BURN-UP CROSS-SECTION OF W-188

Tungsten-189 was produced by irradiating a radioactive target containi ng a known amount of W-188. I, order to reduce the radiation level to an acceptable level (<20% detector dead time), we chemically removed > 90% of Re-188 (the decay product of W-188) prior to irradiation. We we re able to confirm the two predominant gamma-rays in the decay of W-18 9, 260.1+/-1.4 and 421.5+/-1.6 keV. By following the decay of these ga mma-rays in two sets of experiments, a half-life of 10.8+/-0.3 min was obtained for W-189. Based on a knowledge of the W-188 content of targ et (52.6 MBq), neutron flux density of 5 x 10(13) n.s(-1).cm(-2), irra diation time of 10 min and with the assumption of 100% intensity for 2 60.1 and 421.5 keV gamma-rays, a cross-section of 12.0+/-2.5 b was cal culated for burn-up of W-188.