MS in Fire Protection Engineering
College of Engineering
Frederick Mowrer and Christopher Pascual
This report analyzes multiple aspects of fire protection and life safety design for the 2704-HV Building located at the Hanford Nuclear Reservation Site in Washington State. The analysis contained within focuses on both prescriptive and performance-based designs for the fire systems within the structure. The 2704-HV building is a two-story office building containing approximately 90 individual full-office spaces on each floor along with approximately 60 individual cubicle office spaces on each floor. There are various other types of gathering spaces within the 2704-HV layout including: conference rooms, showers, kitchen and dining areas, training rooms, and lobbies.
The 2704-HV building was constructed in 1990 with the intent to serve as the primary Waste Treatment Plant (WTP) Operations Center for the low activity nuclear waste left behind from the Manhattan Project. During the construction of the facility, the building was deemed inadequate to process nuclear waste and therefore repurposed to serve as office space for operations and support personnel. The overall area of 2704-HV is 126,769 ft2 and the overall height of the building is 32 ft. The building’s geometry is rectangular with dimensions of 348 ft by 182 ft.
In the prescriptive analysis, the means of egress, construction type, fire alarm system, and water- based fire suppression system located within the building were analyzed. After the in-depth analysis was performed, no deficiencies were noted in any of the systems. The 2704-HV building construction type, building height, building area, number of stories, and structural fire ratings comply with the International Building Code (IBC).
In the performance-based analysis, three design fire scenarios were selected based on the degree of hazard to the facility and the occupants. Hand calculations were performed for these three fire scenarios, but only one was selected to be modeled using computer-based software known as Fire Dynamics Simulator (FDS).
The first design fire scenario takes place in the main entrance lobby where two upholstered chairs located in the center of the lobby are ignited. Based on the combined peak heat release rate from the fire of these two chairs and external heat flux calculations, a third chair located at a distance of 2 meters across from the on-going fire auto-ignites. For this design fire scenario 1, sprinkler activation and secondary ignition were analyzed.
From the results of fire scenario 1, sprinkler activation occurs at approximately 2.5 minutes or 152 seconds from ignition of a lobby chair. The chair peak HRR output is 4,168 kW at 11.25 minutes. Secondary ignition for the chair at 2 meters across from the on-going fire auto-ignites at approximately 139 seconds or 2.3 minutes. The secondary auto-ignition of the chair at 2 meters is based on an external critical heat flux of 10 kW/m2.
The second design fire scenario takes place in one of the second-floor conference rooms. This scenario assumes that a conference room table and six chairs around it ignite. The heat release rate produced is evaluated along with the time to ignition of one of the chairs located along the wall of the conference room and directly across from the conference room table. For this fire scenario 2, secondary ignition, tenability conditions, and flashover conditions were analyzed.
From the results of fire scenario 2, secondary ignition for a chair directly across from the conference room table against the wall at a distance of 1.52 meters auto-ignites at 1,300 seconds or 21.6 minutes. This assumes a critical heat flux of 10 kW/m2 for the polypropylene chair. Sprinkler activation was not analyzed for this fire scenario, instead untenable conditions were calculated. Untenable conditions per the calculation results show that the conference room becomes untenable very quickly at 35 seconds from the initial fuel package igniting. If the fire is not controlled through fire suppression means, the conference room would experience flashover when the fire reaches 1,538 kW which is approximately 25 minutes from the initial fuel package igniting.
The third design fire takes place on the second floor in a cubicle office. The fire comes from a computer igniting and then secondary ignition occurs when a 7-gallon plastic trash bin within the cubicle auto-ignites. For this fire scenario 3, sprinkler activation, secondary ignition, and tenability conditions were analyzed.
From the results of fire scenario 3, sprinkler activation occurs at approximately 4.6 minutes or 280.0 seconds from ignition of the cubicle computer. Secondary ignition for the 7-gallon trash bin located 1.2 meters from the on-going computer fire auto-ignites at approximately 799.0 seconds or 13.3 minutes. The secondary auto-ignition of the trash bin is based on an external heat flux of 10 kW/m2. Secondary ignition would never occur in this scenario unless sprinkler activation is neglected. This is because the sprinkler located at an approximate distance of 3 meters activates 8.7 minutes before an external critical heat flux of 10 kW/m2 is radiated onto the trash bin. Untenable conditions per the calculation results show that the cubicle area becomes untenable at approximately 8 minutes from the initial fuel package igniting. In this scenario, untenable conditions would not be reached because the fire would be suppressed by the sprinkler.
Fire scenario 3 is the only design fire that was modeled using Pyrosim and Pathfinder. Sprinkler activation was neglected to analyze tenability conditions and to evaluate the available safe egress time versus required safe egress time (ASET Vs. RSET). Heat detection was modeled to determine the RSET detection time. The results for ASET were 16 minutes and 20 seconds and for RSET 6 minutes and 12 seconds. The results from the modeling analysis are satisfactory and validate the fire safety strategy currently installed in the 2704-HV building.