The concept of scuttling a ship rather than allowing it to be captured dates back hundreds of years. It's also a logical concept, losing a ship to capture also meant losing what secrets that vessel held, which could later be used against you. Be those secrets technological or otherwise.
With seafaring vessels, it wasn't too hard to deliberately scuttle your own ship. Punch a few holes in the right places and the hull would fill with water. How this was achieved varied. More modern ships also had protections against flooding, but the crews being aboard could easily circumvent them to ensure the ship went under the waves rather than be captured by hostile boarding parties. Blowing charges in key areas, and leaving hatches open was a surefire way to sink the ship. Another option was to leave a charge in the magazine and allow the resulting flashfire to claim the ship. ɴᴇᴡ ɴᴏᴠᴇʟ ᴄʜᴀᴘᴛᴇʀs ᴀʀᴇ ᴘᴜʙʟɪsʜᴇᴅ ᴏɴ novel⁂fire.net
In space, however, there is no water to fill a ship. Punching holes in the hull merely allows for the air to escape the hull. Life can't survive in a vacuum, but it's not too hard to protect against that, and there isn't a vast ocean to sift through while looking for a sunken hull. As a result more thorough methods were required. Blowing a ship's magazine can still do a fair amount of damage, but another option was to overload the reactors. Further options include placing scuttling charges throughout the vessel. All of which have been experimented with during the century-long period of warfare known as the Colonial Wars.
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Modern vessels however benefit from a mechanism made possible by the discovery of Rydium. Its unique properties for energy conversion and amplification, along with its use in propulsion systems made possible a surprisingly potent method for scuttling a ship.
All Earth vessels are equipped with an overload system that would not only overload all reactors on a ship. Effectively turning each active reactor into a nuke, but they also overload the primary sublight drives. The exact particulars of the process are classified, but the results are something else.
When the Rydium cores surpass critical mass, they unleash a massive thermonuclear shock pulse on the order of several hundred gigatons. The detonation of a capital ship in this manner not only destroys the ship, but also releases a shockwave that is dangerous to any vessel in range of the blast, which in some cases has been deadly as far out as fifty thousand kilometers from the center of the blast, while in the vacuum of space. This fact has also played into Rydium based warheads being researched, with varying degrees of success.
Another item to note about Earth ships, is that they tend to contain an auto-destruct system. Upon sustaining a critical level of damage, one of several computers would automatically initiate an overload of all remaining active systems in an attempt to destroy the ship. This auto-destruct can be manually deactivated only from one of several key control centers. If no counter order is received the auto-destruct will proceed as designed.