Understanding Gamma Ray Intensity with Cobalt-60

What is the gamma ray intensity at 1 ft from a 1 Ci source of radioactive Co-60?

• A. 10 R/h
• B. 15 R/h
• C. 20 R/h
• D. 25 R/h

Answer: (B)

The gamma ray intensity at a specific distance from a radioactive source can be calculated using the principles of radiation dosimetry. Cobalt-60 (Co-60) is a commonly used gamma radiation source, and its properties have been well-studied. For Co-60, the gamma radiation intensity can be expressed in terms of roentgens per hour (R/h) at a distance of 1 foot from the source, based on its activity measured in curies (Ci). The intensity from a 1 Ci source of Co-60 is generally around 15 R/h at a distance of 1 foot. This value is derived from the known gamma emission characteristics of Co-60, which emits two primary gamma photons with energies of 1.17 MeV and 1.33 MeV. The strength of these emissions, combined with the inverse square law of radiation intensity, contributes to determining the exposure rate. The intensity resulting from the 1 Ci source captures the average exposure rate, allowing for practical application in the field. Recognizing this standard value is crucial for professionals working with radiation safety and monitoring, as it provides a baseline for the expected exposure rates associated with commonly used radioactive sources like Co-60.

When preparing for the ASNT Radiographic Testing Test, you might find yourself grappling with complex topics like gamma ray intensity. But don’t worry, we’re here to break it down together! Let’s take a closer look at a common question: What is the gamma ray intensity at 1 foot from a 1 Ci source of radioactive Cobalt-60 (Co-60)?

Now, let’s set the stage. Imagine you have a 1 Curie (Ci) source of Co-60 in front of you (don’t worry, we’ll keep it theoretical). The answer options that pop up are: A) 10 R/h, B) 15 R/h, C) 20 R/h, and D) 25 R/h. Spoiler alert — the correct answer is B) 15 R/h.

So, how do we get here? To understand this, we venture into the realm of radiation dosimetry. You see, Cobalt-60 is a frequently utilized gamma radiation source, and scientists have been studying its properties like it’s their passion project. It emits two primary gamma photons at energies of 1.17 MeV and 1.33 MeV. These numbers might seem just like digits on a page, but they are crucial for calculating exposure rates.

To put it simply, at a distance of 1 foot, the intensity from a 1 Ci source of Co-60 hovers around 15 R/h. Why? Because of the inverse square law of radiation intensity — a fancy way of saying that as you move away from a radiation source, the intensity decreases rapidly. Think of it like holding a flashlight; the farther you hold it from the wall, the dimmer the light appears.

Now let’s connect this to your future career. Recognizing this standard gamma intensity is about more than just numbers; it’s about safety. Professionals working with radiation need to know what’s typical in order to monitor exposure effectively. This knowledge informs their work with both understanding and mitigating risks associated with radioactive materials.

Speaking of safety, it’s important to remember that while we can calculate averages, real-life scenarios can vary. So, when you're establishing protocols in your workplace, think of these calculations as guiding principles rather than absolute truths.

In a nutshell, being familiar with the radiation characteristics of materials like Co-60 sets you up for success in the field of nondestructive testing. Remember that over time, these concepts will become second nature; it just takes a little practice (and maybe some good study snacks!).

As you prepare for your exam, keep diving into topics like this, exploring beyond the basics. Test your knowledge, stay curious, and don’t hesitate to mingle with frameworks applicable in everyday scenarios — it’s all part of the learning journey. You’ve got this!