Raposo improved on his bib number of 19 to break comfortably into the top ten in Romania.
A first run of 53.63 seconds left him lying seventh at the halfway stage and the 17-year-old held nothing back on his second run, clocking a 54.17 seconds for an overall time of 1:47.8, less than a second and a half outside the medal positions.
But, despite the performance, Raposo admitted it was a far from perfect technical display.
"I'm really pleased with the result but not so much with my skiing," he said.
"I felt like I made a few mistakes in the second run when I was pushing really hard, it was right on the edge.
"But that is ski racing for you, these things can happen and I have to pleased with that finish.
"I'm a year younger than a lot of these guys and I beat a lot of people who have better FIS points than me, so I'm really pleased."
Elsewhere, Team GB's Maisie Potter secured an encouraging seventh in the snowboard cross competition.
A tumble in her semi-final cost her a place in the medal race but the 15-year-old produced a strong showing in the B final to finish third.
Short track speed skater Kathryn Thomson, who won 500m silver yesterday, was also back in action competing in the 1000m where she finished up fifth while Mari Deland and Aydin Djemal reached the quarter-finals in their respective events.
But Jack Burrows, a gold medallist 12 months ago at Winter Youth Olympic Games in Innsbruck, was penalised for skating outside of the track and failed to make it out of his heat as a result.
"I left it a bit too late to make my move in the semi-final which was a little bit frustrating because I could have made that final as well," said Thomson, who trains with World Cup champion Elise Christie.
"But overall I am so pleased with the week that I have had, it was a fantastic feeling to get a medal and go to the evening ceremony and celebrate it."
In cross-country skiing Sarah Hale and James Clugnet's struggles continued as they finished 51st and 71st respectively in the classic technique races.
And in the biathlon, the Scottish trio of Sam Cairns, Lachlan Cowie and Robert Sircus finished 69th, 70th and 74th in a tough day's racing in the 12.5km individual.