Question

The half‐life of $^{137}Cs$ is around \rule{1cm}{0.15mm}.

• A. 15 years
• B. 30 years
• C. 45 years
  - Option (D) 60 years

Hint:

Radiation Sources Memory:
- Co-60 = Convenient but short life (~5 years).
- Cs-137 = Constant/Long life (~30 years).

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the half-life of Caesium-137 ($^{137}Cs$), which is one of the two primary isotopes used in industrial food irradiation facilities.

Step 2: Detailed Explanation:

• Food Irradiation Isotopes: To irradiate food, gamma rays are typically sourced from either Cobalt-60 ($^{60}Co$) or Caesium-137 ($^{137}Cs$).

• Half-Life Concept: The half-life is the time required for half of the radioactive nuclei in a sample to decay. It determines how often the source needs to be replenished.

• $^{137Cs$ Data:} Caesium-137 has a half-life of approximately $17$ years. In multiple-choice questions, this is commonly rounded to $30$ years.

• Comparison with $^{60Co$:} Cobalt-60 is much more common in industry but has a much shorter half-life of approximately $5.27$ years.

• Decay Process: $^{137}Cs$ decays into Barium-137m, which then emits a $0.662$ MeV gamma ray used for processing.

Step 3: Final Answer:
The half-life of $^{137}Cs$ is approximately 30 years.