Function Of Shielding Research Articles

Improvement of the performance of carbon based all-inorganic perovskite solar cells by using ammonium acetate modified rutile TiO2 nanorods array as the electron transport layer

Carbon-based all-inorganic perovskite solar cells are currently emerging as a commercial and promising photovoltaic device. Rutile TiO2 has the function of UV shielding and preventing the decomposition of perovskite, furthermore, TiO2 nanorod array provides the direct 1-D electron transmission channel. Herein, vertically oriented rutile TiO2 nanorods array are synthesized on the FTO substrate by a simple one-step hydrothermal process and used as the electron transfer layer. The analysis of characterization illustrates that the prepared TiO2 is a flawless single rutile phase. TiO2 nanorods are employed as an ETL to provide a passage for the rapid and direct charge transfer. The separation of electrons and holes can be enhanced by ammonium acetate treatment of the TiO2 nanorod ETL/perovskite interface, and the carrier recombination can be efficiently lowered. Based on the structure of FTO/TiO2@CH3COONH4/CsPbI2.25Br0.75/C, the best device containing 2.5 mg/mL ammonium acetate modified TiO2 nanorods showed a short-circuit current density of 14.55 mA/cm2, open-circuit voltage of 1.08 V, and fill factor of 69.45 %, yielding a power conversion efficiency of 11.53 %, which show an increase in efficiency of approximately 22.4% when compared with the control cell. The results show that ammonium acetate interface modification is an effective strategy to enhance the photovoltaic performance of PSCs.

Design of a Broadband Switchable Active Frequency Selective Surfaces Based on Modified Diode Model

In this letter, a broadband switchable active frequency selective surfaces (AFSSs) is presented, and the proposed structure is comprised of three metallic layers and two Rogers RT5880 substrates. In order to realize broadband transmission, a second-order bandpass filter is constructed, and the multilayer coupling effect is utilized. A modified equivalent circuit model of the p-i-n diode is proposed to reduce the simulation error and improve the design accuracy. By controlling the bias voltage of the p-i-n diodes, two completely different functions are realized. At the function of dual-polarized shielding, the shielding bandwidth is 2–18 GHz, and the transmission bandwidth is 8.2–10.5 GHz with a fractional bandwidth of 24.6% at the function of dual-polarized transmission. A prototype has been fabricated and measured, and the measurement results are in good agreement with the simulation results, indicating that the AFSSs has good polarization stability for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band radar applications.

Інтер'єрний текстиль з екрануючими властивостями до дії електромагнітного випромінювання

The purpose. An investigation of the shielding effectiveness against electromagnetic radiation (EMR) by woven fabrics that are presented on the Ukrainian interior textile market. Methodology. Theoretical and experimental research is based on the general principles of textile materials science. The shielding effectiveness to EMR of textile fabrics was tested and measured using EM-2107A (Electro Metrics) in accordance with ASTM 4935-10 in the frequency range 30 MHz – 1.5 GHz. Results. Flexible screens based on textile materials are widely used for EMR shielding. The shielding effectiveness against EMR by textile materials can be improved with fabric modifying by metal fibers/threads, metal particles or conductive polymers at various stages of textile production. It possible to substantiate the expediency of using metal-containing textile materials as interior textiles on the result of carried out analysis of the modern assortment of interior textiles and the experimental studies. Studies results have shown that the proposed fabrics have a high shielding ability by the classification "professional use" according to FTTS-FA-003 Specified Requirements of Electromagnetic Shielding Textiles, the shielding efficiency of which is within 30 ÷ 60 dB. Scientific novelty. The expediency of using modern metal-containing textile materials as interior textiles for windows decoration has been substantiated. The studied textile materials make it possible to clarify a new promising segment of the interior textile market - windows decoration. The main goal of such textile - the decoration of the residential and administrative buildings is expanded and supplemented by the function of electromagnetic radiation shielding. Practical significance. The complex of scientific research on the shielding effectiveness against EMR allowed offering a new range of interior textile materials for window decoration.

