Understanding the coupling heat transfer of the three-layer molten pool in the lower head aids in assessing the thermal load on the reactor pressure vessel wall and its integrity. Following 3 previous tests conducted on the TROSE experimental setup, the Test-T4 condition was carried out, featuring approximately equal internal heating power density distributions in the oxide and heavy metallic layers. The simulants employed for the three layers were mineral oil, water, and Cerrobend alloy, with thicknesses of 0.2 m, 0.7 m, and 0.3 m, respectively. The experimental results indicate that the normalized sideward heat flux values ranged from 0.32 to 1.58, with minimum and maximum values located at the bottom and top of the oxide layer. Shell formation in the heavy metallic layer across all tests results in a dominant conduction mode, leading to a decreasing distribution trend with increasing polar angle, contrary to various correlations' predictions.

The formation and coolability of the debris bed play a crucial role in the core meltdown process in nuclear reactors. Previous studies mainly focused on experiments involving interactions between small masses of molten material and water, with emphasis on the steam explosion process, lacking analytical data on debris beds and fragments. Therefore, the formation of the debris bed is studied by visual experiments, along with the relevant models are established and applied in this study. In the experiments, a large mass of zirconium dioxide is heated to a molten state in the crucible and then released into a water tank through the release device. The water tank is equipped with four glass windows and high-speed cameras to capture snapshots. Firstly, experiments on the formation of hundred -kilogram -scale debris beds were conducted using the prototype material, zirconium dioxide. The molten material temperature was 3000 K, the molten material mass ranged from 50 to 100 kg, the jet diameter varied from 10 to 20 mm, the water pool depth ranged from 0.55 to 1 m, and the water subcooling varied from 10 to 80 K. Visualized images of the debris bed formation were obtained, and an experimental database of debris bed formation was established, primarily including key parameters such as debris morphology, debris size, debris bed accumulation form, and debris bed porosity. The results indicate that the rise in the mass of molten material and the decrease in water subcooling increase the proportion of large -sized fragments. The experiments did not form a " cake " debris bed but instead achieved loose debris beds due to the small jet diameter. With an increase in the jet diameter and a decrease in water subcooling, the porosity of the debris bed will also increase. Subsequently, computational analysis codes were developed for the processes of jet break-up, debris bed accumulation, and formation, and finally, the deviation of the predicted accumulation morphology was less than 20 %. The results reveal that the influence of the jet diameter and mass of the molten debris on the deposition characteristics of the debris bed is very pronounced. Experimental research and code development hold significant reference value for the formulation of preventive and mitigative measures for severe accidents in nuclear power plants.

The External Reactor Vessel Cooling (ERVC) is crucial to realizing In-Vessel Retention (IVR) strategy when reactor core degradation happens; consequently, fission products would be limited in Reactor Pressure Vessel (RPV). Because of the fission products in the lower head of RPV, vessel integrity is threatened. Due to the immiscibility of oxide and metal materials, the molten pool in the lower head of RPV would turn to a stratified configuration. Two-layer (light metallic layer atop of oxidic layer) and three-layer (light metallic layer, oxidic layer, heavy metallic layer) configurations have been proposed. The possible heavy metallic layer has a different shape, top boundary conditions, and decay heat compared with the other two layers. Thereby, the objective of the heavy metallic layer experiment is to study its heat transfer characteristics, and two possible top boundary conditions are performed. The heating cables simulating the decay heat are placed in a hemispheric test section (diameter = 2.4 m). Water is used as the experimental simulant with a height of 0.3 m. The experimental results demonstrate that increasing the top cooling rate, the ratio of top cooling power to sidewall cooling power, and the ratio of upward heat flux to sideward heat flux increase. In addition, they share almost the same trend. The central melt temperature rises with the height increment, and the maximum normalized temperature reaches about 1.3 for both top cooling and insulated boundary conditions. Thermal stratification is found in the experiment, and the possible natural convection is limited in the heavy metallic layer. Correlations of UCLA, Mini-ACOPO, and RASPLAV reasonably predict the heavy metallic layer's normalized sideward heat flux distribution.

