Re: at least 13 nukes have to fix cracked reactor nozzles

["julian ginniver" <julian.ginniver@lineone.net>]

Norm,

    Once again I find it difficult to accept statements made by the press

when they contain very significant errors on areas which are not difficult

to check by journalists before submitting their articles for publication.



snip>By raising or lowering rods of neatly stacked cylindrical uranium

pellets,

> > the control rods regulate the intensity of the atomic reaction taking

place

> > inside the reactor core.



Very, very wrong.  Certainly what you do not want is a system for

controlling the reactor that would add neutrons to the reactor if it was

inserted.  Generally most reactor types rely on insertion under gravity as a

final fail-to-safety measure for control rods.  As a result of this you need

a  system that removes reactivity (neutrons) from the core when inserted.

The rods Do Not contain Uranium.  They contain some form of Neutron

Absorber.  For Westinghouse type PWRs (I can't say for other types of water

reactor and therefore won't) they contain an alloy called SINCAD.  This is a

mixture of Silver, INdium and CADmium (hence the name).  In addition some

reactors use Boron Carbide, notably UK Gas reactors and some reactors use

Hafnium (naval PWRs).



snip>Equipment known as control rods pass through the nozzles

> > atop the ``head'' of the reactor.



Once again this is wrong.  Although this is not as serious an error as the

first.  The Control Rods do not pass through the reactor vessel "head".  It

is the Control Rod Drive Mechanism that passes through the head.  The

control rods themselves remain inside the vessel.  Again I can only speak

specifically about Westinghouse model PWRs.  The control rod drive is

operated through an electro-magnetic drive which ensure that during normal

operation there is no requirement for a breach of the reactor pressure

boundary.



snip>The plant was scheduled to shut in April for refuelling and maintenance

> > work, but the work was moved up to February at the NRC's request.



Norm how does the above fit with your view that the NRC has a blatant

disregard for the safety of the public and does not provide effective

regulation of the Nuclear Power Industry in the US?



One final point, if my memory is not playing tricks, cracks around control

rod drive penetrations are not a new phenomenon.  Both the French and the

Japanese have had problems in this area.  The latest generation of French

Nuclear plant (the N4 design) at Chinon etc. had problems in this area.  One

of the reasons for the problems I believe was the pre-treatment of the

vessel head to reduce dose-rates and hence doses to personnel during

operation (At last a radiological bit, albeit small).  I'm not sure quite

effect this will have on the existing plants.  Many people said that SG

replacement was going to kill off the US nuclear plants due to excessive

costs and yet we seem to have more and more plants undertaking these

upgrades.  What is the cost of a replacement vessel head.  If my memory

(again) is correct the cost of the complete Reactor Pressure Vessel (RPV)

for Sizewell B in the UK was approximately £20 million (in 1990's money).

This is not prohibitive especially if the plant has been or is going to be

re-licensed for a full 60 years operation.  In addition the RPV Head is

designed to be removed and is removed during each statutory refuelling to

allow fuel to be removed and replaced (apologies if I'm labouring the

point).   Therfore there would be no requirement for specialist measurement,

modification (de-construction and re-construction) of structure within the

containment building. As such the only constraint may be manufacturing

capability  the time taken from order to delivery of such a specialist item

and the consequent effects, possibly low power operation, all most certainly

extended inspections during outages, the possibility of mid-cycle outages to

allow inspections (as is required for some degraded steam generators).



Coming back to my original point - I do wish that Journalists (and others)

would take the time and trouble to ensure that they get the very basic facts

of their story straight before going to print.



Regards

    Julian Ginniver







************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.