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Thiên tai có rất nhiều loại nhưng có một số loại chắc chắn tàn khốc hơn những thiên tai khác. Ví dụ, một cơn lốc xoáy xé toạc một vùng nông thôn không dân cư ít nghiêm trọng hơn một cơn bão đổ bộ vào các cộng đồng lớn ven biển. Động đất và sóng thần đều là hiện tượng tự nhiên xảy ra do áp lực tích tụ giữa các mảng kiến tạo tạo nên vỏ Trái đất, nhưng nghiên cứu mới cho thấy rằng ước tính của chúng ta về mức độ nguy hiểm của những sự kiện này là chưa đủ. Trong một nghiên cứu mới được công bố trên tạp chí Nature Geoscience, các nhà nghiên cứu từ Đại học New Mexico và Đại học Công nghệ Nanyang đã cung cấp bằng chứng cho thấy hiện tượng gọi là động đất siêu lực bên dưới đại dương của Trái đất thậm chí còn mạnh hơn chúng ta nghĩ. Đây là một nghiên cứu phức tạp nhưng quan trọng có thể giúp các cộng đồng chuẩn bị cho tình huống xấu nhất mà một trận động đất và sóng thần có thể gây ra. Đó là khi các dữ liệu được công nhận và các biện pháp an toàn mới được áp dụng. Một trận động đất có sức mạnh siêu lớn xảy ra trong một khu vực được gọi là vùng hút chìm. Các vùng hút chìm được tạo ra khi một trong các mảng kiến tạo trượt bên dưới một mảng kiến tạo khác. Nếu điều này xảy ra trong đại dương có thể gây ra sóng thần toàn cầu cao hơn mức hiện tại.
Overview on Tsunami Risk Evaluation and NPP Project in Vietnam Le Dai Dien Nuclear safety Center Institute for Nuclear Science and Technology (INST) 179-Hoang Quoc Viet, Caugiay-Hanoi, Vietnam Email: led@vaec.gov.vn Presented at the 1st Kashiwazaki International Symposium on Seismic Safety of Nuclear Installations , 24 - 26 November 2010, NIIT, Kashiwazaki, Niigata, Japan CONTENT I The 1st NPP project : Background II Tsunami Risk Evaluation: Some remarkable notices III External hazards for NPP in Vietnam IV Conclusions and suggestions The presentation is based on: - The PFS for NinhThuan NPP Project by EVN - Tsunami Investigations by: + Marine Management Institute, Vietnam Administration for Sea and Islands + Institute of Geophysics, Vietnam Academy of Science and Technology + and others I The 1st NPP project : Background Long-term strategy for Peaceful Utilization of Atomic Energy up to 2020 is approved by the government (Jan 2006) Prime Minister approved the Master Plan for Implementation of the Long-term Strategy (June 2007) Atomic law is approved (Jan 2008) National Assembly approved for investment project for NinhThuan NPPs (25 nov 2009) VN Government has made a strong commitment on development of nuclear power with the goal for building the first NPP in 2014 and operation by the year 2020 I The 1st NPP project : Background Ninh Thuan I NPP Project Site : Phuoc Dinh Capacity : units x 1000 MW Topographic Conditions for Plant platform are defined based on the requirements: The ability to avoid flooding threat; Surface water is well drained; The Cooling water system is operated economically and realiable; Minimize volume and cost for platform leveling I The 1st NPP project : Background Ninh Thuan I NPP Project I The 1st NPP project : Background Ninh Thuan I NPP Project I The 1st NPP project : Background Ninh Thuan I NPP Project II Tsunami Risk Evaluation: Some remarkable notices Historic documents about tsunami in Vietnam + The first event is abnormal high waves attacking Tra Co coast in 1978 (waves with height of m to m) + The beginning of the 20th century waves with the height of more than 3m attacked the coast of Dien Chau + 1923 - related to the eruption of Hon Tro Volcano, ( caused an earthquake with the magnitude of 6.1 Richter) strong tsunami attacked Mui Ne and NhaTrang However, the recorded data were not reliable enough, and detailed studies are needed II Tsunami Risk Evaluation: Some remarkable notices During November - Dec 2005 and March – April 2006 + Investigated excavation sites at six points: Cua Lo, Song Cau, Nha Trang, Phan Rang, Phan Thiet + Samples at different sediment layers for the analysis + Found that a huge tsunami with the maximum height of 18m attacked a coast of more than 1000 km length at Central Vietnam With investigation results, there are possibilities of the events of tsunami attacking Vietnamese coast II Tsunami Risk Evaluation: Some remarkable notices Institute of Global Physics (Tsunami Warning and Earthquake Information Centre) + Among 25 scripts for earthquakes and tsunamis in Vietnam, scenario (earthquake of 8.6 Richter scale at Manila fault) is chosen as the standard to make economic and social plans for the coastal region and to design the evacuation plan + 24 earthquake observation centres nationwide II Tsunami Risk Evaluation: Some remarkable notices Assessment of Bathymetry Effects on Tsunami Propagation in Viet Nam by Nguyen Anh Duong, Fumiaki Kimata, Irwan Meilano + Research Center for Seismology, Volcanology and Disaster Mitigation Nagoya University - Japan Fronts A and B pointing towards Vietnam coastal area caused by near shore bathymetry The red star shows the Feb 14th 1934 EQ with magnitude of 7.5 on northwest coast of Luzon island which generated tsunami II Tsunami Risk Evaluation: Some remarkable notices Scenario 1: Fault source is moved southward along Manila Trench next to the real EQ with M7.5 in 1934 Tsunami travel time map counted from M7.5 Manila Trench source in 1934 Contour timelines – 15’ from the origin time II Tsunami Risk Evaluation: Some remarkable notices Distribution of tsunami