Premise :- If the check valves in nuclear power plants do not function properly, other parts of the plants’ piping systems can be critically damaged. Check valves cannot be tested in actual operation, but they are disassembled as part of routine annual maintenance and any flawed parts are replaced.
Conclusion:- Therefore, power plant accidents attributable to malfunctioning check valves are unlikely to occur.
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We are asked to weaken the conclusion using 1 of the 5 true statements.

(A) Approximately 80 percent of accidents in nuclear power plants are attributable to failures in piping systems. - The premise states that malfunctioning check valves can lead to piping system damage but that alone cannot be the sole reason. There can be an alternative reason as well and hence this will not weaken.
(B) Check valves in nuclear power plants tend to wear out after a few years in operation.- Contender. But malfunction is not necessarily wearing out and annual maintenance can fix this as said in the argument hence does not weaken though a good trap answer.
(C) Disassembling check valves can expose workers to radiation if precautions are not taken. - exposure to radiations is not accident. This is irrelevant.
(D) Flaws in any part of a check valve can be identified when the valve is disassembled. - This is a repeat of the premise hence a wrong answer.
(E) Errors made in the reassembly of check valves can go undetected. - this is something that the argument misses to mention and hence considering this statement is true, will undermine the conclusion.

Hence my choice is E.

Hey Senthil, Could you please elucidate more on option A? Am a bit confused between Option A and E.

Hi Kshitij92,


The stimulus says....failure of X (check valves) can lead to failure of Y (piping mechanism). X are serviced every year and hence there will not be any problems because of X.

We have to weaken this.
Opn A says 80% of the failures are because of Ys. Well we are not so sure that failure of Y is caused only by that of X. Are we? Had this been mentioned in the stimulus, this would have been a correct answer.
Now, opn E says...Errors while reassembling might go unchecked. So this creates a doubt that...since every year X is serviced, there is a probability that these are not fixed well and can lead to accidents..

Hope this is clear.

I am still NOT clear with the explanation of option A above. Can someone elaborate more on why option A is incorrect. Though I picked E as the answer but was doubtful between A and E.

Please evaluate my reasoning for option A.

(A) Approximately 80 percent of accidents in nuclear power plants are attributable to failures in piping systems. As per my understanding of the above argument, this option statement slightly strengthens the conclusion instead of weakening it. If 80% or majority of nuclear power plant accidents are attributable to piping system failures and those failures are, in turn, caused by the malfunctioning of the check valves, then the routine annual maintenance will detect and fix those malfunctioning valves, and thus power plant accidents attributable to malfunctioning check valves are unlikely to occur. Though, I agree that failures in piping system can occur due to other factors as well, but we are not concerned about the other factors and neither the other factors are in the scope of this argument. The argument's conclusion is restricted to the accidents attributable to the malfunctioning of the check valves.

As per the details given in the argument or basically as per the scope of the argument, I am considering only the failure of piping system as the major impact to power plants by the malfunctioning of the valves. Therefore, option A is incorrect.

Can someone review my point of reasoning? As I am unsure about the same.

the method that I use to find the correct answer is to comprehend the meaning of each option and eliminate wrong options.
Well, it seems that this question does not have any obvious pattern, but ones can choose the right answer by understanding each option.

PREMISES
1) If check valves do not function properly other parts can be critically damaged. However this does not imply that when parts are critically damaged then the check valves are non functional.
2) Flawed check valves are replaced during annual maintenance.

CONCLUSION
Power plants accidents cannot occur because of flawed check valves as they would be replaced during annual maintenance.

Tempting, this option forces us to think that as majority of the accidents are because of failure in piping systems and this failure is because of non functional check valves hence check valves are responsible for these accidents. And remember this what we need to find. We need to find an answer choice that says that even though flawed check valves are replaced, they could still be responsible for power plant accidents. This answer choice though tempting is not the correct answer as I already said above that failure in piping systems does not necessarily imply that check valves are non functional.


these check valves anyways would be replaced in the annual maintenance.


Irrelevant


Opposite of this could have been a good contender.


Best of the lot, even if flawed check valves are replaced with new check valves there is still a possibility that power plants accidents are attributable to check valves. If the check valves are not reassembled the way they should be and this error goes undetected then check valves will probably not be replaced until the next maintenance cycle.

Hey experts,

KarishmaB GMATNinja DmitryFarber ExpertsGlobal5 mikemcgarry AjiteshArun

I am completely not able to understand why option D is incorrect and option E is correct.

Premise :- If the check valves in nuclear power plants do not function properly, other parts of the plants’ piping systems can be critically damaged. Check valves cannot be tested in actual operation, but they are disassembled as part of routine annual maintenance and any flawed parts are replaced.
Conclusion:- Therefore, power plant accidents attributable to malfunctioning check valves are unlikely to occur.

Hi waytowharton,

The part of the argument where the author says check valves "are disassembled as part of routine annual maintenance and any flawed parts are replaced" is strengthened by option D. Look at it this way: if flaws in any part of a check valve CANNOT be identified when the valve is disassembled, then it is less likely that the flawed parts will be replaced (because they can't be identified). On the other hand, if the flawed parts CAN be identified, then it's more likely that they will be replaced.

Option E tell us that the process of fixing the check valves ("reassembly") can itself introduce new problems, which will then most likely go undetected till at least the the next round of routine annual maintenance, which would give other parts of the plants’ piping systems plenty of time to "be critically damaged".
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Unable to understand why option E is correct. Conclusion is malfunction attributed to check valves is unlikely to occur. Weakener for this should be malfunction attributed to check valves is likely to occur. Option E says if errors will go undetected then other parts would also damage and we will not be able to attribute this to check valves. Hence, this is a strengthener.

AjiteshArun,

Apologies I am unable to understand. Could you please help me again? Conclusion is malfunction attributed to check valves is unlikely to occur. Weakener for this should be malfunction attributed to check valves is likely to occur. Option E says if errors will go undetected then other parts would also damage and we will not be able to attribute this to check valves. Hence, this is a strengthener.

KarishmaB

Notice what you said:

Option E says if ERRORS will go undetected

Notice what the conclusion is:

power plant ACCIDENTS attributable to malfunctioning check valves are unlikely to occur

The fact that errors will go undetected does not mean that accidents will not be attributable to malfunctioning valves.

After all, once the accidents occur, even if the original errors were undetected, the accidents could be traced back to malfunctioning valves.
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Try to reason against the stimulus when facing weaken type questions.
Here the stimulus says that the routine repair removes any flaws in check valves. What if I said that those repair works ain't doing their job properly or that those repair works leave parts unrepaired?
You see, a weakener is a counter claim that makes you believe less in the proposed plan. And that's what (E) does here.

Posted from my mobile device
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Hi waytowharton,

But if the malfunctioning valves are causing the ~problems, can't we say that the ~problems are (directly or indirectly) attributable to them?
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