Buium played two seasons for the USA Hockey National Team Development Program. During the 2021–22 season, he recorded four goals and nine assists in 49 games for the Under-17 team, and two goals and three assists in 32 USHL games. During the 2022–23 season, he led all team defensemen with 40 points in 63 total games for the Under-18 team, and two goals and ten assists in 23 USHL games.[2]
College
Buium began his collegiate career for the Denver Pioneers during the 2023–24 season. He was the second-youngest player in NCAA Division I hockey during his freshman year.[3] He was named the National Collegiate Hockey Conference (NCHC) Player of the Month and the HCA National Co-Player of the Month for November 2023. He became the first freshman defenseman to ever win NCHC Player of the Month.[4] He led all NCHC players in points (14), points-per-game (1.75), assists (11) and plus/minus (+13) during the month.[5] With three assists in a game against Western Michigan on December 9, 2023, he extended his scoring streak to 12 games, surpassing Lane Hutson's record for the longest point streak by a freshman defenseman in the last 21 years.[6] He was named the NCHC Rookie of the Month for December 2023. During the month he recorded one goal and six assists in four games. His 1.75 points per game was tied for the most in the NCHC during the month, and his seven points led all league freshmen and defensemen in scoring in that time.[7] Buium led all NCHC freshmen and NCHC defensemen and ranked second behind Jackson Blake with 31 points in 24 conference games, the second-most points ever in NCHC play by a defenseman, trailing only Scott Perunovich's 32 points during the 2019–20 season. His 25 assists in conference play were also second among all skaters and first among defensemen. Following the season he was named to the All-NCHC First Team and All-NCHC Rookie Team.[8] He was also named NCHC Rookie of the Year and NCHC Offensive Defenseman of the Year.[9]
Buium was born to Israeli immigrants Sorin and Miriam Buium. His mother, Miriam, played professional basketball in Israel before an injury ended her playing career and she transitioned to a general manager.[16][17] Buium's older brother, Shai, also played college ice hockey at Denver and was drafted 36th overall by the Detroit Red Wings in the 2021 NHL entry draft.[18] Buium has a tattoo on his left forearm commemorating the dates he won two gold medals and an NCAA title in Hebrew.[19]