Nuclear Power Plant Site Research Articles

Study Plans Concerning Monetary Evaluation of Mitigation Measures for the Fukushima Daiichi Accident

The Fukushima Daiichi accident raises various kinds of social unease in Japan. Especially, unease for radioactive contamination around the Fukushima Daiichi plant is serious. Also, around the other nuclear power plants, local residents would feel unease for a similar accident in the future. Although the government and the electric power companies have already implemented or plan to implement several measures to mitigate such unease, it is difficult to progress their policies effectively because the effect of each measure is not quantitatively clarified. The purpose of our research is to evaluate these effects by analyzing fluctuations in local property values and local residents economic welfare, which are monetary indexes reflecting the social unease, to construct information that is useful to plan an optimal package of mitigation measures in each nuclear power plant site from the viewpoint of cost-benefit analysis. In this paper, we explain the immediate plans of this research and its academic and political contributions.

原子力サイトにおける2011 東北地震津波の検証

東北地方太平洋沖地震による津波は、福島第一原子力発電所の過酷事故をもたらした。同地震による津波の発生メカニズムを分析し、津波波源モデルのすべり量を推定した上で、地震動記録に基づく震源断層モデルのすべり量との比較検証を行った。両モデル共に大きなすべりが日本海溝付近に集中して分布することを示した。さらに、同波源モデルを用いた原子力サイト等での観測津波の再現解析を行うと共に、日本海溝付近の浅い部分での津波地震のすべりや震源破壊の時間差及び津波伝播における時間遅れ等が同サイトでの津波高に大きな影響を及ぼす要因であることを明らかにした。

Review of Characteristics of Post-Accident Waste Generated in Fukushima Daiichi Nuclear Power Plant Site and Issues to be Addressed in Processing and Disposal Stages

Review of Characteristics of Post-Accident Waste Generated in Fukushima Daiichi Nuclear Power Plant Site and Issues to be Addressed in Processing and Disposal Stages The accident at Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station has produced and will continue to produce various types and large amounts of waste contaminated by radionuclides. The literature and published internet information on possible types of waste produced are reviewed from the viewpoint of their characteristics. Issues associated with the waste were selected and analyzed for each stage of the future waste management, considering the characteristics and properties of the waste obtained so far. The stages considered are current (temporary) storage, processing including decontamination and solidification/packaging, storage up to disposal, transportation, and disposal.

Codes on the Safety of Nuclear Power Plants in Relation to Seismic Design

Study on the nuclear Safety laws and regulations, and good grasp of relevant definitions are essential prerequisites for Seismic and geologic siting of nuclear power plants. It can be too strongly emphasized that laws or decrees of issue by government and legislature have profound mandatory binding force. The guides and regulations related nuclear safety belong to directing documents of the specific rules, they have not been mandatory in the law significance, and allow some adaptability to a certain degree. Professionally technical specification is merely the inherent stipulations, besides; it must meet the codes demands in the concrete practice. Finally, the assessment of the capability for surface faulting at nuclear power plant sites belongs to the mandatory claims but not in assessment of active fault.

MODULUS REDUCTION AND DAMPING CURVES FOR SAND OF SOUTH-EAST COAST OF INDIA

Adequate information on dynamic soil properties, especially strain dependent shear modulus (G) and damping ratio (ξ) for each soil layer are the essential input data for seismic ground response analysis and soil-structure interaction studies. In the present study, the shear modulus and damping ratio of sand are estimated for a wide range of strains based on undrained strain-controlled cyclic triaxial tests. The bender elements are also utilized in the cyclic triaxial test to estimate the low strain shear modulus. For this purpose, the soil samples are taken from a nuclear power plant site located at the south-east coastal region of India. Based on the experimental results, an empirical expression is developed to calculate the maximum shear modulus, Gmaxas function of void ratio and effective confining stress. Predictive relationships are also developed for estimating normalized shear modulus and damping ratio curves for the sand. The predictive relationships are based on the hyperbolic model and cyclic triaxial test results. The developed modulus reduction and damping ratio curves from the predictive relationships are compared with the previously available curves in the literature.

