Quantitative risk assessment on fire and explosion impacts for nuclear power plants

The International Atomic Energy Agency (IAEA) requires all nuclear power plant operators to identify, assess and evaluate potential hazards either internal or external, including the potential of human-induced events that can directly or indirectly affect the safety, security, and safeguard of the nuclear power plant (NPP). One of the external hazard that the operator of a licensed nuclear reactors has to consider is that of external explosion with potential for consequential damage to the site. In this study, effects of jet fuel (dedocane and butane) and hydrogen gas induced external explosion from aircraft impact on nuclear plants were investigated and analyzed A turbulence model based on Reynolds-averaged Navier-Stokes in the computational fluid dynamic (CFD) solver called Flame Acceleration Simulator (FLACS) and empirical correlations were used to determine the explosion parameters within the plant vicinity. The influence of obstacle separation distance on explosion severity was investigated with the aim of obtaining the minimum safety distance between buildings. The results of the FLACS simulation and empirical data were analysed and evaluated in order to demonstrate the safety assessment based on two generic plants (Fukushima and Horizon nuclear plants). The simulation results of key explosion parameters for hydrogen show a deflagrative overpressure, Pmax of 0.37 bar, and impulse load of 0.022 bar • s at the exterior walls of building structures. The findings showed that the local temperature of about 1523 K and flame speed of 266 m • s"1 from the hydrogen-air explosion. Butane/air explosion causes an overpressure, Pmax of 0.27 bar, with a maximum positive pressure impulse of 0.015 bar • s. An elevated local temperature of 2030 K and a flame speed of 44 m • s"1 are recorded for this fuel. It was found that for a safety consideration regarding the explosion of these fuel gases, a physical distance of 150 m between the explosion source and the target structure should be sufficient to provide protection against their potential hazards. The computed overpressure and impulsive loadings observed are capable of causing substantial structural damages and vulnerabilities. A significantly elevated flame temperature recorded would have a harmful effect on the safety function of structures, systems and components that are needed to execute reactor shutdown. The analysis also showed that consequential damage of explosion overpressure is strongly dependant on the global load of flammable gas volume and plant layout. In this case, 5000 m3 of hydrogen/butane explosion is sufficient to produce a blast load wave for total plant destruction. The findings of this study may be used to evaluate the safety improvement needed at NPP site with regards to risks and consequences associated with external explosion due to aircraft impact. It is also useful in designing the layout of the NPP and placement of relevant items important to safety

Estrogen receptor modulatory effects of germinated brown rice bioactives in the uterus of rats through the regulation of estrogen-induced genes

PURPOSE: The expression of genes regulated by estrogen in the uterus was studied in ovariectomized (OVX) rats treated with germinated brown rice (GBR) bioactives, and compared to Remifemin or estrogen at different doses to identify the regulation of these genes in the uterus and their molecular mechanisms. METHODS: Rats were treated orally with GBR bioactives (phenolics), acylated steryl glucosides (ASG), γ-amino butyric acid (GABA), and γ-oryzanol (ORZ) at 100 and 200 mg/kg, Remifemin (REM) at 10 mg/kg and 20 mg/kg, or estrogen (EST) at 0.2 mg/kg. Ribonucleic acid (RNA) was extracted from the uterus, and messenger (m)RNA expression of selected genes encoding estrogen receptor-beta (ER-β), calcium-binding protein (CaBP9k), complement protein (C3), heat shock protein 70 kDa (HSP70), and interleukin (IL)-4 receptor were quantified. Similarly, serum steroid hormone concentration was monitored at 2, 4, and 8 weeks after treatments. ER-β antibody binding to the uterus sections was also studied using immunohistochemistry. RESULTS: The group treated with EST (0.2 mg/kg) upregulated ER-β, C3, and IL-4 receptor genes compared to other groups (P0.05) in the progesterone levels in the OVX untreated group compared to the sham and other treated groups. There was a significant increase at 8 weeks in the level of FSH (P0.05) in serum luteinizing hormone (LH) between the OVX untreated group and other groups. The sham and GBR phenolics treated group showed ER-β reactivity at the glandular epithelium, while the group treated with EST showed immunoreactivity at the glandular, luminal, and stromal epithelium. CONCLUSION: GBR phenolics moderately regulate the expression of ER-β, HSP70, and IL-4 receptor genes, and gave a positive immunoreaction to ER-β antigen in the uterus. ASG regulates the expression of CaBP9k and IL-4 receptor genes, and ORZ regulates the expression of the CaBP9k gene, while GABA at 100 mg/kg regulates the expression of the HSP70 gene. GBR and its bioactives might have an effect on estrogen-regulated genes in the uterus of rats

NORMs distribution in coastal soils and sediments of River Yobe, north-eastern Nigeria: an evaluation of the potential radiological hazards

