Date: 201812
Local time of day: 1801-2400
Location: PDX.Airport, OR
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower PDX
Second aircraft: PA-34 Seneca Undifferentiated
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Developmental
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: In-flight; Taxi
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: I taxied Aircraft X to Runway 10L full length with a clearance to cross Runway 21 on Kilo. At the time of this instruction; I had control of Runway 3/21. There were no conflicts along the taxi route so I passed the strip. Aircraft Y had cancelled IFR and the Local 1 Controller made the decision to bring Aircraft Y to Runway 03. This was based on ragged fog at the approach end of Runways 10 left and right as well as the southwest. The LC1 Controller then asked for control of Runway 3. I scanned my strip bay and the runway and seeing no traffic; I gave control of Runway 3 to the LC1 controller. I did not realize Aircraft X had not yet crossed and reached the approach end of 10L. The Clearance Delivery Controller recognized that Aircraft X was in the process of crossing Runway 21 at Kilo as Aircraft Y was on short final. He recognized the conflict and advised the LC1 Controller. The LC1 Controller issued go around instructions to the LC1 Controller. When I heard the LC1 Controller issue go around instructions I scanned the runway and adjacent taxiways for conflicts. My thought was an aircraft in the vicinity of Echo and Foxtrot had mis-executed my instructions. I did not see Aircraft X and recognize the conflict. Additionally; before regaining control of Runway 3/21; I issued taxi instructions to Aircraft Z via Kilo with the clearance to cross 21. I take full and complete responsibility for this incident. It was my responsibility to ensure that no conflicts existed prior to transferring control of Runway 3/21. Additionally; it was my responsibility to protect the runway when I do not have control of it. I did not execute those responsibilities. I expect to be held accountable as I would expect anyone in this organization to be held accountable for mediocre; sub-standard; unsafe performance. I am completely supportive of any and all remedial training opportunities to include classroom training; skill enhancement training and decertification. I do not want to be a minimally competent controller. I welcome the chance to get better. After discussions with senior experienced controllers about their techniques in this type of situation; I am not going to give up control of my runway until visually verifying that all aircraft in the receiving controllers bin are accounted for prior to releasing the runway. I am open to all constructive comments and ideas to be better. I am available for any clarifying questions.




Synopsis: Portland Tower Controller reported a ground conflict and runway incursion were managed by issuance of go-around instructions.