In the present research, a series of experiment was carried out to comprehend the influence of water application on upward flame propagation of combustible material on vertical orientation. Particularly, water delivered density is main parameter of the experiments. The water spray (manufacturer: Ikeuchi corporation, model number: BBXP020) was installed at the opposite side of combustible wall (specimen). Water in tank was pumped up to the spray nozzle. 5 levels of water delivered density (0, 0.2, 0.4, 0.7 and 1.0 g/s/m²) were conducted. Thin flexible urethane foams (Width: 500mm ×Height: 1000mm×100mm thickness) were used as for specimen (combustible wall). And we also conducted another series of experiment to grasp the burning characteristics of the specimen by using Cone Calorimeter Test Apparatus before flame propagation experiments.

 From the results of these experiments, the following facts have been obtained.

 1. Specimen continued to spread upward even though water application had been activating. But flame propagate slower as increasing water delivered density.

 2. Pyrolysis front (height which specimen surface temperature reached pyrolysis temperature) increases exponentially with time regardless of water delivered density. But the value of power of regression equation decreases as increasing water delivered density.

 3. Flame height is directly proportional to heat release rate per unit width; and the constants of proportionality are almost the same regardless water delivered density.

 4. According to the flame propagation theory which is supposed in the previous researches, the value of power of exponential regression γ depends on heat release rate per unit area and ignition time of combustible wall. On the other hand, according to another research, heat release rate per unit area and ignition time under the condition that water applications are activating can be estimated by the models which are based on the heat balance of combustible material surface corresponding to incident heat flux and cooling effect by water. Therefore, we calculated the value of γ using the estimated heat release rate per unit area and ignition time and compared the value of experimental data. From the results, estimated values are approximately the same as experimental results.

 Building Standard Law of Japan (BSL) requires buildings to maintain certain fire safety performance for preventing building-to-building fire spread in urban area. The level of requirement specified in BSL changes with site location, total floor area, and number of floors of the target building in a prescriptive manner. In this study, a performance-based method is proposed for verifying compatibility of fire spread prevention performance of buildings with that required by BSL. The criteria adopted for verification is the risk of fire spread: fire spread prevention performance of the target building is judged as compatible with the required level if the risk of the target building relative to that of the reference building designed under the prescriptive regulation is equal to or smaller than unity.

 Squared value of radiant heat flux passing through the site boundary is used as the risk index that represents the magnitude of fire hazard. However, for the enhancement of lucidity of the risk index, the magnitude of fire hazard is transformed into the fire spread resistive time, which congruently represents the fire spread prevention performance of the target building, by using the theoretical relationship between the time required for an infinitely thick material to get ignited and the external radiant heat. With the transformed risk index, fire spread prevention performance of the target building is judged as compatible with the required level if the fire spread resistive time of the target building relative to that of the reference building designed under the prescriptive regulation is equal to or greater than unity.

 In the proposed method, fire spread resistive time of a fire compartment comprising the target building is evaluated by the event-tree analysis in which the probability for a fire compartment to become a fire source to its adjacent is considered as the probability of successive occurrence of comprising events, i.e., ignition, flashover, and burn-through of compartment boundaries. Probability of each event is formulated as a function of the fire spread resistive time of component building members and equivalent fire duration time inside of the fire compartment. The overall fire spread resistive time of the target building is obtained by the exterior wall length-weighted harmonic average of those of individual fire compartments.

 As a case study, the proposed method is used to evaluate fire spread prevention performance of a building, which heavily use wooden building members and furnishings in the internal space. The result showed that there are several combinations of design options such as the reinforcement of exterior materials, compartmentation, or installation of sprinkler systems that enables the building to maintain equivalent level of requirement in terms of the fire spread risk. Among the design options tested, compartmentation that fragments internal space into several smaller fire compartments was most effective in reducing the fire spread risk of the building. Installation of sprinkler system was also effective, but limited to the internal fire scenario among the two fire scenarios assumed.

 Sound insulation between adjacent houses is one of the fundamental factors in the indoor environmental performance of apartment houses, and inspections are often carried out through level difference measurement at the completion stage of the buildings. Since the characteristics of sound fields due to room modes are considered to have strong influences on level differences at low frequencies, understanding sound transmission phenomenon including the factors due to sound fields is likely to lead to effective control of the sound insulation performance at sites.

