kGy Range Research Articles

Balancing sterilization and functional properties in Poloxamer 407 hydrogels: comparing heat and radiation techniques

Abstract Poloxamer 407, also known as Pluronic® F127, is gaining interest in the cosmetic, biomedical, and pharmaceutical fields for its biocompatibility, safety, and thermosensitive properties. Ensuring sterility is critical in clinical applications, and sterilization is often preferred over aseptic processing. However, sterilization can impact the functional properties of the hydrogel. In this study, we investigate the effects of steam heat (121 °C, 20 min), dry heat (160 °C, 1 h), gamma irradiation (25 kGy), and electron beam (e-beam) irradiation (15 kGy and 25 kGy) on a 30%w/v Poloxamer 407 hydrogel formulation. Our analysis encompasses gelling properties, pH, Fourier-transform infrared (FTIR) spectroscopy, Gel Permeation Chromatography (GPC), Small-angle X-ray scattering (SAXS), rheology, swelling, degradation by-products, and lactate dehydrogenase (LDH) release of the sterilized hydrogels, comparing them to a non-sterile counterpart. We demonstrated that heat sterilization alters the hydrogel’s gelling and structural properties due to water evaporation and oxidation under harsh temperature conditions, especially when applying the dry heat method. Gamma irradiation proved unsuitable, resulting in an acidic and cytotoxic hydrogel due to oxidative degradation. In contrast, e-beam irradiation preserves the hydrogel's elasticity, gelling, and structural properties while enhancing mechanical resilience and moderating swelling. Therefore, e-beam irradiation within the 15–25 kGy range appears to be the most suitable method for sterilizing a 30%w/v Poloxamer 407 hydrogel.

Effect of electron beam irradiation treatment on microstructure, physicochemical properties, and bioactive content of areca nut.

Electron beam irradiation treatment is a novel technology that uses low-dose ionizing radiation for the treatment of crops or food to enhance their quality. This study investigated the effects of electron beam irradiation on the microstructure, physicochemical properties, and bioactive compounds of areca nuts. As the irradiation dose increased, the cellulose, hemicellulose, and lignin content in the areca nuts decreased significantly, whereas the polysaccharide and pectin content increased gradually. The hardness, chewiness, and adhesiveness of areca nuts reached their lowest values when the irradiation dose was within the range of 6-9 kGy, indicating that irradiation effectively reduced the hardness of the areca nut fibers. The decrease in crystallinity led to the formation of loose structures in the fibers upon irradiation, thereby improving their water retention, expansion, and oil-holding capacity, which are beneficial for the subsequent processing of areca nut-based chewable products. The water- and oil-holding capacities of the areca nuts peaked when the irradiation dose was within the 6-9 kGy range. Electron irradiation also affected the content of active substances in the areca nuts, particularly alkaloids, flavonoids, and polyphenols, showing an overall trend of initial increase followed by subsequent decrease. Electron irradiation was not only effective in softening the fibers but it also impacted the overall quality of the areca nuts significantly. The results provide valuable reference data for improving the quality of areca nuts through electron beam irradiation technology. © 2024 Society of Chemical Industry.

Online and offline Radiation-Induced Attenuation measurements on FD-7 radiophotoluminescence dosimeters irradiated at high X-ray doses

Radiophotoluminescence (RPL) FD-7 glass dosimeters find applications in low to high dose radiation environments. This work presents an experimental characterization of RPL glass dosimeter, irradiated with 100 kV X-ray tubes at room temperature at doses ranging from 1.3 kGy to 0.47 MGy, much higher of their common use range. In this study, a customized set-up has been developed, allowing the online investigation of the glass transmission changes with radiation, known as Radiation-Induced Attenuation (RIA), as well as the recovery and post-mortem characterizations up to 2 months after irradiation. Multi-wavelength analysis was performed, focusing on the range between 200 nm and 800 nm. At 700 nm and 800 nm, RIA increases progressively with dose up to about 5 kGy, and tends to approach saturation (2–3 dB/mm) for doses higher than 50 kGy. Higher attenuation is reported at lower wavelengths: 445-nm light transmission reduces to only about 1% of its initial value after 2 kGy. RIA recovery after irradiation was observed, up to 6% at 700 nm wavelength within 3 h from the irradiation conclusion and up to 26% 2 months after, especially at doses in the kGy range. Both online RIA and its recovery are highly dependent on the selected wavelength and on the total absorbed dose. This information is crucial for the extension of the use of these dosimeters up to high doses, complementary to the RPL signal, traditionally used alone for the determination of doses up to the Gy range.

