Radiochemistry

Question 1

Define Dose Equivalent I-131

Answer 1

• Concentration of iodine-131 equivalent to the mixture of all radioiodines present
• Concentration that would produce a thyroid dose as if all iodines were iodine-131

Question 2

Explain the CRUD cycle

Answer 2

1. Corrosion
2. Release
3. Deposition
4. Activation
5. Release
6. Deposition

Question 3

How can CRUD be released

Answer 3

• Changes in Power
• pH Changes
• Rapid Oxidation via air or hydrogen peroxide

Question 4

Describe the production of, and concerns associated wtih, Nitrogen 16 (N¹⁶)

Answer 4

• Oxygen 16 (O¹⁶) is activated and creates a Proton and Nitrogen 16 (N¹⁶)
• N¹⁶ is a high gamma emitter,is the most abundant activation product, and is the most limiting nuclide for shielding installation around the reactor coolant system
• N¹⁶ has a short halflife (7.13 seconds) so it is not a concern outside containment or after reactor shutdown

Question 5

Define Dose Equivalent Xe-133

Answer 5

• Dose Equivalent Xe-133 is based on the acute dose to the whole body and considers the noble gases which are significant in terms of contribution to the whole body dose

Question 6

Describe two methods for monitoring fuel cladding integrity during power operations

Answer 6

• Gross activity - a sample is taken, degassed and counted at exactly 20 minutes after sampling. This eliminates contribution or cariance caused by short half life isotopes
• Iodine 131/133 ratio - because of the difference in half life between iodine 131 and 133 a “normal” ratio will develop. If iodine 133 increases with respect to iodine 131, it is likely that a “fresh” fuel leaker exists

Question 7

Define CRUD

Answer 7

CRUD are activated corrosion products that are either suspended or deposited in the reactor coolant system

Question 8

Describe the hazards associated wtih tritum and the process responsible for the majority of the tirtium in the reactor coolant

Answer 8

• Not removed by tiltration, ion exchange, or evaporation
• Easily inhaled, ingested or absorbed through the skin
• Cannot be detected by a whole body count
• Can accumulate in he body over time
• When Boron 10 (B¹⁰) is activated it produces alpha radiation and about 80% of all Tritium (H³) in the reactor coolant system

Question 9

Describe the two mechanisms of fission product releases to the reactor coolant

Answer 9

• Tramp Uranium - uranium oxide imbedded in fuel cladding. Zircaloy also contains uranium “impurity”
• Cladding Defects - pinholes, cracks, etc. through which fuel generated fission products can leave the fuel and enter the reactor coolant system

Question 10

State three major classifications of activation products and give two examples of each

Answer 10

1. Corrosion products
   
   • Cobalt 60 (Co⁶⁰)
   • Silver 110M (Ag^110M)
2. Water/Water impurities
   
   • Nitrogen 16 (N¹⁶)
   • Sodium 24 (Na²⁴)
3. Tritium
   
   • Boron 10 (B¹⁰) becomes activated and creates alpha radiation and Tritium (H³)