Since oxide and metal materials are not miscible and Uranium extraction, the molten reactor core could turn into a multi-layer configuration molten pool in the Reactor Pressure Vessel (RPV). Three-layeR cOupled heat tranSfer molten pool Experiment (TROSE) is established with a three-dimension hemispheric test section. Two preliminary tests are carried out, and these tests use water to simulate both the top and middle layers and Cerrobend alloy to simulate the bottom layer. TROSE results demonstrate that upward heat transfer direction is found at the interface of the middle and bottom layers, and the power split ratio of the middle layer is about 1.0. The top and middle layers have an increasing trend of sideward heat flux; however, the bottom layer shows a different trend due to crust formation. Generally, the calculated results of Churchill-Chu, BALI, and COPRA correlations are close to the experimental sideward heat flux of the different layers in the multi-layer configuration. This three-dimension study provides additional experiment data for the three-layer configuration in IVR strategy for a new Chinese passive nuclear power plant.

In the postulated severe nuclear accident which caused core degradation, water injection can introduce coolant to cool the molten pool and enhance the effectiveness of In-Vessel Retention (IVR) strategy. However, the existing research did not use the prototypical materials, so the effect of Zirconium-Water reaction (ZWR) was not taken into account. In this study, the wATater injectiOn on molten Zirconium-stainless steel Metallic pool experiment (ATOM) has been established to verify the effect of ZWR during water injection. Neither vapor explosion nor melt ejection found during all tests. The production of hydrogen accounts for only about 1/1000 of total amount of vapor, and the maximum pressure increment is 1.0 kPa. These results show that the existence of Zirconium-water reaction will not damage the safety of water injection strategy, and strongly support the feasibility of water injection strategy in severe nuclear accident. The result also showed that when the content of zirconium is 60%, the H-2 produced by ZWR can be measured. Hydrogen produced in water injection accounted for a small proportion of gas generation, but led to some cavities on the metal production. At the same time, it was found that there were three kinds of oxides on the surface of metal production all of which composed of oxides of iron and zirconium in different proportions.

In the core meltdown accident, fission products are limited in the vessel bottom as indicated in the In-Vessel Retention (IVR) strategy analyses, resulting in forming a three-layer configuration that would threaten the integrity of Reactor Pressure Vessel (RPV). The three-layer test has been carried out with the Three layeR cOupled molten pool heat tranSfer Experiment (TROSE) apparatus to investigate the heat transfer in this threelayer configuration. It uses mineral oil (height = 0.2 m), water (height = 0.7 m), and Cerrobend alloy (height = 0.3 m) as the simulants for the top, middle, and bottom layers, individually. TROSE test section is a threedimension hemispheric facility whose diameter and thickness are 2.4 m and 0.025 m, respectively. Since the sidewall temperature is smaller than the melting point of Cerrobend alloy (70 degrees C), the crust is formed in the bottom layer, affecting its dominant heat transfer mode. The experimental results demonstrate that upward heat transfer is found at the interface of the middle and bottom layers. Besides, the sideward heat flux decreases with the increase of the polar angle. Furthermore, heat transfer correlations of Churchill-Chu, mini-ACOPO, and COPRA could reasonably predict the experimental ratio of top cooling power to sidewall cooling power (Pup/Pdn). Finally, the previous correlations of the sideward heat flux and Nusselt number distributions, such as MiniACOPO correlation, can reasonably predict the experimental results of the middle layer; however, they are not suitable for the top and bottom layers.

The thermal focusing effect is an essential issue in the research of In-Vessel Retention (IVR) because it might cause vessel failure. Late phase in-vessel water injection is applied to the three-layer corium pool surface to alleviate the severe accident and strengthen the IVR strategy. Analyzing the heat transfer in this corium pool after in-vessel water injection is an important issue. A model named "Three-layeR configuration mOlten pool after the late phase in-vessel water Injection under ERVC-IVR Strategy (TROIS)" has been developed for analyzing the heat transfer issues. Its calculated results could reasonably analyze a two-layer case of AP600 and a three-layer experiment with both the top and sidewall cooling conditions. Furthermore, it is applied to analyze the hypothetical core degradation case of AP1000. The calculated results demonstrate that the safety margin of the twolayer configuration is larger than that of the three-layer configuration. And vessel failure would not occur in the three-layer configuration with or without in-vessel water injection, according to the comparison results of local heat flux and CHF. Late phase in-vessel water injection can alleviate this thermal focusing effect and enlarge the safety margin.

