Experiment Engineering

About 35 instrumented test assemblies are loaded in the Halden Boiling Water Reactor (HBWR). The assemblies are fitted with a wide range of instruments in order to characterise a large number of properties of nuclear fuels and materials.

Minagawa, Yoji

Senior Technical Adviser


ifeIn close co-operation with the reactor operators and the reactor chemistry laboratories, about 10 persons are involved with experimental execution and follow up, electronic signal processing and data acquisition. The first instrumented fuel assembly was loaded into the reactor in 1963. Picture is showing parts of the control room at the Halden Boiling Water Reactor.


  • experiments can be performed under native HBWR conditions (240 º C, 34 bar) or typical BWR or PWR conditions with specifi ed water chemistry
  • calibration of fuel power by calorimetric measurements
  • rapid power changes (ramp test, continuous or stepwise power changes) by controlling 3He gas pressure in coils surrounding the fuel. By means of a hydraulic fuel rod drive system, fuel rods can be moved axially in order to operate under high- or low flux conditions.
  • study of entire fuel performance such as stack elongation, cladding elongation, internal fuel rod pressure (fission gas release) and fuel centre temperature
  • measurement of fuel rod diameter profi le by means of a hydraulically driven diameter gauge
  • characterisation of fission products by sweeping out gases from fuel rods. The gases are analysed on line in a gamma spectrometer
  • irradiation of reactor materials to specified fluence levels, at specified temperatures
  • quantification of stress corrosion cracking of reactor materials under influence of different mechanical loads and water chemistry conditions.

Signal processing

The large number of sensors in the test assemblies requires custom designed electronics. In general, a large number of weak signals require effective noise suppression and very high stability electronics. Due to our experience in this field, a variety of measurements are performed successfully, such as:

  • the potential drop method is used to quantify crack length changes in material samples. Resistance changes in the µ? range are measured
  • neutron detectors signals, used for power determination of test fuel, are in the nA range. A large number of these signals are measured throughout the operation cycles of the reactor
  • for special requirements (such as noise analysis etc), a wide selection of high stability amplifiers and active filters are available

Data acquisition

A total of about 1000 raw signals from the test assemblies and the reactor plant are logged by the on-line data acquisition system. In addition to this come a large number of converted and calculated parameters. In normal operation, raw data are logged and converted to appropriate units every 5 seconds. Normally, all data is stored permanently with one-minute intervals. For special purposes (noise analysis etc.), a high-speed data acquisition system is available, capable of logging data every 25ms.