这座城市面临的最大问题就是处理铯—137，这是一种半衰期为30年的放射性同位素。
The city's challenge, chiefly, is to dispose of cesium-137, a radioactive isotope with a half-life of 30 years.
食品中的放射性碘直接引起人们的关注，但是它的半衰期相对较短并将在短时间内自然衰变。
Radioactive iodine in food is of immediate concern, but it has a relatively short half-life and will naturally decay over a short time frame.
放射性碘的半衰期为八天，几周内自然衰变。
Radioactive iodine has a half-life of eight days and decays naturally within weeks.
更妙的是，显然人们可以用放射性作为时钟，用衰变系列的半衰期计算出岩石的年龄。
Better still, it became apparent to him that one could use radioactivity as a clock, with the half-life of a decay series enabling us to calculate the age of a rock.
最为有名的就是铀- 238衰变为铅- 206的半衰期为45亿年，当然放射性铷和钐也同样对测算几十亿年前的物体的年龄很有用。
Most famously, uranium-238 decays into lead-206 with a half life of 4.5 billion years, though radioactive rubidium and samarium are also useful for dating things billions of years old.
与放射性一样，故事有一个半衰期-换言之，就是新推荐的故事从首页到被下放的周期。
As with radioactivity, stories have a half-life-in other words a period by which half of newly promoted stories are relegated to a nether page.
这种放射性元素半衰期约为5700年。
This radioactive element has a half-life of some 5, 700 years.
对放射性强度跨越1000倍动态范围(10个半衰期)的跟踪测量中影响相对峰计数率精确测定的因素进行了讨论。
Factors influencing precise measurement of relative peak counting rates are discussed in time-series measurements over a dynamic range of 1000-fold radioactive intensities (10 half-lives).
不同衰变方式和半衰期的放射性核束在生物医学领域有不同应用。
Radioactive ion beams with different decay modes and half-lives can be applied in many aspects of bio-medical fields.
锕射气氡的一种放射性的，惰性的和气态的同位素，其半衰期为3。92秒。
A radioactive, inert, gaseous isotope of radon, with a half - life of3.92seconds.
如此短的半衰期便于治疗操作，也便于放射性抗体发挥作用。
Such a short half-life to facilitate the treatment of the operation, but also easy to play a role in radioactive antibody.
一种碳的天然放射性同位素，原子量为4，半衰期为5，780年，用于测定古代生物标本，地质标本或考古遗迹的标本的年代。
A naturally radioactive carbon isotope with atomic mass 4 and half-life 5,780 years, used in determining the age of ancient organic, geologic, or archaeological specimens.
当普通钴（59Co）吸收了一个中子后生成的是相对原子量60的钴。钴60有放射性且半衰期超过五年。
When common cobalt (59Co) absorbs a neutron the result is 60Co, which is radioactive and has a half-life of more than five years.
这在放射性方面不是很有意义，因为我们所观察的原子数目通常很大，以至于在实用上我们可以忘记半衰期变短的可能性。
This is not very interesting in radioactivity, because the number of atoms we look at is usually so huge that for practical purposes we can forget about the possibility of half-lifes getting shorter.
放射元素半衰期长，放射性污染物进入土壤会危害农业生态环境，威胁人类的健康和其他生物的生存。
Radionuclide with long half-life causes radioactive contamination and produces a series impact on the ecosystem, threatens human health and survival of other bio-organisms.
放射元素半衰期长，放射性污染物进入土壤会危害农业生态环境，威胁人类的健康和其他生物的生存。
Radionuclide with long half-life causes radioactive contamination and produces a series impact on the ecosystem, threatens human health and survival of other bio-organisms.
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