 In the previous paper, the authors have proposed an experimental method for analyzing the characteristics of the incident sound fields in dwelling rooms under sound insulation measurement, and the method was validated in FE models. The aims of this paper are to validate the proposed method in actual rooms under sound insulation measurement and to investigate experimentally the influence of incident sound fields on the sound insulation between dwelling rooms using the proposed method.

 In the experiment, the proposed method was applied to test rooms separated by an RC wall, where the source rooms were arranged to three different planar geometries using removable partitions. The RC wall was first tested without lining (RC single wall) and then with additional linings (composite wall).

 First, the proposed method was validated through reconstruction of SPL from decomposed sound fields and evaluation of incident directivities.

 Next, sound field analysis using the proposed method was performed in the test rooms along with level difference measurement to investigate the relation between the incident sound field and the sound insulation characteristics. The measured results of level difference D and sound reduction index R for the RC single wall and the composite wall demonstrated that the variation of the incident sound fields due to room geometry affects the sound insulation characteristics at low frequencies. The results of the sound field analysis showed that the transmitted power at low frequencies for the RC single wall is influenced by the matching of the modes between the source and receiving room, particularly by the proximity of the modes close to the normal direction to the wall.

 Furthermore, the sound insulation performance of the composite wall was broken down into sound reduction index R for the RC wall without additional lining and sound reduction improvement index ΔR by the additional lining to clarify the influence of incident characteristics. To analyze the influential factors on ΔR, the oblique incidence absorption coefficients of the composite wall were obtained using the proposed method. The result exhibited the influence of the matching between the incident characteristics and the oblique incidence resonance frequency f(θ) of the wall on the low frequency resonance transmission, suggesting a possibility that strong normal incident power in the frequency range near the normal resonance frequency of the composite wall leads to a decrease in ΔR.

 It is vitally important to estimate visibilities of all visual targets in real environments to maintain visual safety. As luminous color images in real lit environments are relatively easily obtained, it is reasonable to attempt to establish a method to estimate visibilities of objects using these images.

 Authors have proposed C (luminance contrast) -A (adaptation luminance) graph which can estimate visibilities from luminance images using contrast profile method. In other previous studies, authors have proposed a method to analyze effects of color on visibility using XYZ stimulus values and L*a*b* color space. In addition, authors have conducted visibility evaluation experiments using circular objects, varying luminance and chromaticity for common, protan, and deutan color vision type people. Experiment results were analyzed using CIE 1931 xy chromaticity diagram and aC (red-green contrast) - bC (yellow-blue contrast) graph. Experiment results of common, protan, and deutan types were compared respectively and characteristics of each type were acquired. These characteristics are caused by differences in functions of LMS cone cells on the retina among color vision types. In this study, these experiment results were expressed in contrasts of LMS stimulus values which is based on responses of LMS cone cells and the visibility estimation method was considered expecting implementations in color universal design.

 First, XYZ stimulus values of the background and circular targets were converted to LMS stimulus values and LMS stimulus value contrasts were calculated. When the distribution of “invisible” stimuli for common type was expressed on the plane where LCC (L contrast) was represented in horizontal axis, MCC (M contrast) in vertical axis, and SCC (S contrast) was from -0.10 to 0.10, the slope was almost 1. However, the distribution of “invisible” stimuli for the protan type was elongated along LCC axis, and the distribution of “invisible” stimuli for the deutan type was elongated along MCC axis. Using these results, four vertices on the LCC-MCC plane (SCC≒0) were set for each distributions and the visibility threshold estimation method was established. It expresses of “invisible” stimuli as rhombus-like quadrangles. Sizes and angles of quadrangle diagonals differ depending on color vision types. As described above, visibility estimation method expecting to achieve color universal design was established.

 Furthermore, visibilities of red visual objects were estimated from the luminous color images of real lit environments using proposed the visibility estimation method. As it was suggested that it is the possible to estimate visibilities from ratios of visibility threshold luminance contrasts in the previous study of authors, it may also be possible to assume that it is possible to estimate visibilities from ratios of visibility thresholds of contrasts of LMS stimulus values. Based on contrast profile method, and by adjusting detection size and point in order to achieve the maximum aC value, contrast values were obtained for each images. The visibility was estimated from LCC, MCC, and SCC values using the proposed method. As a result, it was seen that the ratios of protan and deutan types were lower than the ratio of common types. For red visual objects, it was estimated that visibility of object is low and unsafe for protan or deutan type people.

 In this study, experiment results of previous studies were shown as contrast of LMS stimulus values, and visibility estimation method expecting to achieve color universal design was established. Furthermore, visibility estimations using the proposed method and luminous color image were conducted. It was confirmed that the method is useful for achieving color universal design.

