加拿大CANDU核反应堆与日本BWR反应堆之比较

小傻

Emeritus Chief 8 Gua
VIP
注册
2002-05-13
消息
5,889
荣誉分数
156
声望点数
173
http://www.nuclearsafety.gc.ca/eng/mediacentre/updates/march-11-2011-japan-earthquake-comparison-candu-and-bwr-reactors.cfm


Comparison of Canadian CANDU Reactors to Japanese BWR Reactors


Many Canadians are curious about the difference between Canadian nuclear power reactors and those that have been affected recently in Japan. Information that may answer those questions includes:
<HR>What kinds of reactors are used in Canada?

All Canadian nuclear power reactors use CANDU reactors, made in Canada by Atomic Energy of Canada Limited (AECL).
What kinds of reactors are used in Japan?

The Japanese nuclear power reactors at the Daiichi, Daini and Onagawa plants are boiling water reactors (BWRs), along with 11 other Japanese plants. Eight Japanese plants use pressurized water reactors (PWRs).
How are CANDU and BWR reactors different?

CANDU reactors use heavy water technology to control nuclear reactions. They have been operating in Canada since 1962, and abroad since 1972. To date, 48 heavy water moderated reactors based on the CANDU design are in operation, under construction, or under refurbishment worldwide.
In BWR reactors, the heat produced by nuclear fission in the reactor core causes circulating water to boil, producing steam. The steam, which is radioactive, drives a turbine directly, after which it is cooled in a condenser (essentially a heat exchanger cooled by sea water, lake water, a large river or cooling tower) and converted back to liquid which circulates back though the reactor. CANDUs don't permit boiling of the primary loop water. This very hot water, which is also radioactive, circulates in a closed loop entirely within containment. It passes through steam generators (heat exchangers) which transfer heat to secondary loops to power steam turbines and associated electrical generators. The residual low-pressure steam is routed back through a condenser, where it becomes water again and is returned back to the steam generators. The steam and water in CANDU’s secondary loops is not radioactive, so in the event that a heat release is required, the secondary side could be safely vented to atmosphere and new plain water introduced once the water inventories are depleted.
CANDU safety features

CANDU reactors can be refuelled while operating, and incorporate dozens of safety features to respond to the stringent safety requirements imposed by the Canadian Nuclear Safety Commission. Safety highlights include:
  • a design that can use passive convection cooling for the primary systems to keep the reactor cool in the absence of power
  • the use of dousing tanks high in the reactor or containment building that work on gravity, which can be used to replenish secondary side inventory and refill the steam generators, as required, to continue heat release in the event of a loss of power
  • use of ceramic uranium fuel pellets that tolerate high temperatures
  • two independent and diverse shutdown systems
  • calandria vessel that contains the fuel rod assembly and heavy water moderator
  • high-density, reinforced concrete containment walls, almost a metre thick
CANDU_e.jpg

Canadian licensing safety conditions

All Canadian power reactors are subject to hundreds of robust safety conditions before they are permitted to be licensed by the CNSC, including the ability to:
  • withstand severe flooding with no significant damage; facilities reduce flooding risk by using engineered shoreline breakwaters, catch basins, berms and storm sewers
  • operate and/or shut down safely during major power failures or blackouts
  • safely survive earthquakes to ensure that:
    • a loss-of-coolant accident does not occur
    • reactors can be shut down and remain shut down
    • heat from reactors can be removed
    • any required release of radioactivity is minimized
    • status of nuclear steam supply system can be monitored
    • no radioactive releases above allowable limits result from any damage to systems other than the core reactor
    • if one power reactor fails, it will not affect the safety of adjacent systems or structures
Canadian Standards Association standards impose a series of technical specifications for structures and containment of nuclear power plants that must be addressed by Canadian companies in order to obtain a licence to operate by the CNSC.
What would happen to Canadian nuclear power reactors if there were no electrical power?

In the unlikely event of a loss of all power at a nuclear power plant, the plant's emergency power supply (EPS) would provide electrical power to certain nuclear safety-related systems that support the capability to control, cool, and contain the fuel. The EPS is started automatically when there is a loss of power or can be manually started from the EPS control room within 30 minutes of an identified need.
The EPS is seismically and environmentally qualified and has sufficient fuel stores to operate unaided for a seven-day period. Seismic qualification requires that equipment and systems retain their specified performance capability following an earthquake. Environmental qualification requires that equipment be protected against steam leaks, water flooding, high-intensity fires or other mishaps, which could disable it.
The EPS is similar to other standby generators but is remotely located from them to reduce chances of it being disabled by the same incident. Cables and control equipment involved in switching the EPS into service are routed through areas that are considered to be at lowest risk of damage.
In the even more unlikely event that EPS systems also become unavailable and all power is lost, all affected Canadian nuclear power reactors would safely shut down and stabilize using CANDU's convection cooling system design. Then, all units would be placed in guaranteed shutdown state until power was restored.
In any power outage affecting Canadian nuclear power plants, the CNSC would work closely with any affected licensees, other government departments and appropriate safety organizations to ensure the safety of workers, citizens and the environment.
What would happen to Canadian nuclear power reactors if there were a flood?

All but one Canadian nuclear power plant are on inland bodies of water with no threat of tsunamis like those affecting Japan. The Point Lepreau Nuclear Power Plant in New Brunswick sits on the shores of the Bay of Fundy which sees tidal flows of 40- 50 feet, a factor that was built into its design capability.
All Canadian nuclear power plants have been licensed on the basis of their proven ability to withstand severe flooding with no significant damage; facilities reduce flooding risk by using engineered shoreline breakwaters, catch basins, berms and storm sewers.
In any flood affecting Canadian nuclear power plants, the CNSC would work closely with any affected licensees, other government departments and appropriate safety organizations to ensure the safety of workers, citizens and the environment.
What would happen to Canadian nuclear power reactors if there were an earthquake?

