Exergetic analysis and evaluation of coal-fired supercritical thermal power plant and natural gas-fired combined cycle power plant

The present work has been undertaken for energetic and exergetic analysis of coal-fired supercritical thermal power plant and natural gas-fired combined cycle power plant. Comparative analysis has been conducted for the two contestant technologies. The key drivers of energetic and exergetic efficiencies have been studied for each of the major sub-system of two contestant technologies. Overall energetic and exergetic efficiency of coal-fired supercritical thermal power plant are found to be 43.48 and 42.89 %, respectively. Overall energetic and exergetic efficiency of natural gas-fired combined cycle power plant are 54.47 and 53.93 %, respectively. The major energetic power loss has been found in the condenser for coal-fired supercritical thermal power plant. On the other hand, the major energetic power loss has been found in both the condenser and heat recovery steam generator for gas-fired combined cycle thermal power plant. The exergetic analysis shows that boiler field is the main source of exergetic power loss in coal-fired supercritical thermal power plant and combustion chamber in the gas-fired combined cycle thermal power plant. It is concluded that natural gas-fired combined cycle power plant is better from energetic and exergetic efficiency point of view. These results will be useful to all involved in the improvement of the design of the existing and future power plants.     

Measurement of natural radioactivity and dose rate assessment of terrestrial gamma radiation in the soil of southern Punjab, Pakistan

Activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in soil samples collected from the most populous area of southern Punjab of Pakistan have been measured by gamma-ray spectrometry. The measured activity concentrations for these radionuclides are compared with the reported data from different other countries and it is found that measured activity concentrations are comparable with the worldwide measured average values reported by the UNSCEAR. Subsequently assessed radiological effects show that the mean radium equivalent activity (Ra(eq)) is 96.7 +/- 15.2 Bq kg(-1) and air absorbed dose rate (D) is 46.1 +/- 7.3 nGy h(-1). The values of internal and external radiation hazard indices are found to be less than unity. The annual effective radiation dose is calculated to be 0.28 +/- 0.05 mSv, which is well below the limit of 1.0 mSv y(-1) recommended by the International Commission on Radiological Protection, for the general public.     

Radionuclide content and associated radiation hazards of building materials and by-products in Baoji, West China

Seven types of common building materials and by-products of coal-fired power plants collected from Baoji, West China, were analysed for the natural radioactivity of 226Ra, 232Th and 40K using gamma ray spectrometry with an NaI(Tl) detector. The average activity concentrations vary from 23.0 to 112.2, 20.2 to 147.5 and 113.2 to 890.8 Bq kg(-1) for 226Ra, 232Th and 40K, respectively. The measured activity concentrations for these radionuclides were compared with the data reported from other countries and with the worldwide average activity of soil. As a measure of radiation hazard to the people, the radium equivalent activities, total annual effective dose and activity concentration index were estimated. The radium equivalent activities of the studied samples are below the internationally accepted values. The calculated total annual effective dose and the activity concentration index of seven types of common building materials are <1 mSv y(-1) and 1, respectively. But fly ash and bottom ash exhibit the higher values that exceed and be close to the acceptable values, respectively. This study shows that the measured building materials do not pose any significant source of radiation hazard and are safe for use in the construction of dwellings. Nevertheless, when fly ash and bottom ash are used in dwelling construction, it is important to assess their radiation potential.     

Assessment of natural radioactivity and the associated hazards in Iranian cement

This paper presents the finding of a study undertaken to determine natural radioactivity and associated hazards in local types of cement in Iran. A total of 42 samples were collected from various manufacturers and suppliers and analysed using a shielded HPGe gamma-ray spectrometer. The specific activities of 232Th, 226Ra and 40K were measured in samples and results ranged from minimum values of 8, 16, 101 Bq kg(-1) to maximum values of 17, 43 and 141 Bq kg(-1), respectively. On the basis of activity concentration index (I), it could be shown that, the radioactivity of local cement samples was not greater than the established standard values in other countries.     

Measurement of natural radioactivity from soil samples of Sind, Pakistan

Natural radioactivity has been measured from the soil samples collected from the Sind province of Pakistan. The measured activities of 22?Ra, 232Th and ??K were found in the range of 18-47, 24-69 and 254-769 Bq kg?1, respectively. The calculated values of the absorbed dose rate in air and the annual effective dose were in the range of 33-87 nGy h?1 and 0.16-0.43 mSv, respectively. The measured results of activity were found compatible with the worldwide findings.     