Radiation Dose in a Reactor Service Area of the AP-1000 Based on the Fukushima Accident

Cooling water as a radiation shield from a reactor core originates from the reactor core. In the case of an accident, when the cooling water level inside a pressure vessel decreases, the function of water as a radiation shield decreases as well. After the time passage of the reactor shutdown, the strength of gamma (γ) radiation source from the reactor core decreases. The combination of the decrease of the water that reduces the function of radiation shielding and the decrease of the source strength will affect the pattern of dose rate in the reactor service area (RSA) after an accident takes place. This paper discusses γ dose rate in an RSA of an advanced pressurized water reactor (PWR) (AP1000) nuclear power plant (NPP) based on the accident of Fukushima No. 1 reactor. The referred accident is the decrease in the level of cooling water until the it reached half of the height of the reactor core. The reactor core was not damaged since the γ source is still trapped in the matrix of the reactor core. The highest dose rate occurs when the water level decreases to the upper level of the reactor core. The dose rate above the pressure vessel at the RSA prior to the decrease of the water level was 0.7 rad/h, while the dose rate reached 740 rads/h when the water level reaches to the middle of the reactor core. Indeed, the dose rate at a point of 17.5 m horizontally from the center of the core tank was 0.057 rad/h. This condition requires highly selective control to enable entry to the area of the accident. Indeed, a large γ radiation rate due to a decline in the surface horizontal distance is around 6,404 times greater than those of cosmic and natural γ rays.

Calibration and Initial Results of Space Radiation Dosimetry Using the iMESA‐R

AbstractThe integrated Miniaturized Electrostatic Analyzer‐Reflight (iMESA‐R) is a space weather instrument designed to measure plasma density, temperature, and spacecraft charging, along with total ionizing dose and dose rate. A constellation consisting of five nearly identical instruments has been designed and developed to act as science payloads hosted on‐board Department of Defense satellites operating in low‐Earth orbit. To validate the dosimetry component of the iMESA‐R, a radiation test study was performed to calibrate the dosimeter and ascertain the attenuation due to the instrument aluminum housing. An 80 curie Cobalt‐60 radioisotope source emitting beta, X‐ray, and gamma ray radiation decay products was used to calibrate the dosimeter response as a function of distance and instrument shielding. We present results of the calibration study along with initial on‐orbit data presented from the first operational iMESA‐R hosted on‐board Space Test Program Satellite 5 in a polar Earth orbit. The initial on‐orbit data demonstrate the ability to map the radiation environment, particularly the South Atlantic Anomaly and the auroral regions using total ionizing dose rate due to electrons of E &gt; 1.5 MeV and protons of E &gt; 25 MeV.

A Modelling of Paraffin Shielding for BNCT Facility at Kartini Reactor Research using MCNPX

The development of cancer in the world is very high. According to the World Health Organization (WHO) 1.69 million people die from cancer per year in the world, while the cases of cancer in Indonesia are also not much different. Some areas have a high prevalence of cancer, namely D.I Yogyakarta. Cancer has become a scourge for many people. There are many treatments available, such as chemotherapy, surgery, and radiation. Additionally, there is radiotherapy using neutron capture of boron-10 with energy 0.025 Ev. This treatment does not damage other tissue because the resulting particles such as He-4 and Lithium-7 have ranges that are a distance of 4.5-10 μm, so that the deposited energy is limited to the diameter of a single cell. The treatment is called Boron Neutron Capture Therapy (BNCT). There are several BNCT facilities such as a reactor, radial piercing beam port, thermal column, and shielding. The function of shielding is to absorb the neutron and alpha radiation. The shielding is made using paraffin material that is excellent in absorbing neutron radiation. In addition to paraffin there are also other materials, such as lead, used as paraffin casing. In a shielding simulation using MCNPX software, the resulting dose rate of radiation exposure outside of the BNCT facility in vitro and vivo tests is equal to 6.5 μSv / h. The thickness of the shielding paraffin used is 40 cm, Pb casing 25 cm, and 5 cm soft tissue.

