Reactor simulation for antineutrino experiments using DRAGON and MURE

Abstract

Rising interest in nuclear reactors as a source of antineutrinos for experiments motivates validated, fast, and accessible simulations to predict reactor fission rates. Here we present results from the DRAGON and MURE simulation codes and compare them to other industry standards for reactor core modeling. We use published data from the Takahama-3 reactor to evaluate the quality of these simulations against the independently measured fuel isotopic composition. The propagation of the uncertainty in the reactor operating parameters to the resulting antineutrino flux predictions is also discussed.PACS numbers: 14.60. Lm,14.60.Pq, 28.41.Ak, 28.50.Hw As new high-power reactors come online, opportunities for reactor-based antineutrino experiments are rising. Three experiments searching for the last unknown neutrino oscillation parameter, θ 13 [1], have released results [2][3][4][5][6][7]. New short-baseline reactor oscillation experiments [8] are motivated by the "reactor antineutrino anomaly", a recent analysis with results that are consistent with neutrino oscillations at ∆m 2 ∼ 1 eV 2 [9]. Searches for neutrino-nucleus coherent scattering [10] and studies of antineutrino-electron scattering [11] using reactor sources are also underway. Precise measurements of antineutrino rates may also permit a real-time, nonintrusive assay of the entire reactor core for nonproliferation applications [12,13].In the reactor core, neutron-rich fission products β-decay creating antineutrinos. The prediction of the antineutrino flux proceeds in two steps. First, the fission rates of the primary fissile isotopes are calculated. Then, this output is convolved with the antineutrino spectrum, the sum of the spectra from the β-decay of each isotope's fission products. The antineutrino spectral predictions have recently been updated to include more detailed information on the daughter β-decay isotopes and higherorder corrections to the β energy spectrum [14,15]. In this paper, we focus on understanding the systematic uncertainties involved in the first step, the fission rate simulations. We introduce two codes: DRAGON [16], a fast 2D parameterized simulation, and MURE (MCNP Utility for Reactor Evolution) [17, 18] a 3D Monte Carlo simulation. While neutrino experiments require fission rate predictions, reactor core simulations in industry focus on other quantities. In particular, the DRAGON code was modified by the authors to produce fission rates, whereas MURE already possessed this ability. DRAGON and MURE are used in the recent Double Chooz result [3], and DRAGON is used by the Daya Bay experiment [5].In this work, we compare our DRAGON and MURE simulations to the Takahama-3 benchmark. This benchmark allows a comparison of absolute predictions of fissile material production to measurements from destructive assays of fuel rods from the Takahama-3 reactor in Japan [19]. The Takahama-3 benchmark is the most complete and therefore most common data set to benchmark codes against, though other data sets exist [20]. By focussing on this bench...

Improved measurements of the neutrino mixing angle θ 13 with the Double Chooz detector

“…Evolution of each fractional fission rate and associated errors are evaluated using a full core model and assembly simulations developed with the MURE code [21,22]. Benchmarks with other codes have been performed [23] in order to validate the simulations. Locations and initial burn-up of each assembly are provided by EDF for every reactor fuel cycle with approximately one year in duration and used as input to the core simulation.…”

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

“…Table III shows the assumed sources of systematic error and their magnitudes, expressed as a percentage of the detected rate. Systematic uncertainties on the fission fractions of each isotope are taken from an analysis of the Takahama benchmark [19]. At 11%, 241 Pu has the highest uncertainty in fission fraction, partially offset by its relatively small contribution to the total fission rate.…”

The measurement of the neutrino mixing angle θ13 with reactor neutrino experiments

“…Then, a full core simulation was performed using MURE for each fuel cycle that overlaps with the data taking period [86][87][88]. Event selection: Now, the measured rate and prompt energy spectrum of neutrino capture events (after subtracting candidates with the same signature, but induced by backgrounds) can be compared with the predicted reference based on the reactor data.…”