Evaluation of natural radioactivity levels and radiation hazards of some industrial Egyptian ores

The activity concentration of natural radionuclides (²³⁸U, ²³²Th, and ⁴⁰K) in three industrial Egyptian ores including manganese ore (M), white sand (W), and dolomite ore (D) collected from Sinai area in Egypt were evaluated. The sample morphology was studied by EDS-XRD and SEM. Radiometric measurements were based on the characteristic spectral peaks of each radionuclide. The observed high activity of ²³⁸U confirmed that the natural radioactivity of the ores studied is mainly due to the uranium series. The calculated radium-equivalent activities (Ra-eq) were found to be 6553, 2848, and 431 Bq kg^?1 for M, W, and D respectively. For M and W samples, the Ra-eq values are higher than the permissible level recommended in Egypt (1000 Bq kg^?1). The annual effective doses were found to be 4.3 ± 0.3, 1.36 ± 0.02, and 0.66 ± 0.01 mSv year^?1, respectively. The recorded data of the radioactivity background levels in the industrial samples studied can be used as reference values not only to assess the anthropogenic activities in the environment, but also to explain the metamorphic cycles of these radionuclides due to geological processes.     

Measurement of thermal fluxes in power plant components

A method of recovering the thermal flux acting on a sensing element with respect to measurements of sensing element signals is described.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 6, pp. 990–994, June, 1985.     

Measurement of natural radioactivity in beach sands from Rizhao bathing beach, China

The natural radioactivity of (226)Ra, (232)Th and (40)K was determined for beach sand samples collected from Rizhao bathing beach, China, using gamma ray spectrometry. The measured activity in beach sand ranges from 7.6 to 17.2, 7.8 to 25.1 and 883.4 to 1313.6 Bq kg(-1) for (226)Ra, (232)Th and (40)K with mean values of 12.0, 15.2 and 1079.2 Bq kg(-1), respectively. The activity concentrations of (226)Ra and (232)Th in beach sands are lower, while (40)K is higher than the world average. The radium equivalent activity in all beach sand samples is lower than the safe limit set in the OECD report (370 Bq kg(-1)). The values of the external hazard index are less than unity. The mean outdoor air absorbed dose rate is 59.8 nGy h(-1) and the corresponding outdoor effective dose rate is 0.073 mSv y(-1).     

A life cycle assessment of biomass cofiring in a coal-fired power plant

The generation of electricity, and the consumption of energy in general, often result in adverse effects on the environment. Coal-fired power plants generate over half of the electricity used in the U.S., and therefore play a significant role in any discussion of energy and the environment. By cofiring biomass, currently operating coal plants have an opportunity to reduce the impact they have, but to what degree, and with what trade-offs? A life cycle assessment has been conducted on a coal-fired power system that cofires wood residue. The assessment was conducted in a cradle-to-grave manner to cover all processes necessary for the operation of the power plant, including raw material extraction, feed preparation, transportation, and waste disposal and recycling. Cofiring was found to significantly reduce the environmental footprint of the average coal-fired power plant. At rates of 5% and 15% by heat input, cofiring reduces greenhouse gas emissions on a CO₂-equivalent basis by 5.4% and 18.2%, respectively. Emissions of SO₂, NO _x , non-methane hydrocarbons, particulates, and carbon monoxide are also reduced with cofiring. Additionally, total system energy consumption is lowered by 3.5% and 12.4% for the 5% and 15% cofiring cases, respectively. Finally, resource consumption and solid waste generation were found to be much less for systems that cofire. Electronic Publication     

Measurement of radioactivity in the soil of Bahawalpur division, Pakistan

Bahawalpur is the largest division of the Punjab province in Pakistan. It is larger than many countries of the world. Gamma activity from the naturally occurring radionuclides namely 226Ra, 232Th, the primordial radionuclide 40K and the artificial radionuclide 137Cs was measured in the soil of the Bahawalpur division using gamma spectrometry technique. The mean activity of 226Ra, 232Th, 40K and 137Cs were found to be 32.9 +/- 0.9, 53.6 +/- 1.4, 647.4 +/- 14.1 and 1.5 +/- 0.2 Bq kg(-1), respectively. The mean radium equivalent activity Raeq, external hazard index, internal hazard index and terrestrial absorbed dose rate for the area under study are 158.5 +/- 4.1 Bq kg(-1), 0.4, 0.5 and 77.32 nGy h(-1), respectively. The annual effective dose equivalent to the public was found to be 0.5 mSv.     

Measurement of the whole-body 137Cs in residents around the Chernobyl nuclear power plant

To understand the current situation of internal radiation exposure in the population around the Chernobyl Nuclear Power Plant (CNPP), we examined the 137Cs body burden in six residents of Belarus, Ukraine and Russia in 2002 and 2004 using the whole-body counter (WBC) at Nagasaki University (Japan). The data were compared with those of our previous study performed in 1993-1994 using the same method. In 2002 and 2004, peaks of 137Cs were detected in two residents from Gomel, which was heavily contaminated by the CNPP accident, one from Minsk (Belarus) and one from Kiev (Ukraine), but another resident from Minsk showed no 137Cs peaks. The results of the present study suggests that residents around the CNPP are still exposed to chronic 137Cs internal irradiation, probably due to the daily consumption of contaminated domestic foods, but the risk of any disease by the irradiation is quite low. Long-term follow-up of WBC around the CNPP is useful and may contribute to radiation safety regulation together with a reduction of unnecessary radiophobia for the residents.     

