Hydrogen fix for Japanese reactors

[Marlin]

I have not worked a Power Plant since 1994 but I remember a H2 recombiner in every containment. It seems a little incredulous that there aren't any in the Japanese plants. Comments from Ops types would be appreciated.


Areva is to fit all 23 Japanese pressurized water reactors with hydrogen recombiners that help to prevent the explosive gas building up in emergency situations.
http://www.world-nuclear-news.org/RS_Hydrogen_solution_for_Japanese_reactors_1910121.html

[Fermi2]

Late 90s the NRC allowed utilities to remove REcombiners from TS to the TRM and if they so desired to get rid of them.
Given they were junk anyway...

[a|F]

I have not worked a Power Plant since 1994 but I remember a H2 recombiner in every containment. It seems a little incredulous that there aren't any in the Japanese plants.

That article is complete BS.  Propaganda at it's finest.  

A solution for Japanese reactors?  A solution for the explosions at Fukushima?

NOT EVEN IN THE BALLPARK!

Are there any BWR's that have them?  We rely on nitrogen purge to protect us.  Incredulous is right.  

/rant

[Marlin]

Are there any BWR's that have them?  We rely on nitrogen purge to protect us.  Incredulous is right.  

Some of the explosions in Japan were in the spent fuel area weren't they?

[Higgs]

BV's hydrogen recombiners have been RIP for a decade or so now.

Justin

[roadhp]

GG has them and igniters as well

[Fermi2]

Some of the explosions in Japan were in the spent fuel area weren't they?

No.

[Fermi2]

GG has them and igniters as well

BWR $ Mark 1 do not have igniters.

[Xenon_Free]

Some of the explosions in Japan were in the spent fuel area weren't they?

Yes.

[Xenon_Free]

Still, it is ridiculous to point out the lack of H2 recombiners.  They need power to operate, which they did not have.  Although some kind of gas igniter system on the vent does seem at least plausible - but not necessarily a good idea.

XF

[Marlin]

Still, it is ridiculous to point out the lack of H2 recombiners.  They need power to operate, which they did not have.  Although some kind of gas igniter system on the vent does seem at least plausible - but not necessarily a good idea.

XF

I don't know how the combiners the US used work(ed) but the ones Areva are installing do not use power.

"The French company announced a contract to provide a bulk order of its passive autocatalytic recombiners. The devices use catalytic oxidation to turn traces of hydrogen into steam, a process that works constantly and requires no power. They will be fitted in the reactor unit containment vessels to help prevent hydrogen explosions and "preserve the integrity of the reactor," said Areva."

[Xenon_Free]

Nice, I did not know about that.  Very interesting!

Thanks Marlin!
XF

[HydroDave63]

"The French company announced a contract to provide a bulk order of its passive autocatalytic recombiners. The devices use catalytic oxidation to turn traces of hydrogen into steam, a process that works constantly and requires no power. They will be fitted in the reactor unit containment vessels to help prevent hydrogen explosions and "preserve the integrity of the reactor," said Areva."

Recombining requires energy, in this case heat, over a catalytic grid. Basically a giant automobile catalytic converter. Probably great for slow fart releases like TMI, probably ineffective for the magnitude of Fukushima's H2 buildup in a short acute timeframe.   

[Marlin]

Nice, I did not know about that.  Very interesting!

Thanks Marlin!
XF

Recombining requires energy, in this case heat, over a catalytic grid. Basically a giant automobile catalytic converter. Probably great for slow fart releases like TMI, probably ineffective for the magnitude of Fukushima's H2 buildup in a short acute timeframe.  

I was just citing the original article. I was just looking for some insight from operations. They seemed to be a big deal at one time, perhaps "momma factor" would better describe them from the input I am getting.

[Cellman]

Curious how recombiners would work in an inerted containment? If they are producing steam, they are combining hydrogen with oxygen. If there is very little oxygen in an inerted containment, there is nothing to combine it with unless oxygen in introduced into the process. I'm sure someone smarter than I has thought of this, just trying to figure out how they work.

[spentfuel]

If there is very little oxygen in an inerted containment, there is nothing to combine it with unless oxygen in introduced into the process

There are breathable levels of oxygen in BWR/PWR drywell/reactor building/containments

I don't recall any explosions in the SFP's either but they were pumping sea water into at least one through damage in the roof caused by H2 ignition in the reactor building. 