Modelling of the spent fuel heat-up in the spent fuel pools using one-dimensional system codes and CFD codes

Abstract The main functions of spent fuel pools are to remove the residual heat from spent fuel assemblies and to perform the function of biological shielding. In the case of loss of heat removal from spent fuel pool, the fuel rods and pool water temperatures would increase continuously. After the saturated temperature is reached, due to evaporation of water the pool water level would drop, eventually causing the uncover of spent fuel assemblies, fuel overheating and fuel rods failure. This paper presents an analysis of loss of heat removal accident in spent fuel pool of BWR 4 and a comparison of two different modelling approaches. The one-dimensional system thermal-hydraulic computer code RELAP5 and CFD tool ANSYS Fluent were used for the analysis. The results are similar, but the local effects cannot be simulated using a one-dimensional code. The ANSYS Fluent calculation demonstrated that this three-dimensional treatment allows to avoid the need for many one-dimensional modelling assumptions in the pool modelling and enables to reduce the uncertainties associated with natural circulation flow calculation.

The effect of wind shielding and pen position on the average daily weight gain and feed conversion rate of grower/finisher pigs

Pigs are known to be particularly sensitive to heat and cold. If the temperature becomes too low, the pigs will grow less efficiently and be more susceptible to diseases such as pneumonia. If the temperature is too high, the pigs will tend to foul the pen, leading to additional risks of infection. Furthermore, unpublished data show that the temperature within a single section of grower/finisher pigs can vary considerably from pen to pen, and previous studies have shown that pigs can be significantly affected by wind, even when not directly exposed to it. To address this latter concern, some pig producers and research stations have implemented a shielding to prevent winds from blowing between separate sections of the pig housing buildings. However, according to our search of the literature, no published studies have ever investigated the effectiveness of such shielding.To determine the significance of the effects of wind shielding, linear mixed models were fitted to describe the average daily weight gain and feed conversion rate of 1271 groups (14 individuals per group) of purebred Duroc, Yorkshire and Danish Landrace boars, as a function of shielding (yes/no), insert season (winter, spring, summer, autumn), start weight and interaction effects between shielding and start weight and shielding and insert season. Such a model was fitted separately to the data collected for each breed. Shielding was found to have significant interaction effects with season (p=0.007) and start weight (p=0.0002) for Duroc pigs, but no effect could be shown for Yorkshire or Danish landrace.To determine the effect of a group׳s placement relative to the central corridor of a grower/finisher station, a similar model was fitted to the data for Duroc pigs, replacing shielding with distance from the corridor (1st, 2nd, 3rd or 4th pen). The effect could not be tested for Yorkshire and Danish Landrace due to lack of data on these breeds. For groups of pigs above the average start weight, a clear tendency of higher growth rates at greater distances from the central corridor was observed, with the most significant differences being between groups placed in the 1st and 4th pen (p=0.0001). A similar effect was not seen on smaller pigs. Pen placement appears to have no effect on feed conversion rate.No interaction effects between shielding and distance to the corridor could be demonstrated. Furthermore, in models including both factors, the effect of distance to corridor completely dominated over the effect of shielding, suggesting that shielding should at most be considered of secondary importance.

