RE: RBMK Design Flaws

["Lieskovsky, Miro" <MLieskovsky@nbpower.com>]

Group:
If I remember well then:
1) the NPP in the former East Germany were based on VVER440 reactor (PWR);
2) RMBKs were known before the Chernobyl accident for having a 'positive
void coefficient';
3) Iran is buying VVER1000.
Regards,
Miro

-----Original Message-----
From: Harry Anagnostopoulos [mailto:ANAGHW@doe-md.gov]
Sent: January 18, 2000 7:28 AM
To: Multiple recipients of list
Subject: RBMK Design Flaws


Emil wrote:
"The only design flaw - design of the emergency rods tips, which led to
the accident, has been discovered after the accident." and
"The positive temperature coefficient is not a design flaw but a boiling 
reactor's feature."

I'm no expert in RBMK or any reactor design, but I thought that there were
several design flaws in the RBMK. Some might include:
- The use of graphite in the core, which can ignite
- The lack of a containment building capable of holding some amount of
pressure
- The use of a concrete slab, with no hold-down bolts (?) as the
reactor pressure vessel lid.
- The use of pressure tubes which are welded to the concrete vessel lid.
Movement of the lid broke all of the pressure tubes. Although the
"movement" was severe in this case, it seems like even a moderate
seismic event would rupture the pressure boundary (tubes)
- And of course, the negative temperature coefficient...

I'm digging deep into some dusty memories of Navy Nuke Power School
days, but I believe the temperature coefficient is a function of the
metal-to-water ratio in the core, and is a function of the core design.
There are no commercial BWRs in the US (that I know of) that have a
positive temperature coefficient. It might even be against the law to have
such a design, since it is so unstable.

It's just personal opinion, but it seems that the RBMK design is fairly
low-tech and driven by the need for simple fabrication techniques and
inexpensive materials. In this case, to the detriment of safety.

Clearly my ramblings only.....
Harry Anagnostopoulos, CHP
anaghw@doe-md.gov
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