Neutron & Gamma detectors for nuclear reactors & waste management
When the French nuclear-power programme was starting to take shape in the sixties the French Atomic Energy Commission, CEA, selected the Brive factory as its technological partner for a co-operative development of neutron detectors. Three basic types were developed:
- Boron-lined proportional counters working in pulse mode for the start-up range to get a better technology in hand than the standard BF3 counters used by Westinghouse in the pressurised water reactors (PWRs) at the time. Since 1966 many tests have been made resulting in improved detector designs and boron-lining processes. For the last 15 years the lining is made by a unique chemical vacuum deposition (CVD giving excellent boron-layer adherence and resulting in long-life counters. Today, over 60 FRAMATOME power plants use 2 or 4 of these CPNB44 out-of-core boron counters in the start-up safety instrumentation channels made by Schneider, France, where the detectors are now changed only every five year on average.
- Fission chambers for in-core monitoring of the reactor fuel burn-up. These fission chambers are moved inside monitoring channels by a special propulsion cable. Today, each FRAMATOME power plant uses 5 or 6 of these CFUF43 fission chambers in a system from FRAMATOME-ATEA.
- Fission chambers for start-up, intermediate and power range. The sensitivity of the detector and the signal-to-noise ratio obtained with the electronics of the sixties were not good enough for pulse-mode operation. Therefore, the boron-lined-counter solution was chosen for the start-up range of the French PWR programme. However, today, a wide-range fission-chamber solution is clearly the best choice.
Phenix and Superphenix breeder reactors
In the CEA-guided development of high-temperature, high-flux detectors for the French breeder-reactor research programme the Brive team learnt a lot on how to understand material and gas interactions and failure mechanisms at 600°C in an extreme neutron and gamma flux environment.Although the breeder programme is only continuing on very low key, it brought a lot of basic know-how to PHOTONIS and helped make our detector technology a world-best as to reliability and life performance. This programme also proved that the only reliable way is to integrate the detector and the mineral-insulated cable to avoid contact problems or contact noise.
Wide-range BWR instrumentation
For Studsvik Instrument, Sweden, we have developed a special wide-range version of the CFUE32 fission chamber operating in pulse mode during start-up and in fluctuation (Campbell) mode in the intermediate range up to full power.
An elegant Studsvik mechanism allows the 10 m straight detector with mineral-insulated cable to glide up and down inside the core, excess flexible cable being rolled-up in a small container.
When the reactor has reached full power the detectors are pulled out and parked below the core where they are exposed to only a very low neutron flux. Therefore the detectors will last more than 10 years - a very economic solution.
This system works perfectly in eight ABB-ATOM BWRs, six in Sweden and two in Finland, as part of the reactor safety instrumentation.
This is a more elegant and cheaper long-term solution than fixed in-core start-up and intermediate range detectors with a mixture of 234U and 235U. Although the 235U isotope is renewed from neutrons reacting on the 234U, such fixed in-core detector life is not uranium-limited.Other material-dependent failure mechanisms dominate, limiting the life to only a few years instead of the 7 - 8 expected, a lesson PHOTONIS learnt from the Superphenix high-temperature, high-flux experience.
Wide-range PWR instrumentation
For Siemens-KWU and together with the end user, NOK at Beznau, Switzerland, PHOTONIS made LOCA and post-LOCA qualification of our CFUG08 wide-range fission chamber for the safety instrumentation channels.
So far, four detectors have been installed in one of the two Westinghouse PWR blocks covering 11 decades - from a cold reactor start-up to the full power range.
PHOTONIS is proud of its successful participation in this unique project, a valuable reference for a new generation of wide-range fission chamber safety instrumentation in many ageing PWRs.
Upgrading Russian VVER reactors
Schneider, France, has successfully installed 12 of our boron-lined counters in the safety instrumentation channels in two 440 MW VVER blocks 1 in Kozloduy, Bulgaria.
For Siemens-KWU we have adapted the CFUL08 fission chamber for the wide-range safety instrumentation of two 440 MW blocks in REKON Bohunice V1, Slovakia and 12 fission chambers have been installed in the safety instrumentation channels of both blocks.
Fuel reprocessing plants - gamma ionisation chambers
PHOTONIS has developed and adapted many of its boron-lined counters and fission chambers for the French COGEMA fuel reprocessing plants in Marcoul and La Hague. Moreover, a range of nitrogen- or xenon-filled gamma ionisation chambers has been developed for the above plants. In addition, we have the capability to make customised versions.
Connections
As connections are the critical points in power-plant instrumentation, PHOTONIS will always propose an integral detector-cable-connector as the only good solution.
Therefore, we have developed a series of proprietary connectors with ceramic insulators. Integrated with our detectors and mineral insulated cable, they are LOCA and post-LOCA approved |
