In this paper the origin and properties of radioactive waste as well as its classification scheme (low-level waste - LLW, intermediate-level waste - ILW, high-level waste - HLW) are presented. The ...various options for conditioning of waste of different levels of radioactivity are reviewed. The composition, radiotoxicity and reprocessing of spent fuel and their effect on storage and options for final disposal are discussed. The current situation of final waste disposal in a selected number of countries is mentioned. Also, the role of the International Atomic Energy Agency with regard to the development and monitoring of international safety standards for both spent nuclear fuel and radioactive waste management is described.
Raised beach ridges are prograded sequences of wave-built deposits that may provide valuable information about past relative sea-level changes, climate change and coastal evolution. In the Limfjord ...in northern Denmark, the Early and Middle Holocene sea-level changes are well-constrained. However, our understanding of Late Holocene sea-level fluctuations is limited, and the exact period when the coastal barrier between the Limfjord and the North Sea formed remains uncertain. In this study, we use optically stimulated luminescence (OSL) dating to determine the age of raised beach ridges at Gjellerodde in the western part of the Limfjord. The OSL ages presented here indicate that the beach ridges formed during three periods at 3.3–2.7, 1.4–1.0, 0.2–0.1 ka. In addition our data suggest a c. 0.2 mm/yr relative sea-level fall during the Late Holocene. The three distinct periods of beach-ridge formation coincide with periods when the Limfjord was open towards the North Sea as documented in historical records and marine records. This suggests that OSL dating of beach ridges can be used as a potential indicator for determining when the connection between the Limfjord and the North Sea was open in the Late Holocene.
The present study was carried out to investigate the wound healing potentials of 17 medicinal plants historically used in Ghana for wound healing. Warm and cold water extracts were prepared from the ...17 dried plant species and tested in vitro in the scratch assay with NIH 3T3 fibroblasts from mice. The wound healing scratch assay was used to evaluate the effect of the plants on cell proliferation and/or migration in vitro, as a test for potential wound healing properties. After 21 hours of incubation increased proliferation and/or migration of fibroblasts in the scratch assay was obtained for 5 out of the 17 plant species. HPLC separation of the most active plant extract, which was a warm water extract of Philenoptera cyanescens, revealed the wound healing activity to be attributed to rutin and a triglycoside of quercetin. The present study suggests that Allophylus spicatus, Philenoptera cyanescens, Melanthera scandens, Ocimum gratissimum, and Jasminum dichotomum have wound healing activity in vitro.
Hyperon production in the threshold region was studied in the reaction pp→K+Λp using the time-of-flight spectrometer COSY-TOF. Exclusive data, covering the full phase-space, were taken at three ...different beam momenta pbeam=2.59, 2.68 and 2.85 GeV/c (corresponding to excess energies of ɛ=85, 115 and 171 MeV). Total cross-sections were deduced to be 7.4±0.5 μb, 8.6±0.6 μb and 16.5±0.4 μb, respectively. Differential observables including Dalitz plots were obtained. From the investigation of the Dalitz plot at pbeam=2.85 GeV/c a dominant contribution of the N∗(1650)-resonance to the reaction mechanism was found. In addition the pΛ-final-state interaction turned out to have a significant influence on the Dalitz plot distribution even 171 MeV above threshold.
Excitation functions were measured for the
180
W
(
n
,
2
n
)
179mW,
182
W
(
n
,
p
)
182Ta,
182
W
(
n
,
p
)
182m2Ta,
182
W
(
n
,
α
)
179m2Hf,
183
W
(
n
,
p
)
183Ta,
183
W
(
n
,
α
)
180mHf,
184
W
(
n
,
...p
)
184Ta,
184
W
(
n
,
α
)
181Hf,
186
W
(
n
,
p
)
186Ta,
186
W
(
n
,
α
)
183Hf,
186
W
(
n
,
n
′
α
)
182mHf, and
186
W
(
n
,
2
n
)
185W reactions from 13.4 to 14.9 MeV. The data of these reactions that are dominant for neutron-induced activation in tungsten were in most cases either defective or incomplete. The experimental results are compared with the results of calculations including all activation channels for the stable W isotopes up to a neutron incident energy of 20 MeV, using two global- and one local-parameter approaches which take into account direct reaction, pre-equilibrium emission (PE), and compound nucleus contributions. The sensitivity of the calculated cross sections to various model approaches and parameters is derived and discussed also in connection with the deviation from unity of calculated-to-experimental activity ratios from benchmark experiments with natural W irradiated by D–T fusion neutrons. The particular importance of the charged-particle emission in this atomic-mass range for PE model validation is discussed and the need for additional data for incident energies above 15 MeV is demonstrated.
The radiation source ELBE (
Electron
Linear accelerator with high
Brilliance and low
Emittance) at Forschungszentrum Dresden-Rossendorf uses the high brilliance electron beam from a superconducting ...LINAC to produce various secondary beams. Electron beam intensities of up to
I
e
-
=
1
mA
at energies up to
E
e
-
=
40
MeV
can be delivered with a pulse width of less than 10
ps.
