Adam Bernstein

Nuclear reactor safeguards and monitoring with antineutrino detectors

Cubic-meter-sized antineutrino detectors can be used to non intrusively, robustly, and automatically monitor and safeguard a wide variety of nuclear reactor types, including power reactors, research reactors, and plutonium production reactors. Since the antineutrino spectra and relative yields of fissioning isotopes depend on the isotopic composition of the core, changes in composition can be observed without ever directly accessing the core itself. Information from a modest-sized antineutrino detector, coupled with the well-understood principles that govern the core’s evolution in time, can be used to determine whether the reactor is being operated in an illegitimate way. A group at Sandia is currently constructing a 1 m3 antineutrino detector at the San Onofre reactor site in California to demonstrate these principles.

Monitoring large enrichment plants using thermal imagery from commercial satellites: A case study

Thermal imagery from currently operating commercial satellites is an interesting candidate technology for monitoring certain types of fissile material production sites. Potential applications include the Fissile Material Cutoff Treaty (FMCT) or a Fissile Material Production Moratorium. To help determine the capabilities and limitations of such imagery as a monitoring tool, I have examined archived LANDSAT‐5 images of the Portsmouth Gaseous Diffusion Plant, a large U.S. uranium‐enrichment facility in Ohio. My analysis indicates that large‐scale gaseous diffusion plants (GDPs) can very likely be recognized as operational with thermal imagery throughout most of the year in clear weather conditions. It may also be possible to identify certain other large‐scale changes in operations, such as the shut‐down of a single process building in a plant, by comparing rooftop temperatures of neighboring operational process buildings. However, uncertainties in the current data set prevent a definitive conclusion regarding the latter capability. This study identifies intrinsic weaknesses, including vulnerability to countermeasures, that prevent thermal imagery from satellites (at current resolutions) from being a robust stand‐alone verification tool, even for very large plants. Nonetheless, the imagery may be useful to trigger an on‐site inspection, to alert and train inspectors prior to an inspection, and to reduce the frequency of on‐site inspections required at a given site. It could have immediate utility for monitoring the two large GDPS in the United States and the French plant at Tricastin, and possibly for determining the operational status of two GDPS in China as well ‐ a total of five plants worldwide. The ease of acquisition and modest cost of thermal commercial imagery further increase its attractiveness as a verification tool.

The "Radiation Continuity Checker": an instrument for monitoring nuclear disarmament treaty compliance

We describe the design and construction of an instrument designed to monitor compliance with future arms control treaties. By monitoring changes in the gamma-ray spectrum emitted by a stored nuclear weapon, our device is able to sense perturbations in the contents of a weapon storage container that would indicate treaty non-compliance. Our instrument (dubbed the Radiation Continuity Checker or RCC) is designed to detect significant perturbations in the gamma-ray spectra (indicative of tampering) while storing no classified information about the weapon, and having a negligible false alarm rate. In this paper we describe the technical details of two prototype instruments and describe the strategies we have adopted to perform signal processing in these instruments. Our first instrument prototype uses a scintillation spectrometer and a massive tungsten alloy collimator to reject the gamma-ray background. Our second prototype instrument makes use of an active collimation scheme employing a multiple detector Compton scatter approach to reject background radiation. The signal processing method we employ uses linear algorithms applied pulse by pulse. This eliminates the need for storage of pulse height spectra, which are in many cases classified.

ANTINEUTRINOS FOR REACTOR SAFEGUARDS: EFFECT OF FUEL LOADING AND BURNUP ON THE SIGNAL

Various types of nuclear reactor related information, including relative power level and fuel evolution parameters, can be inferred remotely using antineutrino detectors. We show that it is possible to verify assembly-level burnup using information derived from an antineutrino detector if the nominal reactor fuel loading is known. Alternatively, if the core power is measured using an independent method, for example, a thermal hydraulic element, and the nominal core behavior is known, the antineutrino detector has a capability to determine previously unknown MOX loading in the core.

