萃取液闪法测定尿中^（239，240）Pu

EXTRACTION-LIQUID SCINTILLATION COUNTING OF ^(239,240)Pu IN URINE

从２４ｈ尿中取样７５０ｍｌ，加入ＨＮＯ３－Ｈ２Ｏ３，以温式友化去除有机物。在０．５－１．０ｍｏｌ／ｌＨＮＯ３介质中，用３０％ＴＲＰＯ－二甲苯萃取２３９，２４０Ｐｕ等α核素。在Ｈ２Ｏ２作用下，Ｎｐ为Ｎｐ（Ⅴ），其萃取分配比极低；Ａｍ（Ⅲ）等核素被萃取，用５．５ｍｏｌ／ｌＨＮＯ３洗涤去除。以０．０１ｍｏｌ／ｌＨＮＯ３洗涤有机相，去除绝大部分被萃ＨＮＯ３后，加入ＵｌｔｉｍａＧｏｌｄＦ闪烁液，于低本底ＴＲＩ－ＣＡＲＢ２５５０ＴＲ／ＡＢ液闪仪上测量α放射性计数率。根据２３９，２４０Ｐｕ测量窗的计数效率，扣除尿样α本底值后计算出从事钚操作职业人员尿中２３９，２４０Ｐｕ的放射性活度。取样７５０ｍｌ，方法对α的最低检测限为０．７ｍＢｑ。经示踪法检验，方法精密度为３％，放化回收率为９９％±３％。

HNO3-H2O2 is added to 750 ml urine sample taken from 24h excreted urine, and the sample is evaporated to near dryness for wet ashing of organic materials. 239,240Pu, U, Am and rare earth elements in the sample are extracted by 30 % TRPO-Xylene. HNO3, Am and rare earth elements extracted into the organic phase are removed by washing with 5. 5 and 0. 01 mol/l HNO3 orderly. Then, ultima Gold F scintillator is added to the organic phase and α- activity is counted in a low background TRI-CARB 2550TR/AB liquid scintillation analyzer under pulse decay discrimination time 145 PDD (87ns). Final, α-activity in urine is calculated according to the counting efficiency of 239,240Pu under certain window windth. 239,240Pu activity in urine of professional person from hot cell and plutonium plant is obtained by substraction uranium α-activity in same person' urine using laser-phosphoroscope analysis. The whole procedure reagent blank is 0. 07 min-1 with a measuring time of 1000 min, the minimum detectable α-activity is 0. 7 mBq in 750 ml urine sample. Precision of the method is 3 % and chemical recovery is (99±3) %.