The nuclear safety and the integrity of the Reactor Pressure Vessel (RPV) could be ensured by the In-Vessel Retention (IVR) strategy during the severe nuclear accident. The HEat transfer behavior of Light Metallic layer experiment for the Low aspect Ratio (HELM-LR) has been established to investigate the heat transfer characteristics and the concentration factor of the light metallic layer in a three-dimensional molten pool. The melt simulant is water. The test section is heated from below and can be cooled from both top and side. The experimental results demonstrate that the melt temperature increases along the vertical direction and decreases along the radial direction. The possible natural convection in the light metallic layer is formed, due to the temperature difference between the melt near the center and the melt near the sidewall. However, the effect of the natural convection would be limited with the low aspect ratio (H/D). Increasing the top cooling could lead to reducing the concentration factor (qside/qinput). When the bottom heat flux is 1 MW/m2 and the concentration factor is below 204%, the heat flux transferred to the AP1000 sidewall would not exceed the Critical Heat Flux (CHF) and the effect of IVR strategy would be enhanced. Consequently, it could avoid the vessel failure during the nuclear severe accident.

External Reactor Vessel Cooling (ERVC) could be accompanied by the in-vessel water injection to alleviate the thermal focusing effect of the light metallic layer and enhance the In-Vessel Retention (IVR) strategy. Through the wATer injectiOn on molten Zirconium-Stainless steel Metallic pool experiment (ATOM), the effects of different temperatures, mass flow rates of water injection, and different mass percentages of Zr on the heat transfer characteristics after water injection have been investigated. The mass flow rate of water injection ranges from 0.05 kg/s to 0.10 kg/s, and the mass percentage of Zr ranges from 13% to 60%. Eight tests were carried out, and the maximum upward heat flux removed from the melt surface ranged from around 800 to 1400 kW/m(2). A higher water injection mass flow rate and a lower Zr mass percentage could lead to a higher steam generation rate. After water injection, the experimental melt temperature and concentration factor decrease. By applying the ATOM heat transfer coefficient as the input data in the nuclear reactor case, the calculated results indicate that the thermal focusing effect inducing by the decrease of the light metallic layer's height could be highly mitigated by water injection. As a result, the integrity of the RPV could be enhanced. During the whole experiment for all the tests, no vapor explosion and melt ejection were found.

In-Vessel Retention (IVR) strategy with in-vessel water injection could mitigate the thermal focusing effect of the light metallic layer, and reduce the possibility of vessel failure and the release of fission products. Water injection on the molten Zirconium-Stainless steel metallic pool experiment (ATOM) has been performed to investigate the effect of water injection on the heat transfer of the molten pool. After water injection, a film boiling is formed on the top of the molten pool. With Taylor instability, a simplified model is used to derive the form of the film boiling. By fitting it with the ATOM experiment data, a new correlation of water injection on the prototype material for the possible stratified layer molten pool is obtained. The ATOM correlation could predict the experimental results well. The maximum relative error for the ATOM experiment is 28.5%, for the ELIAS experiment is 77.3%, and for the ANAIS experiment is 15.0%. By applicating the ATOM correlation of the heat transfer coefficient as a function of surface temperature to the reactor case, it is found that the vessel failure might not occur with the large aspect ratio ( H / D ) in the light metallic layer and with the top boundary condition of a water layer.

Water injection on the surface of the molten pool could enhance the effectiveness of In-Vessel Retention (IVR) strategy and mitigate the thermal load on the vessel wall. The wATer injectiOn on molten Zirconium-Stainless steel Metallic pool experiment (ATOM) has been established to investigate the effect of water injection on the molten pool for IVR strategy. The mass percentage of Zr is 59.5% for the simulant. The mass flow rate of the water injection is 0.10 kg/s, and the maximum heat flux removed by water is 1.18 MW/m(2). The experimental results indicate that water injection on the surface of the light metallic layer can significantly reduce the heat flux transferred to the sidewall and mitigate the thermal focusing effect on the Reactor Pressure Vessel (RPV). Hydrogen is produced during the water injection. Neither the vapor explosion nor the melt ejection is found during the whole experiment. (C) 2021 Elsevier Ltd. All rights reserved.