From what I recall I think TMI used their glow plugs a few times to try to burn down the H2 concentrations but also think It was later questionable as to the need or the value of what they did.

sf

[Fermi2]

There are breathable levels of oxygen in BWR/PWR drywell/reactor building/containments

I don't recall any explosions in the SFP's either but they were pumping sea water into at least one through damage in the roof caused by H2 ignition in the reactor building. 

From what I recall I think TMI used their glow plugs a few times to try to burn down the H2 concentrations but also think It was later questionable as to the need or the value of what they did.

sf

Incorrect, BWR Mark 1 Containments are inerted to 97% Nitrogen concentration minimum by Tech Specs. Last I checked 3% Oxygen was not breathable.

[RDTroja]

Incorrect, BWR Mark 1 Containments are inerted to 97% Nitrogen concentration minimum by Tech Specs. Last I checked 3% Oxygen was not breathable.

Sure its breathable... for about one breath.

[Xenon_Free]

All of the [big] explosions occurred in the spent fuel area, the cause just may not have been the spent fuel itself.  May have been due to venting operations on containment and valve failure positions on loss of power.  I do not recall the specifics but I will look into it when I get a chance.

XF

[Fermi2]

It was due to venting the containment via non qualified ductwork which leaked hydrogen everywhere. Japanese EOP philosphy is VERY different than US Philosophy and EOP Guidance. Japanese use the Double Containment Pressure philosophy of when containment pressure is double design pressure then vent.

US BWRs do not get anywhere near design pressure.

[Xenon_Free]

Curious how recombiners would work in an inerted containment? If they are producing steam, they are combining hydrogen with oxygen. If there is very little oxygen in an inerted containment, there is nothing to combine it with unless oxygen in introduced into the process. I'm sure someone smarter than I has thought of this, just trying to figure out how they work.

Hmmm, Well if you have a loss of coolant accident that pressurized the drywell the nitrogen in the drywell is displaced by steam and the nitrogen would move through the down comers and wind up in the torus.  Prolonged radiolytic decomposition of water creates H2 and O2 thereby increasing the O2 content in the drywell.  Zirc water reaction also creates H2, so there you go.  No LOCA?  Process would be the same but the steam/H2-O2 mixture goes through RCIC or HPCI systems along with SRV's into the torus and eventually the torus air space.  As pressure builds up in the torus due heat and gas buildup it is relieved to the drywell, and it would work similarly.

Of course low O2 is the point, if oxygen is low the process would not work.  But then it would not matter since the H2 would not be able to explode [deflagration]
The problem is that with high containment pressure, that they had, either venting or through leakage out of the drywell this h2 can and will escape, then you have the O2...and the explosion.

XF

[Fermi2]

Hmmm, Well if you have a loss of coolant accident that pressurized the drywell the nitrogen in the drywell is displaced by steam and the nitrogen would move through the down comers and wind up in the torus.  Prolonged radiolytic decomposition of water creates H2 and O2 thereby increasing the O2 content in the drywell.  Zirc water reaction also creates H2, so there you go.  No LOCA?  Process would be the same but the steam/H2-O2 mixture goes through RCIC or HPCI systems along with SRV's into the torus and eventually the torus air space.  As pressure builds up in the torus due heat and gas buildup it is relieved to the drywell, and it would work similarly.

Of course low O2 is the point, if oxygen is low the process would not work.  But then it would not matter since the H2 would not be able to explode [deflagration]
The problem is that with high containment pressure, that they had, either venting or through leakage out of the drywell this h2 can and will escape, then you have the O2...and the explosion.

XF

Incorrrect. You will not create enough O2. W ould you care to debate this with a Former BWR 4 SM who taught accident analysis?

[Xenon_Free]

Incorrrect. You will not create enough O2. W ould you care to debate this with a Former BWR 4 SM who taught accident analysis?

Debate?  Sure.  I am not sure what your Former status as a super special someone has to do with your statement - will not create enough O2 for what?

XF

[Fermi2]

It means I have forgotten more about the subject than you will ever know, both from an accident and EOP status.
You were the one that started the babble about O2 generation.

[Xenon_Free]

In an attempt to not hijack this thread anymore than it already has, I will simply ask again.

Will not create enough O2 FOR WHAT???

Please explain your position in this debate.

XF

[Fermi2]

Explain how Radiolytic Decomposition of water occurs during this event...

[Xenon_Free]

Low reactor water level, beta, alpha, gamma decomposition of water is as follows:

H2O > H + OH

H + H > H2

OH + OH > H2O2

H2O2 + OH > HO2 + H2O

HO2 + OH > H2O + O2

And

HO2 + HO2 > H2O2 + O2

And

H2O2 + HO2 > H2O + OH + O2


XF

[HeavyD]

I always thought the radiolytic decomposition of water was the action of a neutron flux breaking down water into separate hydrogen and oxygen molecules.

