射(she)線(xian)(xian)防護材料對電離輻射(she)的屏蔽機(ji)理是通過材料中(zhong)所含吸(xi)(xi)(xi)收(shou)(shou)物(wu)(wu)質(zhi)(zhi)(zhi)(zhi)對電離輻射(she)的吸(xi)(xi)(xi)收(shou)(shou)完成的。射(she)線(xian)(xian)防護材料中(zhong)吸(xi)(xi)(xi)收(shou)(shou)物(wu)(wu)質(zhi)(zhi)(zhi)(zhi)對射(she)線(xian)(xian)的吸(xi)(xi)(xi)收(shou)(shou)大體(ti)是以(yi)能(neng)(neng)量(liang)吸(xi)(xi)(xi)收(shou)(shou)和粒(li)(li)子(zi)(zi)吸(xi)(xi)(xi)收(shou)(shou)這兩(liang)種方式(shi)進行(xing)。能(neng)(neng)量(liang)吸(xi)(xi)(xi)收(shou)(shou)是以(yi)射(she)線(xian)(xian)與(yu)物(wu)(wu)質(zhi)(zhi)(zhi)(zhi)粒(li)(li)子(zi)(zi)發生(sheng)彈性和非彈性散(san)射(she)方式(shi)進行(xing)，如康普(pu)頓(dun)散(san)射(she)；粒(li)(li)子(zi)(zi)吸(xi)(xi)(xi)收(shou)(shou)以(yi)射(she)線(xian)(xian)粒(li)(li)子(zi)(zi)與(yu)物(wu)(wu)質(zhi)(zhi)(zhi)(zhi)的原(yuan)子(zi)(zi)或(huo)原(yuan)子(zi)(zi)核發生(sheng)相互作用(yong)方式(shi)進行(xing)，如光電效應。當(dang)物(wu)(wu)質(zhi)(zhi)(zhi)(zhi)與(yu)高(gao)能(neng)(neng)X射(she)線(xian)(xian)作用(yong)時，能(neng)(neng)量(liang)吸(xi)(xi)(xi)收(shou)(shou)占主導(dao)地位；當(dang)物(wu)(wu)質(zhi)(zhi)(zhi)(zhi)與(yu)中(zhong)能(neng)(neng)和低能(neng)(neng)X射(she)線(xian)(xian)作用(yong)時，粒(li)(li)子(zi)(zi)吸(xi)(xi)(xi)收(shou)(shou)占有重(zhong)要地位。
能量吸收的(de)大(da)小與吸收物質原子序數的(de)4次方成正比。
鉛的(de)原子序(xu)數為82，具(ju)有良好(hao)的(de)能量(liang)吸收特性，且易獲(huo)得，是(shi)一種用以屏蔽高能電離輻射(she)的(de)理想材(cai)料(liao)，傳統的(de)射(she)線防護材(cai)料(liao)主要(yao)為鉛橡膠和鉛塑(su)料(liao)。
人(ren)們用(yong)鉛當(dang)量(liang)來衡(heng)量(liang)射(she)線(xian)防(fang)護(hu)材料對電離(li)輻射(she)射(she)線(xian)的(de)(de)(de)吸收能力。國內外X射(she)線(xian)防(fang)護(hu)標準中規定的(de)(de)(de)鉛當(dang)量(liang)值，根據人(ren)體(ti)(ti)防(fang)護(hu)部(bu)位(wei)(wei)、照射(she)條件(jian)等因素的(de)(de)(de)不同一般在(zai)0.1～1.0mmpb之間。在(zai)X射(she)線(xian)照射(she)量(liang)較低(di)的(de)(de)(de)作業(ye)環(huan)境中可選用(yong)0.1mmpb的(de)(de)(de)防(fang)護(hu)服，既使(shi)作業(ye)人(ren)員(yuan)減輕了負(fu)重和疲勞，又(you)可達(da)到(dao)防(fang)護(hu)的(de)(de)(de)目的(de)(de)(de)；而(er)對于(yu)人(ren)體(ti)(ti)重點防(fang)護(hu)部(bu)位(wei)(wei)，如性腺和生殖(zhi)系(xi)統，則應選用(yong)0.5mmpb和1.0mmpb的(de)(de)(de)防(fang)護(hu)服或(huo)用(yong)具。