Question

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2. Circle the designator in front of the correct answer() from the list following each question or statenent. (o) A radioactive sample with Ti 10 hours earlier? (10 pointa 2h has an activity of I mCl sow. What wns ite activity i. 32.0 mCi ii. 10.0 mCI ii. 6.0 mCi iv. 2.0 mC v. 0.2 mC (b) The water in the primary loop of a typical PWR is used as (10 pointal i. a coolant ii, a fuel ili, a moderator iv. a control rod v. none of the above (o) The radionuclide 137 Cs beta docays to a metastable state of 137Ba, which emits a 661.6- keV photon with a frequency of 89.78%. The uncollided flux density of 6615-keV photons at a distance of 20 cm from a 5 mCI polnt source of STCs in water is approximately [10 points i. 66.2 cm-2 -1 ii. 5.9 x 10 em s- iii. 8.4× 105 can-2s-1 iv. 3.9 × 10'an-2 s-1 v. 4.8 x 10° cm 2 -1 (d) A beam of 1-MeV gamma rays irradiates a 1-gram sample of water. If the flux of the bearn is 1.5 x 10 gammas em 2 s-1, which of the following is closest to the kerma rate in the water? [10 points i. 2.5 Gy s-1 ii. 2.7 x 10-2 Gy s-1 ili. 4.5 x 10- Gys iv. 7.2 x 10-6 Gy s-1 v. 7.5 x 10-7 Gy s-1 (e) The meun fre path length of s 1-MeV photon in concrete is about (10 points i. 500 cm ii. 50 cm iv. 0.5㎝ v. 0.05 cm

Answer 1

2a. given half life period = 2 hour and present amount = 1 mCi and before 10 hour amount of substance present = 32 mCi

Reason : 32 mCi ---(2 hr)--->16 mCi----(2 hr)--->8 mCi------(2 hr)--->4 mCi----(2hr)---->2 mCi----(2 hr)---> 1 mCi

b. the water in the primary loop of a typical Pressurized Water reactor is used as a coolant .