Hi Anantha,
Residual Risks are expected to continue to exist after planned responses have been taken, as well as those that have been knowingly accepted.
Secondary Risks, on the other hand, arise as a direct consequence of implementing a risk response.
For example, if you are teaching someone how to ride a bike, to reduce the risk of injury, you provide a helmet and clear a sidewalk of extraneous rocks and foliage. There is still a residual risk of riding off the curb and falling over, however.
A secondary risk is a direct result of implementing a risk response. For example, by cleaning up the sidewalk, you inadvertently opened up bigger cracks in the pavement. There is now a risk of people riding over an open crack in the pavement and falling over.
In many circumstances, just like in teaching someone how to ride a bike, you’ll find it’s impossible to completely eliminate the risk. The degree of risk that remains after you’ve implemented controls is residual risk. As you assess the risks in the risk register, if you determine that the residual risks are too high (you can’t put controls in place that reduce the risk to an acceptable level), you may have to abandon or adjust the activity or think of other controls to put in place to reduce the risk.
Hope this helps you and others better understand Residual Risk and Secondary Risk. If you’re looking for more detail or other examples, Cornelius talks about both Residual Risk and Secondary Risk in his PM PrepCast training video, Plan Risk Responses – Part 2.