Belkis Cabrera-Palmer

Advances towards readily deployable antineutrino detectors for reactor monitoring and safeguards

The large flux of neutrinos that leaves a nuclear reactor carries information about two quantities of interest for safeguards: the reactor power and fissile inventory. Our SNL/LLNL collaboration has demonstrated that antineutrino-based nuclear reactor monitoring is feasible using a relatively small cubic scale detector made of Gadolinium loaded liquid scintillator at tens of meters standoff from a commercial Pressurized Water Reactor, deployed in an underground gallery that lies directly under the containment.

Advances toward a transportable antineutrino detector system for reactor monitoring and safeguards

Nuclear reactors have served as the neutrino source for many fundamental physics experiments. The techniques developed by these experiments make it possible to use these very weakly interacting particles for a practical purpose. The large flux of antineutrinos that leaves a reactor carries information about two quantities of interest for safeguards: the reactor power and fissile inventory. Our SNL/LLNL collaboration has demonstrated that such antineutrino based monitoring is feasible using a relatively small cubic meter scale liquid scintillator detector at tens of meters standoff from a commercial Pressurized Water Reactor (PWR). With little or no burden on the plant operator we have been able to remotely and automatically monitor the reactor operational status (on/off), power level, and fuel burnup. The initial detector was deployed in an underground gallery that lies directly under the containment dome of an operating PWR. The gallery is 25 meters from the reactor core center, is rarely accessed by plant personnel, and provides a muon-screening effect of some 20–30 meters of water equivalent earth and concrete overburden. Unfortunately, many reactor facilities do not contain an equivalent underground location. We have therefore attempted to construct a complete detector system which would be capable of operating in an aboveground location and could be transported to a reactor facility with relative ease. A standard 6-meter shipping container was used as our transportable laboratory — containing active and passive shielding components, the antineutrino detector and all electronics, as well as climate control systems. This aboveground system was deployed and tested at the San Onofre Nuclear Generating Station (SONGS) in southern California in 2010 and early 2011. We will first present an overview of the initial demonstrations of our belowground detector. Then we will describe the aboveground system and the technological developments of the two antineutrino detectors that were deployed. Finally, some preliminary results of our aboveground test will be shown.

A High-Sensitivity Fast Neutron Imager

Several improvements were made to the NSC over the course of this project. The liquidscintillator-cell configuration was changed from nine cells in each plane to 16 cells in each plane (2” deep, 5” diameter cells in the front plane, 5” deep, 5” diameter cells in the rear plane). The cells were mounted in a new shock-proof frame that also provided motorized adjustment of the spacing between the two planes. To simplify transporting the system, the liquid scintillator material itself was changed from EJ-301 to the less-hazardous EJ-309 (higher flashpoint, more benign chemical content). Dual-mode imaging capabilities were implemented in software, enabling simultaneous Compton-camera gamma imaging in addition to the neutron imaging. Data acquisition was converted to an all-digital system using a newly available VME digitizer system, leading to both enhanced data analysis capabilities, and to a much more portable configuration (with a large separate electronics rack replaced by a single VME crate attached to the scatter-camera frame, as shown in Fig. 1). Maximum-Likelihood Expectation-Maximization (MLEM) methods were added to our image reconstruction toolkit.

Development of coherent germanium neutrino technology (CoGeNT) for reactor safeguards.

Antineutrinos are extremely penetrating elementary particles that have unique features of interest for safeguards at nuclear reactors. Current antineutrino detectors systems have large size and often use hazardous materials, presenting concerns to the safeguards agencies. We propose a new antineutrino detector, based on HPGe detector technology, which is much smaller and safer and therefore more likely to find widespread acceptance as a monitoring tool. The proposed system should be sensitive to a universally predicted but as-yet undetected antineutrino signature, the coherent neutrino-nucleus scattering, for which an unprecedentedly low noise threshold is required. Based on the noise analysis of an existing HPGe detector and the results of noise tests, a new system was designed and fabricated in collaboration with LBNL, though a full noise optimization has not been possible. Shielding design has been analyzed in the context of other deployment results, and an anticoincidence veto with high neutron efficiency has been tested.