Alpha power increases in right parietal cortex reflects focused internal attention

This study investigated the functional significance of EEG alpha power increases, a finding that is consistently observed in various memory tasks and specifically during divergent thinking. It was previously shown that alpha power is increased when tasks are performed in mind—e.g., when bottom-up processing is prevented. This study aimed to examine the effect of task-immanent differences in bottom-up processing demands by comparing two divergent thinking tasks, one intrinsically relying on bottom-up processing (sensory-intake task) and one that is not (sensory-independence task). In both tasks, stimuli were masked in half of the trials to establish conditions of higher and lower internal processing demands. In line with the hypotheses, internal processing affected performance and led to increases in alpha power only in the sensory-intake task, whereas the sensory-independence task showed high levels of task-related alpha power in both conditions. Interestingly, conditions involving focused internal attention showed a clear lateralization with higher alpha power in parietal regions of the right hemisphere. Considering evidence from fMRI studies, right-parietal alpha power increases may correspond to a deactivation of the right temporoparietal junction, reflecting an inhibition of the ventral attention network. Inhibition of this region is thought to prevent reorienting to irrelevant stimulation during goal-driven, top-down behavior, which may serve the executive function of task shielding during demanding cognitive tasks such as idea generation and mental imagery.

Optimizing moderation of He-3 neutron detectors for shielded fission sources

The response of a 3He neutron detector is highly dependent on the amount of moderator incorporated into the detector system. If there is too little moderation, neutrons will not react with the 3He. If there is too much moderation, neutrons will not reach the 3He. In applications for portal or border monitors where 3He detectors are used to interdict illicit importation of plutonium, the fission source is always shielded to some extent. Since the energy distribution of neutrons emitted from the source depends on the amount and type of shielding present, the optimum placement of moderating material around 3He tubes is a function of shielding. In this paper, we use Monte Carlo techniques to model the response of 3He tubes placed in polyethylene boxes for moderation. To model the shielded fission neutron source, we use a point 252Cf source placed in the center of polyethylene spheres of varying radius. Detector efficiency as a function of box geometry and shielding is explored. We find that increasing the amount of moderator behind and to the sides of the detector generally improves the detector response, but that incremental benefits are minimal if the thickness of the polyethylene moderator is greater than about 5–7cm. The thickness of the moderator in front of the 3He tubes, however, is very important. For bare sources, about 4–5cm of moderator is optimum, but as the shielding increases, the optimum thickness of this moderator decreases to 0.5–1cm. Similar conclusions can be applied to polyethylene boxes employing two 3He tubes. Two-tube boxes with front moderators of non-uniform thickness may be useful for detecting neutrons over a wide energy range.

Electromagnetic Shielding Effectiveness of Cement-Matrix Composite Containing Nickel Fiber

The cement-matrix composite with the function of building structure and electromagnetic interference shielding was prepared by filling nickel fiber into cement. The dispersion of nickel fiber in cement-matrix composite and the shielding effectiveness of composite containing various volume fractions of nickel fiber were investgated in this paper. The electromagnetic interference shielding effectiveness in the frequency range of 0.1 MHz to 1.5 GHz and the conductivity of composite were measured by coaxial cable method and two-probe method, respectively. The dispersion of nickel fiber in cement was characterized by EPMA. The results indicated that the dispersion property of nickel fiber by sodium hexametaphosphatecan was better than sodium carboxymethylcellulose. The optimum contents of nickel fiber in composite was 5 vol.%, the maximum shielding effectiveness was 45.7 dB in 140 MHz and the minimum shielding effectiveness was 36 dB in 1240 MHz. The shielding effectiveness of composite with 7 vol.% nickel fiber was lower than that with 5 vol.% nickel fiber due to the tendency of nickel fiber cling to each other.

Noise Shielding Using Acoustic Metamaterials

We exploit theoretically a class of rectangular cylindrical devices for noise shielding by using acoustic metamaterials. The function of noise shielding is justified by both the far-field and near-field full-wave simulations based on the finite element method. The enlargement of equivalent acoustic scattering cross sections is revealed to be the physical mechanism for this function. This work makes it possible to design a window with both noise shielding and air flow.