 Introduction

 Recently, highly insulated housings are increasing nationwide. Especially in Hokkaido, the development of wooden high insulated housing has been developed from the early days. The number of those housing supplied to the market was growing after the 1980s. Nowadays, those housings are renovating. It is a good opportunity to observe how various methods have influenced insulation performance and deterioration. The purpose of this research is to give insight into distribution of second-hand housing. We analyzed insulation performance such as Q-value and air-tightness of the housings with entire insulation renovation and the existing housings in Hokkaido.

 Methods

 First, we conducted a questionnaire survey. The target housings are 51 housings (Hoppougata-Jyutaku) built in Asahikawa city, Sapporo city (Kita-ku, Toyohira-ku), Kitahiroshima city in the 1990s. Next, we conducted an inspection of the target housings. The target housings consist of 13 renovated houses (a1-a13) in Sapporo city, Kitahiroshima city, Tomakomai city and 17 existing houses in Sarufutsu town, Shimokawa town, Asahikawa city, Sapporo city and Takasu town (b1-b17).

 Summary

 1) The most frequent renovation was "painting or replacement the outer wall and roof." Also, there were many answers which conducted "replacement of heating and hot-water supply equipment at the same time."

 2) About C-value of renovated housings, the RMSE of C-value was 0.56 cm²/m² and the average absolute error rate was 43%. The C-value in the inspection, about ten years after renovation, were higher than the values just after renovation in many houses, and the airtightness was somewhat deteriorated. However, in most housings, no significant deterioration of the air-tightness was confirmed even after ten years from the renovation. It was confirmed that the performance can be maintained when wooden houses are adequately insulated and repaired.

 About C-value of existing housings, those can be classified into the values under 2.0 that provide sufficient air-tightness compared with new houses and the values over 3.5 that not provide enough air-tightness. There were deteriorations such as moisture problem, dew, and fungi when the air-tightness was not enough.

 3) About the Q-value, the average error between calculation values and measurement value was 0.32 W/m²K, and the average reliable section width was 0.36 W/m²K. Also, 36.4% of calculated values were within the reliable section, and few housings were below the calculation values. In the future, it is predicted that more reliable values can be calculated by conducting detailed examination of the heating area.

 4) In this report, the housings with entire insulation renovation, the deterioration of insulation performance was hardly confirmed. However, in the case of cold climate areas, there is the possibility of deterioration in partial insulation renovation. Therefore, we will consider the finance system to achieve full insulation renovation, not partial renovation in the future.

 In this study, field surveys in actual bedrooms in summer and winter were conducted with the purpose of verifying that the evaluation of the thermal environment in bedrooms by calculating the human heat load on the human body is effective in different seasons. The measurements were undertaken in two seasons; the summer period was July, August and September of 2017 and 2018, the winter period was December of 2017, and January and February of 2018. In the calculation of the human heat load, the actual basal metabolic rate of the subjects was substituted for the metabolic rate in formula proposed by Akiyama et al. during sleep. The quality of sleep was evaluated based on the physiological parameter during the sleeping period, including sleep stage, by measuring the electroencephalogram, electrooculogram, and electromyogram and the subjective sleeping feeling at the time of waking up. We evaluated that sleep quality was good as there were more appearances of deep sleep and less appearances of wake time. Also, OSA sleep inventory was used for subjective evaluation of the sleeping feeling.

 Since the relation between human heat load and percentage of sleep stages in winter was similar to that in summer, it was shown that the evaluation of the thermal environment in bedrooms due to human heat load may be effective even in different seasons. In both seasons, the colder environment when the human body thermal load is smaller than 0 W / m² decreased the quality of sleeping, but it tended to be different in warm environments when the human heat load was greater than 0 W / m² ; especially around 45 minutes after turning over, there was a tendency that the percentages of stage wake, REM sleep, and shallow sleep are the smallest and the percentage of deeper sleep is the largest in the vicinity of the steady state where the heat loss to the bedding from the human body is nearly 0 W / m².

 The value after sleep onset immediately was taken as the initial value, and the heat radiation amount or endotherm amount added every 30 seconds was calculated as ΣL_m. The closer the ΣL_m is to 0 kJ/m² the higher the percentage of deep sleep. That is, the quality of sleep tended to be improved in the state where the heat radiation amount and the endotherm amount were about the same.

