LSAT 151 | Section 4 | Logical Reasoning: Q24

LR Question 24 Explanation

QUESTION TEXT: After a nuclear power plant accident, researchers…

QUESTION TYPE: Most Strongly Supported

FACTS:

1. Materials found after a nuclear plant accident: iodine, tellurium, cesium. No heavy isotopes found.
2. Only possibilities were spent fuel, and the core. The core could have sent materials directly into the atmosphere, or or indirectly from steam.
3. Spent fuel has no tellurium. [This rules fuel rods out as a sole cause]
4. Material directly from the core would have heavy isotopes. [This rules out direct from the core]
5. The core has iodine, tellurium, and cesium isotopes, and all of these are dissolved by steam.

ANALYSIS: This is a heavy question, with a lot of moving parts. I had to read it 2-3 times to get a sense of it, but after that it was clear. If you have the time left in the section, it’s worth spending the time on the stimulus to clear things up. As long as there are still thing you know you can figure out, it makes sense to stay on the stimulus rather than look at the answers.

This is a “most strongly supported” question, so it doesn’t have to be 100% true. We know three things:

• Fuel rods can’t have accounted for all of the material: they don’t have enough tellurium
• It can’t have been directly from the core: that would have produced heavy isotopes.
• Steam from the core would have had the right elements: iodine, tellurium, and cesium

Based on this, it seems very likely steam was the cause. You might be wondering about the heavy isotopes. Well, we know this:

1. Direct emission would cause heavy isotopes. But steam isn’t direct emission.
2. Further, steam dissolves cesium, iodine and tellurium.

Does “dissolving” an isotope make it not heavy? Eh, probably. Like I said, this is “most strongly supported”. You know from common sense that dissolving a thing tends to make it less solid. Plausibly, this applies to heavy isotopes as well. Since we ruled out all other possibilities, we can be fairly confident in steam.

Note: though I made no diagrams, I think this is the type of question where you would want to write some sort of notes. Maybe sketching out possibilities. There’s no correct way, I just think it’s more than can be comfortably held in the head. I used this explanation to take stuff out of my head and understand the setup.

___________

1. The stimulus clearly says that the core has tellurium, so we would expect tellurium to leave the core if the core’s contents were directly ejected.
    
   It’s fuel rods that lack tellurium.
2. CORRECT. See the analysis above. Only the core has the three elements, and steam offers the only possibility of getting them out of the plant apart from direct ejection. (Direct ejection would have heavy isotopes.)
3. This is a trap. We know that the fuel rods can’t account for all of the radioactive material seen. Tellurium was seen, and fuel rods don’t have enough tellurium.
    
   But….it’s possible the radioactive material came from more than one source. The emissions could have come from “steam from the core” and from “fuel rods”. The fuel rods have no unique material that we know of, so their emissions could have mixed in with the steam. Thus, the fuel rods could have been damaged and leaked iodine and cesium. Remember: many things have multiple causes.
4. This could have been tempting had it said “material that was released from the core via steam”. We know that direct emissions from the core would include heavy isotopes, and no heavy isotopes were found.
    
   However, even then I don’t think this would have been right. It’s possible that some material escaped the fuel rods, but we have no evidence that this happened. This answer treats this as a certainty.
5. We have no idea if this is true. The author implies this by not mentioning the possibility, but they didn’t actually give us any evidence to support this answer. An answer doesn’t have to be 100% true, but it needs at least some evidence to support it. Omission isn’t enough.