There are various interpretations of this song. The PV can be literally interpreted as Rin jumping into a nuclear reactor to commit a martyred suicide or figuratively as Rin trying to get rid of her past or to purge herself of her sins, and leave it behind in order to grow up and become an adult.
Iroha says the lyrics and video represent conflicts of inner psychological world. In the video, Rin jumps into a reactor core/nuclear reactor and chokes someone, possibly to death. The little Rin stands for innocent childish mind inside her. The choking scene symbolizes erasing her past self and starting a new. 
There was a controversy over the video related with the Weekly Vocaloid Ranking. Taking advantage of the Vocaloid Ranking's score system, the people made dummy accounts and put the song on their MyList, just to increase its score in the ranking, making it stay in the top 20 indefinitely. Though iroha(sasaki) asked the viewers to stop the illegitimate scoring, it did not end and in retaliation, Iroha deleted the video from his account and put it up on Nagimiso.SYS's. This disqualified the video from being in the Rankings as one of the requirements is that the original composer must submit it.
This raised the awareness of the cheating behind the Rankings. The score system of the ranking was modified, thus taking many long-lasting regulars such as Hatsune Miku no Shoushitsu, Miku Miku ni Shite Ageru, and World is Mine off the list altogether.
The new PV put up on Nagimiso.SYS's account features several touched-up areas including a different-looking reactor, new countdown text, and added detail in certain scenes.
A popular remix of Meltdown done by CosMo and illustrated again by Nagimiso.SYS. This version features a different music arrangement as well more expressiveness in Rin's voice, with various intentional voice breaks and changes of tone.
The PV also features a new design for Rin, looking like a young teenager dressed in a monochrome lolita dress and holding a golden electric guitar with the shape of the song's logo. This new design resulted in being more popular than her original one. The Hard R.K. mix received its own figurine, an inspired Meltdown's module for Project Diva 2nd, and a MikuMikuDance model created by popular modeler, ISAO.
A Techno remix by baker of Kagamine Rin's original Meltdown, sung by Hatsune Miku. The video was able to climb all the way up to No.2 in the Nico Nico Daily charts and was able to receive around 44,000 views in a very short period of time since it was uploaded.
A parody song and a sort of answer song to the KAITO's version of Loli Yuukai. On this versions the roles are swapped and now KAITO is the sexually harassed.
Rin, Miku and Luka are obsessed with KAITO, with each one caressing their own fantasies of what to do with him. Although in the beginning, they competed against each other, when they saw that their individual approaches and attempts didn't work, they decided to put those differences aside and join forces.
The song was well received, winning a place on the weekly ranking staying on the top 5 during two weeks (#118, #119).
This parody is about "Chunibyo" (中二病: 8th grade syndrome). Simply, one of the most typical symptoms of Chunibyo is that teens often fantasize about themselves as something special or transcendental being.