Hanford only ever had one reactor that produced electricity, the N reactor, and that wasn't built until 1963:
So we can address that immediately: without the Hanford site, Japan would not have surrendered without an invasion of the home islands. Maybe not even then. It was the "new and cruel bomb," as the Emperor of Japan described it while citing it as the reason for surrender in his speech. That "new and cruel" bomb meant an alternative to reenacting the Battle of Iwo Jima (which I would describe as "fucked up" for both sides without question) a thousand times. Battles to the last cartridge. Forgetting completely about the lives of Allied and Axis soldiers, you realize the death toll that would have on the civilians of Japan? They were on the hook for all kinds of atrocities all over Asia and the Pacific, in the context of total war they pissed off the rest of the world way too hard for the Allies to declare a truce. Just in Korea alone, the stories are just...let's not talk about that, let's stick to what is fucked up within nuclear science.
Japanese were subscribed to the idea that their genocide was preferable to surrender. So that's why the bomb, and by extension the Hanford site, were so important. In practice the nukes in Japan explosives second, fireworks first. Napalm was a much better explosive for the money, in terms of the destruction it could produce. The really bad bombings in WWII were in Tokyo and Dresden, a hundred thousand dead per bombing, a new climactic event called a "Firestorm," terrible burns, pavement getting goopy, high winds--I claim those bombings were worse. But they weren't as flamboyant as a star.
But nobody knew about that when Hanford was set up and running, before then.
The firestorms were horrendous for the population, which had no influence on leadership, and were anyway ineffective against industrial production, so were doubly pointless. Blockade was massively underused in the Pacific theater.
Recall the Battle of Carrhae? Recap: Crassus was at the head of a Roman legion inside Parthia (meaning "Persian"; modern-day Iran). Totally flat. Then they started getting shot with arrows. Crassus and his legion would march toward the archers, but as they got close, the archers would stop shooting long enough to take vehicles drawn by horses away from the Roman soldiers, until they were far enough they could resume shooting arrows. The battle is well-known, but the detail I'd like to call attention to is that in Suetonius's "The Twelve Caesars" (IIRC) it says when the soldiers figured out the heavy rain of arrows would never stop, the soldiers ordered Crassus to surrender. Screaming at him and threatening him! So that's what he ended up having to do. Mutiny is no joke.
That is my thesis for the Japanese surrender. Perhaps the military leadership was too nicely tucked into safe bunkers near anti-aircraft turrets (I don't know what Japan had, but Berlin had four of these and they worked great against bombers, really scared the birds away quite nicely, guaranteed Killed-in-Action if you got too close). Whatever, the military leadership could relax if all they had to fear was conventional warfare, whatever the hell that meant by that particular month of 1945.
But nukes changed everything. Wrath of GOD, basically. After one bomb, Japanese leadership I imagine asked their internal Manhattan Project--they were working on the atomic bomb too at the time--what was happening. Presumably they were told it was a one-off thing, because uranium was too difficult to make. What really changed the game was the second bomb, which meant America could mass-produce them--thanks to Hanford, in particular--and then it was like, are we going to get another one of these new and cruel bombs every three days indefinitely? Where are they going to drop them in the future? What are the consequences of the starburns on the survivors, are the ones that lived going to be recover their health...ever? Are they dropping the next one on the Imperial Palace in Tokyo, and killing Hirohito as promised to the people of America? WHY ARE THE GODS SO ANGRY AT US, WERE WE WORSHIPPING SATAN THE WHOLE TIME? WILL THE PEOPLE OF JAPAN MUTINY WHEN THEY SEE A STAR ABOVE TOKYO? WHAT DO JAPANESE PEOPLE DO WHEN THEY MUTINY, IT'S OBVIOUSLY GOING TO HAPPEN EVEN IF IT'S NEVER HAPPENED BEFORE, WHAT WILL THE PEOPLE DO TO US? WHY DIDN'T WE CAVE IN TO THAT BEAUTIFUL ULTIMATUM THREATENING TO BRING ABOUT OUR "PROMPT AND UTTER DESTRUCTION," WHAT A BEAUTIFUL GIFT, why didn't we listen and surrender like they asked?
(I claim writing in all caps like this is justified. That is the literary freedom I ask for, and the site allows it in theory. Not doing so does an injustice to the degree of alarm imminent destruction brings about. The inner monologue when that destruction makes itself known sounds something along the lines of "OH FUCK OH FUCK OH FUCK!". All caps in your inner monologue. That's just for your personal reference, haven't seen it well-portrayed in movies much. It's not like anything else, maybe someday you'll see for yourself, dear reader. I hope not.)
