JCC-71/72/73: Neutron Coincidence Collars
|
Features
- Designed for neutron coincidence measurement of uranium in PWR, BWR and CANDU fuel assemblies, or plutonium in MOX fuel assemblies.
- Variable sample cavity size (Model JCC-71).
- Fast Amptek electronics.
- 3He detectors.
- Transportable.
- Optional transport container.
- Authorized for routine inspection use as the Uranium Neutron Collar (UNCL and UNCL II).
Description
The Model JCC-71 Neutron Coincidence Collar is based upon technology
transfer from the Los Alamos National Laboratory. It is a passive/active
neutron counter for the measurement of the 235U content per
unit length in fresh PWR, BWR and CANDU fuel assemblies in the active
mode, and the plutonium content of MOX fuel in the passive mode. In
the active mode, an AmLi source is required to interrogate the fuel,
and coincidence counting of the induced fission neutrons from 235U
is performed. To measure the 238U content, the AmLi source
is removed, a fourth bank of 3He detectors is added, and
the counter is operated in a passive mode, counting the coincidence
neutrons from spontaneous fission of 238U. The collar measures
the 235U and 238U content along the axis of the
assembly, not the enrichment. Since the 235U content is of
primary interest for safeguard purposes, only the active measurement
is necessary. Pu-containing fuel rods are measured in the passive mode
because of the high spontaneous fission rate. A JSR-12 Neutron Coincidence
Analyzer, a computer and analysis software are required for coincidence
counting but are not included with the JCC-71, 72 and 73.
For the passive mode, there are four counter banks composed of high-density polyethylene for moderation of the fission neutrons. If operated in the active mode, one bank of detectors is replaced with a polyethylene bank containing the AmLi interrogating source. The AmLi source is ordered separately.
The JCC-71 Neutron Coincidence Collar is designed to allow modification
of the geometry to close-couple the detectors with the fuel type. For
the smaller BWR fuel, the side detector banks are moved into the inner
screw hole position. The fourth bank of tubes (passive mode) is hinged
to facilitate placing the counter around fuel assemblies. For the active
mode, the fourth side of the counter is a polyethylene moderator with
a tungsten source bottle for the AmLi source. The AmLi neutrons are
thermalized in the polyethylene and induce fission in the 235U.
The average energy from the induced fission is higher than the moderated
AmLi neutrons and gives fast neutron multiplication which allows the
measurement to penetrate into the interior of the fuel assemblies. For
HEU fuel, cadmium liners can be added to improve neutron penetrability.
The Neutron Coincidence Collar is designed to be insensitive to parameters such as open channels for control rods, enrichments, angular orientation of the fuel in the Collar, fuel pellet density, and any protective bagging. Cladding type (zinc alloy or stainless steel), different fuel pellet diameters, and neutron absorbers (Gd2O3) can affect the measurement.
Since more neutron collars are being installed at facilities for measuring designated fuel types (BWR or PWR), the Neutron Coincidence Collar was redesigned by Los Alamos National Laboratory to make two separate counters: the JCC-72 for BWR and CANDU fuel assemblies and the JCC-73 for PWR fuel assemblies.
|
| Top of Page |
Note to our International Customers: If you would like a quote on this product, please contact your Local Sales Office for assistance. |
||
| Models | Description | |
| JCC-71 | Neutron Coincidence Collar | |
| JCC-72 | Neutron Coincidence Collar | |
| JCC-73 | Neutron Coincidence Collar | |
| JCT-01 | Cart | |