Diffusion length of thermal neutrons in water from 23°c to 244°C

Reier, M.; Juren, J.A. De

doi:10.1016/0368-3230(61)90069-6

Cited by 9 publications

(6 citation statements)

References 3 publications

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“…4. The attenuation length of neutrons in water at room temperature is 2.8 cm and increases at higher temperatures (21). Because of the high absorption cross-section of 35 Cl, seawater has more attenuation.…”

Section: Resultsmentioning

confidence: 99%

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive³⁵S in California

Priyadarshi

Domínguez

Thiemens

2011

Proc. Natl. Acad. Sci. U.S.A.

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A recent earthquake and the subsequent tsunami have extensively damaged the Fukushima nuclear power plant, releasing harmful radiation into the environment. Despite the obvious implication for human health and the surrounding ecology, there are no quantitative estimates of the neutron flux leakage during the weeks following the earthquake. Here, using measurements of radioactive 35 S contained in sulfate aerosols and SO 2 gas at a coastal site in La Jolla, California, we show that nearly 4 × 10 11 neutrons per m 2 leaked at the Fukushima nuclear power plant before March 20, 2011. A significantly higher 35 SO 4 2− activity as measured on March 28 is in accord with neutrons escaping the reactor core and being absorbed by the coolant seawater 35 Cl to produce 35 S by a (n, p) reaction. Once produced, 35 S oxidizes to 35 SO 2 and 35 SO 4 2− and was then transported to Southern California due to the presence of strong prevailing westerly winds at this time. Based on a moving box model, we show that the observed activity enhancement in 35 SO 4 2− is compatible with long-range transport of the radiation plume from Fukushima. Our model predicts that 35 SO 4 2− , the concentration in the marine boundary layer at Fukushima, was approximately 2 × 10 5 atoms per m 3 , which is approximately 365 times above expected natural concentrations. These measurements and model calculations imply that approximately 0.7% of the total radioactive sulfate present at the marine boundary layer at Fukushima reached Southern California as a result of the trans-Pacific transport.gas to particle conversion | radioactive sulfur-35 T he Fukushima nuclear power plant, situated in northeastern Japan, is one of the largest nuclear power stations in the world, consisting of six boiling water reactors. A recent massive earthquake (9.0 magnitude) (http://earthquake.usgs.gov/ earthquakes/eqinthenews/2011/usc0001xgp/) on March 11, 2011, followed by a deadly tsunami has extensively damaged the power plant by disabling the reactor cooling system, which led to nuclear radiation leaks and activation of a 20-km evacuation zone surrounding the plant (http://www.iaea.org). Three weeks subsequent to the earthquake, evidence surfaced of a partial nuclear meltdown in units 1, 2, and 3, visible explosions in units 1 and 3, and a possible uncovering of spent fuels pool associated with units 1, 3, and 4 (http://www.iaea.org). It is suspected that the explosions at unit 3 may have damaged the primary containment vessel. The events at units 1, 2, and 3 have been rated at level 7 (major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures) on the International Nuclear Event Scale (http://www.iaea.org). The earthquake triggered the automatic shutdown of the three operating reactors-units 1, 2, and 3-and the control rods were completely inserted to terminate the nuclear fission reaction occurring within the fuel core. The details of a nuclear reactor design and operations...

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Section: Resultsmentioning

confidence: 99%

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive³⁵S in California

Priyadarshi

Domínguez

Thiemens

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…Physically, experimental data has been shown to follow the form ‫ܮߩ‬ = ܶ ோ , where ܴ is slightly less than 0.5. Reier and de Juren [35] give ܴ = 0.4343 for measurements from 23 °C to 244 °C, while Besant and Grant [44] give ܴ = 0.487 for measurements over the narrower range of 24 °C to 82 °C. Each of these empirical values was derived from only one experimental data set.…”

