Let's see:
Science = the intellectual and practical activity encompassing the systematic study of the structure and behavior of the physical and natural world through observation and experiment.
Circular reasoning = a logical fallacy in which the reasoner begins with what they are trying to end with. The components of a circular argument are often logically valid because if the premises are true, the conclusion must be true. Circular reasoning is not a formal logical fallacy but a pragmatic defect in an argument whereby the premises are just as much in need of proof or evidence as the conclusion.
It's not entirely clear where the original poster is trying to go with this. I think there can be some confusion between these two uses of the word Science:
1) Science as a mental technique, a set of tools used to attempt to classify or give logical structure that which is being observed. We all do it naturally--try to make sense of the world. Whether you believe there is a "physical" world or if you think it's all subjective and internal hardly matters. Science in this regard (in the way scientiests themselves think of it) is just taking the collective striving of many people over a long time and trying to distill the techniques that seemed to do best at structuring the observed phenomena.
2) Some people tend to think of Science as just another religion (set of beliefs), even if they wouldn't state it in such terms themselves. For example, evolution, gravity, structure of the cosmos, etc, are beliefs to be accepted or rejected, just like the beliefs in their own religion.
But science is a kind of training. It structures the mind. It's true that after this training, the mind is more inclined to believe some kinds of things not other kinds of things. It might, for example, balk at the idea of the universe being created in 6 days. It might subsequently ask, 6 of what kind of days? How long was each day? This is just an example of what Science, defined as the training or technique, might prompt a mind to ask. So it's not entirely unfair to see Science as a bucket full of beliefs. Which is probably how a scientist defines a religion.
Since most religions don't do the best job of organizing their beliefs, formally defining terms and concepts, or scrutinizing the origins of those beliefs, it would be natural for a religious person to not understand why science is ALSO a technique, and NOT just a bag full of beliefs. And scientists themselves usually don't buy 100% into any of the prevailing theories. In fact, I would venture to guess that an academic researcher actually hopes the prevailing belief is inaccurate in some way, thus opening the door for them to discover a different belief that is more consistent with observed phenomena (and thereby acquiring fame / accolades for themselves).
Now, I am going to take a guess at the original poster's purpose in writing about circular reasoning. And this is just my personal opinion. When you examine any of the dominant beliefs held by the scientific community, you see that knowledge is kind of like a building or structure, built upon more and more fundamental building blocks of knowledge or theorems. At some point, those ideas bottom out at a piece of fundamental observation that is neither provable nor easily deconstructed.
For example, let's examine the idea that heat is really thermo-kinetic energy. It's been redefined as the degree of movement of molecules comprising a substance. This definition / understanding helps us invent devices that manipulate heat or cold, like refrigerators, air conditioners, heaters, etc.
However, we could easily imagine a naive conversation:
Q: What are molecules?
A: Molecules are composed of atoms.
Q: What are atoms?
A: Atoms are made up of subatomic-particles.
...
This is what I think the original poster was hinting at, or at least how I choose to interpret it. At some point, we reach the edge of what we can easily describe, the envelope of our shared collective knowledge as a scientific community.
But that's not exactly circular reasoning, is it? At least, it's not the term I would have chosen for the idea that our scientific knowledge is built out of smaller pieces until a piece is irreducible or is itself unsupported. A better examples of circular logic might be:
"It is not raining today because no water is falling from the sky."
This is circular because the premise offers nothing really distinct from the conclusion. It's really just re-stating the conclusion.
Somewhat better might be:
"It is not raining today because there are no clouds in the sky."
This is not circular reasoning because it implies a causal relationship between clouds and rain. If we were to delve further into our collective knowledge about clouds and rain, we'd eventually come up against the wall (or edge) of our knowledge I defined earlier.
I'm going to really guess now. I obviously don't know the mind of the original poster (OP from now on). It's almost as if the OP recognizes, at least sub-consciously, the central problem with the world's major religious: they contain a lot of contradictory beliefs. Or at least, beliefs that are not supported by satisfying explanation or further clarification. It's almost like a sort of half-hearted counter-attack to say, "Science is based upon circular reasoning." If you knew the proper definitions for these terms, you'd realize the science practically demands that anything worth writing down must provide something information by way of improved explanatory power or greater consistency among existing well-established observations. Science was a technique that was developed over the ages specifically to counteract the human tendency to answer the question "Why" with "that's just the way it is."
I'm going to leave off with just this one last comment. The educated mind realizes that Science and Religion are not at odds. Science is a technique that tries to make sense of the this experience we call life. Religion is a collection of beliefs. Experience and observation leads most of us to eventually form beliefs. Therefore, science is merely a tool by which one can help oneself choose between competing beliefs, or reject entire subsets of beliefs entirely. These two concepts, Science and Religion, are only ever at odds inside of the lazy mind. Put even more simply, science can help you choose a specific religion, or no religion at all (although everyone believes something, whether it's an established religion or just lazy pop-culture philosophy.)
TLDR: Science is NOT based upon circular reasoning, practically by definition. And science and religion are not opposed, except in the lazy mind.
EDIT: yes, I know that science defines cold as an absence of heat. I specifically wrote it that way to demonstrate how classifying phenomena helps us organize things in our mind in such a way that leads to practical application--like a refrigerator.