FW: Dateline NBC TMI story - A different evaluation

["Careway, Harold A. (PS, NE)" <Harold.Careway@gene.GE.com>]

Such failures of the vessel and containment are considered in the

probabilistic risk assessment portion of the licensing documentation.  This

is to separate it from the design basis portion of the licensing

documentation which is used to address specific regulatory rules.  The PRA

assess both equipment failure and human failure in the event progression.

You are required in the probabilistic portion to evaluate the probability of

a (1) core damage event, (2) vessel melt through, and (3) containment

failure events and to determine what design applications could most

significantly modify those probabilities, i.e., if a design change of

$100,000 could reduce the probability of core melt a factor of ten, then you

would do it; whereas a design change of $20,000,000 for a reduction of 4%

would not be done (4% is way below the precision of such calculations).

Even so the regulators have the right to negotiate modifications based upon

such studies (the NRC also does their own study as opposed to relying on

just the utility licensing input).



With respect to the potential for ground water contamination, it is

typically not considered in the design of the reactor building but is

considered in the design of the radwaste building.  This is due to the fact

that designing the reactor building for seismic and leakage constraints most

often results in a containment impervious to such melt through leakage to

the ground water.  When you think of a reactor building, don't think of the

kind of building you work in, consider 5 meter thick concrete basemats,

reinforcing steel woven so thick you can barely stick your finger between

the bars, one meter concrete floors, steel lined containments so tight that

the allowable leakage area is about that of a 0.5mm pencil lead area,

passive flooding systems, and basaltic concrete designed to withstand melted

steel/corium.  These are truly tough buildings, most of which are

underground.



-----Original Message-----

From: Jacobus, John (OD/ORS) [mailto:jacobusj@ors.od.nih.gov]

Sent: Friday, August 17, 2001 5:52 AM

To: Franz Schoenhofer; Ted Rockwell; Michael Stabin;

radsafe@list.vanderbilt.edu

Subject: RE: Dateline NBC TMI story - A different evaluation





Franz and Ted,

.....



I do not know a lot of nuclear engineers, so again I ask if the idea of a

core meltdown that lead to a failure of the containment vessel and

containment building was considered follow a loss of coolant, AND failure of

the emergency core cooling system.  (Gee, that sounds like what happened at

TMI when the control room turned off the emergency fuel pumps.)



..... 

-- John 



John Jacobus, MS

Certified Health Physicist 

3050 Traymore Lane

Bowie, MD  20715-2024

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