Dosimetry for low-energy electron beam applications at Fraunhofer FEP

Abstract Accelerating electrons to achieve chemical and biological effects is a well-established competence of Fraunhofer FEP. Today, there is a large variety of low-energy electron beam applications with a broad range of absorbed doses, e.g. modification of plastics, plasma-chemical syntheses, pollutant removal in wastewaters and exhaust gases, sterilization of medical products, disinfection of seeds, biocompatible functionalization of implants and stimulation of biotechnological processes. This calls for reliable, sensitive, and flexible methods for dosimetry. Radiochromic films are suitable tools to measure electron dose distributions for the characterization and quality control of Fraunhofer FEP’s irradiation facilities. Risø B3 radiochromic film from DTU Health Tech, the dosimeter of choice at FEP, reliably detects doses in the range of 10–100 kGy. However, with new upcoming applications, doses in the single-digit kGy range and even lower come to the fore. Hence, the palette of dosimeters at FEP must be extended. Gafchromic’s HD-V2 film is a welcome complement and widens the accessible dose range down to 10 Gy. Using a UV-VIS spectrophotometer for read-out of the films and custom analysis algorithms further increase the sensitivity of the dosimetric setup. Additionally, dosimeters based on the optically stimulated luminescence (OSL) of beryllium oxide offer a wide dose range and high sensitivity. They were used to measure doses induced by secondary X-ray components to gain more information about a specific radiation field. The work gives an overview of the dosimetric toolbox at Fraunhofer FEP and the efforts to implement new methods of detection for low-dose applications and X-ray dosimetry.

Liquid dosimeter with sensitivity in low-kGy range for the characterization of a new module for EB wastewater treatment

Abstract In recent years, the use of low-energy electrons in various ecological and biotechnological applications has become increasingly relevant. One important application is the treatment of wastewater, wherein highly reactive species produced by water irradiation are used to oxidize pollutants. Low-energy electron irradiation has several advantages, such as minimal demands on radiation protection and electron beam (EB) source dimensions. However, to play into the main advantages of this technology and keep it economically viable, it is necessary to keep the absorbed dose as low as possible. This calls for a liquid dosimeter with sensitivity in the single digit kGy range. An extract from natural Hibiscus sabdariffa (Roselle) has been reported to show a radiochromic effect in this dose range. In the present work, Roselle dosimeter solutions were closely investigated and optimized to characterize a new module for EB wastewater treatment. Upon EB irradiation, the dosimeter solution demonstrated a dose-dependent fading in color, making it useful in the 0.3–7.5 kGy dose range.

A new initiators-free technique for synthesizing stable amine-impregnated polymeric aerogel using electron beam radiation for CO2 capture

New research in reducing CO2 emissions is ongoing to mitigate global warming. New ways are continuously sought to efficiently capture flue gases emitted by industries, one of which is using porous adsorbents like aerogels. The use of chemical initiators is the traditional way of synthesizing aerogels for CO2 capture; however, it pollutes the environment to some extent. This study finds an initiator-free method of synthesizing the aerogel which is faster and more stable yet green. The method involves exposing oil-in-water emulsions containing monomer mixtures along with other chemicals to a radiation dose of 10–50 kGy range using an electron accelerator. The polymeric aerogel was formed within 5 min after exposure to optimum dosage, which was then characterized to evaluate the physio-chemical changes. The test revealed that the aerogel synthesized at 40 kGy EB radiation dose exhibits the maximum PEI loading capacity of 4.1 g/g of aerogel. Furthermore, the CO2 adsorption performance of an optimized amine-impregnated polymeric aerogel was 4.45 mmol/g at 30 °C. Interestingly, this aerogel was able to preserve the initial capacity without significant decrease even after five adsorption-desorption cycles. The proposed method is likely to be of great significance in the field of CO2 capture.

