PWC/CCD: Pressurised Water Capsule/Cycling and Calibration Device

The PWC/CCD irradiation rig consists of two parts: the PWC capsule and the CCD calorimeter.

The PWC ( Pressurised Water Capsule) is an instrumented irradiation capsule for the testing of single fuel rod segments with a diameter of 8-15 mm and an active length up to 1000 mm, under steady-state or transient conditions.

The target fuel segment, which can be equipped with a thermocouple, is placed into the stainless steel capsule filled with demineralised stagnant water.

The CCD ( Cycling and Calibration Device) is a dedicated flow calorimeter that is designed to monitor the thermal performance of the coolant flowing through it, using a diaphragm flow meter and thermocouples placed at inlet and outlet. The internal diameter of the stainless steel tube is about 34 mm. A 1 m high helium screen, placed on the outer surface of the CCD, serves as a thermal shield to minimise heat leaks. The fuel rod heating is adjusted by varying the BR2 reactor power during dedicated short reactor cycles.

PWC-CCD

Exploded 3D view of the PWC/CCD assembly

The PWC water can be pressurised in the range of 0.1 to 16 MPa. The heat generated in the rod is dissipated radially towards the outer surface of the pressure tube by natural convection, with or without boiling, depending on the irradiation programme. The PWC capsule is cooled by the reactor water flowing (at a typical temperature of 40-50 °C) through the CCD calorimeter. The nominal flow rate is 0.001 m³/s, leading to a heat transfer coefficient of about 20 W/(m²·K) at the outer surface of the capsule pressure tube.

PWC

Exploded 3D view of the PWC capsule with fuel segment

Thermocouples have been installed to monitor the temperatures on the outer surface of the fuel rod at its mid-plane and in the stagnant water of the PWC. Water samples of the PWC water can be taken before, during and after reactor operation for monitoring the fission product activity in order to detect a possible fuel rod failure.

The PWC/CCD device has been applied successfully in several fuel ramping tests during the last 30 years.

Further developments are foreseen with the introduction of a variable screen filled with borated water, which concentration is varied during transient to avoid the shortcomings of dedicated BR2 cycles.

References:

  • Philippe Gouat, "SCK•CEN: Your partner in fuel research", SCK•CEN – ER-15 (2006) Download ER-15 (91 MB)

  • Ludo Vermeeren, Jean Dekeyser, Philippe gouat, Silva Kalcheva, Edgar Koonen,Vadim Kuzminov, Alfons Verwimp, Marcel Wéber, "Qualification of the on-line power determination of fuel elements in irradiation devices in the BR2 reactor", SCK•CEN – BLG-1006 (January 2005) Download BLG Report 1006 (663 kB)
  • J. Dekeyser,V. Sobolev, M. Decréton, "Heat transfer through vertical annulus with stagnant water", 4th World Conference EXHFT-4. Brussels, Belgium, June 2-6, 1997

For further information please contact:

Dekeyser Jean