see the file attached

You are a Health Physicists at a University and you knew it was going to be a bad day when on the way to work, a TTC bus splashed rain water on you after driving over the biggest pot hole on Young Street. You decide to go into the laboratory to change your wet clothes and have a cup of coffee to settle the nerves. Feeling better, you go into the next laboratory to visit your friend and discover that the interlock system on the 60Co irradiation source wasn’t working and you had just walked through a radiation field. Feeling shaken again, you quickly retreat to your laboratory to do a final experiment with 131I. Your horrible day continues as you accidentally add HNO3 instead of a reducing agent to the iodide solution, and as a result, you spill the solution and create some 131I vapor. Fortunately, an iodine monitor was operational during this episode. You decide to retreat to your office and calculate your personal dose. Unfortunately, you have loaned your ICRP Annals to a student, and so you have to do the calculations from first principles.

You remember that 60Co decays with the emission of 1.17 and 1.33 MeV gamma-rays, each of 100% abundance. And that 131I emits both gamma and beta radiation and that the average energy of each 131I beta particle is:

Energy (MeV/transition)

Yield, f

0.0701

0.016

0.0955

0.069

0.1428

0.005

0.1917

0.904

0.2856

0.006

1

PCS406 Assignment #2 Winter 2018

(A) For 60Co

You walked toward the 60Co source at a rate of 1.5 m/s, at a distance of 2 m you stopped to look into the 60Co (20 Ci) source for 20 seconds realizing that the interlock system is not operating and that the source is not in its shield, and you run out of the laboratory at a rate of 5 m/s.

1. 1)  Calculate your total absorbed dose from vising your friend’s laboratory and report your answer in SI units.

2. 2)  Calculate the absorbed dose rate to the cortical bone, skeletal muscle tissue, adipose tissue, lung tissue and water from this incident. Mass energy absorption coefficients (μen/ρ) can be found at the NIST database Photon Cross Section Database: Material Specific”. The link is provided at the end of this assignment.

3. 3)  Calculate your effective dose from this exposure to 60Co.

4. 4)  Based on actual measurements two days later, you determine that the source was 18.5 Ci. If the source

   was retracted in the shielding made of 10 cm lead and you passed 2 meters in front of the shielded 60Co source and you estimate your exposure time was 20 seconds, as described in the incident, calculate the change in your equivalent dose compared to the incident scenario.

(B) For 131I

1. 1)  Luckily you had an air sampler in the breathing zone when your disaster occurred. Air is pumped at a rate of 0.02 m3 min-1 through a charcoal filter with an iodine collection efficiency of 100%. Both the sampling time and inhalation time were 10 minutes and the filter was counted immediately after collection. The room volume is 72 m3. If the corrected activity on the filter was 8.2 x 106 disintegration per minute (dpm), what was your skin dose being immersed in this environment?

   [Note for now we will neglect the internal dose due to the inhalation of radioactive 131I.]

2. 2)  Due to the spill of the 131I (300μCi) solution, a circular area of 0.5 m in diameter was contaminated on the bench. What is the maximum equivalent dose rate at a distance of 30 cm from the contaminated area?

3. 3)  You have to clean this spill as soon as possible. What is the equivalent dose rate if a 50 cm long tongs are used during the cleaning of this spill, which can take up to 5 min to complete?

(C) For the incident itself:

1. (1)  What value would you quote for your effective dose of this day at work?

2. (2)  How does your effective dose from all these incidents compares to the Canadian annual radiation dose to

   an occupational exposed person such as you? Do you need to stop or modify your work habits?

3. (3)  If the risk factor for mortality is 1.25 x 102 per Sv, what is your risk from this incident?

4. (4)  The previous incident has left you shaken to such an extent that you start smoking cigarettes. If the risk

   is 2 x 10-1 per cigarette, how long do you have to smoke a package of 20 cigarettes a day to equal the

   risk from your blundering in the laboratory?

5. (5)  You decide to quit smoking. To help, you take a vacation to Rockies, where you will climb a few

   mountains and do some canoeing. During you vacation, you drive your car for a total of 100 h, you canoe for another 100 h and climb for an additional 50 h. If these activates have the risk factors of 0.95 x 10-6 h-1, 1 x 10-5 h-1 and 4 x 10-5 h-1, respectively, what effective dose corresponds to the same risk of mortality as your vacation?