Effect of γ-Irradiation on the Semitransparent Gray Color Obsidian in the 5 to 500 kGy Range

Effect of γ-Irradiation on the Semitransparent Gray Color Obsidian in the 5 to 500 kGy Range

PLA Renewable Bio Polymer Based Solid-State Gamma Radiation Detector-Dosimeter for Biomedical and Nuclear Industry Applications.

Polylactic acid (PLA) as a "green," renewable corn-soy based polymer resin was assessed as a novel solid-state detector for rapid-turnaround gamma radiation dosimetry in the 1-100 kGy range-of significant interest in biomedical and general nuclear industry applications. Co-60 was used as the source of gamma photons. It was found that PLA resin responds well in terms of rheology and porosity metrics with an absorbed gamma dose (Dg). In this work, rheological changes were ascertained via measuring the differential mass loss ratio (MLR) of irradiated PLA placed within PTFE-framed (40 mm × 20 mm × 0.77 mm) cavities bearing ~0.9 g of PLA resin and pressed for 12-16 min in a controlled force hot press under ~6.6 kN loading and platens heated to 227 °C for the low Dg range: 0-11 kGy; and to 193 °C for the extended Dg range: 11-120 kGy. MLR varied quadratically from 0.05 to ~0.2 (1σ ~ 0.007) in the 0-11 kGy experiments, and from 0.05 to ~0.5 (1σ ~0.01) in the 0-120 kGy experiments. Rheological changes from gamma irradiation were modeled and simultaneously correlated with void-pocket formations, which increase with Dg. A single PLA resin bead (~0.04 g) was compressed 5 min at 216 °C in 0-16 kGy experiments, and compressed 2 min at 232 °C in the 16-110 kGy experiments, to form sturdy ~100 µm thick wafers in the same press. Aggregate coupon porosity was then readily measurable with conventional optical microscope imaging and analyzed with standard image processing; this provided complementary data to MLR. Average porosity vs. dose varied quadratically from ~0 to ~15% in the 0-16 kGy range and from ~0 to ~18% over the 16-114 kGy range. These results provide evidence for utilizing "green"/renewable (under $0.01) PLA resin beads for rapid and accurate (+/-5-10%) gamma dosimetry over a wide 0-120 kGy range, using simple to deploy mass and void measuring techniques using common laboratory equipment.

Investigations on electron beam irradiated rare-earth doped SrF2 for application as low fading dosimeter material: evidence for and DFT simulation of a radiation-induced phase

A recent approach to measure electron radiation doses in the kGy range is the use of phosphors with an irradiation dose-dependent luminescence decay time.

Distributed fiber optic radiation sensors

Abstract. The international research efforts focused on the development of radiation sensors based on optic fibers have their origins in the 1970s (Evans et al., 1978). Generally, the lightweight fiber optic sensors are immune to electromagnetic field interference and high voltages making them deployable in harsh environments at hard to reach areas where conventional sensors usually will not work at all. A further advantage of such radiation sensors is the possibility of remote and real-time monitoring (Huston et al., 2001). In this work, we present our results achieved in several research activities for development of fiber optic dosimeters. The findings show that both the measurement of the radiation-induced attenuation (RIA) along the entire sensing fiber and the accompanying change in the refractive index of the fiber core can be used for distributed radiation monitoring in the kGy and MGy range, respectively. Depending on the fiber type and material the RIA shows varying response to dose rates, environmental temperatures and the wavelength of the laser source used. Thereby, an operation with visible laser light provides most favorable performance in terms of high radiation sensitivity. Operating at these wavelengths, RIA monitoring could yield high-sensitivity dose measurement with sub-gray resolution and accuracy (Stajanca and Krebber, 2017b); however, conventional optical time-domain reflectometry (OTDR) systems for RIA measurements operating in the visible range suffer from low-spatial resolution, long measurement times and poor signal-to-noise (SNR) ratio. The limitations of the OTDR performance can be overcome by the incoherent optical frequency domain reflectometry (I-OFDR) developed by the Federal Institute of Materials Research and Testing (BAM, Liehr et al., 2009) with potential for dynamic real-time measurement. Over the years, several highly radiation sensitive fibers, such as perfluorinated polymer optical fibers (PF-POF, Stajanca and Krebber, 2017a), phosphorous-doped silica optical fibers (SOF, Paul et al., 2009), aluminium-doped SOF (Faustov et al., 2013) and erbium-doped SOF (Wosniok et al., 2016) have been identified and are commercially available. As mentioned before, the radiation-induced RIA increase is associated with an increase in the refractive index leading also to material compaction in the fiber core. The latter two effects can be used for measuring radiation distribution based on Brillouin scattering in the range of high radiation doses of several MGy (Phéron et al., 2012; Wosniok et al., 2016). When using fiber optic sensors for radiation monitoring, the existing post-irradiation annealing behavior of the optical fiber sensors must also be considered.

