If you were to log in, you'd be able to get more information on your fellow community member.
Not pretty at all but it works...
CREATE OR REPLACE FUNCTION interval_to_seconds(x INTERVAL DAY TO SECOND ) RETURN NUMBER IS
s VARCHAR2(26);
days_s VARCHAR2(26);
time_s VARCHAR2(26);
N NUMBER(10,6);
BEGIN
s := TO_CHAR(x);
days_s := SUBSTR(s,2,INSTR(s,' ')-2);
time_s := SUBSTR(s,2+LENGTH(days_s)+1);
N := 86400*TO_NUMBER(days_s) + 3600*TO_NUMBER(SUBSTR(time_s,1,2)) + 60*TO_NUMBER(SUBSTR(time_s,4,2)) + TO_NUMBER(SUBSTR(time_s,7));
IF SUBSTR(s,1,1) = '-' THEN
N := - N;
END IF;
RETURN N;
END;