Archon Engineering, PC

Tornado Missile Impact

All nuclear plants have requirements that their safety related equipment be protected from missiles generated by tornados. The missiles range from a 1” steel rod up to an automobile. The velocities involved approach 200 ft/sec.


Tornado Missile Impact on a Projecting Fuel Line:

This project was performed for a nuclear power plant. The concern was that a fuel line, projecting outside of a safety related building could be struck by a tornado missile and driven inside the building, affecting connected safety related piping. Several missiles were reviewed. The missile shown in the images was for a 12” diameter pipe traveling at 154 ft/sec. The piping and reinforced concrete wall were modeled in ANSYS “Explicit” Finite Element Analysis (FEA) software.

The conclusion in the calculation stated that the bond between the pipe and concrete would fail but the plastic strains within the safety related piping, within the building, were below material rupture limits. Based on the above, we concluded that the piping was functional and past operability issues were not a concern.

It should be noted that by using ANSYS “Explicit” the FEA model accounted for material damage by eroding the elements that reached failure limits. This accounted for material destruction during the impact event.

Based on our analysis the client was not required to develop and install a costly barrier to protect the fuel line.


Protection from Tornado Missiles during Construction Iteration:

New safety related piping was to be installed at this nuclear power plant. Excavations would expose the existing piping, which had to remain functional. Archon was contracted to design tornado missile resistance covers for the trenches and building penetrations that would protect the safety related piping.

Our approach was to model various cover designs in our event simulation Finite Element Analysis (FEA) software. We determined the controlling missile size and performed impact analysis on the covers.

Our analysis provided a cost effective design that would provide protection of the safety related piping from tornado missiles during the construction duration.


Tornado Missile Impact on Soil Cover Plate:

Due to an excavation, protective soil was removed from around a safety related pipe. The concern was that the removal of soil would reduce the pipe's general stability and a tornado missile striking the ground above the pipe would damage the pipe.

Archon’s solution was to model the cover plates, soil and pipe in our Finite Element Analysis (FEA) software and review the pipe damage after simulating a controlling tornado missile impact.

From our review of deflections in the 30” pipe, we were able to determine that the pipe would remain functional after a tornado missile impact.