With these parameters the electron beam allows to generate sub-ns neutron pulses by stopping the electrons in a heavy (high atomic number) radiator and producing neutrons by bremsstrahlung photons through (γ,
n)-reactions. In order to enable measurements of energy resolved neutron cross sections like (n,
γ), (n,
n′γ), (n,
p), (n,
α), and (n,
f) at a time-of-flight arrangement with a short flight path of only a few meters it is necessary to keep the volume of the radiator for neutron production as small as possible to avoid multiple scattering of the emerging neutrons, which would broaden the neutron pulses. It is the primary physics objective of this neutron source to measure neutron cross sections firstly for construction materials of fusion and fission reactors, for which it is important to select materials with low activation cross sections, and secondly for the handling of waste from such reactors, especially in order to find processes which transmute long-lived radioactive nuclides into short-lived and finally stable ones. Furthermore experiments can be performed which address problems of nuclear astrophysics.
The power deposition of the electron beam in the small neutron radiator volume of 1
cm
3 reaches up to 25
kW. This is such a high power density that any solid high
Z number material would melt. Therefore, the neutron radiator consists of liquid lead circulated by an electromagnetic pump. The heating power introduced by the electrons is removed through the heat exchanger in the liquid lead circuit. Typical flow velocities of the lead are between 1
m/s and 5
m/s in the radiator section. From the thermal and mechanical point of view, molybdenum turned out to be the most suited target wall material in the region where the electrons impinge on the neutron radiator.
To reduce the radiation background at the measurement position, the neutrons are decoupled from the radiator at an angle of about 90° with respect to the impinging electrons. Particle transport calculations using the Monte Carlo codes MCNP and FLUKA predict a neutron source strength in the range of
7.9
×
10
12
n
/
s
to
2.7
×
10
13
n
/
s
for electron energies between
E
e
-
=
20
and 40
MeV. At the measuring place 3.9
m away from the radiator, a neutron flux of about
1.5
×
10
7
n
/
(
cm
2
s
)
will be obtained. The short beam pulses allow for a neutron energy resolution of better than 1% for neutron energies between
E
n
=
50
keV
and 5
MeV. The usable energies range up to about 10
MeV.
Luminescence dating of rock surfaces is an emerging absolute chronological technique that has the potential to determine how long a rock surface has been exposed to daylight and/or how long it has ...been buried. By measuring the OSL signal as a function of depth into the rock surface, it is possible to determine how long the rock surface has been exposed to daylight by fitting a luminescence kinetic model to the measured luminescence-depth profile. Despite increasing use of this technique, the possible dependence of derived ages on the chosen model has not been examined. Existing studies are based on the assumption that first-order kinetics apply and a first order model (F.O.M.) has been used. In this study, we use (i) a general-order kinetics model G.O.M., (McKeever and Chen, 1997) and (ii) a localised recombination model here referred to as the fading model, F.M., (Jain et al., 2015) to develop new analytical expressions for luminescence-depth profiles in rocks. These models are tested using both simulated and experimental data based on the IR50 signal. Based on these tests it is concluded that the derived apparent exposure ages are dependent on the chosen model. This model dependence occurs despite the fact that the speed of progression of the bleaching front into the rock surface is model independent. The reasons for this apparent discrepancy are discussed in details. Calibration with a single known-age sample (Sohbati et al., 2012b) gives inaccurate exposure ages for all investigated models unless the appropriate model is applied and/or the age of the calibration profile is of the same order of magnitude as the age of the unknown profile, but using the G.O.M. improves the accuracy of age estimates for IRSL profiles. An alternative approach to exposure dating is presented here as “Exposure Response Curve” calibration. We conclude that using inflection points, to avoid the difficulties caused by fitting parameter correlation, proves model-independent, and is a promising method for further investigation in Rock Surface Luminescence Exposure dating.
•Develop new analytical expressions for luminescence-depth profiles in rocks.•Testing models using simulated and experimental data based on the IR50 signal.•Model dependence occurs despite that the speed of progression is model independent.•The general order model improves the accuracy of age estimates for IRSL profiles.•Calibrating by using Exposure Response Curve (ERC) proves model independent.
We report on a determination of the analyzing power Ay in the p→p→ppω reaction studied with the TOF spectrometer located at the COSY-accelerator (Forschungszentrum Jülich, Germany). This spectrometer ...is very well suited for polarization measurements due to its rotational symmetry and full coverage of the azimuthal angle. For a beam momentum of p=3065 MeV/c corresponding to an excess energy of ϵ=129 MeVAy is found to be compatible with zero.
Two experiments were carried out and analysed in order to test tools used for the nuclear design of fusion devices. Neutron and photon flux spectra were measured in a thick tungsten assembly during ...irradiation with D-T neutrons. They were analysed with the Monte Carlo transport code MCNP-4C using nuclear data of the libraries FENDL-2, EFF-2.4 and JENDL-3.3. Small pieces of tungsten were irradiated with D-T neutrons, and the neutron-induced activities measured after the irradiation, were analysed with the inventory code FISPACT using data of the libraries EAF-2003 and FENDL/A-2. Deviations of experimental from calculated results show that an improvement of the tungsten data base is required. Tungsten is widely proposed for use in plasma facing components of future fusion devices.
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