So in a major LOCA scenario, assuming the reactor is scrammed, wouldn't the vast majority of the neutron flux be gone?  Realizing of course there is still some residual flux due to the small amount of ongoing fission, but still.

I admit it has been quite some time since I sat and thought about the ins and outs of reactor physics and the interaction of the various radiation fluxes on matter, so I could be confusing things here.

[Xenon_Free]

That's true, neutrons contribute far more to the radiolytic decomposition than gamma.  However, it still occurs with gamma and add to that the low water level there is still a contribution from neutrons which will remain at higher energies for a longer period of time.  So their contribution would remain significant.

XF

[HydroDave63]

Boiling water reactors use high purity water as the neutron moderator and primary coolant in the production of steam. In an operating BWR, most of the radiolysis occurs in the high flux core region. Under normal operating conditions, the core contains an average steam void of ~30% and the core radial average void fraction increases from 0 at core inlet to ~70% at the top of the core.

A brief overview of radiation chemistry in the BWR coolant has been reported by The radiation energy generated in the reactor core and absorbed in the coolant is mainly attributed to fast neutrons and gamma rays; the contributions from thermal neutron and beta particles are relatively small.

The core average total neutron dose rate is estimated at 1.5×10⁹ R/hr and the total gamma dose rate is estimated at 3.1×10⁸ R/hr for a 50 W/cm3 power density standard plant. The total radiation dose rate in the core region

http://www.nap.edu/openbook.php?record_id=9263&page=125

[Cellman]

I can see that you would get some oxygen from radiolysis of water. I was under the impression that most of the H2 comes from the Zircalloy oxidation reaction scavenging the oxygen from the water molecule. This would leave the hydrogen, but the oxygen would not be released to containment in gaseous form. Thanks for the discussion so far.

[spentfuel]

Incorrect, BWR Mark 1 Containments are inerted to 97% Nitrogen concentration minimum by Tech Specs. Last I checked 3% Oxygen was not breathable.

Thanks for the correction at least I did learn something I was not aware of.  I have only made two BWR power entries,  one at VBWR and one at the Ferry.  I guess that was why we wore air packs at the Ferry 

I thought we were just being over conservative 

And by the by I was half correct 

I would add that the H2 generation at Fuk was also due to hydrolysis from the addition of salt water or at least thats what I recall

but I will admit I could be half wrong

sf

[Xenon_Free]

I can see that you would get some oxygen from radiolysis of water. I was under the impression that most of the H2 comes from the Zircalloy oxidation reaction scavenging the oxygen from the water molecule. This would leave the hydrogen, but the oxygen would not be released to containment in gaseous form. Thanks for the discussion so far.

That seems correct.  Btw, I did not state that there would be a tremendous amount of O2, just that it would be developed.  Any that would accumulate can be removed by the recombiners.  I am not sure what BZ wants to debate.

XF

[HeavyD]

I, for one, learn new stuff everyday I read these types of discussions.

As a retired Navy nuke, I realize that what we spent years operating are vastly different; in operation, response time and the affect various transients have on the plant to name just a few areas.

As a tried and true nuke geek, I love nuclear power.  Working in QA, there are times when I miss being involved in operating the plant.  However, my days of working shift work are long gone 

Kudos to the operators, and it is good to see that I still remember some stuff

[RDTroja]

I am not sure what BZ wants to debate.

He doesn't really want to. His idea of debate is "The Great and Powerful Bz has spoken!"

[HydroDave63]

He doesn't really want to. His idea of debate is "The Great and Powerful Bz has spoken!"

The first 8 seconds...

[Fermi2]

You realize in these conditions radiolysis doesn't really occur right?

[Xenon_Free]

Because of hydrogen suppression, or low LET gamma?  I covered the later and the former needs some type of recirculation flow to truly be effective, which will not be occurring since the reactions and steam formation is happening as fast as you add the water.

Interested to see what you've got though.

XF

[Xenon_Free]

Interesting read on accident sequence with some specific focus on radiolysis of water.

http://pbadupws.nrc.gov/docs/ML0716/ML071620344.pdf

Check out pages 2-7 to 2-10, they describe pieces of what I have been describing pretty well.  This is on the NRC website.  I admit I have not yet gotten through the whole thing.

XF