近來,核能發電的議題持續發燒,反核者一再主張,萬一核能發電廠發生災變導致輻射外洩,可能會造成重大傷亡。由於核能發電具有減少空氣污染與溫室氣體的排放等優點,現在有科學家從另一個角度來研究,核能發電運轉至今,是否已經避免了人命的損失? 根據即將出版的新一期《環境科學與技術》(Environmental Science & Technology)期刊中,有一篇由NASA氣候科學家Pushker A. Kharecha與James E. Hansen共同撰寫的論文:〈從歷史與規劃中的核能發電,探討其所避免的死亡人數與溫室氣體排放量〉(Prevented Mortality and Greenhouse Gas Emissions from Historical and Projected Nuclear Power)指出: 在2011年3月日本福島第一核電廠事故發生後,未來核能發電在全球能源供應的貢獻,已經變得有些不確定。由於核能發電是一個豐富、低碳的基本負載電力的來源,它對減緩全球氣候變遷與空氣污染,有著相當大的貢獻。根據歷史數據,研究者計算出,在1971年至2009年間,全球核能發電大約造成5千人因輻射導致的癌症與工安事故而死亡,但也防止大約184萬人免於因空氣污染而死亡、以及來自於燃燒化石燃料所產生的640億噸二氧化碳當量的溫室氣體排放。又此處所謂的死亡,並不包括因長期健康問題所可能減短的壽命,研究者也沒有試圖估計與氣候變遷有關的潛在死亡人數。 接下來,研究者以推估數據為基礎發現,到2050年為止,如果以天然氣來取代全球規劃將要使用的核能發電,將會多造成42萬人死亡、並多排放出800億噸二氧化碳當量的溫室氣體;如果是以煤來取代,則會多造成704萬人死亡、並多排放出2400億噸二氧化碳當量的溫室氣體。換句話說,核能發電,到2050年為止,將能避免全球42萬到704萬人死亡、以及800億到2400億噸二氧化碳當量的溫室氣體排放。因此,研究者評估大規模使用天然氣,並不會減緩氣候問題;而其所導致的死亡人數,將遠遠比大規模發展核能發電還多。
Radioactive trace elements Coal is a sedimentary rock formed primarily from accumulated plant matter, and it includes many inorganic minerals and elements which were deposited along with organic material during its formation. As the rest of the Earth's crust, coal also contains low levels of uranium, thorium, and other naturally occurring radioactive isotopes whose release into the environment leads to radioactive contamination. While these substances are present as very small trace impurities, enough coal is burned that significant amounts of these substances are released. A 1,000 MW coal-burning power plant could have an uncontrolled release of as much as 5.2 metric tons per year of uranium (containing 74 pounds (34 kg) of uranium-235) and 12.8 metric tons per year of thorium.[31] In comparison, a 1,000 MW nuclear plant will generate about 30 metric tons of high-level radioactive solid packed waste per year.[32] It is estimated that during 1982, US coal burning released 155 times as much uncontrolled radioactivity into the atmosphere as the Three Mile Island incident.[33] The collective radioactivity resulting from all coal burning worldwide between 1937 and 2040 is estimated to be 2,700,000 curies or 0.101 EBq.[31] During normal operation, the effective dose equivalent from coal plants is 100 times that from nuclear plants.[31] Normal operation however, is a deceiving baseline for comparison: just the Chernobyl nuclear disaster released, in iodine-131 alone, an estimated 1.76 EBq.[34] of radioactivity, a value one order of magnitude above this value for total emissions from all coal burned within a century, while the iodine-131, the major radioactive substance which comes out in accident situations, has a half life of just 8 days.