The first half was relatively even with the Blues leading 10-6 at the interval courtesy of a try from Rhys Williams, and a conversion and penalty from Joe Deacon. The Scarlets struck back with two penalties from Daniel Newton, but after the interval the Blues ran riot with Christian Dacey, James Loxton, Rhys Downes and Lloyd Williams all adding tries.
Deacon added another conversion for good measure as the Scarlets found life increasingly difficult, despite the home advantage.
Meanwhile, the Ospreys proved far too strong for the Dragons at St Helens, winning 44-14.
Ryan Bayliss put the Ospreys on the board with an early try. They swept into a 17-0 interval lead thanks to a try from hooker Joe Beddow and two conversions and a penalty from last season's U16 captain Daniel Biggar.
The Dragons hit back after the break with tries from Kyle Price and John Burgess, with Danny Ellis adding two conversions. However, the Ospreys proved too strong in the final quarter with Bayliss adding his second try and Sam Williams and Scott Hancock making sure of the bonus point.
Biggar added two conversions and replacement Matthew Jarvis a third, whilst Biggar kicked a penalty and a drop goal to finish with seventeen points.
High Performance manager Dai Arthur said: "We were good early on and later on in the game, but all credit to the Dragons, they came back in the second half and made a real contest of it."