavko, Simulation of containment thermal-hydraulics in the Marviken blowdown experiment with the CONTAIN code, Proceedings of Int.Conf. “Nuclear Energy for New Europe 2008”, Portorož, Slovenia, September 8-11, 2008.

No:	209
Conference:	Nuclear Energy for New Europe 2009
Title:	Simulation of Containment Thermal-Hydraulics in the Marviken Blowdown Experiment with ASTEC and CONTAIN Codes
Theme:	Thermal Hydraulics
Author(s):	Ivo Kljenak, Borut Mavko
Contact :	Ivo Kljenak
E-mail:	ivo.kljenak@ijs.si
Address:	Institut "Jožef Stefan" R4 1001 Ljubljana
Country:	Slovenia

The Marviken Boiling Heavy Water Reactor (BHWR) nuclear power plant in Sweden was completed in 1971 up to light water commissioning tests, but the reactor never operated. The BHWR reactor and containment were used to perform experiments of containment behaviour at accident conditions. In the period 1972-1973, 16 blowdown experiments were performed. In the proposed work, the simulation of the test Blowdown 16 is presented. The pressure vessel, which is situated in a pressure suppression containment, was filled with 3 times the normal quantity of water. The initial pressure in the containment was 1.1 bar, and the initial relative humidity 100% in all compartments. The test simulated a large water line break in the lower drywell of the containment: about 200 tons of water were discharged from the steam line (from time 0 s to 83 s) and from the feedwater line (from time 10 s to 283 s). The pressure in the containment increased up to 2.9 bar. In an earlier work (Kljenak and Mavko, 2008), a simulation of the thermal-hydraulic phenomena in the Marviken containment during the Blowdown 16 test with the lumped-parameter code CONTAIN was presented. In the present work, a simulation performed with the ASTEC V1.3 code is also included. On one hand, simulations with different codes provide opportunities to compare the adequacy of the codes for simulating specific transients. On the other hand, a relatively good agreement of the results obtained by both codes with experimental results increases the trust in future theoretical predictions by either code. Separate input models consisting of 18 cells (representing 15 rooms in the actual containment) and 31 flowpaths between cells were developed for both codes. The connection between the header and the wetwell pool was modelled separately, using adequate models that are included in both codes. The discharge from the pressure vessel was modelled by prescribing measured water mass flow rates from the steam and feedwater lines as sources in the input model. The simulation reproduced the first 500 s of the test (including the blowdown phase, which lasted about 290 s). The simulated thermal-hydraulic conditions (pressure and atmosphere temperature) in different rooms of the containment, as well as the conditions of the water pool in the wetwell, are compared with experimental results. Reference: I.Kljenak, B.Mavko, Simulation of containment thermal-hydraulics in the Marviken blowdown experiment with the CONTAIN code, Proceedings of Int.Conf. “Nuclear Energy for New Europe 2008”, Portorož, Slovenia, September 8-11, 2008.