A Newly Designed Seed-Loading Device for Verifying the Safety of 125I Implants to the Canine Carotid Artery.

A seed-loading device was designed and modeled using the Monte Carlo method to verify the biological effect of iodine-125 (125I) particles on blood vessels through animal experiments. The dose distribution characteristics of irradiated vessels were established by adjusting the design variables and geometry. The deviation between the actual value and the theoretical value was verified in vitro by the thermoluminescence dosimetry (TLD) method. After verification, the device was used to examine the biological effect of 125I irradiation of canine carotid arteries in two dogs (and one control dog) for 180 days. The hollow cylinder seed-loading device was constructed with an inner diameter of 0.5 cm and a length of 3.3 cm. When six seeds were loaded into a single layer, the source strength ratio of the intermediate layer to the edge layer was 0.7:1. When six layers of seeds were arranged at 0.45-cm intervals, the deviations between the maximum, minimum and mean energy fluence within 2.25 cm of the vessel wall were 2.19% and -4.12%, respectively, and -9% and 4%, respectively, when verified in vitro using TLD. The carotid arteries showed good tolerance to 0.56 kGy (range of 0.51-0.58 kGy) after 180 days of irradiation. In conclusion, this 125I seed-loading device overcomes the random distribution of seeds and lays an accurate radiophysical foundation for subsequent biological experiments. The preliminary results showed that the carotid artery has good tolerance to 0.56 kGy irradiation.

A kinetic model for the thermoluminescent high dose response of LiF:Mg,Cu,P (MCP-N)

This contribution describes a kinetic model attempting to reproduce the response of the thermoluminescent material LiF:Mg,Cu,P when it is irradiated to absorbed dose values in the kGy range. The modelling is based on the hypothesis of a relationship between the irradiation time (i.e. the absorbed dose) and the density of trapping/recombination centres.X-ray diffraction and thermal X-ray diffraction measurements have been performed to investigate the potential radiation and thermal damage on the structure of the material, including the possibility of partial phases. The proposed kinetic model qualitatively reproduces the observed changes in the TL glow curve for temperatures above the main peak as well as the two observed regions of absorbed dose response: linear and sub-linear.

Supplementary comparison APMP.RI(I)-S1 of standards for absorbed dose to water in 60Co gamma radiation at radiation processing dose levels

Main textFour national standards for absorbed dose to water in 60Co gamma radiation at the dose levels used in radiation processing have been compared over the range 0.1 kGy to 50 kGy using alanine dosimeters of the Office of Atoms for Peace (OAP) as transfer dosimeters. The comparison was piloted by the OAP who also participated. Two laboratories from the original six were forced to withdraw due to equipment problems. The results at low doses (0.1 kGy) showed a much wider spread (up to 17%) than at the other doses, most likely as a result of random variations in the alanine readout at OAP at these dose levels. Results in the 0.1 kGy range were excluded from the analysis because the variation between the laboratories' doses is overshadowed by the variation in the readout of the alanine. Above 1 kGy the results indicated reasonable agreement between the laboratories, with the majority of results within 2 % of the reference value. All of these results were within two combined standard uncertainties of the reference value, with the exception of the INER at 50 kGy point which was within three combined standard uncertainties. Within the stated uncertainties, the results establish the equivalence of the laboratories at radiation processing levels, for the range in which they participated: NIS (3 - 10) kGy, NIM (3 - 30) kGy, INER (3 - 50) kGy, OAP (3 - 50) kGy.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