An assessment of antineutrino detection as a tool for monitoring nuclear explosions

The antineutrino is the only real-time nuclear signature from a fission explosion that propagates great distances through air, water, and ground. The size and sensitivity of antineutrino detectors has increased dramatically in the last decade, and will continue to do so in the next, thanks in part to the renewed interest in neutrino physics brought on by the recent discovery that neutrinos may have mass. The evolution of antineutrino detectors, and the evident interest of the signature as a means for monitoring nuclear tests motivates this review of the capabilities of existing and possible future detectors as test ban verification tools. The authors find that existing liquid scintillator ionization detectors, operating a few tens of meters below the Earths surface and containing a few thousand tons of active material, could be used to monitor an area of a few square kilometers for nuclear explosions at the 1 kt level. Purified water Cerenkov detectors of sizes comparable to existing detectors (50,000 m{sup 3}) could be used to detect 1 kt explosions at distances of a few tens of kilometers. If neutron-absorbing dopants such as sodium chloride or gadolinium could be added to purified water, the resulting background reduction would allow extension of the range for sensitivity to a pulse of 10 antineutrino events from a 1 kt explosion out to approximately 1000 km. Beyond 1000 km, backgrounds from the worlds nuclear reactors would become prohibitively large. The engineering hurdles for such detectors would be formidable. The size of a doped detector operating at the 100 km range, suitable for cooperative monitoring of existing nuclear test sites, is about 60 times that of the largest existing water detector, and would require a factor of several dozen more photomultiplier tubes than what is now used in large scale physics experiments. At a price per phototube of

Reactors as a Source of Antineutrinos: Effects of Fuel Loading and Burnup for Mixed-Oxide Fuels

1000, capital costs would amount to several billions of dollars, even for a detector at this modest range. This cost is perhaps the key obstacle to construction, along with excavation requirements and the requirement of high radiopurity for large volumes of water and dopant. Detectors sensitive to a 1 kt explosion at a few kilometer distance would still cost tens of millions of dollars, and are unlikely to be useful except in the context of confidence-building measures.

Design and Fabrication of Cherenkov Counters for the Detection of SNM

In a conventional light water reactor loaded with a range of uranium and plutonium-based fuel mixtures, the variation in antineutrino production over the cycle reflects both the initial core fissile inventory and its evolution. Under the assumption of constant thermal power, we calculate the rate at which antineutrinos are emitted from variously fueled cores, and the evolution of that rate as measured by a representative ton-scale antineutrino detector. We find that antineutrino flux decreases with burnup for Low Enriched Uranium cores, increases for full mixed-oxide (MOX) cores, and does not appreciably change for cores with a MOX fraction of approximately 75%. Accounting for uncertainties in the fission yields, in the emitted antineutrino spectra, and the detector response function, we show that the difference in core-wide MOX fractions at least as small as 8% can be distinguished using a hypothesis test. The test compares the evolution of the antineutrino rate relative to an initial value over part or all of the cycle. The use of relative rates reduces the sensitivity of the test to an independent thermal power measurement, making the result more robust against possible countermeasures. This rate-only approach also offers the potential advantage of reducing the cost and complexity of the antineutrino detectors used to verify the diversion, compared to methods that depend on the use of the antineutrino spectrum. A possible application is the verification of the disposition of surplus plutonium in nuclear reactors.

Sensitivity of seismically-cued antineutrino detectors to nuclear explosions

The need for large‐size detectors for long‐range active interrogation (AI) detection of SNM has generated interest in water‐based detector technologies. Water Cherenkov Detectors (WCD) were selected for this research because of their transportability, scalability, and an inherent energy threshold. The detector design and analysis was completed using the Geant4 toolkit. It was demonstrated both computationally and experimentally that it is possible to use WCD to detect and characterize gamma rays. Absolute efficiency of the detector (with no energy cuts applied) was determined to be around 30% for a 60Co source.