CORRECTION OF 241am FOR CONTRIBUTION OF 155 Eu DOE/ERSP TECH NOTE NO.3.0 DATED: November 1977 AUTHOR: F. Tomnoveec, EG&G The EG&G IMP detects the presence of 241Am by measuring the 59.553 keV gamma-ray emitted by this isotope. Quite often in the gamma-ray spectrum measured by the IMP there is a quantity of 155fu, This isotope of europium has three gamma-rays. The energies and branching ratios for the two gammarays of interest are 60.01 keV, 1.32%; 86.55 keV, 32.2%. From the branching ratios we compute that for every 100 of the 86.55 keV gamma-rays there are 4.1 of the 60.010 keV gamma-rays. The resolution of the IMP detector system is approximately 1 keV; therefore, we are unable to resolve the 60.010 keV gamma-ray of 155Eu from the 59.553 keV gamma-rayline of 41am. Whenever the 155—y 86.550 keV gamma-ray exceeds 10 pCi/gm we make a correction to the lam by subtracting 4.1% of the 155Eu 86.550 keV gamma-ray from the 241am. Table B-3-1 shows the correction for Pearl, the only island to need any corrections at this time. TABLE B-3-1. 155Ey CORRECTION TO 2414m DATA ON PEARL Run 118 120 122 123 125 101 102 103 105 169 96 68 76 20 22 34 Stake No. 155Fy(86.550 keV) (pCi/g) 1-N-1 0-N-1 0-BL-0 0-5-1 -1-BL-0 3-8-2 3-N-1 2-N-1 2-BL-0 2-S-1 3-N-2 4-N-2 6-N-2 4-§-3 5-5-3 5-54 155Fu(60.010 keV) 24lam (pCi/g) 21.7 13.8 13.3 12.9 12.2 14.1 11.9 14.3 13.0 14.2 11.3 10.5 10.6 12.3 22.9 12.6 (pCi/g) 0.89 0.57 0.55 0.53 0.50 0.58 0.49 0.65 0.53 0.58 0.46 0.43 0.43 0.50 0.94 0.52 35.2 23.2 24.0 22.5 19.7 22.2 20.6 21.0 19.5 23.8 23.8 22.9 21.1 21.0 35.9 22.3 241 Am Corrected (pCi/g) 34.3 22.6 23.4 22.0 19.2 21.6 20.1 20.4 19.0 23.2 23.3 22.5 20.7 20.5 35.0 21.8 REVISION OF 155&zu CORRECTION FACTOR FOR 24lAm DOE/ERSP TECH NOTE NO,3.1 DATED: 22 March 1979 AUTHOR: R. Jaffe, EG&G A slight correction is recommended to the original Technical Note 3 subtraction factor that accounts for the 60.0 keV gamma from the 155—y which appears in the 59.5 keV gamma peak used to detect 24l1Am. The factor of 4.53% of the 155Eu should be used, rather than the 4.1% originally calculated. The 4.53% factor accounts for the greater penetration of the predominant 86.5 keV gamma used to calculate 155—y, as discussed in EG&G Report RSSD-78-177, "In Situ Determination of 2414m at Enewetak Atoll," by Tipton, Fritzsche, and Villaire (Aug. 1978). The formula to correct 241 Am concentration is: 241 Am (corrected) = 241Am - 0.0453 155 Eu Only where 195£uy is greater than half of the 24l1Am concentration is a correction factor above about 2% required. This condition was encountered at a few locations on Pearl and corrected values furnished with Tech Note 3. No changes to those values are necessary. B-3-1