3D relative dose measurement with a μm thin dosimetric layer

A μm thin dosimetric coating material based on inorganic phosphor particles NaYF4:Yb3+, Er3+ has been developed. A dose dependency of the luminescence decay time is observed in the μs - ms domain which allows relative dose measurement in the kGy range. Dose values are obtained from decay time evaluation which facilitates a measurement independent of luminescence emission intensity. Here, near-IR luminescence after excitation with 5 ms pulses of near-infrared light is analyzed. The dosimetric material can be directly sprayed onto the surface of objects and therefore renders particularly useful for dose distribution measurements on non-planar geometries. Because of the μm thickness and the direct contact of the dosimetric material to the entire surface of an object, the results can be considered as ‘true’ surface doses. Three dimensional dose maps were derived by scanning the entire surfaces of irradiated objects. Proof-of-concept is provided by good agreement in dose results as well as dose pattern with film dosimetry (Risø B3 strips) and the approach therefore qualifies especially for use in 3D dose mapping of complex geometries. This novel approach provides unprecedented insights into dose distributions of irradiated objects of complex geometries, as exemplified by dose results for outer and inner surfaces of e-beam irradiated bottles for two different irradiation set-ups.

Thermoluminescence features of Er3+ doped BaO-ZnO-LiF-B2O3 glass system for high-dose gamma dosimetry

Transparent 10BaO-20ZnO-20LiF-(50-x) B2O3-xEr2O3 glasses with x = 0, 0.1, 0.5, 0.7 and 1 mol % were synthesized using melt-quench method. Their amorphous nature was confirmed from X-Ray Diffraction (XRD). The glasses were irradiated with 3 kGy gamma dose, among which the sample with 0.7 mol % Er2O3 doping showed the highest integrated thermoluminescence (TL) intensity. The dose-response was evaluated by irradiating the sample with 0.25- 30 kGy gamma doses. The highest integrated TL intensity was obtained at 3 kGy dose. Fourier Transform Infrared (FTIR) spectra of the 0.7 mol % Er2O3 doped glass after 3 kGy gamma irradiation predicted the creation of new bonds and rise in the Non-Bridging Oxygens. UV–Vis–NIR absorption spectra recorded after 3 kGy gamma irradiation accounted for the formation of color centers due to an increase in the total absorption of the glass, a decrease in the bandgap and an increase in the Urbach energy. The sample exhibited good linearity in the 0.25 to 3 kGy range with high sensitivity of 27021 counts g-1kGy-1 and a minimum detectable dose of 0.201 kGy. TL signal faded by just 4% after a week of storage. The annealing condition for reusability and the effective atomic number of the glass were examined. Trap parameters like activation energy, frequency factor and lifetime, determined using Computerized Glow Curve Deconvolution (CGCD) and Chen's peak shape methods supported the low fading of the sample. Overall, the remarkable TL dosimetry characteristics present the usefulness of the titled glass system in radiation processing of food products and high-dose (0.25 to 3 kGy) gamma environment.

Gamma-irradiation-induced micro-structural variations in flame-retardant polyurethane foam using synchrotron X-ray micro-tomography.

Flame-retardant polyurethane foams are potential packing materials for the transport casks of highly active nuclear materials for shock absorption and insulation purposes. Exposure of high doses of gamma radiation causes cross-linking and chain sectioning of macromolecules in this polymer foam, which leads to reorganization of their cellular microstructure and thereby variations in physico-mechanical properties. In this study, in-house-developed flame-retardant rigid polyurethane foam samples were exposed to gamma irradiation doses in the 0-20 kGy range and synchrotron radiation X-ray micro-computed tomography (SR-µCT) imaging was employed for the analysis of radiation-induced morphological variations in their cellular microstructure. Qualitative and quantitative analysis of SR-µCT images has revealed significant variations in the average cell size, shape, wall thickness, orientations and spatial anisotropy of the cellular microstructure in polyurethane foam.

