Bruno,

Your situation does not preclude the use of a surrogate key at all. As a matter of fact, if you had a cirtuit table and created a new record init for the new order, used the surrogate PK for all related tables, then when the circuitID became available you would only need to update the circuit table with the ID. Since no other tables actually contain that value there is no need to touch them.

As well as the advantages of using surrogate PKs, there is a considerable value is being consistent with all table designs. For me, no matter what every table has a surrogate PK. All natural keys are relagated to candidates.