 It is known that deep sleep appears longer during the initial part of 90 minutes after sleep onset, and the sleep becomes shallow in the latter part of sleep. In this study, the deep sleep time overnight tended to be longer when a longer deep sleep time was obtained within 90 minutes after sleep onset. In addition, the longer the deep sleeping time in one night, the more the subjective feeling of sleep when waking up tended to be improved. Therefore, in this study, it was shown that, in order to improve the quality of sleep, it is important to keep the body posture in the bed long in a low-humidity and warm environment because the heat flow to the bedding from the human body continues in the steady state quantitatively. Finally, it was shown that it is important to get a longer deep sleeping time from both viewpoints of physiological evaluation and psychological evaluation for sleep.

 In this study, experiments were carried out on working at desks in the summer to clarify the relationship between temperature and air flow control, work efficiency, psychology, and physiology. This was done by evaluating the air flow environment, work efficiency, psychology, and physiological volume by controlling the vertical temperature difference. The participants were young people in their 20s (five males and five females). In previous studies, although the influence of upper and lower temperature boundaries and an extreme temperature difference on work efficiency is obvious, it is unsuitable for a real environment. To improve feasibility, we evaluated the effectiveness of the upper and lower temperature boundaries recommended by ASHRAE within 3 °C and the local airflow effect in an environment where the humidity was below 50%.

 In summer, while performing information processing work, males exhibited high scores for the condition of “keeping the head warm and the feet cool, ” while females had high localized air flow status scores. While performing intellectual work, males scored higher “keeping the head cool and the feet warm” scores but it did not differ significantly among them; females had a higher score for the condition of “keeping the head warm and the feet cool.” In relation to physiology, for males, the heart rate was low in conditions when the scores for the intellectual production work task was high, and the blinking rate of eyes was low when the score of information processing task was high. In females, the pupil diameter shrank in conditions when the score of the information processing task was high, and there was no significant influence in conditions when the score of the intellectual production work task was high. For males performing information processing work, the higher the comfort of the lower body, the higher the scores. For females, a higher score implied that their the lower body was uncomfortable. In this case, the sense of tension increased owing to the increasing discomfort; this “awakening effect” was considered to affect the results. A comparison of participants wearing contact lenses with those using the naked eye during intellectual work showed that the former increased their blinking rate in conditions of upper airflow. The feeling of dryness in the eyes was predicted to increase when wearing contact lenses; this was believed to have a greater influence on blinking with an increase in air flow.

 Based on the logistical analysis results, for information processing work, males were greatly influenced by the differences in the upper and lower temperature boundaries, whereas females were more influenced by local air flow. For intellectual work, males were more affected by their heart rate, and females were more influenced by the differences in the upper and lower temperature boundaries.

 In this study of work productivity in the summer, conditions under which the temperature in the upper and lower zones varied within 3 °C (i.e., when the upper zone had a temperature of 25 °C, the lower zone had a temperature of 28 °C, and vice versa), conditions of uniform temperature in the upper and lower zones, and conditions with upper or lower local air flows were verified. As a result, it was confirmed that the environment and physiology affect intellectual productivity and work performance. Based on practical applicability, it is predicted that the method of using air conditioning to advance automatic control will progress over time.

 There are various indexes to evaluate daylighting performance such as Daylight Factor (DF) and Daylight Autonomy. Moreover, space brightness affected by light reflection on walls and a ceiling is becoming popular to evaluate indoor light environment, while the conventional indexes focus on virtual horizontal surface at the desktop height. These trends must affect optimal opening placements to maximize the active usage of daylight. In this paper, the influences are investigated by dynamic daylighting simulations. First, a case study using a model with clear glass windows is performed to check the influence. As it is known, ribbon window at high position becomes the optimal one when the conventional index such as DF and uniformity that evaluate daylight on the virtual surface at the desktop height is used. On the other hand, the optimal placements become relatively low height when luminous radiance as an index related to space brightness is used. Moreover, lower aspect windows located at the center of façade is selected as the optimal one, because lower positioned and centralized opening is effective to enlighten the inner walls and the ceiling. It indicates that the ribbon windows at high position that is generally recognized as the best window placement for daylighting design is not the absolute solution when the evaluation index is gaining its diversity. In case that Daylight Autonomy is used, the optimal solution becomes similar with those using DF and uniformity. The uniformity is controlled by the selected luminance threshold.