In-Vessel Retention (IVR) strategy can ensure nuclear safety and the integrity of Reactor Pressure Vessel (RPV) during the severe nuclear accident. The Molten pool Oxide-layer heat tRaNsfer experiment (MORN) has been built to investigate the heat transfer characteristics of oxide layer in a three-dimensional molten pool. In this experiment, water, nitrate, and oxide were used as the simulants to carry out the experimental research under high temperature and high heat flux. The results demonstrated that the relationship of Nu-Ra was coincident well with the existing correlation with the experiment of water and nitrate simulants. Cooling boundary conditions of the molten pool affected the ratio of upward heat flux to downward heat flux. Also, the heat flux of the low polar angle was lower than that of the high polar angle and the correlations of heat flux distribution were fitted by the experiment of nitrate and oxide simulants. (C) 2020 Elsevier Ltd. All rights reserved.

In-Vessel Retention (IVR) strategy with water injection on the molten pool can ensure the nuclear safety and reduce the possibility of vessel failure. The wATer injectiOn on molten Zirconium-Stainless steel Metallic pool experiment (ATOM) has been performed to investigate the effect of water injection on the heat transfer of the molten pool. The simulant of the molten pool contains the low mass fraction of Zirconium (13%). Two water injections are carried out with the same mass flow. When water is injected on the melt surface, the heat flux transferred to water of the first and the second water injection are about 1.3 MW/m2 and 1.7 MW/m2, respectively. The heat flux in ATOM test is larger than that of the calculated result of Berenson film boiling correlation by 5.3 times for the first water injection and 8.0 times for the second water injection. When water is injected, the melt temperature could be cooled effectively and the heat flux to the sidewall is reduced too. The results indicated that water injection on the surface of the light metallic layer could effectively cool the molten pool and reduce the thermal focusing on the RPV. Neither vapor explosion nor melt ejection is found for the low mass fraction of the Zirconium test.

目的 了解海宁市年老年人的健康状况,为更有针对性的老年健康服务提供依据.方法 参照《浙江省基本公共卫生服务项目规范(2013版)》,《浙江省基本公共卫生服务项目(第四版)》,对海宁市2016—2018年65岁以上老年人的健康体检状况进行调查分析.结果 ①2016—2018年体检人数基本持平,但体检率呈下降趋势.② 从年龄来看,三年间的体检率、肥胖与中心性肥胖检出率均随年龄的增大呈下降趋势,中心性肥胖的检出率都要显著高于肥胖.③ 高血压、高血糖、贫血检出率均在2018年出现大幅升高,且2018年高血压与贫血检出率随年龄的增大呈上升趋势,而高血糖检出率各年龄组间变化不大.④2018年的肝功能异常与肾功能异常检出率均随年龄的增大呈上升趋势.结论 海宁市65岁以上老年人的血压、血糖、血脂控制率仍不乐观,应提升社区医师的高血压、糖尿病防治管理能力和业务水平.

目的 了解无锡市荣巷街道法定传染病流行病学特征,为进一步制定传染病疫情防控措施提供科学依据.方法 运用描述流行病学方法,对2014-2018年法定传染病疫情资料进行统计分析.结果 2014-2018年共报告法定传染病13种1 937例,年均发病率为446.09/10万,其中乙类传染病为130.35/10万,发病率趋势相对稳定;丙类传染病为315.74/10万,呈隔年升高趋势.肠道传染病、呼吸道传染病和血源及性传播传染病年均发病率依次为210.95/10万、89.90/10万和79.91/10万.发病居前5位的病种为手足口病、病毒性肝炎、肺结核、流行性感冒和其他感染性腹泻.发病高峰为4-7月和11月,以散居儿童、幼托儿童为主,分别占30.41％、26.43％.结论 无锡市荣巷街道今后应加强对手足口病、病毒性肝炎、肺结核和流行性感冒等重点传染病的防控工作,采取针对性预防和控制措施.

目的 通过暗访调查,评估浙江省医疗卫生机构无烟环境创建情况,为持续开展控烟工作提供科学依据.方法 2019年采取隐蔽拍摄、填写问卷的方式对浙江省医疗卫生机构开展暗访,从环境指标和吸烟状况两方面评估无烟环境创建情况.结果 共暗访医疗卫生机构612家,全省综合评估得分(80.0±12.3)分,其中县(区)级高于其他级别,公共卫生机构高于其他机构.环境方面,47.7％的机构按要求张贴了禁烟标志,24.0％的机构设置两种及以上宣传材料,18.1％的二级及以上医疗机构设立了戒烟门诊.吸烟状况方面,38.7％的机构在室内发现烟头,15.7％的机构内发现吸烟现象.结论 浙江省医疗卫生机构控烟工作仍需加强,全省各级机构加强宣传,营造全社会参与支持氛围;强化责任,有效落实各项禁烟措施;加强督导,推进全面无烟环境建设.

