Tuesday, January 22, 2013

Unsafe NRC Computer Model Requires Investigation

Snip from:

The validity of the ATHOS T/H computer model for San Onofre Unit 2 at Main Steam Line Break  conditions requires that the NRC Office of Nuclear Reactor Regulations complete a Qualifying Investigation to assure steam generator tube integrity before any restart decision is made.

PROBLEM STATEMENT: The computer thermal-hydraulic models cannot account for all the mechanical factors and extremely narrow tube-to-tube clearance differences, which would very likely contribute to catastrophic tube-to-tube wear (fluid elastic instability) in San Onofre Unit 2In light of the 8 tube failures of Unit 3 at Main Stream Line Break testing conditions, fluid elastic instability can cause cascading tube leakages/ruptures in Unit 2 even at 70% power due to Steam Generator pressure and temperature changes caused by, for example, a main steam line break, earthquake, loss of offsite power, stuck main steam safety valve and/or other operational transients.  The cascading tube failures would “pop like popcorn” (as described by nuclear expert Arnie Gundersen) and cause excessive offsite radiation exposures.  Operator Action as claimed by Edison to re-pressurize the steam generators is not feasible to stop a major nuclear accident in Unit 2 in the first 15 minutes of a Main Stream Line Break,  stuck open SG safety valve, earthquake, steam generator tube ruptures and other operational transients during the preposed 5-month trial TEST PERIOD.

INVESTIGATION REQUEST: The DAB Safety Team seeks to assist the NRR by requesting a Qualifying Investigation, as noted above and by providing additional information, as noted below.

Some useful nuclear phrases:

Normal operational conditions
Normal operational conditions mean that the nuclear power plant is operated according to the Technical Specifications and operational procedures. These also include tests, plant start-up and shutdown, maintenance and refueling.

Anticipated operational transient
An anticipated operational transient means a deviation from normal operational conditions, which is milder than an accident and which can be expected to occur once or several times over a period of a hundred operating years.

 Unanticipated operational transient
An unanticipated operational transient means a deviation from normal operational conditions, which is not proceduralized and Plant Operator does not recognize that condition.   A good example are the so called SONGS Unit 3 false alarm from loose parts vibration monitoring system for which there is no explanation from SCE, NRC or Westinghouse.  Another example would be a leakage from a pump pumping radioactive fluid without any area radiation monitors to warn the operators of the leakage.


An accident means such a deviation from normal operational conditions as is not an anticipated operational transient. There are two classes of accident: postulated accidents and severe accidents. Based on the initiating event, postulated accidents are further divided into two sub-classes whose acceptance criteria are described in Guide YVL 6.2.

Postulated accident
A postulated accident means such a nuclear power plant safety system design-basis event as the nuclear power plant is required to withstand without any serious damage to the fuel and without discharges of radioactive substances so large that, in the plant’s vicinity, extensive measures should be taken to limit the radiation exposure of the population.

Severe accident
OMG................. Talk about SanO Nuclear Denial* “severe accident” is not even listed in the 130 page NRC Collection of Abbreviations, but if you do a computer search for it on the NRC website you find this:
Severe accident
A type of accident that may challenge safety systems at a level much higher than expected.

* http://is.gd/XPjMd0
The illogical belief that Nature cannot destroy any land based nuclear reactor, any place anytime

The illogical belief that Nature cannot destroy any land based nuclear reactor, any place anytime