 Next, a case study using a model with diffusing glass windows is performed to check the influence how the window optical properties affect the optimal placements. The trend, that the window position and the aspect ratio become lower when space brightness is used as the evaluation index, is more significant. Sunlight is widened when it goes through the window with diffusing transmittance property, and it produces sunlight with upward vector. These diffused sunlight is useful to enlighten the inner walls and the ceiling.

 These results are expected to contribute accumulating knowledge to check the adequacy of outputs analyzed by daylighting simulation. For example, another case study using a combination of clear glass windows and translucent panels with diffusing transmittance property is performed. This case study is simulating a façade design utilizing translucent wall that could be realized by using transparent thermal insulation materials such as aerogels. In the optimal solution, the translucent panels are set at the lower part of the clear glass windows. The reason is fully explained above mentioned knowledge accumulated by this study.

 Daylighting simulation is becoming more popular for advanced façade design for sustainable building designs. However, it is too troublesome to carry out an enormous trials to check all design possibilities to search for the optimal solution. Then, it requires a black boxed optimization algorithm to lead the solution efficiently. To check the adequacy of the selected solution, more knowledge like this study lead should be continuously accumulated.

 The proposed air-conditioning system with under-floor chambers utilizes the under-floor to circulate the supply air throughout the house. Thus, thermal simulations for this system differ from those for conventional systems, and require innovative investigation of the relevant simulation techniques. Below is a summary of the proposed system’s simulation techniques, based on the analyzed thermal and air-flow characteristics in the under-floor. The validity of the simulations utilizing these techniques was confirmed through empirical comparison with the measurements for the full-scale single-room test unit (part of a larger dwelling) in Parts1 and 2 of this study.

 (1) The under-floor chambers are divided so as to reproduce the air flow and temperature distribution in the chambers, which is generated by the location of air inlets and outlets.

 (2) Since the thermal characteristics of the under-floor chambers depends on the temperature of the air supplied to the under-floor, the temperature of the supply air (i.e., the temperature of the air-conditioning room) is set every hour.

 (3) The convective heat transfer coefficient in the floor chambers is set responsively, in order to reproduce the differences between the upper and lower surfaces in both heating and cooling.

 The existing detached house differed from the full-scale test unit in being constituted of multiple rooms and in the influence of the outside conditions. For this reason, to create a methodology for designing the relevant system, it was necessary to independently confirm the validity of the simulations utilizing the proposed techniques, in the case of a detached house. The simulations inputted the detached-house specifications, and employed original weather data calculated from measurements conducted for three cases (Calc. 1-3). The results were then compared to the measurements in Part 4 of this study, which focused on a detached house.

 In Calc. 1, the standard case for this simulation, the under-floor chambers were divided such that the calculation was not complicated, the temperature of the air-conditioning room was adjusted hourly based on empirical measurements and the convective heat transfer coefficient in the floor chambers was set at values calculated by the method developed in Parts1 and 2 of this study. The conditions in Calc. 2 and Calc. 3 were identical to those of Calc. 1, with the following exceptions: in Calc. 2, the convective heat transfer coefficient was uniformly set at 2.0 W/(m²·K); in the Calc. 3, the temperature of the air-conditioning room was uniformly set at 24°C in the heating period and 26°C in the cooling period.

 The results of the simulations were compared during the heating, cooling and intermediate periods. Calc. 1 and 2 were in good agreement with the measurement results. Therefore, the simulation was validated even for an existing detached house, and it was clear that simplification in setting the convective heat transfer coefficients had a profound influence on the simulation results. In Calc. 3, since the temperature of the air-conditioner room was fixed, the air-conditioner operating conditions were not consistent with actual usage; thus, the simulation and measurement results differed.

 In the case of annual thermal-load estimation not involving an existing detached house, it is impossible to measure the temperature of the supply air, or configure the operating conditions of the air conditioner in advance. Therefore, an effective method for setting the temperature of the supply air, based on reasonable assumptions, is required (as in Calc. 3); and for this, further study is needed.

 In Japan, a unified system to measure environmental loads in administrative areas has not been officially established for environmental accounting at the local government level. As a consequence, environmental accounting has not been adopted by local governments as widely as private companies.

 Life cycle impact assessment (LCIA) is one aspect of research in the field of life-cycle assessment, whereby environmental loads throughout the life cycle of products and services are measured in a quantitative way. Research in which environmental loads are determined according to geographic location has become more and more important. This study therefore focused on Japanese minimum administrative divisions (municipalities) and attempted to quantify the annual environmental loads emitted within each division in the year 2015 using the LCIA method. For this, this study leveraged the assessment theory Life-Cycle Impact Assessment Method Based on Endpoint Modeling 2 (LIME2). This method is able to calculate assessment results in monetary units called the “Eco-index Yen” (unit: Japanese yen) while integrating the environmental loads of several impact categories, such as “Global warming” and “Land use”, based on environmental conditions and knowledge unique to Japan.

