High-intensity Neutron Flux Research Articles

Development of fission micro-chambers for nuclear waste incineration studies

The Incineration by Accelerator (INCA) project of the Directorate for Science of Matter of the French Atomic Energy Authority (CEA/DSM) aims to outline the ideal physical conditions to transmute minor actinides in a high intensity neutron flux obtained either by hybrid systems or innovative critical reactors. To measure on-line the incineration rates of minor actinides, we are developing an innovative Double Deposit Fission Chamber (DDFC) working in current mode. Our method is based on a comparison between the isotope under study and a reference material whose nuclear parameters are well known, as 235U and 239Pu. This new fission chamber will be used in the High Flux Reactor in Grenoble/France in a neutron flux of 1.2×10 15 n cm −2 s −1 for 50 days, the operating cycle of the reactor. These specific experimental conditions require substantial modifications of the existing chambers. The first experiment will be carried out in fall 2000.

Incineration of 241Am induced by thermal neutrons

An experimental study of the 241Am incineration in a high-intensity thermal neutron flux was carried out at the high-flux reactor of the Institut Laue-Langevin in Grenoble. The combination of nuclear γ-ray spectroscopy and off-line mass spectrometry methods made possible the measurement of several parameters of the transmutation chain and the first experimental determination of the unknown 242gsAm thermal neutron capture cross section, which plays an essential role in the 241Am incineration process. During a 19 days irradiation in a thermal neutron flux of 5.6×10 14 n/( s cm 2) , (46±5)% of the initial 241Am was transmuted by neutron capture of which (22±8)% was incinerated by nuclear fission. A value of the thermal neutron cross section of 242gsAm( n,γ ) of (330±50) barns was obtained. We show that this keeps the option open to incinerate 241Am by high-intensity moderated neutron fluxes.

A high power symmetrical cockcroft-Walton type voltage multiplier circuit using silicon diodes

A 200 kV, 200 mA de power supply for charged particle accelerators is described. It will be used eventually for accelerating a mixture of deuterium and tritium ions to obtain a high intensity neutron flux. The rectifier circuit is a 3 stage symmetrical Cock-croft-Walton type voltage multiplier using small silicon diodes driven by a 1 kC ac power source. The voltage drop in the rectifier circuit is only 7.7 kV at 200 mA, and the ripple voltage is 5.0 V/mA.