A 150-Ci sealed Na-24 source is to be stored in a pool at a depth of...

 

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A 150-Ci sealed Na-24 source is to be stored in a pool at a depth of 150 cm. Na-24 decays by beta emission to 24mMg (metastable state). This is followed by the emission of two gamma rays per disintegration (2.75 MeV gamma and 1.37 MeV gamma) to reach the stable ground state of 24M9. You may ignore the lower energy gamma ray in any buildup factor calculations. Given: For this problem, the interpolated buildup values and other constants are provided below: H= 0.043 cm for the 2.75 MeV gamma Pz = 0.061 cm for the 1.37 MeV gamma The gamma ray constant for 24Na, r = 1.8 R-m2 /hr-Ci Buildup factors for 2.75 MeV photons - isotropic point source in water: Photon ux Energy (MeV) 4 6 7 8 10 5.88 5.02 2.0 2.77 4.88 7.24 8.46 9.76 12.4 2.75 2.50 4.15 5.88 6.78 7.70 9.57 3.0 2.42 3.91 4.68 5.44 6.23 7.02 8.63 A. What would the dose rate be at 5 meters above the source? (15 points) B. What would the dose rate be at the surface of the water? (5 points) A 150-Ci sealed Na-24 source is to be stored in a pool at a depth of 150 cm. Na-24 decays by beta emission to 24mMg (metastable state). This is followed by the emission of two gamma rays per disintegration (2.75 MeV gamma and 1.37 MeV gamma) to reach the stable ground state of 24M9. You may ignore the lower energy gamma ray in any buildup factor calculations. Given: For this problem, the interpolated buildup values and other constants are provided below: H= 0.043 cm for the 2.75 MeV gamma Pz = 0.061 cm for the 1.37 MeV gamma The gamma ray constant for 24Na, r = 1.8 R-m2 /hr-Ci Buildup factors for 2.75 MeV photons - isotropic point source in water: Photon ux Energy (MeV) 4 6 7 8 10 5.88 5.02 2.0 2.77 4.88 7.24 8.46 9.76 12.4 2.75 2.50 4.15 5.88 6.78 7.70 9.57 3.0 2.42 3.91 4.68 5.44 6.23 7.02 8.63 A. What would the dose rate be at 5 meters above the source? (15 points) B. What would the dose rate be at the surface of the water? (5 points)