A preliminary study which aimed to establish a reference data on naturally occurring radioactive materials (NORMs) for River Yobe has been conducted. Soil and sediment samples were collected along the coastal areas of the river and analyzed to determine the specific activities of NORMs such as 238U, 232Th and 40K. Gamma spectrometry technique using NaI (Tl) detector was employed to determine the specific activities f the natural radionuclides. The mean activity concentration in the soil samples for 238U, 232Th and 40K were found to be 23±1.5, 36±2.5 and 395±9.1Bq kg−1 and for the sediment samples are 60±2.6, 45±3.6 and 324±6.8Bq kg−1 respectively. These values, in some cases exceed the world reference values of 30, 35 and 400 Bq kg−1 for 238U, 232Th and 40K respectively. Parameters of radiological hazard, were also estimated based on specific activity of the radionuclides to assess the radiological impacts due to exposure on the users of the river. The results were found to be within the worldwide recommended safety limits.Keywords: Annual effective dose, NORMs,238U.232Th.40K. River Yob

The impact of polio eradication on routine immunization and primary health care: a mixed-methods study.

BACKGROUND: After 2 decades of focused efforts to eradicate polio, the impact of eradication activities on health systems continues to be controversial. This study evaluated the impact of polio eradication activities on routine immunization (RI) and primary healthcare (PHC). METHODS: Quantitative analysis assessed the effects of polio eradication campaigns on RI and maternal healthcare coverage. A systematic qualitative analysis in 7 countries in South Asia and sub-Saharan Africa assessed impacts of polio eradication activities on key health system functions, using data from interviews, participant observation, and document review. RESULTS: Our quantitative analysis did not find compelling evidence of widespread and significant effects of polio eradication campaigns, either positive or negative, on measures of RI and maternal healthcare. Our qualitative analysis revealed context-specific positive impacts of polio eradication activities in many of our case studies, particularly disease surveillance and cold chain strengthening. These impacts were dependent on the initiative of policy makers. Negative impacts, including service interruption and public dissatisfaction, were observed primarily in districts with many campaigns per year. CONCLUSIONS: Polio eradication activities can provide support for RI and PHC, but many opportunities to do so remain missed. Increased commitment to scaling up best practices could lead to significant positive impacts

Evaluation of Gamma Radiation Dose Level in Mining Sites of Riruwai, Kano, Nigeria

Communication in Physical Sciences, 2022, 8(1): 101-108 Authors: Aminu Ismaila*, Abubakar Sadiq Aliyu and Yakub Viva Ibrahim Received: 15 February 2022/Accepted 16 April 2022 Some radioelements are natural with redistribution related to human activities like mining. Human beings are constantly associated with these radioelements through water and food intake and may be exposed to background natural radiation from terrestrial and cosmic sources. Among all types of radiation, gamma rays are the most penetrating radiation that emanates from natural and artificial sources. External exposure to gamma radiation varies from one location to another, depending on the geological composition, and elemental content (especially those of U, Th and K in rocks of a particular region). In this study, gamma radiations around mining areas in Riruwai were measured using RadEye Portable Radiation Detector. Gamma dose measurements were taken from 40 sampling locations and at 1 m above the soil surface. Geographical coordinates of the locations were taken using a Global Positioning System (GPS). The analyses show that the gamma radiation dose level attended a mean value of 749 nGy/hr which is thirteen times greater than the maximum permissible value (57-59 nGy/hr) recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The mean indoor and outdoor annual effective doses (AED) were 0.91 and 3.65mSv/yr, which are about three and four times more than their respective world average values of 0.3 mSv/y and 1mSv/y respectively. The Excess Lifetime Cancer Risk (ELCR) factors were 2.51 ×10-3 and 10.5 ×10-3 for indoor and outdoor respectively and these correspond to a nine-fold increase of their world average values of 0.29 × 10−3 and 1.16 × 10−3 as prescribed by the UNSCEAR. The computed data indicated that miners and the public residing close to the mining zone may be at risk and there is a need for an urgent remediation process. The results of this study can provide valuable information on radiological risk which could be used for radiation safety and protection and in the utilization of the soil in the region for agriculture and domestic use. It also contributes to baseline radiological data that could be used by the policymakers and for future studie

Assessment of safety distance between components of nuclear plant and study of the vulnerabiliy of the damage caused by an explosion

This paper deals with the assessment of external explosion, resulting from accidental release of jet fuel from the large commercial airliner in the nuclear power plant (NPP). The study used three widely prediction methods such as Trinitrotoluene (TNT), multi energy (TNO) and Baker-strehow (BST) to determine the unconfined vapour cloud explosion (UVCE) overpressure within the distances of 100-1400 m from the first impact location. The containment building was taken as the reference position. The fatalities of persons and damage of structures was estimated using probit methodology. Analysis of the results shows that both reactor building and control-room will be highly damaged with risk consequences and probability, depending on the assumed position of the crash. The structures at the radial distance of 600 m may suffer major structural damage with probability ranging from 25 to 100%. The minor structural damage was observed throughout the bounds of the plant complex. The people working within 250 m radius may get affected with different fatality ranging from 28 to 100%. The findings of this study is valuable to evaluate the safety improvement needed on the NPP site and on the risk and consequences associated with the hydrocarbon fuel release/fires due to external hazards

