Number: 5749916
Country: Luxembourg
Source: TED
Supply contract regarding the purchase of 3He filled proportional counters (for thermal neutrons) based on recovery and purification of gas from spare 3He counter tubes
The present call for tender is part of the work required to build an improved version of a neutron coincidence detector for the verification of fresh low enriched uranium fuel assemblies.
The Commission intends to place a contract to have built 61pc of 3He gas-filled proportional counters for two Fast Neutron Coincidence Collars – starting from recycled and purified gas from spare 3He counters, which DG ENER will provide.
The tasks will be performed on the Contractor"s premises.
Neutron coincidence measurements of fresh fuel assemblies are widely used during safeguards inspections in low-enriched uranium (LEU) fuel fabrication plants in Europe. One instrument type of choice currently used for these measurements is the Neutron Coincidence Collar (NCC), which was originally designed by Los Alamos National Laboratory (LANL). This instrument uses an Americium Lithium external neutron source to induce fission in the U-235 in the assembly. The neutrons resulting from those fissions are slowed down (thermalised) in the polyethylene detector slabs (3 sides, surrounding the fuel element-under-test) and then detected in He-3 gas-filled proportional counters, embedded therein.
As the design of LEU assemblies is gradually optimized by the nuclear industry, the fuel elements become more complex and the need for an improved verification tool has developed. Therefore an optimised design for a Fast NCC was made in the context of a cooperation agreement between the European Commission and LANL in the US.
The present tender"s purpose is to award a contract for the production of (at least) 61 counter tubes, needed for two Fast NCCs. Both NCCs are based on the same type and model of thermal neutron counter tubes (3He gas filled at 10 bar pressure, 1-inch outer diameter). The full detailed specifications are given in the Technical Annex.
Seen the global scarcity and the resulting cost of 3He gas, the 61 new counter tubes will be filled with 3He gas recovered from spare neutron counter tubes. DG ENER will provide the spare tubes and after signature of the contract, transport at its own expenses to the tenderers premises.
It is emphasized that the contract is based on the recovery and purification of 3He gas from spare counter tubes (93 pieces, with various lengths, all filled to 4 bar pressure of 3He) to produce and fill at minimum 61 new counter tubes (33cm active length, filled to 10 bar pressure of 3He gas plus a suitable quantity of quench gas). It is expected that the recovered volume of 3He gas from the 93 old tubes (4 bar pressure) is sufficient to fill the 61 new counter tubes (10 bar pressure). The 93 spare tubes have recently undergone functional tests (with a neutron source) and the recorded results indicate that all of them are fully operational and, therefore, must contain the original amount of 3He gas. The test data is available upon request of the tenderer(s).
After assembly, each item of the new proportional counters will be individually tested and the results documented. From the test data, the range of thermal neutron efficiency over the batch of 61 tubes should be within 5 % - relative to the average value.
Any remaining (surplus) 3He gas - after filling of the 61 new tubes - should be used to fill additional counter tubes (of the same design and characteristics) – and those will also be purchased by DG ENER. It is expected that only a few additional tubes can result from this approach.