All Canadian nuclear power plants have been licensed on the basis of their proven ability to withstand seismic events like earthquakes. Structures and systems have been designed to safely survive earthquakes to ensure that:
    • a loss-of-coolant accident does not occur
    • reactors can be shut down and remain shut down
    • heat from reactors can be removed
    • any required release of radioactivity is minimized
    • status of nuclear steam supply system can be monitored
    • no radioactive releases above allowable limits result from any damage to systems other than the core reactor
    • if one power reactor fails, it will not affect the safety of adjacent systems or structures
Canadian Standards Association standards impose a series of technical specifications for structures and containment of nuclear power plants that must be addressed by Canadian companies in order to obtain a licence to operate by the CNSC. The CNSC ensures that all nuclear power plant licensees comply with regulatory requirements.
In any earthquake affecting Canadian nuclear power plants, the CNSC would work closely with any affected licensees, other government departments and appropriate safety organizations to ensure the safety of workers, citizens and the environment.
 
加拿大发展的压力管式重水反应堆(PHWR),也称坎杜堆(CANDU)。自1962年首
台核电机组投入运行以来,到目前为止,加拿大境内已拥有22台CANDU反应堆核电机组,
并先后出口到印度、巴基斯坦、韩国、阿根廷、罗马尼亚和中国,共12台机组。中国的
秦山核电三期工程就采用了加拿大CANDU6反应堆。1.CANDU反应堆概述CANDU反应堆的
独有特征是可以使用天然铀燃料,用压力管替代压力容器,用重水作慢化剂和冷却剂,
以及不停堆换料,高压冷却剂与低温、低压慢化剂分离。在CANDU反应堆中,排管容器
(CALANDRIA)在低温(接近70℃)并低压(接近大气压力)条件下,充满重水(D2O)
慢化剂。几百根装有铀燃料棒束的压力管穿过这个容器。反应堆的冷却剂也采用D2O,用
泵将其送入并通过装有燃料的压力管,带走裂变热,冷却剂再流向蒸汽发生器,将热量
传给管外的普通水使其产生蒸汽。
  在反应堆处于满功率运行的同时,可用遥控装卸料机更换燃料,装卸料机也可及时
不停堆地移出和更换有缺陷的燃料,以减少因破损带来的放射性影响。排管容器是一个
水平圆柱体(直径7.6m),其端部是平板形的排管容器侧管板。每个管板钻有正方形排
列的小孔,其间距为0.286m。很多平置并排的锆-2合金管的两头分别与排管容器每一
端部管板上的小孔相联接。这些管子(称为排管)被冷的低压重水所包围,每一个排管
里放有压力管,它与排管同轴。压力管与排管之间充有干燥并且循环的CO2气体,可连续
监测压力管内的高压重水可能产生的任何泄漏。高压冷却水将压力管内燃料棒束传出的
热量带走。CANDU堆重水慢化剂的温度为70-80摄氏度。如果压力管由于某种严重事故
发生温度升高的现象,膨胀到或下垂到与排管相接触的程度,热量便会传到冷的重水慢
化剂中,从而维持压力管排管组件的完整性。试验证明,这种用冷的慢化剂围绕排管的
办法,有助于在严重事故的情况下防止压力管熔化并限制氢气的产生。
  2.CANDU反应堆的安全系统
  CANDU反应堆核电站采用“纵深防御”的概念,即按事故防御、事故缓解、事故管
理三个层次进行设防。秦山三期CANDU6反应堆核电站的安全设计考虑了四种基本的安全
功能:①反应堆停堆并将反应堆维持在安全停堆状态;②有效地将燃料中的衰变热移
出;③维持屏障的完整性以限制放射性对公众和电站人员的释放;④给操作员提供必要
的信息以监测电站的状态。为了实现以上四种基本安全功能,专门设计了用于缓解工艺
系统失效后果的系统,它们被称为专设安全系统。在CANDU6设计中有1号停堆系统、2
号停堆系统、应急堆芯冷却系统(ECCS)以及安全壳系统这样4个专设安全系统。其他一
些给专设安全系统提供安全相关服务的系统,例如电力、冷却水、空气等,称为安全支
持系统。为了保证安全系统和安全支持系统高可靠度地执行它们的安全功能,在设计中
采用了多重性、多样性、隔离、设备鉴定、质量保证以及使用合适的设计法规和标准等
设计手段。如两个独立的、不同的、分开的停堆系统,每个系统都能在任何假想事故下
使反应堆停堆。

《科技日报》2000-11-14第5版
 
一个是重水堆。。。一个轻水堆。。。。一个使用普通铀,一个使用浓缩铀。
 
CANDU具有绝对优势.
 
缺点是不能产生核武原料:p:D:D 呵呵,加拿大人民爱好和平啊:cool::cool:

呵,看问题深刻啊。所以,很多国家不买。

这次地震,为加拿大做了个大广告,有钱赚了。

是啊。加拿大生化也是一流的,就是不搞武器。加拿大是爱好和平的。
 
呵,看问题深刻啊。所以,很多国家不买。

这次地震,为加拿大做了个大广告,有钱赚了。

是啊。加拿大生化也是一流的,就是不搞武器。加拿大是爱好和平的。

其实candu也产生钚239,但因为使用乏燃料和钚的再裂变,钚的浓度仍然很低。
 
CANDU具有绝对优势.
嘿,加拿大产的东西关键的时候掉链子那是常有的事。
随便听听就算了,还真信?:D
 
后退
顶部