Preferential Groundwater Flow Pathways and Hydroperiod Alterations Indicated by Georectified Lineaments and Sinkholes at Proposed Karst Nuclear Power Plant and Mine Sites

Sustainable development of any type that utilizes water or involves excavations in karst aquifer systems, such as the regional Floridan aquifer system (FAS), requires knowledge of preferential groundwater flow pathways that can extend adverse impacts beyond the development site and alter natural hydroperiods. Such pathways include fractures and other types of karst conduits that are associated with modern and relict sinkholes. Developments, including power plants and mines, that have not accounted for these features have caused induced recharge, altered hydroperiods and saltwater intrusion in the FAS, resulting in destruction of wetlands and adverse impacts to other surface waters, wildlife habitat and threatened and endangered species. This study analyzed indicators of preferential groundwater flow by considering surface expressions of underlying geological conditions (lineaments and modern sinkholes) in the FAS, which coincide with the United States southeastern coastal plain. Lineament mapping by Vernon (1951) and the Florida Department of Transportation (FDOT, 1973), incorporating analog mapping techniques and hardcopy prints of satellite imagery, preceded extensive urbanization, groundwater extractions, and mining in the region. All of these alterations limit the ability to identify fractures using lineaments by reducing groundwater discharges and vegetation indicative of those discharges. In this study, established methods for georectification, including control-point identification and spatial matching of scanned maps and remotely sensed images, were applied to these previously mapped lineaments. These results were applied to the environmentally sensitive karst study area of Citrus and Levy Counties, Florida in the southern extent of the FAS. Geospatial analyses of lineament distribution and modern sinkhole locations from the state database showed a dense network of lineaments with associated sinkholes throughout the study area and seven surrounding counties, including the proposed sites for a nuclear power plant and two mines in Levy County. Proposed excavations and water use for construction and operation of the power plant and mines would result in irreversible adverse environmental impacts on extensive depressional wetlands beyond the surface-footprint impact of these developments via these preferential flow pathways that were not evaluated during the review process.

Copula-Based Statistical Health Grade System Against Mechanical Faults of Power Transformers

A health grade system against mechanical faults of power transformers has been little investigated compared to those for chemical and electrical faults. This paper thus presents a statistical health grade system against mechanical faults in power transformers used in nuclear powerplant sites where the mechanical joints and/or parts are the ones used for constraining transformer cores. Two health metrics-RMS and root mean square deviation of spectral responses at harmonic frequencies-are first defined using vibration signals acquired via insite sensors on 54 power transformers in several nuclear powerplants in 16 months. We then investigate a novel multivariate statistical model, namely copula, to statistically model the populated data of the health metrics. The preliminary study shows that the proposed health metrics and statistical health grade system are feasible to monitor and predict the health condition of the mechanical faults in the power transformers.

Study on Vertical Motions by Rocking Responses of Reactor Buildings

Earthquake observation records were observed in reactor buildings of Kashiwazaki-Kariwa Nuclear Power Plant Site during the Niigata-ken Chuetsu-oki earthquake in 2007 (NCO). Some studies on the seismic response and simulation analyses were performed to investigate dynamic characteristics of the structures. In particular, it was clarified that the vertical motions of the reactor building of Unit 6 were greater than those of adjacent reactor buildings of Unit 5 and Unit 7. This paper discusses the causes of this by earthquake observation records and simulation analyses of the reactor buildings. In general, seismic response of vertical motions is relatively well-simulated using lumped mass model with stick elements that have vertical stiffness and with the soil spring between the basemat and support ground. However, vertical motions are influenced by rocking motions with horizontal response in some cases. This paper focuses on relationships between the vertical responses and the vertical motions induced by the rocking motions with simulation analyses and observation records during both NCO earthquake and aftershock of NCO. The reasons why the vertical motions of the reactor building of Unit 6 were larger are discussed.

Statistical Health Grade System against Mechanical failures of Power Transformers

A health grade system against mechanical faults of power transformers has been little investigated compared to those for chemical and electrical faults. This paper thus presents a statistical health grade system against mechanical faults in power transformers used in nuclear power plant sites where the mechanical joints and/or parts are the ones used for constraining transformer cores. Two health metrics—root mean square (RMS) and root mean square deviation (RMSD) of spectral responses at harmonic frequencies—are first defined using vibration signals acquired via in-site sensors on fifty-four power transformers in several nuclear power plants in sixteen months. We then investigate a novel multivariate statistical model, namely copula, to statistically model the populated data of the health metrics. The preliminary study shows that the proposed health metrics and statistical health grade system are feasible to monitor and predict the health condition of the mechanical faults in the power transformers.

