[ RadSafe ] New Russian Power Reactor

Sat Nov 14 11:10:26 CST 2009

Hi Peter:

Google "Load Following" and RBMK.  The Chernobyl reactor was in a
load-following mode directly prior to the accident leaving it with very low
excess reactivity when it was finally shut down that day. That I do remember
and this characteristic was discussed at length following the accident at
the IAEA.  The power plant was in the process of being shut down (had
reached about 50% power) when another power plant went offline. They were
asked to increase power, which they did to cover Kiev's power requirements,
and ran at 100% until they were allowed to shut down. The experiment
proceeded following this immediate operating history without waiting for the
Xe neutron poisons to decay.

I know that other RBMKs were regularly load following e.g. Bilibinsk nuclear
power plant, and experiments were performed on the Leningrad RBMK plant in
the early 80s to test / stress the reactor for load-following among other
things.

The very feature that you mentioned, power asymmetries, left portions of the
core more or less reactive (more or less poisoned by Xe) and the design of
the neutron flux measuring system, accurate at high power, was insensitive
to local variations. That's why more neutron detectors were installed.  My
understanding is that load following worked well above 50% power, but the
reactor was not designed to load follow from a shut-down condition since it
required time for the neutron poisons to decay following a high-power run.

Again, forgive the generalizations and inaccuracies of a geologist!

Dan ii

--
Dan W McCarn, Geologist
3007 S. St. Francis Drive #818
Santa Fe, NM 87505
+1-505-310-3922 (Mobile - New Mexico)
HotGreenChile at gmail.com (Private email)

-----Original Message-----
From: Peter Bossew [mailto:Peter.Bossew at reflex.at] 
Sent: Saturday, November 14, 2009 06:49
To: hotgreenchile at gmail.com
Cc: blreider at aol.com; radsafe at radlab.nl
Subject: Re: [ RadSafe ] New Russian Power Reactor

Dan,

Dan W McCarn <hotgreenchile at gmail.com> writes:
>Hi Peter & Barbara:
>
>Recalling discussions at the IAEA decades ago, and remembering that I am a
>mere geologist: 
>
>One additional change was to place neutron sensors throughout the core in
>order to detect criticality & neutron flux everywhere. The original design
>only measured "average" neutron flux in the middle of the reactor. The
>accident was in part precipitated when a localized portion of the core
>overheated (not much excess reactivity overall), and because of the high
>positive void coefficient, the excursion began. The centrally located
>neutron detector did not detect the increased neutron flux at a distance
>from the detector.

Yes I forgot mentioning this.
>
>
>The RBMK was originally designed and used as a load-following reactor
>rather
>than base-load. I am uncertain how they are operated now, but this feature
>had it's part in the accident allowing the flawed low-power experiment to
>proceed. 

This is new to me. As far as I know, the RBMK is not easy to regulate,
because it is prone to power asymmetries (as you mention above) and
oscillations. Remember the core is very large. Therefore I would not see a
RBMK as a natural candidate for load-following regime; but maybe I am
wrong. Do you have references for this ? 

As to the accident: one unfortunate factor was that during the phase when
they decreased the power (the experiment was (ironically) a safety
experiment designed to check if the inertia of the turbogenerators is
sufficient to drive the main circulation pumps for a time, in case of
station blackout, in a certain power regime), still according to plan,
they got a call from the load distributor in Kiev asking them to postpone
the experiment and raise power again, because some distant coal power
plant in E Ukraine had some minor disruption (coinciding just by chance)
and therefore they needed the power. Unfortunately the Chernobyl operators
complied, ignoring the complications with Xe poisoning and possible power
asymmetries. They could further run the reactor only with a series of
violations of safety regulations (about which there are disputes), more or
less stabilize it on a higher power level, but in the end they lost. Maybe
it was some local asymmetry which caused the fluctuations of water level
in the drum separators which they could not interpret properly (the lack
of information on spatial distribution of n flux), and reacted by
initiating the scram.  (Some say that without pressing AZ5 (the scram) the
accident could have been avoided... I don't know.)

So, this was sort of load-following, under illegal conditions though, and
not quite successful (to put is cynically), but I don't know to which
extent this was common practice in normal power regime.

As an anecdote: Russians (=constructors) and Ukrainians (=operators) are
quarreling about the "real" cause of the accident until today. I remember
a conf. in Kiev years ago, when  honorable members of the respective
academies of science, white beard and all, started attacking each other
with their walking sticks in course of a heated dispute on this subject.
Their respective entourage finally managed to separate them, but it was a
bit embarrassing to the organizers; and good fun for us few gringos
present.

