CSNI0076 BETHSY/6.9C.

1. NAME OF EXPERIMENT:  BETHSY/6.9C.

3. DESCRIPTION OF TEST FACILITY

The BETHSY integral test facility located in the Nuclear Research Center in Grenoble (France) is a scaled down model of a 3 loop 900 eMW FRAMATOME PWR; the overall scaling factor applied to every volume, mass flowrate and power level is close to 1/100, while elevations are 1/1 in order to preserve the gravitational heads.
  
BETHSY facility is a 3-loop replica of a 900 MWe FRAMATOME PWR
- 428 heater rod core simulation, electrically heated
- 3 secondary steam generators equipped with 34 U-tubes of original dimensions
- primary system pressure up to 17.2 MPa, secondary side pressure up to 8 MPa
- initial power level of test section allows for 10 % of scaled nominal full power
- heat losses controlled by external heater system
- HPIS and LPIS available
  
Scaling Information:
- power and volume scaling 1/100 corresponding to FRAMATOME BWR of the 900 MWe class
- full length core simulator, decay power level and nominal flow rates scaled 1/100
- geodetical elevations of all components preserved 1/1 to simulate gravitational head
- loop piping diameter of hot legs dimensioned to preserve FROUDE number criterion of full size plant

4. DESCRIPTION OF TEST

The aim of this test performed in 1992 was to study the accident transient following a failure of the residual heat removal system with the pressurizer and SGI outlet plenum manways open. There was no non condensable gas in the test.
The objectives were:
Simulation of integral plant behaviour under atmospheric conditions (open system) with anticipated loss of Residual Heat Removal System during mid-loop operation
- study physical phenomena under very low system pressure, in particular the behaviour of pressurizer and surge line
- core uncovery and reflooding
- effects of loss of primary coolant and refilling by RHRS
- 'open' calculations requested to allow assessment of code applicability for conditions not anticipated during development of codes (extreme low pressure)

6. PHENOMENA TESTED

Analyze reactor system response to a loss of the Residual Heat Removal System during Mid-loop operation. The overall aims of the exercise are:
- to show the status of model development and computer codes in addressing low power (0.5%), low pressure (1 bar) transients,
- compare different computer models, and
- increase the common understanding of transients at mid-loop (shutdown) operating conditions.

- G. Kimber, C. Leveque and G. Lavialle:
ISP-38 on BETHSY Test 6.9C
Final Report NEA/CSNI/R(97)38 Vol. 1 and 2 (June 1998)
- BETHSY General Description:
Note SETh/LES/90-97 (Avril 1990)
- Ph. Gully and R. Deruaz:
BETHSY Measurement System, Note SETh/LES/87-27 (Oct. 87)
- BETHSY Measurement System, Updating (April 1990) of report SETh/LES/87-27
- P. Bazin:
BETHSY: Data Base, Note SETh/LES/87-28 (Mars 1988)

11. TEST DESIGNATION:  6.9c.

15. ESTABLISHMENT

CEA Grenoble, France
AEA Technology plc, UK
Tractebel SA, Belgium