Section: Temperature Dependence Of the Diffusion Length In Light Watermentioning

confidence: 94%

“…where ߢ = ‫.ܮ/1‬ For a real system, Eq. ( 6) still describes the asymptotic solution far from a source or boundary, and the spatial eigenvalue ߢ will depend on the physical ‫.ܮ‬ Experimentally, one common method of determining ‫ܮ‬ for this stationary case is by using a 25 keV Sb-Be photoneutron source and indium activation foils to measure the spatial flux decay, with appropriate source corrections, far from a boundary [35,36]. Other stationary experiment techniques exist as well, including the poisoning technique commonly used to evaluate the spectrally averaged ߑ ୟ for the pure medium [36,37].…”

Section: Theoretical and Experimental Aspects Of Neutron Diffusionmentioning

confidence: 99%

“…( 4) can be equivalently determined in the stationary case using the poisoning technique [41]. The non-stationary PNDA method allows more direct access to the expanded diffusion coefficients but can be subject to ambiguities in fitting and in the calculation of ‫ݖ‬ and ‫ܤ‬ ଶ [35]. Both methods have been extensively used.…”

Section: Theoretical and Experimental Aspects Of Neutron Diffusionmentioning

confidence: 99%

“…The temperature dependence of ‫ܮ‬ in water has been studied extensively by various stationary and nonstationary experimental methods [28,30,31,[35][36][37][42][43][44], and several different empirical functions have been proposed [28,31,35,43,44]. The physical variation of ‫ܮ‬ with ܶ depends on the non-linear relationship of density (ߩ) vs. ܶ as well as on changes in the dynamics of H2O molecules (such as changes in clustering [42,44].…”

Section: Temperature Dependence Of the Diffusion Length In Light Watermentioning

confidence: 99%

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Validation of Thermal Scattering Laws for Light Water at Elevated Temperatures With Diffusion Experiments

2021

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Light water is the most important neutron moderator in many reactor applications. Thermal neutron scattering kernels for H bound in H2O are represented by ENDF-format thermal scattering laws (TSLs) evaluated at discrete temperatures T. Nuclear data evaluations are conventionally validated utilizing a combination of critical benchmarks and experimental cross section data. Existing public critical benchmarks may be inadequate for testing water TSLs over the full range of T of interest in reactor applications, and experimental thermal scattering cross section data for water is sparse at elevated T. In this work, MC21 is used to simulate the decay of the equilibrium thermal neutron flux in light-water spheres of several radii. The fundamental-mode time eigenvalue α is calculated at 22 °C and 227 °C (at saturation pressure) for each sphere using three different H-H2O TSLs. Fitting α to a polynomial function of geometric buckling allows calculation of the thermal neutron diffusion length L. Extrapolation lengths are treated as a function of the transport mean free path and geometry. Experimental L data from 25 publications at 49 temperatures (from 10 °C to 295 °C), computed by several different time-dependent and space-dependent decay methods, is used to develop an empirical fit of L vs. T. The MC21-calculated L for the TSLs tested are within ±1% of the predicted values at 22 °C and 227 °C. This validation approach, which may be repeated at arbitrary T, constitutes an integral benchmark specific to and characterizing the detailed physics of the thermal scattering kernel applied.

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Investigation of the Diffusion of Thermal Neutrons by Stationary Methods

Beckurts

Wirtz

1964

Neutron Physics

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Diffusion length of thermal neutrons in water from 23°c to 244°C

Cited by 9 publications

References 3 publications

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive³⁵S in California

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive³⁵S in California

Validation of Thermal Scattering Laws for Light Water at Elevated Temperatures With Diffusion Experiments

Investigation of the Diffusion of Thermal Neutrons by Stationary Methods

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Diffusion length of thermal neutrons in water from 23°c to 244°C

Cited by 9 publications

References 3 publications

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive35S in California

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive35S in California

Validation of Thermal Scattering Laws for Light Water at Elevated Temperatures With Diffusion Experiments

Investigation of the Diffusion of Thermal Neutrons by Stationary Methods

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Product

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Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive³⁵S in California

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive³⁵S in California