Further results in search for transuranium element

Authors: Z Hölgye E Schlesingerová

Publish Date: 2010/08/27

Volume: 286, Issue: 2, Pages: 341-345

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Abstract

In this work we present data on transuranium nuclides 238Pu 239240Pu 241Am 242Cm and 244Cm in effluents discharged to air activity concentrations and annually discharged activities of individual radionuclides from 7 stacks in 2004–2009 In the effluents discharged to air from one stack low activities of transuranium nuclides were observed throughout the studied period Transuranium nuclides had been discharged to air from this stack also in previous years since 1996 when defect in the cladding of a fuel element and consequent contamination of the primary circuit occurred In the effluents discharged to air from another stack transuranium nuclides were observed only in some monitoring periods of studied years We could not prove the presence of transuranium nuclides in the effluents of the other stacks up to 2006 The transuranium nuclides in discharged effluents were registered in the second halfyear of 2006 In 2007–2008 especially low activities of 241Am were found in these effluentsEven under normal operation of nuclear power plants NPPs discharges of radioactive substances into the atmosphere take place Considerable attention is given to monitoring of radioactive noble gases iodine 14C fission and activation products in particulate form in airborne effluents The annual discharged activities of these radionuclides have been reported by individual NPP 1 On the other hand there is little information given on the monitoring of the release of biologically important 239240Pu 238Pu 241Am and other transuranium nuclides TRU from NNPs under normal operation conditions 2Monitoring of TRU in effluents discharged to air from NPPs started in our institute in 1985 The main objective was to obtain discharge data on TRU for each nuclear power plant operated in the Czech Republic and Slovak Republic Up to 2003 we had searched for TRU in effluents discharged to air from five stacks stacks 1 and 2 of the former V1 and V2 NPP Jaslovské Bohunice stacks 3 and 4 of the former V3 and V4 NPP Dukovany and stack 5 of NPP Temelin At four of these stacks stacks 1–4 the effluents come from the main production building with two pressurized water reactors of 440 MWe power of each reactor and from the auxiliary service building for the primary system At stack 5 the effluents come from the main production building with one pressurized water reactor of 1000 MWe power The results obtained were from time to time published and observations made during all the study are summarized in the previous paper 2 They are 1 238Pu 239240Pu 241Am 242Cm and 244Cm can be present in effluents discharged to air Their activity concentrations and discharged activities from individual stacks however vary in wide range The presence of TRU in effluents from the stack 5 was not proved at all and their activities in effluents from stacks 2 and 4 were either lower than their limits of detection or only slightly exceeded these limits in some monitoring periods On the other hand during all the nine years of study measurable activities of TRU were found in the effluents discharged to air from stack 1 and from stack 3 since the third quarter of 1996 as a result of a defect in the fuel cladding At the stack 3 further increases of TRU activities in effluents occurred in the third quarter of 1999 and the third quarter of 20032 Two phases can be distinguished in the time course of TRU discharge the first phase represents the first quarter when the increase begins and the second phase represents a further time period with lower discharges The second phase can last many years In all the three events at the stack 3 the activity of 242Cm reached the highest value in TRU mixtures in the first phase of the discharge Nevertheless several other substantially lower increases of TRU discharge with maximum 242Cm content were also registered during the study Those however lasted for one or two following quarters only3 There exist definite activity ratios of TRU in effluents discharged to air So activity ratio of 238Pu/239240Pu in effluents from the stack 1 was approximately 10 during all the 9 years’ study The activity ratios in effluents are given by the ratio of these radionuclides in fuel from which the contamination has originated We calculated for definite conditions the activity ratios of 238Pu/239240Pu 241Am/239240Pu 242Cm/239240Pu and 244Cm/239240Pu in fuel for different burnup values4 TRU discharged to air from the studied stacks contribute very little to further contamination of the environment For example the largest annual discharge of 239240Pu 66 kBq from the stack 1 was equivalent to the activity of these radionuclides from atmospheric nuclear tests fallout in top soil for an area 1100 m2 in our geographic positionSeven stacks were studied in 2004–2009 Two of them stacks 3 and 4 belong to NPP Dukovany and five stacks 5–9 to NPP Temelin At the stack 7 the effluents come similarly to stack 5 from the main production building with one pressurized water reactor of 1000 MWe power At stacks 6 and 8 the effluents come also from the main production buildings and they are released mainly during shutdown periods Stack 9 discharges effluents from the auxiliary service building for the primary system

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