Ice Thermal Storage Systems for Nuclear Power Plant Supplemental Cooling and Peak Power Shifting

Availability of cooling water has been one of the major issues in the selection of nuclear power plant sites. Cooling water issues have frequently disrupted the normal operation at some nuclear power plants during heat waves and long droughts. One potential solution is to use ice thermal storage (ITS) systems that reduce cooling water requirements and boost the plants’ thermal efficiency in hot hours. The ITS uses cheap off-peak electricity to make ice and uses the ice for supplemental cooling during peak demand time. The ITS also provides a way to shift a large amount of electricity from off-peak time to peak time. For once-through cooling plants near a limited water body, adding ITS can bring significant economic benefits and avoid forced derating and shutdown during extremely hot weather. For the new plants using dry cooling towers, adding the ITS systems can effectively reduce the efficiency loss during hot weather so that new plants could be considered in regions with a lack of cooling water. This paper will review light water reactor cooling issues and present the feasibility study results.

Detection of low level gaseous releases and dose evaluation from continuous gamma dose measurements using a wavelet transformation technique

Measurement of environmental dose in the vicinity of a nuclear power plant site (Tarapur, India) is carried out continuously for the years 2007–2010 and attempts have been made to quantify the additional contributions from nuclear power plants over natural background by segregating the background fluctuations from the events due to plume passage using a non-decimated wavelet approach. A conservative estimate obtained using wavelet based analysis has shown a maximum annual dose of 38μSv in a year at 1.6km and 4.8μSv at 10km from the installation. The detected events within a year are in good agreement with the month wise wind-rose profile indicating reliability of the algorithm for proper detection of an event from the continuous dose rate measurements. The results were validated with the dispersion model dose predictions using the source term from routine monitoring data and meteorological parameters.

Probability-based PGA estimations using the double-lognormal distribution: Including site-specific seismic hazard analysis for four sites in Taiwan

This study develops a probabilistic approach for examining site-specific seismic hazards using data from 438 Mw≥5.5 earthquakes and attenuation relationships local to the region around Taiwan. These are combined to generate semi-observed peak ground accelerations, in a form which can be modeled by a double-lognormal distribution. This model, which satisfies statistical goodness-of-fit, provides the relationship between the exceedance probability and a given ground motion level. The study includes site-specific seismic hazard analysis for four nuclear power plant sites in Taiwan. The results show that the seismic hazards at the four sites are not the same. While no seismic hazard analysis is without challenge, a troublesome trend appears that many applications of decision making are being influenced by the complexity of the calculation, instead of how well the fundamentals of the analysis are understood and can be verified. The study provides an analysis which is not overly complicated, is in good agreement with an empirical control, and offers transparency, traceability, and verifiability.

Assessment of Liquefaction Potential Index Using Deterministic and Probabilistic Approaches

Liquefaction is a devastating effect of earthquakes resulting in sudden decrease in shear strength due to excess pore water pressure generation, resulting in differential settlement of structure, inducing severe damages. Assessment of liquefaction hazard for a given site is important for planning out mitigation works. In this paper the liquefaction susceptibility using deterministic and probabilistic methodologies was assessed and results are presented in terms of liquefaction potential index (LPI) for a nuclear power plant site. The results of this study are explored further in the article.

