[ RadSafe ] Japan Debates Safety After Quake

Sun Jul 22 03:10:37 CDT 2007

Dear John,

The uncertainties in identifying regions with quake potential are difficult to understand. 

One of the worrying factors in the recent earthquake is the finding that the peak acceleration levels observed at the power station was much higher than those  for which the plant was designed. Nuclear community may have to find convincing  reasons to argue that the NPP is still safe. In this instance, it is not difficult as the activity  released was minuscule. But a pessimist (there are quite a few of them around) may argue that if the quake intensity was slightly higher the unplanned releases may become several orders of magnitudeds higher. 

Once I had  to argue for an hour with some well meaning specialists to desensitize them about the 50% increase  (one Bq /l of Cs-137 to 1,5 Bq/l) in  samples of water fro a monitoring well.

The safety report NO 28  from the International Atomic Energy Agency  writes thus:

" It is a  known technical finding that well designed industrial facilities especially NPPs have an inherent  capability to resist earthquakes  higher than the earthquake used in their original design".   The report states that it is a direct  consequence of the conservatism that exists in seismic design procedures and is usually described in tems of 'seismic design margin".

The issue is the upper limit of design margin obtainable in such a case!The magnitude of the margin for various systems, structures and components may vary and may depend on many factors.

Interestingly, the report  says that although peak ground acceleration (PGA) is a widely used parameter to scale the seismic input, it is also known that the capacity of seismic input motion to cause damage is poorly correlated to the PGA level.

According to the report, it is known that near field earthquakes with  small magnitude may produce significant PGA levels but do not produce signifiant damage to  the structures; it may produce  spurious behaviour of electrical  and/orinstrumention and control systems. 

I spent some time with my  "quake" specialists. They had several interesting arguments. Translating them for convincing  different stake holders including the public may be an uphill task.

Regards
K.S.Parthasarathy

----- Original Message ----
From: John Jacobus <crispy_bird at yahoo.com>
To: "Earley, Jack N" <Jack_N_Earley at RL.gov>; Sandy Perle <sandyfl at cox.net>; radsafe at radlab.nl; powernet at hps1.org
Sent: Sunday, 22 July, 2007 3:59:12 AM
Subject: RE: [ RadSafe ] Japan Debates Safety After Quake

Just because fault lines do not exist in the immediate
area, does not mean earthquakes can occur. An
earthquake occurred near Charleston, SC, in 1886
resulting in widespead damage to the city.

http://en.wikipedia.org/wiki/Intraplate_earthquake
"Historic examples of intraplate earthquakes in North
America include those in Boston in 1755, New York City
in 1737 and 1884 (both quakes estimated at about 5.5
magnitude), and the Charleston earthquake in South
Carolina in 1886 (estimated magnitude 6.5 to 7.3). The
Charleston quake was particularly surprising because
unlike Boston and New York the area had almost no
history of even minor earthquakes (to put in
perspective, in addition to the three northeastern
U.S. events previously mentioned, a more moderate
magnitude 4 earthquake was recorded just north of New
York City in 1985).

"The cause of these earthquakes is often uncertain. In
many cases, the causative fault is deeply buried, and
sometimes cannot even be found. Under these
circumstances it is difficult to calculate the exact
seismic hazard for a given city, especially if there
was only one earthquake in historical times."

Interesting maps of this area starting on page 4
http://earthquake.usgs.gov/research/hazmaps/whats_new/workshops/CEUS-WORKSHP/Tuesday/Talwani-Boston_TALK_5-9-05.pdf

That being said, Jack is right about what we should
focus on.  Safety systems worked.

--- "Earley, Jack N" <Jack_N_Earley at RL.gov> wrote:

> "There's also uncertainty about where the next quake
> will strike. The
> Kashiwazaki facility underwent a tectonic survey
> last year to reevaluate
> the site's quake resistency and update it in
> accordance with new
> government guidelines. That survey concluded there
> were no active faults
> in the vicinity."
> 
> 
> I guess I just don't understand, but it seems to me
> that someone's
> missing the big picture here. The plants shut down
> as designed, so no
> "nuclear calamity" occurred, particulates in the
> exhaust, toppled
> barrels, and spent fuel pool spill notwithstanding. 
> 
> On the other hand (the economist in me tends to
> say), there might be a
> problem with the survey methodology that determined
> that there were no
> active faults in the vicinity. And last I heard, the
> only way we can
> know for sure that an earthquake is about to strike
> is to watch the
> animals--probably not the best way to run any
> industry, nuclear or
> otherwise. But I guess if you're "against"
> something, any excuse will
> do.
> 
>  
> Jack Earley
> Health Physicist
> 509.372.9532
> 
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+++++++++++++++++++
““Few of their children in the country learn English... The signs in our streets have inscriptions in both languages ... Unless the stream of their importation could be turned they will soon so outnumber us that all the advantages we have will not be able to preserve our language, and even our government will become precarious.”
-- Benjamin Franklin, circa 1750, on German immigration to Pennsylvania

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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