The passive safety commercial pressurized water reactors (PWRs), AP1000 and CAP1400 are equipped with the automatic depressurization system (ADS). The fourth stage of ADS (ADS-4) has the largest discharging capacity among the all ADS stages. During a small break loss-of-coolant accident (SBLOCA), only when the system is fully depressurized by the ADS-4 to near the containment atmospheric pressure, the in-containment refueling water storage tank (IRWST) can deliver the large coolant inventory for the long-term core cooling by its water head. Before the IRWST injection, the core reaches its minimum inventory. So the transition from the ADS-4 depressurization to the IRWST injection is a very challenging period in a SBLOCA. Therefore, to evaluate the passive system performance by the integral effect test (IET), the transition must be simulated properly. This work conducted the scaling analysis for the ADS-4 depressurization and the IRWST injection for designing the related components of the ACME IET facility. A uniform scaling law based on the existing T-branch liquid entrainment models was proposed. For scaling the onset of the IRWST injection, the requirement for reproducing the synergetic effect in an IET was introduced in order to preserve the important event/process occurrence time with the proper conditions, and the scaling laws for the full pressure IRWST injection were obtained. For investigating the transition thermal hydraulic behaviors and the ADS-4 configuration influences on the core safety, one cold leg break test and three double-ended direct-vessel-injection (DEDVI) line break tests with the different ADS-4 failure modes were selected from the ACME SBLOCA test matrix, and the main test data related to the core safety were analyzed and compared. It was found that the ADS-4 actuation significantly accelerated the system depressurization but worsened the core inventory depletion at the same time. In addition, the break condition and the ADS-4 failure mode could differently affect the system depressurization and the core level. The ACC injection during the ADS-4 depressurization in DEDVI was critical for the core level makeup. The insufficient ADS-4 venting capacity delayed IRWST injection, but also mitigated the core inventory depletion. It suggests the ADS-4 design can be potentially optimized in the passive safety system design. (C) 2019 Elsevier Ltd. All rights reserved.

目的:了解当地农村、社区成年居民中心性肥胖的情况及危险因素.方法:通过多阶段分层整群抽样,随机抽取辖区内3个村的18岁及以上居民共393人进行问卷调查、体格检查及实验室检测.结果:农村社区成年人中心性肥胖患病率为34.35％,其中男性为32.64％,女性为36.00％,单因素分析结果显示年龄大、血脂异常、高TG血症和低HDL-C血症为危险因素,多因素分析显示年龄大和高TG血症为危险因素.结论:农村居民中心性肥胖患病率较高,在健康管理中积极结合危险因素采取针对性措施,降低发病率.

目的:分析2014-2017年海宁市手足口病的流行病学特征,为手足口病防控提供依据.方法:收集2014-2017年传染病报告信息管理系统中报告的海宁市辖区内手足口病人的个案资料,采用描述性流行病学方法进行分析.结果:2014-2017年海宁市累计报告手足口病例7 392例,平均发病率为225.21/10万,发病年龄主要集中在4岁以内,男性平均发病率高于女性,以散居儿童和幼托儿童居多.采集的样本258份,阳性率为46.51％,其中EV71阳性率为9.69％,Cox A16阳性率为13.95％,其他肠道病毒阳性率为22.87％.结论:手足口病是海宁市重要传染病之一,应加强相应的监测及防控工作.

目的:了解农村地区学校学生的因病缺课情况及原因,为学校传染病防制工作提供科学依据.方法:以辖区内所有学校为监测点,监测内容包括学校基本情况、每日因病缺勤、发热、咳嗽、皮疹、呕吐和腹泻等症状,监测时间持续一个学年.结果:2015年10个监测点学校共缺课8145人次,其中因发热症状缺课1132人次,占13.90％;因呼吸道症状缺课6669人,占81.88％;因腹泻症状缺课180人次,占2.21％;因呕吐症状而缺课124人次,占1.52％;因皮疹症状缺课40人次,占0.49％.结论:加强监测,及时分析各类症状发生数异常升高现象,对于早期发现疫情、预防传染病在学生中的暴发和流行及保障辖区内公共卫生安全是非常重要的.