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RE: UCS- NRC Relies on Falsified Safety Studies

Norm et al.

The contention in this paper (http://www.ucsusa.org/energy/nuc_risk.html)


"Nuclear plant risk assessments are really not risk assessments because

potential accident consequences are not evaluated. They merely examine

accident probabilities -- only half of the risk equation."

is a false statement when applied to the reactor license renewal process,

which has been implemented ever since the Calvert Cliffs plant first applied

to NRC for such a renewal over 10 years ago.  It should be noted that the

majority of US nuclear power plants are planning to renew their licenses and

must therefore go through a similar process.  To date, at least a dozen

reactors have or are conducting detailed quantifications of off-site

accident consequences. And when any new reactors are sited, these will also

have to undergo similar analyses before they can be licensed.  This process

is summarized below.

I have been intimately involved in the off-site dose/economic consequence

aspects of this process for the last year or so.  As part of the

environmental report that accompanies each license renewal application, the

utility must perform a so-called SAMA (Severe Accident Mitigation

Alternatives) analysis . Basically, this is a risk-based cost/benefit

analysis to determine whether the probabilities and consequences of severe

accidents warrant the implementation of accident mitigation alternatives

that can reduce such probabilities and/or consequences.

A major part of such an assessment is the calculation of off-site dose and

economic consequences, weighted by the risk and magnitude of releases from

postulated accident sequences.  These calculations cover all three levels of

probabilistic risk assesments (PRAs).  

The first step is to conduct a baseline analysis.  The process of

quantifying accident sequences start with a Level 1 PRA, which essentially

estimates the core damage frequencies for various initiating events. The

analysis takes into account probabilities of hardware failures and/or human

error in stopping the propagation of the sequence of events that would

eventually lead to core damage.  These sequences are then extended in a

Level 2 PRA, which estimates the frequencies and release fractions of

radionuclides that escape the containment, including the timing of such

releases.  The Level 3 PRA analysis typically uses a code called MACCS2,

which is used to estimate the doses to the offsite population and economic

impacts within 50 miles of the reactor site from each accident sequence

provided by the Level 2 PRA.  Level 3 analyses are still probabilistic in

the sense that they account and sample for weather variability over a full

year and agricultural growing season effects.  That is, the accident

sequences are assumed to occur at random times throughout the year (with

different meteorological conditions and agricultural production stages), and

the cumulative distribution of potential impacts is then estimated by the


The dose/cost risk is then calculated by converting off-site consequences

(doses) to costs at the tune of $2000 per person-rem, multiplying the

resulting collective dose costs by the annual frequencies of the accident

release sequences that are analyzed, and finally estimating the Net Present

Value (NPV) of such costs extended over the 20-year license renewal period.

The same is done for off-site economic costs.

The baseline analysis is not limited to monetizing the off-site impacts, but

also monetizes the dose impacts to on-site workers, the economic costs of

decontaminating the damaged reactor and the costs of providing replacement

power.  The latter impacts are dependent only on the Level 1 PRA analysis,

since large costs are incurred in dose to workers and economic consequences

to the utility even for sequences that do not result in off-site releases,

but only in damage to the core (as was the case for Three Mile Island, where

the off-site releases were minor and did not result in significant OFF-SITE

dose/economic impacts as would have been the case in some of the more severe

accident sequences that are currently analyzed) 

The baseline is then used to screen out cost-ineffective SAMAs. Any SAMA

that costs more than the baseline cost-risk is excluded because no SAMA can

reduce the risk to less than zero.  And just because a SAMA may reduce the

risk of severe consequences, it is not automatically adopted if

implementation costs are greater than the net cost/beneit of the risk

reduction.  In other words, if a SAMA costs $100,000 to implement, but will

only reduce the cost/risk by $10,000 (perhaps because it does not

substantially lower the overall accident frequency or the severity of any

off-site consequences), then it is not considered cost-beneficial and is

screened out.  Only those SAMAs that are considered cost-beneficial are

retained and implemented.  Once this is done, the PRA models are revised to

include the effects of the SAMAs that were implemented.

Ernesto Faillace, Eng.D, CHP

Nuclear Engineer/Health Physicist

Tetra Tech NUS

900 Trail Ridge Rd

Aiken, SC 29803

(803) 649-7963 x303

(803) 642-8454 (fax)


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

From: Norman Cohen [mailto:ncohen12@comcast.net]

Sent: Wednesday, March 20, 2002 10:15 PM

To: radsafe@list.vanderbilt.edu; Know_Nukes@yahoogroups.com; UNPLUG

Salem Campaign; JerseyShoreNuclearWatch@yahoogroups.com

Subject: UCS- NRC Relies on Falsified Safety Studies

HI all,

The URL below leads to both the Executive Summary and a link to the

entire report.

reactions welcomed.


> http://www.ucsusa.org/energy/nuc_risk.html


Coalition for Peace and Justice and the UNPLUG Salem Campaign; 321 Barr

Ave., Linwood, NJ 08221; 609-601-8537 or 609-601-8583 (8583: fax, answer

machine);  ncohen12@comcast.net  UNPLUG SALEM WEBSITE:

http://www.unplugsalem.org/  COALITION FOR PEACE AND JUSTICE WEBSITE:

http://www.coalitionforpeaceandjustice.org   The Coalition for Peace and

Justice is a chapter of Peace Action.

"First they ignore you; Then they laugh at you; Then they fight you;

Then you win. (Gandhi) "Why walk when you can fly?"  (Mary Chapin



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