Computation of relative dose distribution and effective transmission around a shielded vaginal cylinder with Ir192 HDR source using MCNP4B

The present work is primarily focused on the estimation of relative dose distribution and effective transmission around a shielded vaginal cylinder with an 192Ir source using the Monte Carlo technique. The MCNP4B code was used to evaluate the dose distribution around a tungsten shielded vaginal cylinder as a function of thickness and angular shielding. The dose distribution and effective transmission of 192Ir by 0.8 cm thickness tungsten were also compared with that for gold and lead. Dose distributions were evaluated for different distances starting from 1.35 cm to 10.15 cm from the center of the cylinder. Dose distributions were also evaluated sequentially from 0 degrees to 180 degrees for every 5 degrees interval. Studies show that all the shielding material at 0.8 cm thickness contribute tolerable doses to normal tissues and also protect the critical organs such as the rectum and bladder. However, the computed dose values are in good agreement with the reported experimental values. It was also inferred that the higher the shielding angles, the more the protection of the surrounding tissues. Among the three shielding materials, gold has been observed to have the highest attenuation and hence contribute lowest transmission in the shielded region. Depending upon the shielding angle and thickness, it is possible to predict the dose distribution using the MCNP4B code. In order to deliver the higher dose to the unshielded region, lead may be considered as the shielding material and further it is highly economic over other materials.

Surface characteristics of electroless nickel plated electromagnetic shielding wood veneer

Wood is a kind of porous natural material with very poor electro-conductivity, and it has almost no function of electromagnetic shielding. The method of electroless nickel plating was used to produce wooden material with electrical and effective electromagnetic shielding properties. Ni−P alloy layer was obtained on wood surface. The surface feature of plated wood veneer was observed by SEM and the surface composition and microstructure of the layer under different conditions were investigated by EDS and XRD respectively. Mean-while, the relevant surface resistivity and electromagnetic shielding effectiveness were measured. Correlations of the phosphorous content in the layer to the structure of Ni−P alloy, electro-conductivity and electromagnetic shielding of plated veneers were discussed. SEM photos showed that the surface of electroless nickel plated veneers were covered with Ni−P alloy layer entirely, which made wood veneers more like metal. At the same time, the results showed that with the decreasing of the phosphorous content in the layer, the microstructure of Ni−P alloy layer transformed to be microcrystalline and electro-conductivity and electromagnetic shielding effectiveness were imrpoved. When the phosphorous content was less than 2.37wt pct in the layer, the microstructure of Ni−P alloy layer was microcrystalline structure and its surface resistivity and electromagnetic shielding effectiveness were nearly 0.5 Ω/⊥ and 55–60dB respectively.

The hazards of space travel.

Exploration is an important survival strategy in evolution. The migration of expansive species depends on exploring their immediate or distant surroundings for new food sources or safe habitats; it can also come as a result of population pressures or environmental changes. The human species has added another reason for exploration, namely curiosity. This intellectual urge to explore the unknown led the great European explorers to the Americas, Australia and Antarctica between the fifteenth and seventeenth centuries. Inquisitiveness about nature is also the driving force behind humans exploring the polar caps, climbing mountain peaks and diving into the abysses of the oceans. Now, the ultimate frontier to explore in the twenty‐first century is space. Astronomical observations and satellites have already yielded immense knowledge about our solar system and the universe beyond. But these technologies can provide only a limited picture of what is out there; eventually humans themselves will have to travel to other planets to investigate them in more intimate detail. Tremendous advances in rocket and spaceship technologies during the past 50 years, driven mainly by national security considerations, the need for better communication or a desire to observe environmental changes and human activity on the ground, have made it possible to send humans into near‐Earth orbit and to the Moon. Conceivably, these advances will eventually make it possible to transport astronauts to other planets, and Mars in particular (Fig. 1). Figure 1. Late spring on Mars. Source: NASA. But there are significant differences between exploring Earth and exploring space. First and foremost, space is an unforgiving environment that does not tolerate human errors or technical failure. For humans leaving Earth's orbit for extended periods, there are even more dangers. One is the near absence of gravity in space; the presence of high‐energy, ionizing cosmic ray (HZE) nuclei is another. Because …

Site-specific PEGylation of hemoglobin at Cys-93(beta): correlation between the colligative properties of the PEGylated protein and the length of the conjugated PEG chain.