height caused by fault source moved southward along Manila Trench next to the real EQ (1934 – M7.5) II Tsunami Risk Evaluation: Some remarkable notices The project “Tsunami Risk Assessment and mitigation in S&SE Asia – Phase 2” : Evaluation tsunami hazard in Vietnam and Gulf of Thailand by NGI (The Norwegian Geotechnical Institute) 2009 30 minutes hour hours Snapshots of the simulated tsunami generated by the Mw8.2 Manila Trench scenario EQ Conservative case: EQ with magnitude 8.2 in the northern part of the Manila Trench is selected II Tsunami Risk Evaluation: Some remarkable notices Project: Tsunami Hazards, Risk and Preparedness for Vietnam With support from New Zealand NZAID Asia Development Assistance Facility (2007 – 2009) Design of seismic and tsunami monitoring system III External hazards for NinhThuan NPP Safety against external hazards to nuclear installations: + Earthquakes, + Flooding, + Tsunami and + Meteorological hazards (typhoon, cyclone…) III External hazards for NinhThuan NPP Seismic issues Map of active faults and distribution of earthquake epicenters in Vietnam and surrounding countries for the period from 1067 to 2002 Green circles indicate historical earthquakes over the period from1067 to 1900 Huang, B.-S., et al Portable broadband seismic network in Vietnam for investigating tectonic deformation, the Earth’s interior, and early-warning systems for earthquakes and tsunamis Journal of Asian Earth Sciences (2009) III External hazards for NinhThuan NPP Seismic issues Research project of the Vietnam Institute of Geophysics (VIG): “Research and Forecasting Earthquakes and Ground Movements in Vietnam” : 114 - 2003 1,645 recorded EQ with magnitude (M) of or > on Richter scale The Ministry of Construction (MOC) has recently issued the new VN EQ loading standard TCXDVN 375:2006 It has been found that the lack of historical data and lack of information on the local site soil conditions has created difficulties in using the code for design or assessment of structures in Vietnam, A review of the Current Vietnamese Earthquake Design Code-T.D Ngo, M.D Nguyen,, D.B Nguyen Earthquake Engineering in the low and moderate seismic regions of Southeast Asia and Australia (2008) III External hazards for NinhThuan NPP Seismic issues Southern Vietnam was always considered as a region with low seismicity, compared to the North On August 2005, an EQ occurred offshore of Vung Tau city with M = 4.6 On November 2006: EQ with Magnitude 5.5 (HCM city) with original center some 100 km off the coast of Vung Tau This EQ was considered as the strongest EQ in the South of Vietnam III External hazards for NinhThuan NPP Hydrology and tide regimes (Ninh Thuan NPP site): (Data from Center for Meteorology and Climatology-Institute of Meteorology and Hydrology) +) Tide level at Vĩnh Trường village (by National Coordinate Sys VN2000) - Average sea water level : -0,26m - Maximum of highest rise of tide : Pmax =1,18m - Minimum of lowest rise of tide : -1,65m +) Highest wave (east direction) : Hsmax=6,21m +) Water level rised by typhoon : Hd =0,89m +) Historical flooding trace by Cái Phan Rang river : 2,74 m III External hazards for NinhThuan NPP Groundworks and Foundation Design suggested for NPP Based on the experiences for selecting the plant platform level of Coal fire plants by former Soviet Union, Platform leveling for Ninh Thuan Plant is estimated by: Hmin = Pmax + Hsmax + Hd + a a : safety coefficient is taken by 0,5m Hmin = 1,18 + 6,21 + 0,89 + 0,5 = 8,78 m => Lowest leveling for plant platform should be 8,8m To discharge the surface water the slope coeficient should be 0.5% down grade to the sea by TCVN 4514:88 III External hazards for NinhThuan NPP Typhoon Typhoon season in NinhThuan is from september to december In average, 9-10 typhoons per period of 10 years Among recorded typhoons, wind speed did not larger than 35 m/s (maximum recorded one in the North reached 80 m/s in Hai Phong) Rain: Ninh Phuoc Distric where Phuoc Dinh site situated belong to the region of most dry climate of the country Maximum recorded rainy water during 24 h by typhoon in Ninh Thuận: 323,2 mm (16 Nov1979) III External hazards for NinhThuan NPP Risk and Environmental Impact Assessment (EIA) According to investigations, there exists inactive fault at the site In the general design layout, some of important parts of the plant are moved to other side with distance of 50m from the fault line However, this still needs more detail investigations to gain an acceptance IV Conclusions and suggestions • From the analysis of collected data => Risk of tsunami at VN coastline is not so high • The damage due to tsunami, once it happens, may be very large Thus, the risk of tsunami should be carefully investigated • The scenarios for tsunami that hit NPP site, at least the intake could be affected, should be considered in safety analysis • The detailed guidelines for assessment of seismological hazard at NPP site and estimation of design basis parameters should be provided IV Conclusions and suggestions • Seismic conditions as well as tsunami for our chosen sites are in need for more detail investigations • Needs of efforts from national organizations and a wide international cooperation with developed nuclear power countries • Nuclear Safety Center – VAEI would be a contact point to connect the IAEA – ISSC (International Seismic Safety Centre) to the related organizations of VN