 Using statistical information that was reliable, verifiable, and comparable, the environmental damage amount for the whole of Japan was calculated to be 8.53 trillion yen. The top five amounts were “Global warming” (2.82 trillion yen), “Land use” (2.33 trillion yen), “Waste (domestic)” (1.24 trillion yen), “Biological toxicity” (0.63 trillion yen), and “Atmospheric pollution” (0.61 trillion yen). When the damage amounts were divided by the population of each municipality, the average amount per capita for all Japanese municipalities was calculated to be 67,100 yen per capita (population-weighted average). These damage amounts per capita were placed on a map of Japan according to type of impact category and type of business to visualize the regionality of environmental loads nationwide. The values for “Global warming” and “Land use” tended to be lower in the central parts of large urban areas, and the values for “Global warming” and “Atmospheric pollution” tended to be higher in areas where industries are concentrated. The values for “Primary industries” (which include agriculture) as well as “Manufacturing” were particularly indicative of local industrial activity. Tendencies related to population distribution and industrial activity were easy to see from the map.

 Next, standard deviation and variation coefficient for the damage amounts per capita were calculated for each region in order to statistically capture the disparities of environmental loads according to impact category and type of business. The disparities of environmental loads that were deeply related to housing, such as “Waste (domestic)” and “Land use”, tended to be narrow among municipalities whereas disparities for “Manufacturing” were particularly wide because manufacturers are concentrated in certain parts of the country. From these results, this study revealed Japanese environmental impacts from the perspective of several categories, thus providing information useful for making decisions about environmental policies.

 The authors aim to establish a method for predicting radiation environment and facilitating architectural measures to reduce the radiation space dose rate in a building prior to the construction of a new building in the area affected by the nuclear power plant accident. In order to clarify the formation mechanism of the dose rate distribution in the building, in situ measurement of gamma ray incidence characteristics on the outer wall is necessary. Several methods for directional radiation measurement have been proposed in the past; however, there are no measuring instruments perfectly suited for this purpose. This paper reports a directional gamma ray measurement instrument developed by the authors.

 In this study, the authors developed a directional radiation air dose rate measuring instrument using a lead shielding disk against gamma rays from radionuclide 137Cs which is dominant in the affected area. Prior to the development of the instrument, two kinds of directional radiation measuring methods intended for field survey were examined. One method is shielding the radiation by a cylindrical collimator excluding a specific direction of a scintillator (Fig. 2), and the other method is obtaining the difference by subtracting the measurement result with lead disk shielding a specific direction, from the measurement result without shielding (Fig. 3, 4). Matters taken into account in the selection of a method include the configuration of the instrument consisting of a 3 × 3φ inch NaI (Tl) scintillator and a lead shield, the instrument’s viewing angle, sensitivity cutoff performance and weight. In this research, the emphasis is placed on the ease of handling in the field measurement, thus the latter method was chosen which is easy to realize good cutoff performance with a lightweight shield although measuring errors possibly occur due to the radiation from outside of the viewing angle.

 Since the viewing angle of the directional radiation is determined by the shielding disk diameter D and the distance L between the disk and the scintillator, the combinations of D and L were investigated using the radiation analysis code PHITS by JAEA.

 The authors defined the equivalent viewing angle φeq and the ratio of sensitivity concentration RC to evaluate the combination of D and L. When the integrated value of the directional sensitivity of a certain combination is the same as the ideal viewing angle φ, the viewing angle of the combination is defined as the equivalent viewing angle φeq. The coefficient RC is the ratio of integrated sensitivity within the angle φeq to the total sensitivity, and the sharpness of sensitivity cutoff near the viewing angle was evaluated. Using these coefficients, the characteristics based on some combinations of D and L were compared and studied. We designed D and L to make viewing angle +/- 45 °. Finally, the lead shielding disk of 150 mm diameter and 50 mm thickness was selected and placed with the scintillator 35 mm apart, realizing the equivalent viewing angle φeq to be +/- 45 °. In order to verify the validity of the designed measuring instrument, experiments were carried out using a 137Cs point source and the actual measuring instrument, confirming good agreement between the PHITS analysis and the experimental results.