Good reading: IAEA's INSAG-7.

Peter
>
>
>Are these reactors now used for base-load?
>
>Dan ii
>
>--
>Dan W McCarn, Geologist
>3007 S. St. Francis Drive #818
>Santa Fe, NM 87505
>+1-505-310-3922 (Mobile - New Mexico)
>HotGreenChile at gmail.com (Private email)
> 
>-----Original Message-----
>From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
>Behalf
>Of Peter Bossew
>Sent: Friday, November 13, 2009 18:52
>To: blreider at aol.com; radsafe at radlab.nl
>Subject: Re: [ RadSafe ] New Russian Power Reactor
>
>Barbara,
>
>to my knowlege (I am no expert in the field !!!) the main fixes after
>Chernobyl were,
>
>1) removal of the graphite tips on the lower end (within the reactor) of
>the control rods. These have been ultimately responsible for the accident
>(though not the "root cause", which I would think was typical SU
>sloppiness, administrative unclarity and and neglect of existing
>regulation), since insertion of the rods caused a short reactivity *input*
>of around 0.5 beta, which under the circumstance (low power, more rods
>than allowed withdrawn, high void fraction) was enough for prompt
>criticality. The reason for these tips was that they increase the reactor
>power a bit. - Ironically, the constructors had recommended removing them
>time before the accident, but they used the prescribed bureaucratic
>channels and the document was lost in the labyrinth of the Minergoatom
>(maybe on purpose) (At least that's what I have heard there). 
>
>2) Change of the reactor core design in terms of fuel enrichment. This led
>to avoiding large positive void coefficients. The RBMK is
>thermohydraulically very complex (to my knowledge mainly due to the
>complicated behaviour of the drum separators) and the flow regime must be
>controlled particularly carefully, also in order to avoid unintended
>increase of the fraction of steam bubbles (this happened in Chernobyl). - 
>Initially the core was designed for low enrichment (cheaper fuel), it has
>now been increased to above 2.5 %, in parts of the core. If my
>interpretation of pic. 39 is correct, most elements are in the range of
>2-2.5 % in Smolensk. 
>
>3) QA of procedures which deserves the name was introduced. The chain of
>wrong decisions, from the planning of that experiment until its execution,
>was, to me, the main cause of the accident.
>
>The claim that they had no accidents and therefore needed no containment
>may have been propaganda for outsiders. The argument which I have heard -
>although related to the VVER 440/230, and certainly not true for the RBMK
>-, was that basic material reliability (like steel and welding quality)
>was so high, and that the reactors were so well behaved, due to their
>neutronic and  thermohydraulic designs (very large negative temp. coeff.,
>very large water volume, 6 loops in the VVER 440 !) that the probability
>of severe accidents could be neglected. - They have changed that view in
>the mean time.  (Whatever one thinks about that technology, the old
>VVER440s - with all their questionable features -  are remarkably reliable
>workhorses.)
>
>-- Comments by specialists ? I am sure there must be some in this list who
>know all this much better than I do.
>
>Peter
>
>
>
>
>
>blreider at aol.com writes:
>>Peter,
>>
>>Yes it was Ignalina, outside Vilnius.
>>http://www.iae.lt/inpp_en.asp?lang=1&subsub=9  Someone pointed out
>>Belarus across the lake.  
>>
>>You do seem to know a lot about these reactors.  I believe you are
>>correct about containment although I don't know much about the later
>>generations or the fixes that were made.  I do remember an article
>>(pre-Chernobyl) in Nucleonics Week in which the Russians said they didn't
>>need containments and secondary safety systems as there had been no bad
>>power reactor accidents.
>>
>>
>>Barbara Reider, CHP
>>
>>-----Original Message-----
>>From: Peter Bossew <Peter.Bossew at reflex.at>
>>To: blreider at aol.com; radsafe at radlab.nl
>>Cc: WesVanPelt at verizon.net
>>Sent: Fri, Nov 13, 2009 6:35 pm
>>Subject: Re: [ RadSafe ] New Russian Power Reactor
>>
>>
>>
>>blreider at aol.com writes:
>>Wes, et al:
>>
>>Thanks for posting these pics.  I loved the pic of the wall of gauges.  
>>They indicate the level of insertion of control elements. 
>>
>>
>>Although not a rector HP, during the course of my career I have been to
>>many plants of different kinds in various countries, PWR, BWR, HTGR,