Current knowledge and research opportunities in nuclear fire safety: a technical overview on aircraft impact upon nuclear containment

This paper scrutinizes the available literature and presents a comprehensive overview of nuclear fire safety, acknowledging some areas for future research. Methods/Statistical Analysis: Relevant literatures on the aircraft impact upon nuclear reactor containment were reviewed. Scope, findings and limitations of major researches in this field were presented and possible areas of future research were highlighted. A statistical analysis on the number of scientific publications on nuclear fire safety per five years which present the progress in the subject matter was reported. The analysis considered 1968 and 2015 as the base and end years respectively. Findings: In general, some of the identified challenging issues and limitations of nuclear fire studies are: (i) there are limited experimental data on real nuclear fire (ii) studies which considered the impact of external events like aircraft crash on containment gave little or no considerations to tendon gallery, openings and penetrations as in most cases, crash were hypothetically assumed to occur at the midpoint of the cylindrical portion of the containment and near the junction of dome without making recourse to the other portions of the containment e.g. roofing and reactor base (iii) Most reactor fire analysis do not consider material properties at elevated temperatures (iv) in the hazard analysis concerning aircraft impact, assessment of hazards from fireball and pool fire are yet to be fully considered (v) there are very limited data concerning structural failure modes caused by near- field explosive loading. Application/Improvement: The findings of this article could be used to improve the existing methodologies of nuclear fire safety assessment in order to address some of the identified challenging issues

Assessment of safety distance between components of nuclear plant and study of the vulnerabiliy of the damage caused by an explosion

This paper deals with the assessment of external explosion, resulting from accidental release of jet fuel from the large commercial airliner in the nuclear power plant (NPP). The study used three widely prediction methods such as Trinitrotoluene (TNT), multi energy (TNO) and Baker-strehow (BST) to determine the unconfined vapour cloud explosion (UVCE) overpressure within the distances of 100-1400 m from the first impact location. The containment building was taken as the reference position. The fatalities of persons and damage of structures was estimated using probit methodology. Analysis of the results shows that both reactor building and control-room will be highly damaged with risk consequences and probability, depending on the assumed position of the crash. The structures at the radial distance of 600 m may suffer major structural damage with probability ranging from 25 to 100%. The minor structural damage was observed throughout the bounds of the plant complex. The people working within 250 m radius may get affected with different fatality ranging from 28 to 100%. The findings of this study is valuable to evaluate the safety improvement needed on the NPP site and on the risk and consequences associated with the hydrocarbon fuel release/fires due to external hazards

Some Elements in The Fruit: An Assessment of Gingerbread Plum from Sokoto, Nigeria

A region like Sokoto that is been challenged by series of problems such as double burden of diseases, malnutrition, and food insecurity should utilized the available fruits for their inherent nutrient’s compositions. Therefore, the objective of this study was to assess the proximate and elemental contents (sodium, phosphorus, potassium, calcium, and magnesium) in gingerbread plum (Neocarya macrophylla) fruit which are essential for normal growth and development of body tissues for the human health. Neocarya macrophylla fruit is screened for certain nutritionally needed elements and proximate compositions using standard methods. Results obtained show that, crude protein with (2.70 ± 0.0057%) has the lowest concentration, the moisture content was 5.83 ± 0.57 percent, ash content was 5.33 ± 1.54 percent, crude lipid was 5.23 ± 0.15 percent, and crude fiber was 13.33 ± 4.48 percent. The determined levels of mineral elements (calcium, magnesium, phosphorus, sodium, and potassium) reveal 30.25000 ppm, 4.9001 ppm, 90. 1000 ppm, 40.563 ppm, and 67.5601 ppm, respectively. Therefore, the plant is nutritious and vital for metabolic processes

Effects of aqueous extracts of <i>Acacia albida</i> stem bark on Wistar albino rats infected with <i>Trypanosoma evansi</i>

<div><p>The effect of aqueous extract of <i>Acacia albida</i> stem bark was investigated in Wistar albino rats infected with <i>Trypanosoma evansi</i>. The extract showed highest reduction in parasitemia at the dose of 600 mg/kg body weight (bw). A dose of 300 mg/kg bw improved packed cell volume the most by 14.35%. The group treated with 150 and 600 mg/kg bw of the extract showed significant decrease (<i>P</i> < 0.05) in alanine transaminase and aspartate transaminase levels which were lower than those of the group treated with diminazene aceturate. The group treated with 150 mg/kg bw of the extract showed the least urea, albumin and protein level and lowest relative organ weight. There was a significant difference (<i>P</i> < 0.05) in the levels of catalase and Thiobarbituric acid reactive substances in liver and kidney of the animals in the infected-untreated group and the extracts-treated groups. The results of this study show that the extracts of <i>A. albida</i> have antitrypanosomal activity against <i>T. evansi</i> infection.</p></div