Quartz thermoluminescence spectra in the high-dose range

The red thermoluminescence (RTL) emission of quartz is associated with advantageous features such as high saturation dose and good reproducibility. Previous studies, however, noted inexplicable RTL glow curve shapes with new peaks at large doses (kGy range). Here we present TL spectra of two granitic quartz samples over the additive γ-dose range 0.1–47.9 kGy. While for doses between 0.4 and 1 kGy the TL spectra are dominated by the red emission at 1.95 eV (630 nm), a blue emission at 2.67 eV (465 nm) becomes prominent for higher doses. For one sample, this blue component completely dominates the spectrum for doses > 12.2 kGy with intensity maxima around 200 °C and > 350 °C (heating rate 2 K s−1). The other sample still contains well resolvable red and blue emissions at the largest dose with similar TL peak positions. Signal saturation for the blue emission in the glow curve range 260–300 °C is not yet reached following an additive γ-dose of 47.9 kGy, whereas the red emission generally shows a more subdued signal response for doses > 5–12 kGy. These findings agree qualitatively with additional monochromatic blue and red TL measurements on the same samples. The evolution of supplementary radiofluorescence spectra over the entire γ-dose range is more complex, but suggests that the sensitisation of the blue wavelength region occurs during heating and not during irradiation and through creation of electron traps rather than recombination centres (most likely [AlO4]0 sites). The sharp sensitivity increase at 1 kGy might likewise be related to alkali ion redistribution and/or the removal of non-radiative competitive recombination pathways. While the blue emission still requires thorough investigation, care should be taken when recording RTL using optical filters since significant portions of the registered TL could originate from the blue component entering the RTL transmission window. In practical terms, the dose-dependent change in relative intensities of blue and red TL emissions might help in detecting exposure to high doses.

Radiochromic film containing poly(hexa-2,4-diynylene adipate) as a radiation dosimeter

A radiation-sensitive polymer poly(hexa-2,4-diynylene adipate) (PHDA) was synthesized and incorporated into polyvinyl butyral films for radiation dose measurements in the 0.5 – 60 kGy range. PHDA undergoes crosslinking polymerization upon exposure to γ-rays, which changes its color from very pale yellow to deep orange-yellow. The color change is directly related to the absorbed dose. The absorption spectrum of the irradiated films features one absorption band around 500 nm with a shoulder around 465 nm. With increasing absorbed dose, the two bands grow in intensity and move towards higher wavelengths. The dosimeter is nearly insensitive to variations of the humidity in the range of 0–54% and temperature in the range of 30–45 °C during irradiation. The color intensifies after irradiation, both in the dark and in the light at room temperature, which reflects the continuing crosslinking polymerization. However, at − 4 °C, the color intensity does not change with time.

Exfoliated graphite with graphene flakes as potential candidates for TL dosimeters at high gamma doses

Graphite powder (GP) subjected to microwave radiation (MWG) results in exfoliation of graphite particles into few-layered graphene flakes (GF) intermixed with partially exfoliated graphite particles (PEG). Characterization of MWG by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Raman spectroscopy reveal few-layer GF with sizes ranging from 0.2 to 5 µm. Raman D, G, and 2D (G′) bands characteristic of graphitic structures include evidence of the presence of bilayered graphene. The thermoluminescent (TL) dosimetric properties of MWG are evaluated and can be characterized as a gamma-ray sensitive and dose-resistant material with kinetic parameters (activation energy for the main peak located at 400 and 408 K is 0.69 and 0.72 eV) and threshold dose (~1 kGy and 5 kGy respectively). MWG is a low-Z material (Zeff = 6) with a wide linear range of TL dose-response (0.170–2.5 kGy) tested at doses in the 1–20 kGy range with promising results for applications in gamma-ray dosimetry. Results obtained in gamma irradiated MWG are compared with those obtained in graphite powder samples (GP) without microwave treatment.

Physicochemical Study of Gamma-irradiated mono azo dye in aqueous Solutions as liquid dosimeter

AQUEOUS solutions of pH indicator (mono azo dye) Amacid Yellow M (AYM) dye were titrated by different concentrations of (H+) resulting from irradiation decomposition of trichloroethylene (ClHC=CCl2) (TCE) solution for possible use as an monitoring device (label) for gamma radiation. The titrated solutions were readout spectrophotometrically. These solutions can be used qualitatively as routine indicators in the 0.5–5 kGy range because they have stable change in color for (AYM) from yellow to red at 540 nm depending on irradiated trichloroethylene [H+]. The effective dose range exceeds in this technique due to avoiding direct exposure of dye to gamma radiation, utilizing back titration technique followed by color measurements using spectrophotometer. Moreover, the useful measuring range was found to be 5kGy. The solutions can be used qualitatively as routine indicators in the range of 0.5 to 2kGy. Further calculations such as rate of reaction (r) and kinetic constant (k) have been assigned.