The phrase "an integral portion" is correct and usable in written English.
It can be used to describe something that is a necessary or essential part of a whole.
Example: "The research findings are an integral portion of our understanding of climate change."
Alternatives: "a crucial part" or "an essential component".
We propose three new (4; 2) compressors via improving best previous designs by replacing an integral portion of relevant logical circuits by an optimized CMOS full-adder.
Our system is an interwoven major component and an integral portion of America's economy.
Despite being an integral portion of the music ecosystem since its inception nearly 40 years ago, rap has largely been overlooked in other major Grammy categories as well.
However, there have been several interesting demonstrations of nucleic acid circuits that rely upon proteins for an integral portion of their function.
We are an integral part of an integrated European economy.
Testbenches are an integral part of model development and a significant portion of the total effort.
It might also take part in visuo-spatial attention shifting, along the anterior portion of the PMC, which is an integral part of the TPN.
Although I never adopted the spiritual portion of TM, the physical practice became an integral part of my daily routine.
By contrast, a system reliant on recycling often creates waste as an integral part of its production process in the hope that a portion of it may eventually be recycled.
It is suggested that portions of the EGMB must have been an integral part of Peninsular India at the time of deposition of these sediments.
"The University of Ottawa considers that postdoctoral fellows (PDF) are an integral part of the University community and contribute to its mission," reads a policy statement on the FGPS portion of the university's Web site.
