Acta Facultatis Ecologiae - Technická univerzita vo Zvolene

86Alpha spectrometryAlpha spectrometry with Dual alpha spectrometerwas realized before SIMS analysis. Activitieswere obtained from counts and calculated fromEquation 1:( nd− nb)A = , (1)e.Rwhere A is an activity of sample [Bq]; n dis a countrate of isotope [s –1 ]; n bis a count rate of background[s –1 ]; ε is efficiency of detector; R is recoveryof electrodeposition (R = 0.86 according to [16]).Uncertainities of alpha activity measurements werecalculated from Equation 2:AuA= ± .1.96 , (2)NDwhere A is alpha activity [Bq]; N Dis number ofcounts obtained from alpha spectrometry measurements.Results obtained from Eq. 1 and Eq. 2 aredescribed in Tab. 2:Relatively high difference between relationships234 U/ 238 U and 235 U/ 238 U are caused bylow activities of uranium isotopes at low-activesamples. These low-active samples were close tobackground.Conversions of activities to weights by Eq. 3are summarized in Tab. 3:A.Arm = . T1/ 2 , (3)N A.ln 2where m is weight of uranium isotope [g]; A isactivity [Bq]; A ris relative atomic weight; N AisAvogadro’s constant; T 1/2is half time of decay [s].Surface area after electrodeposition was 2.97 cm 2 .Values of surface’s weights of uranium in g.cm –2are summarized in Tab. 3.SIMS resultsDiscs prepared by electrodeposition after alphaspectrometry were measured at the InternationalLaser Center in Bratislava by TOF-SIMS IVTab. 2 Results from alpha spectrometry234U235U238U234U/ 238 U235U/ 238 UDisc# 1Disc# 2Disc# 3Disc# 4Disc# 5.A [Bq] 0.0068 0.0002 0.0042 1.619 0.0476u A[±Bq] 0.0017 0.0003 0.0013A [Bq] 0.0124 0.0003 0.0102 1.216 0.0294u A[±Bq] 0.0023 0.0004 0.0021A [Bq] 0.0202 0.0014 0.0173 1.168 0.0809u A[±Bq] 0.0029 0.0008 0.0027A [Bq] 0.5687 0.0153 0.5152 1.1038 0.0297u A[±Bq] 0.0646 0.0090 0.0615A [Bq] 1.086 0.0267 1.128 0.9628 0.0237u A[±Bq] 0.089 0.0127 0.091Tab. 3 Values of weights and surface’s weights of uranium isotopesDisc No.234 235 238U U Um [g] m s[g.cm –2 ] M [g] m s[g.cm –2 ] m [g] m s[g.cm –2 ]Disc # 1 2.95⋅10 –11 2.93⋅10 –12 2.69.10 –9 9.07.10 –10 3.38.10 –7 1.14.10 –7Disc # 2 5.38.10 –11 1.81.10 –11 4.04.10 –9 1.36.10 –9 8.23.10 –7 2.77.10 –7Disc # 3 8.79.10 –11 2.96.10 –11 1.75.10 –8 5.90.10 –9 1.39.10 –6 4.70.10 –7Disc # 4 2.47.10 –9 8.32.10 –10 1.91.10 –7 6.44.10 –8 4.14.10 –5 1.39.10 –5Disc # 5 4.72.10 –9 1.59.10 –9 3.34.10 –7 1.13.10 –7 9.07.10 –5 3.06.10 –5