Low background gamma spectrometry was used to measure the radionuclides activity of <sup>238</sup>U, <sup>232</sup>Th, and <sup>235</sup>U series as well as <sup>40</sup>...Low background gamma spectrometry was used to measure the radionuclides activity of <sup>238</sup>U, <sup>232</sup>Th, and <sup>235</sup>U series as well as <sup>40</sup>K and <sup>137</sup>Cs in a sediment sample. The goal of the study was to measure the <sup>238</sup>U (63.3 keV peak of <sup>234</sup>Th;1001 keV peak of <sup>234m</sup>Pa) and <sup>235</sup>U (143.76 keV, 163.33 keV, and 205.31 keV peaks) activity by low background gamma spectrometry in sediment sample. <sup>235</sup>U activity in environmental samples is difficult to accurately measure by gamma spectrometry due to its low abundance in nature and low gamma line intensities at 143.76 keV, 163.33 keV, and 205.31 keV. We have shown that by using low background gamma spectrometry, it is possible to accurately measure the <sup>235</sup>U activity in sediment samples. The <sup>235</sup>U activity was measured without using the major peak of 185.7 keV (I<sub>γ</sub> = 57.2%) which requires interference correction from 186.21 keV of <sup>226</sup>Ra. <sup>226</sup>Ra activity was determined by measuring <sup>222</sup>Rn daughters (<sup>214</sup>Pb and <sup>214</sup>Bi). The precision and accuracy of the gamma activity measurement in the sediment sample were verified by using the HPGe detectors with Certified Reference Material (CRM) Irish Sea Sediment (IAEA-385). The results obtained for the 63.33 keV energy line of <sup>234</sup>Th are compared with the 1001 keV energy line of <sup>234m</sup>Pa. The values of <sup>238</sup>U and <sup>235</sup>U activities, as well as <sup>40</sup>K, <sup>137</sup>Cs, and <sup>226</sup>Ra, agreed with the certificate values of CRM. The results show that the <sup>238</sup>U is in equilibrium with its daughters (<sup>234</sup>Th, <sup>234m</sup>Pa, and <sup>210</sup>Pb). <sup>232</sup>Th is also in equilibrium with its daughters (<sup>228</sup>Ra, <sup>212</sup>Pb, <sup>212</sup>Bi and <sup>208</sup>Tl). <sup>235</sup>U/<sup>238</sup>U activity ratio of 0.046 ± 0.007 in the sediment is constant in nature but fluctuates due to geological processes. A value of 0.055 ± 0.008 was found in our sediment sample.展开更多
文摘Low background gamma spectrometry was used to measure the radionuclides activity of <sup>238</sup>U, <sup>232</sup>Th, and <sup>235</sup>U series as well as <sup>40</sup>K and <sup>137</sup>Cs in a sediment sample. The goal of the study was to measure the <sup>238</sup>U (63.3 keV peak of <sup>234</sup>Th;1001 keV peak of <sup>234m</sup>Pa) and <sup>235</sup>U (143.76 keV, 163.33 keV, and 205.31 keV peaks) activity by low background gamma spectrometry in sediment sample. <sup>235</sup>U activity in environmental samples is difficult to accurately measure by gamma spectrometry due to its low abundance in nature and low gamma line intensities at 143.76 keV, 163.33 keV, and 205.31 keV. We have shown that by using low background gamma spectrometry, it is possible to accurately measure the <sup>235</sup>U activity in sediment samples. The <sup>235</sup>U activity was measured without using the major peak of 185.7 keV (I<sub>γ</sub> = 57.2%) which requires interference correction from 186.21 keV of <sup>226</sup>Ra. <sup>226</sup>Ra activity was determined by measuring <sup>222</sup>Rn daughters (<sup>214</sup>Pb and <sup>214</sup>Bi). The precision and accuracy of the gamma activity measurement in the sediment sample were verified by using the HPGe detectors with Certified Reference Material (CRM) Irish Sea Sediment (IAEA-385). The results obtained for the 63.33 keV energy line of <sup>234</sup>Th are compared with the 1001 keV energy line of <sup>234m</sup>Pa. The values of <sup>238</sup>U and <sup>235</sup>U activities, as well as <sup>40</sup>K, <sup>137</sup>Cs, and <sup>226</sup>Ra, agreed with the certificate values of CRM. The results show that the <sup>238</sup>U is in equilibrium with its daughters (<sup>234</sup>Th, <sup>234m</sup>Pa, and <sup>210</sup>Pb). <sup>232</sup>Th is also in equilibrium with its daughters (<sup>228</sup>Ra, <sup>212</sup>Pb, <sup>212</sup>Bi and <sup>208</sup>Tl). <sup>235</sup>U/<sup>238</sup>U activity ratio of 0.046 ± 0.007 in the sediment is constant in nature but fluctuates due to geological processes. A value of 0.055 ± 0.008 was found in our sediment sample.