Assessment of radioactivity and the associated hazards in local and imported cement types used in Sudan

Activity concentration of 232Th, 226Ra and 40K in local (Atbra and Rabak) and imported cement types (Jordanian, Indonesian and Seabulk) has been measured using high-resolution gamma-spectrometry. The average values obtained for 232Th, 226Ra and 40K activity concentrations in different cements are lower than the corresponding global values reported in UNSCEAR publications. The radium-equivalent activity (Raeq) of the samples was calculated and compared with similar data reported in the literature. The comparison has revealed that Raeq values obtained fall far below the criterion limit specified for building materials. The potential radiological hazard of the different samples was estimated using different approaches: representative level index and annual dose limit (dose due to gamma radiation inside the room and inhalation of radon). The estimated representative level index for all the samples is less than unity (the upper limit) indicating that the associated gamma radiation level is low. The annual dose limit falls within 0.19 to 0.30 mSv, which is an order of magnitude below the criterion limit specified for building materials in the literature.     

Natural and artificial radionuclide measurements and radioactivity assessment of soil samples in eastern Sichuan province (China)

The activity concentrations of natural and artificial radionuclides were measured in the eastern region of Sichuan province (China). One hundred and ninety-three soil samples from this region were collected and analysed by high-purity germanium gamma spectrometry. The measured results show that the average radioactivity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in the soil samples are 26, 49, 440 and 6 Bq kg(-1), respectively. The calculated average radium equivalent activity is 130 Bq kg(-1), which is less than the recommended limit of 370 Bq kg(-1). The absorbed dose rate and annual effective dose are 60 nGy h(-1) and 74 μSv, respectively. This is the first time the absorbed dose rate in the east region of Sichuan has been mapped. Overall, the environmental radiation background is greater in the southern part of the area studied than in the northern.     

Measurement of natural radioactivity in bottled drinking water in Pakistan and consequent dose estimates

Natural radioactivity was determined in 11 different brands of commonly sold bottled drinking water in the federal capital Islamabad and Rawalpindi city of Pakistan using gamma spectrometry technique. Mean concentrations of 226Ra, 232Th and (40)K were found to be 11.3 +/- 2.3, 5.2 +/- 0.4 and 140.9 +/- 30.6 mBq l(-1), respectively. The annual cumulative effective doses due to all three natural radionuclides for different age groups of 1-5 y, 5-10 y, 10-15 y and adults (>or=18 y) were estimated to be 4.0, 3.4, 3.1 and 4.1 microSv y(-1), respectively. Among the three natural radionuclides, annual effective doses for all age groups from 226Ra were significant. Children in the age group of 1-5 y appeared to be at risk with respect to the annual effective doses from 226Ra as compared to the other age groups. Results obtained in this study are compared with the reported values from other countries of the world and it was observed that measured activity concentrations of three natural radionuclides in the bottled drinking water were lower than these values. Annual estimated effective doses for all four age groups from the intake of natural radionuclides in bottled drinking water were also found below the World Health Organisation (WHO) recommended limit of 0.1 mSv y(-1) as well as the average radiation dose of 0.29 mSv y(-1) received per head worldwide due to ingestion of natural radionuclides assessed by UNSCEAR (2000).     

热电厂采用热电冷联供的适用性分析

利用等效发电效率概念,以300MW级抽凝式供热机组为例,对热电冷联供的适用性进行分析。在目前电、热价格以及发电机组装备水平的基础上,提出城市热电厂推广使用热电冷联供的约束性条件。     

Contamination assessment of copper, lead, zinc, manganese and nickel in street dust of Baoji, NW China

Street dusts collected from Baoji, NW China were analyzed for Cu, Pb, Zn, Mn and Ni by using PANalytical PW-2403 wavelength dispersive X-ray fluorescence spectrometry and assessed the contamination level of heavy metals on the basis of geoaccumulation index (I(geo)), enrichment factor (EF), pollution index (PI) and integrated pollution index (IPI). The results indicate that, in comparison with Chinese soil, street dusts in Baoji have elevated metal concentrations as a whole. The concentrations of heavy metals investigated in this paper are compared with the reported data of other cities. The calculated results of I(geo) and EF of heavy metals reveal the order of I(geo) and EF are Pb>Zn>Cu>Ni>Mn. The high I(geo) and EF for Pb, Zn and Cu in street dusts indicate that there is a considerable Pb, Zn and Cu pollution, which mainly originate from traffic and industry activities. The I(geo) and EF of Mn and Ni are low and the assessment results indicate an absence of distinct Mn and Ni pollution in street dusts. The assessment results of PI also support Pb, Zn and Cu in street dusts presented serious pollution, and IPI indicates heavy metals of street dust polluted seriously.     