>>graphite core, swimming pool, small research...  I believe these are
>>graphite block reactors, technology same as Chernobyl as Peter said.
>>
>>ttp://en.wikipedia.org/wiki/RBMK 
>>(but there are some inaccuracies in the article, I think. The dangerously
>>igh pos. void coeff. was valid only for low power. To my knowlege the
>>BMKs have not been used for mil. Pu production, because the SU had enough
>>rue Pu prod. reactors. In the RBMK, designed as power reactors, this
>>ould be very uneconomical. As to safety, the rudimentary containment,
>>alled confinement, can contain the break of only a few pressure tubes,
>>ike 10 out of around 1670. Further problematic points are lack of
>>edundancy and lack of separation of vital components. - I would guess
>>hat the few RBMKs (11 reactors in 4 locations; the 4 small units in
>>ilibino are rather harmless I think)  contribute some 3/4 of the
>>umulated risk of all ca. 400 NPPs; this may have changed after their
>>efurbishment, however.)
>>
>>  I was in a similar nuke plant in Lithuania in about 1990.
>>This is Ignalina, 2 blocks of 1500 MWe, the largest version so far. It
>>orresponds ca. generation 2, acc. to OPB-82 standards, but with some
>>mprovements. Block 1 has been closed 2004, block 2 is supposed to close
>>nd of this year. This was a condition of the Eur. Un. that Lithuania can
>>oin.
>>Peter
>>
>>>  It was not quite so clean looking as this, I think due to ugly foam
>>that looked like after the fact fire added protection or insulation.  I
>>didn't see the reactor core area.    Not everyone going into the reactor
>>I went into was given individual monitoring, but the Russian scientists
>>working there had TLDs.  
>>
>>The reason the pond has great fishing is probably because it is not
>>reserve water but they are releasing their secondary side coolant water
>>in the pond.  I had heard from the workers at the plant that I visited
>>that the secondary side water was used to heat the town - indeed I found
>>it quite warm temperature wise in the hotel!
>>
>>Would love to see more people's input about pics.
>>
>>Barbara Reider, CHP
>>
>>
>>-----Original Message-----
>>From: Peter Bossew <Peter.Bossew at reflex.at>
>>To: WesVanPelt at verizon.net; radsafe at radlab.nl
>>Sent: Fri, Nov 13, 2009 3:42 am
>>Subject: Re: [ RadSafe ] New Russian Power Reactor
>>
>>
>>
>>Wes
>>"fairly new"....   this is a typical RBMK-1000, of which they have 2 of
>>eneration 2 (=Chernobyl 3+4)(pic. 1) and one of generation 3 in Smolensk.
>>ll definitively obsolete technology.
>>he pictures seem to be taken in unit 1 or 2, according to the design,
>>hich I know from Chernobyl. On picture 28, panel 1T, you can see the
>>in)famous AZ5 button (the red one under the protective cover)(I think at
>>east).
>>n pic. 40 you can see the flow scheme of the primary loop quite well.
>>ote the four drum steam separators; the red lines (labelled "par na TG")
>>ead to the turbines. Lower left and right you see the feedwater pumps, of
>>hich the engine heads are shown in pics. 16 and 17.
>> find pic. 39 particularly interesting, this seems to be a relatively new
>>eature (I haven't seen it so far). The curve on the left side seems to be
>>he axial power distribution, while the big graph (a layout of the reactor
>>ore) seems to display enrichment. 
>>ote also the fuel changing machine, pics. 19 and 23, which allows
>>efuelling during operation.
>>
>>eter
>>
>>"Wes" <WesVanPelt at verizon.net> writes:
>>Radsafers,
>>I came across this web site with dozens of pictures of a fairly new
>>Russian
>>nuclear power reactor. The author is clearly not highly skilled in
>nuclear
>>technology, but has taken some spectacular inside pictures.
>>
>>http://englishrussia.com/?p=2660 
>>
>>Can the power reactor types on Radsafe compare and contrast this site
>with
>>US and other power reactors? I was impressed with how clean it seems.
>>
>>Best regards,  Wes
>>Wesley R. Van Pelt, PhD, CIH, CHP 
>>Wesley R. Van Pelt Associates, Inc.  
>> 
>>
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>
>
>
>---------------------
>
>Dr. Peter Bossew
>Physics en gros & en detail
>Georg Sigl-Gasse 13/11
>A-1090 Vienna, Austria
>ph. +43-1-3177627
>
>
>
>
>
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---------------------

Dr. Peter Bossew
Physics en gros & en detail
Georg Sigl-Gasse 13/11
A-1090 Vienna, Austria
ph. +43-1-3177627