The phrase "upon the breakup" is grammatically correct and usable in written English.
It can be used in a variety of contexts, usually to expressing an event or circumstance that immediately follows something else. For example: "The couple decided to go their separate ways upon the breakup of their five-year relationship."
The barrage of publicity was an embarrassment to Prince Rainier and his wife, especially when it grew fierce upon the breakup of the young couple.
After the sultan's death, it fell to the Bahmanī sultanate (of which it was the capital between 1347 and c. 1424) and, upon the breakup of that power, to Bijapur (Vijayapura).
This is certainly the case when it comes to determining custody of a companion animal upon the breakup of pet parents.
Yankovic wrote the song for a woman he was dating in homage of her previous boyfriend who, upon the breakup asked her, "I'm such a groovy guy!
Although the piece reflects upon the breakup of families, homes, and communities, presenting these parts as a unified structure points to hope for the future.
Tajikistan became independent upon the breakup of the Soviet Union, after which it endured a period of devastating civil war.
But others say Mr. Merrill and the other founders brought the breakup upon themselves.
Neither she nor all of Kierkegaard's torrential comments, direct and indirect, upon the matter ever quite explained the breakup, which had outraged her family and titillated local society.
With the breakup of the empire upon Alexander's death in 323 bce, control of the city passed to his viceroy, Ptolemy I Soter, who founded the dynasty that took his name.
In all of these cases, the formation of PFAFs was rationalized by side-reactions with small amounts of the RF radicals (mostly CF3) resulting from an advanced fullerene fluorination leading to the breakup of the cage upon high-temperature treatment with high-valency metal fluorides.
Upon re-entry, hot gases entered the breach, causing the breakup of the spacecraft.