Creep behavior of seam-welded reheat steam pipes in thermal fossil power plant: feedback analysis and life assessment methodology

A methodology is developed to evaluate a residual life of the oldest seam-welded reheat pipes. The first step consists of a design concept based using a weld parameter depending on welding process, in order to classify pipes by their creep life fraction. This part is in progress. The second step consists of a metallurgical approach to optimize life assessment of the most damaged pipes, by estimating a residual life before crack initiation in the intercritical zone of a pipe tempered weld. Creep tests on a simulated intercritical microstructure were subjected to different creep life fractions. Creep damage was identified as the creep cavity density evaluated by image analysis. Tests results have shown that creep damage appears in the intercritical microstructure in the very end of life (last 16 ± 2 % of creep life). These results warrant a residual life of at least 24000 hours for a 150000 hours aged pipe under operating conditions, if no creep damage was found. Extra examinations have been performed on the oldest seam-welded (MMA process) reheat pipe of EDF thermal fossil power plants. Application of this metallographic approach have enabled one to estimate a residual life of at least 9000 hours before the creep crack initiation stage, in good agreement with creep tests performed on extracted welds. Applicability of this new approach seems to be very interesting for in service seam-welded reheat pipes, but it requires the previously identification of the most creep damaged section. In that way, NDT must be improved to be able to detect creep damage in the bulk.     

Distribution of tritium in water vapour and precipitation around Wolsung nuclear power plant

The distribution of tritium in water vapour and precipitation with discharge of tritiated water vapour and meteorological factors was studied around the Wolsung nuclear power plant (NPP) site during the period 2004-2008. The tritium concentrations in atmospheric water vapour and precipitation had a temporal variation with relatively high values in the early summer. Spatial distribution of tritium concentrations was affected by various factors such as distance from the NPP site, wind direction, tritium discharge into the atmosphere and atmospheric dispersion factor. The annual mean concentrations of atmospheric HTO and precipitation were correlated with the amount of gaseous tritium released from the Wolsung NPP. The tritium concentrations in precipitation decrease exponentially with an increase of the distance from the Wolsung NPP site.     

Distribution patterns of natural radioactivity and delineation of anomalous radioactive zones using in situ radiation observations in Southern Tamil Nadu, India

In situ radiation measurements in the beach sectors and adjacent hinterlands and along rivers in the interiors of southern peninsular India were carried out using a portable radiation survey meter. A very high intrinsic anomalous radioactivity >26microGy/h has been observed in the hinterlands within a fresh quarry and weathered boulders in the syenite rock body around Puttetti in the western Kanyakumari district of southern Tamil Nadu. Over the weathered hillocks in the hinterlands adjacent to the coast around Inayam, Kurumpanai and Midalam, the in situ radiation measurements have also exhibited high radioactivity ranging from 4 to 22microGy/h which is significantly higher than the radiation exposure rates (RER) observed along the beach sectors at various locations from Chavara to Tuticorin (1-14microGy/h). The observed radiation levels are presumably the highest concentration in southern India and it is the first time that such a high intrinsic radiogenic source in the hinterlands is reported in southwest coast of India. It is also observed based on the laboratory analysis of samples and in situ radiation data that the rivers/channels in this region contain insignificant level of radioactivity concentration and hence they do not contribute much to the placer deposits on the beaches. The placer deposits associated with significant RER (both in situ observations as well as laboratory estimates from samples) in the beach sectors from Kadiapattanam to Inayam are inferred to be derived through the country rocks/weathered hillocks in the immediate hinterlands.     

Simultaneous in situ measurement of CO,H2O,and gas temperatures in a full-sized coal-fired power plant by near-infrared diode lasers

We present what is to our knowledge the first near-infrared diode-laser-based absorption spectrometer that is suitable for simultaneous in situ measurement of carbon monoxide, water vapor, and temperature in the combustion chamber (20-m diameter, 13-m path length) of a 600-MW lignite-fired power plant. A fiber-coupled distributed-feedback diode-laser module at 1.56 microm served for CO detection, and a Fabry-Perot diode laser at 813 nm was used to determine H2O concentrations and temperature from multiline water spectra. Despite severe light losses (transmission, <10(-8)) and strong background radiation we achieved a resolution of 1.9 x 10(-4) (1sigma) fractional absorption, equivalent to 200 parts in 10(6) by volume of CO (at 1450 K, 10(5) Pa) with 30-s averaging time.