암반 지반의 재해도 스펙트럼에 기반한 토사지반 원전 부지의 등재해도 스펙트럼 평가 기법

암반지반에 주어진 등재해도 스펙트럼에 상응하는 원전부지 토사지반에서의 등재해도 스펙트럼을 도출하기 위한 확률론적 방법론을 제시하였다. 이를 위해 지진 운동 및 지반의 불확실성을 고려한 지반응답 해석을 통해 토사지반 지표에서의 지진동 증폭계수를 산정하였다. 증폭계수는 가장 상관관계가 높은 지반운동의 스펙트럴 가속도 규모와의 회귀분석을 통해 계산되었다. 이 방법론을 적용하여 국내 KNGR (Korean Next Generation Reactor) 및 APR1400 (Advanced Power Reactor 1400) 원전의 포괄부지 지반 중 B1, B4, C1 및 C3 지반을 대상으로 등재해도 스펙트럼을 도출하였다. 등재해도 스펙트럼을 통해 지진동 발생 빈도 별 위험 주파수 대역을 평가하고 분석하였다. 이 결과는 원전의 종합적 지진리스크 평가 결과를 보다 합리적으로 개선하는 데에 활용될 수 있으며, 향후 다양한 종류의 토사지반에 대한 등재해도 스펙트럼을 평가하는 데에 적용할 수 있을 것으로 기대된다. We propose a probabilistic method to evaluate the uniform hazard spectra (UHS) of the soil of nuclear power plant(NPP) sites corresponding to that of a bedrock site. To do this, amplification factors on the surface of soil sites were estimated through site response analysis while considering the uncertainty in the earthquake ground motion and soil deposit characteristics. The amplification factors were calculated by regression analysis with spectral acceleration because these two factors are mostly correlated. The proposed method was applied to the evaluation of UHS for the KNGR (Korean Next Generation Reactor) and the APR1400 (Advanced Power Reactor 1400) nuclear power plant sites of B1, B4, C1 and C3. The most dominant frequency range with respect to the annual frequency of earthquakes was evaluated from the UHS analysis. It can be expected that the proposed method will improve the results of integrated risk assessments of NPPs rationally. We expect also that the proposed method will be applied to the evaluation of the UHS and of many other kinds of soil sites.

Determination of thorium concentrations in soil and sand samples using instrumental neutron activation analysis

Thorium along with its daughter products present in the soil is one of the major contributors to the external gamma dose in the environment. To establish the dose levels, quantification of thorium contents in soil samples is very important. As a part of pre-operational environmental radiological surveillance, a total of 23 soil and six sand samples were collected from different locations around the proposed nuclear power plant site of Jaitapur, Maharashtra. Thorium concentrations in these samples were determined by instrumental neutron activation analysis (INAA). Samples were irradiated with neutrons in Apsara reactor at a neutron flux of ~5 × 1011 cm−2 s−1 and radioactive assay was carried out using high resolution gamma ray spectrometry. Relative method of INAA was used for quantification of thorium utilizing 311.9 keV gamma ray of 233Pa, the daughter product of 233Th. The concentrations of thorium in the soil and sand samples were in the ranges of 4.0–18.8 and 1.2–6.2 mg kg−1 respectively.

Tomography of the 2011 Iwaki earthquake (M 7.0) and Fukushima nuclear power plant area

Abstract. High-resolution tomographic images of the crust and upper mantle in and around the area of the 2011 Iwaki earthquake (M 7.0) and the Fukushima nuclear power plant are determined by inverting a large number of high-quality arrival times with both the finite-frequency and ray tomography methods. The Iwaki earthquake and its aftershocks mainly occurred in a boundary zone with strong variations in seismic velocity and Poisson's ratio. Prominent low-velocity and high Poisson's ratio zones are revealed under the Iwaki source area and the Fukushima nuclear power plant, which may reflect fluids released from the dehydration of the subducting Pacific slab under Northeast Japan. The 2011 Tohoku-oki earthquake (Mw 9.0) caused static stress transfer in the overriding Okhotsk plate, resulting in the seismicity in the Iwaki source area that significantly increased immediately following the Tohoku-oki mainshock. Our results suggest that the Iwaki earthquake was triggered by the ascending fluids from the Pacific slab dehydration and the stress variation induced by the Tohoku-oki mainshock. The similar structures under the Iwaki source area and the Fukushima nuclear power plant suggest that the security of the nuclear power plant site should be strengthened to withstand potential large earthquakes in the future.

Probabilistic approach to modeling lava flow inundation: a lava flow hazard assessment for a nuclear facility in Armenia

Probabilistic modeling of lava flow hazard is a two-stage process. The first step is an estimation of the possible locations of future eruptive vents followed by an estimation of probable areas of inundation by lava flows issuing from these vents. We present a methodology using this two-stage approach to estimate lava flow hazard at a nuclear power plant site near Aragats, a Quaternary volcano in Armenia.