Increasing the molecular size of acellular hemoglobin (Hb) has been proposed as an approach to reduce its undesirable vasoactive properties. The finding that bovine Hb surface decorated with about 10 copies of PEG5K per tetramer is vasoactive provides support for this concept. The PEGylated bovine Hb has a strikingly larger molecular radius than HbA (1). The colligative properties of the PEGylated bovine Hb are distinct from those of HbA and even polymerized Hb, suggesting a role for the colligative properties of PEGylated Hb in neutralizing the vasoactivity of acellular Hb. To correlate the colligative properties of surface-decorated Hb with the mass of the PEG attached and also its vasoactivity, we have developed a new maleimide-based protocol for the site-specific conjugation of PEG to Hb, taking advantage of the unusually high reactivity of Cys-93(beta) of oxy HbA and the high reactivity of the maleimide to protein thiols. PEG chains of 5, 10, and 20 kDa have been functionalized at one of their hydroxyl groups with a maleidophenyl moiety through a carbamate linkage and used to conjugate the PEG chains at the beta-93 Cys of HbA to generate PEGylated Hbs carrying two copies of PEG (of varying chain length) per tetramer. Homogeneous preparations of (SP-PEG5K)(2)-HbA, (SP-PEG10K)(2)-HbA, and (SP-PEG20K)(2)-HbA have been isolated by ion exchange chromatography. The oxygen affinity of Hb is increased slightly on PEGylation, but the length of the PEG-chain had very little additional influence on the O(2) affinity. Both the hydrodynamic volume and the molecular radius of the Hb increased on surface decoration with PEG and exhibited a linear correlation with the mass of the PEG chain attached. On the other hand, both the viscosity and the colloidal osmotic pressure (COP) of the PEGylated Hbs exhibited an exponential increase with the increase in PEG chain length. In contrast to the molecular volume, viscosity, and COP, the vasoactivity of the PEGylated Hbs was not a direct correlate of the PEG chain length. There appeared to be a threshold for the PEG chain length beyond which the protection against vasoactivity is decreased. These results suggest that the modulation of the vasoactivity of Hb by PEG could be a function of the surface shielding afforded by the PEG, the latter being a function of the disposition of the PEG chain on the protein surface, which in turn is a function of the length of the PEG chain. Thus, the biochemically homogeneous PEGylated Hbs described in the present study, surface-decorated with PEG chains of appropriate size, could serve as potential candidates for Hb-based oxygen carriers.

Theoretical current response of silicon detectors to fast neutron beams in mixed n, γ fields

A theoretical approach is presented improving the knowledge on real time fast neutron dosimetry in intense fields. The detector is a reverse biased silicon junction operating at room temperature. The signal readout is a current measurement for which the leakage current of the sensor sets the detector threshold in the range of 1 Sv s −1 dose rates. The dosemeter energy response as a function of shielding, polyethylene neutron converters and diode characteristics has been computed to provide a tissue equivalent neutron monitor which is as insensitive as possible to the gamma photon background. Two Monte Carlo codes, one for the fast neutrons (SEMIC) and for the photon background (MCGET), are used to calculate the current response of the device irradiated by monoenergetic radiations (n or γ) as well as neutron sources.

