Posted by: Harold Ennulat | February 4, 2010

Digital Controls: Safe For Nuclear Industry

According to a recent article in Nuclear Engineering International Magazine,  Digital systems have a reliability on par with or even better then non digital systems and on par with or better than most industry accepted actuators, even for the nuclear industry.  This article cites reliability figures and the difficulty of assessing reliability that takes in to account all the factors.

The probability of failure of a digital I&C system is in the order of  1×10-4 up to 1×10-5 probability of failure on demand.  This is in line with mechanical actuator probabilities of failure (in the order of 1×10-4) the author  (Dr. John H. Bickel) states.

In safety applications it is common to increase control system reliability by putting in redundancy which ends up increasing reliability to 1×10-9 (1×10-4 x 1×10-5).  The author considers this unnecessary when the end point actuator failure probabilities are still in the  1×10-4 range.

The diagram indicates where the main errors in digital control systems occur.

Dr. Bickel quite simply concludes his article with “properly designed digital I&C systems are reliable enough”.

Updated 2/5/2010 9:52 am  | Created 2/4/2010 5:00 pm

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