Stability Analysis of Shallow Stratum in Jiangshidi Nuclear Power Plant Site and its Surrounding Areas

The differential GPS navigation and positioning technique, multi-channel shallow seismic exploration and high resolution single channel seismic technique were used for the geophysical exploration of the shallow stratum in Jiangshidi nuclear power plant site and its surrounding areas. Based on seismic data post processing results, the seismic section interpretation was performed, combined with regional geological background, borehole data and shallow anatomy data. Five main seismic reflection surfaces were recognized by using seismic stratigraphic method, and eight breakpoints were found according to the active fault discrimination criteria. Then the distribution and activity characteristics of main faults were obtained. The results show that any fault and marked deformation in the quaternary sediments has not been observed in the range of 5 km away from Jiangshidi nuclear power plant site. So the stability analysis results of shallow stratum in target area can meet the requirement of nuclear power plant site selection code.

Accurate Measurement of Velocity and Acceleration of Seismic Vibrations near Nuclear Power Plants

Abstract In spite of all prerequisite geological study based precautions, the sites of nuclear power plants are also susceptible to seismic vibrations and their consequent effects. The effect of the ongoing nuclear tragedy in Japan caused by an earthquake and its consequent tsunami on March 11, 2011 is currently beyond contemplations. It has led to a rethinking on nuclear power stations by various governments around the world. Therefore, the prediction of location and time of large earthquakes has regained a great importance. The earth crust is made up of several wide, thin and rigid plates like blocks which are in constant motion with respect to each other. A series of vibrations on the earth surface are produced by the generation of elastic seismic waves due to sudden rupture within the plates during the release of accumulated strain energy. The range of frequency of seismic vibrations is from 0 to 10 Hz. However, there appears a large variation in magnitude, velocity and acceleration of these vibrations. The response of existing or conventional methods of measurement of seismic vibrations is very slow, which is of the order of tens of seconds. A systematic and high resolution measurement of velocity and acceleration of these vibrations are useful to interpret the pattern of waves and their anomalies more accurately, which are useful for the prediction of an earthquake. In the proposed work, a fast rotating magnetic field (RMF) is used to measure the velocity and acceleration of seismic vibrations in the millisecond range. The broad spectrum of pulses within one second range, measured by proposed method, gives all possible values of instantaneous velocity and instantaneous acceleration of the seismic vibrations. The spectrum of pulses in millisecond range becomes available which is useful to measure the pattern of fore shocks to predict the time and location of large earthquakes more accurately. Moreover, instead of average, the peak values of these quantities are helpful in proper design of earthquake resistant nuclear power plants, buildings and structures. The proposed measurement scheme is successfully tested with a microprocessor based rocking vibration arrangement and the overall performance is recorded at dynamic conditions.

福島原子力発電所の東日本大震災被害からみた1980年の国土庁によるエコロジカル・プランニング調査の現代的意義

One of advantage in ecological planning method of Ian L. McHarg is synthesis of respective optimal landuse (non optimal landuse). The earthquake and tsunami damage in March 11, 2011 recalled us the importance of the comprehensive optimal landuse evaluation. Especially, damages of the Fukushima nuclear plants were catastrophic. This study focused on the criteria of land evaluation paper data in report of "Land Use Aptitude Evaluation Technique Investigation based on Ecological Planning" by National Land Agency Japan in 1980. We traced 5 paper maps (geological map, landform classification map, slope distribution map, vegetation map, and soil cartography map) for digital map, and inclination in coastal areas in where the two Fukushima nuclear plants exist. In addition, we made risk hazard maps (landslide, earthquake resistant, and flood, tsunami damage estimation) on each disaster with above 5 divisions maps and the table risk scores in the Land Agency Report 1980. Finally, we developed a comprehensive hazard map with overlaid a previous evaluation result and evaluation of optimum area of nuclear plant. An actual nuclear power plant site was selected to the coast for the reasons of barren ground bought easily. However, our results indicate that the nuclear power plant site was relative dangerous location in the sight of overall disasters vulnerability by the overlay analysis in 1980 data.