Permeation through an open channel: Poisson-Nernst-Planck theory of a synthetic ionic channel

The synthetic channel [acetyl-(LeuSerSerLeuLeuSerLeu)3-CONH2]6 (pore diameter approximately 8 A, length approximately 30 A) is a bundle of six alpha-helices with blocked termini. This simple channel has complex properties, which are difficult to explain, even qualitatively, by traditional theories: its single-channel currents rectify in symmetrical solutions and its selectivity (defined by reversal potential) is a sensitive function of bathing solution. These complex properties can be fit quantitatively if the channel has fixed charge at its ends, forming a kind of macrodipole, bracketing a central charged region, and the shielding of the fixed charges is described by the Poisson-Nernst-Planck (PNP) equations. PNP fits current voltage relations measured in 15 solutions with an r.m.s. error of 3.6% using four adjustable parameters: the diffusion coefficients in the channel's pore DK = 2.1 x 10(-6) and DCl = 2.6 x 10(-7) cm2/s; and the fixed charge at the ends of the channel of +/- 0.12e (with unequal densities 0.71 M = 0.021e/A on the N-side and -1.9 M = -0.058e/A on the C-side). The fixed charge in the central region is 0.31e (with density P2 = 0.47 M = 0.014e/A). In contrast to traditional theories, PNP computes the electric field in the open channel from all of the charges in the system, by a rapid and accurate numerical procedure. In essence, PNP is a theory of the shielding of fixed (i.e., permanent) charge of the channel by mobile charge and by the ionic atmosphere in and near the channel's pore. The theory fits a wide range of data because the ionic contents and potential profile in the channel change significantly with experimental conditions, as they must, if the channel simultaneously satisfies the Poisson and Nernst-Planck equations and boundary conditions. Qualitatively speaking, the theory shows that small changes in the ionic atmosphere of the channel (i.e., shielding) make big changes in the potential profile and even bigger changes in flux, because potential is a sensitive function of charge and shielding, and flux is an exponential function of potential.

An Analysis of Interplanetary Space Radiation Exposure for Various Solar Cycles

The radiation dose received by crew members in interplanetary space is influenced by the stage of the solar cycle. Using the recently developed models of the galactic cosmic radiation (GCR) environment and the energy-dependent radiation transport code, we have calculated the dose at 0 and 5 cm water depth; using a computerized anatomical man (CAM) model, we have calculated the skin, eye and blood-forming organ (BFO) doses as a function of aluminum shielding for various solar minima and maxima between 1954 and 1989. These results show that the equivalent dose is within about 15% of the mean for the various solar minima (maxima). The maximum variation between solar minimum and maximum equivalent dose is about a factor of three. We have extended these calculations for the 1976-1977 solar minimum to five practical shielding geometries: Apollo Command Module, the least and most heavily shielded locations in the U.S. space shuttle mid-deck, center of the proposed Space Station Freedom cluster and sleeping compartment of the Skylab. These calculations, using the quality factor of ICRP 60, show that the average CAM BFO equivalent dose is 0.46 Sv/year. Based on an approach that takes fragmentation into account, we estimate a calculation uncertainty of 15% if the uncertainty in the quality factor is neglected.

Ionizing radiation exposure of LDEF (pre-recovery estimates).

The long duration exposure facility (LDEF), launched into a 258 nautical mile orbit with an inclination of 28.5 degrees, remained in space for nearly 6 yr. The 21,500 lb NASA satellite was one of the largest payloads ever deployed by the Space Shuttle. LDEF completed 32,422 orbits and carried 57 major experiments representing more than 200 investigators from 33 private companies, 21 universities and nine countries. The experiments covered a wide range of disciplines including basic science, electronics, optics, materials, structures and power and propulsion. A number of the experiments were specifically designed to measure the radiation environment. These experiments are of specific interest, since the LDEF orbit is essentially the same as that of the Space Station Freedom. Consequently, the radiation measurements on LDEF will play a significant role in the design of radiation shielding of the space station. The contributions of the various authors presented here attempt to predict the major aspects of the radiation exposure received by the various LDEF experiments and therefore should be helpful to investigators who are in the process of analyzing experiments which may have been affected by exposure to ionizing radiation. The paper discusses the various types and sources of ionizing radiation including cosmic rays, trapped particles (both protons and electrons) and secondary particles (including neutrons, spallation products and high-LET recoils), as well as doses and LET spectra as a function of shielding. Projections of the induced radioactivity of LDEF are also discussed.