NukeWorker Forum
Reference, Questions and Help => Nuke Q&A => Lessons Learned => Topic started by: wlrun3@aol.com on Mar 30, 2007, 09:57
-
...do all bwr's add hydrogen for corrosion control...how does zinc injection work...how does noble metal injection work...what are the electron capture isotopes responsible for "electron capture areas" and how are these isotopes produced...
-
Not being a chemist, I really don't understand all that stuff. ???
But I do know that since VY started H2 inj, and now zinc, our dose rates are up in primary systems. And everytime we have H2 trip, we have a nice crud burst.....hot spots everywhere....20 R/hr RWCU HX and stuff.... :(
I know it's supposed to help the long term reliability of the plant, but as an HP tech, I'm not a big fan right now.
-
Not being a chemist, I really don't understand all that stuff. ???
But I do know that since VY started H2 inj, and now zinc, our dose rates are up in primary systems. And everytime we have H2 trip, we have a nice crud burst.....hot spots everywhere....20 R/hr RWCU HX and stuff.... :(
I know it's supposed to help the long term reliability of the plant, but as an HP tech, I'm not a big fan right now.
...do you post electron capture areas...peach bottom and limerick do...frisker efficiency less then five percent for electron capture isotopes...
-
We are (PWR) about to start zinc injection on both units. Got the pieces parts installed.
Dose will go up and then down and then up and then down towards a lower equillibrium, but the crappiest part for chemistry is all the new analytical equipment that was purchased to measure the zinc et al. Many many tens of thousands in capital for the new wam-o-dyne Ion Chromotagraphy systems plus all the man hours setting it up, QC/QA checks, training, etc etc etc ad NAUSEAUM.
Hopefully the fuel savings (is this the reason: better fuel life?) will make up for the capital expenditure and labor costs.
Maybe a lurking nuclear fuels financial analyst has a bead on this.
-
The H2 is to protect a weld in the Core Shroud. At Fermi it was known as the H8 Weld. Its very low in the shroud and it's the one cylindrical weld which can not be replaced or repaired. The concern is if the weld cracks you'll not be able to meet your ECCS Criteria. The H2 of course scavenges Oxygen and without O2 the weld cannot crack my chemical means.
The Zinc overall will extend Plant life and in the long run lower all dose rates because it forms a layer and the Zinc Isotope is less active than Cobalt.
If I recall correctly when we started H2 injection at Fermi overall dose rates went up, but overall dose went down because we had to work smarter and stopped doing a lot of things we used to do for no apparent reason.
As for the crud burst, PWRs intentionally cause these when shutting and cooling down for an RFO.
Gotta do what's right by the plant.
Mike
-
As always, thanks for your brain pickins.
;D
-
We are (PWR) about to start zinc injection on both units. Got the pieces parts installed.
Dose will go up and then down and then up and then down towards a lower equillibrium, but the crappiest part for chemistry is all the new analytical equipment that was purchased to measure the zinc et al. Many many tens of thousands in capital for the new wam-o-dyne Ion Chromotagraphy systems plus all the man hours setting it up, QC/QA checks, training, etc etc etc ad NAUSEAUM.
Hopefully the fuel savings (is this the reason: better fuel life?) will make up for the capital expenditure and labor costs.
Maybe a lurking nuclear fuels financial analyst has a bead on this.
Actually the fuels guys will tell you they hate zinc. Causes spalling on the fuel. There's a fine balance between how much can be added and not cause the spalling and what needs to be added to maintain a Co/Zn ratio good enough to keep dose rates down.
The hydrogen changes the chemistry environment from oxidizing to reducing lowering the Electrochemical Potential (ECP) below which IGSCC won't occur (about -230 SHE).
There are different type of hydrogen plants (basically low and high). High plants inject hydrogen at a high enough level to maintain the low ECP in the cracks all the time. Low plants treat with Noble Metals which allows a lower hydrogen injection rate for the same protection (in the existing cracks). The problem with low is the plant has to maintain essentially >98% hydrogen availability since with no hydrogen, the cracks begin to grow and now the new crack surface area has no protection (even when hydrogen is restored) until the next NMCA treatment. (Called Crack Flanking.
The advantage of the low is the lower dose rates from the steam lines.
THe Noble Metals
-
The electron capture issue most likely came from Limerick. When they first started zinc injection (I guess they were one of the first) they used non depleted zinc. That was pretty much a bad idea. In their RR and RWCU systems the electron capture isotope ratio was so high it forced them to use frisker effciencies < 1%.
-
Monticello was the same way, you count a smear that showed a few hundred
counts on a frisker, but, then after you got the results back from isotopic
you really had more like a hundred K......
-
...do pwr's add hydrogen continuously during power generation, as with bwr's, to reduce corrosion...
...has there ever been a core shroud (barrel) replacement due to corrosion induced weld integrity compromise...
...what is fuel spalling...
..with zinc addition, is the corrosion product Zn 65 the main electron capture isotope...
...with noble metal addition, do the noble metals platinum and rhodium produce electron capture isotopes...
-
AWESOME DISCUSSION. ;D
-
1: No. Commercial PWRS use Hydrogen Overpressure on their Volume Control Tank or Make Up Tank (Nomenclature depends on Reactor Vendor. The Chargining Pumps that control pressurizer level take a suction off this tank and thus inject Hydrogen "Saturated" Water to the Primary. To change H2 Concentration you change the Overpressure. When one shuts down we change the Hydrogen blanket for Nitrogen Blanket then add Hydrazine as an Oxygen Scavenger for cold shutdown.
2: No, It's impossible, thus the BWR concern for Hydrogen Injection. At my old BWR we injected Hydrogen at a certain flowrate into the Condensate System upstream of the Feedpumps. Since Hydrogen carried over into the OffGas system we had to inject Oxygen into the Inlet to the Off Gas system in order to ensure proper recombination of the H2 so there wouldn't be an H2 buildup to an Explosive Combination. I bet M1Ark remembers a VERY interesting even he and I had in August of 1999 when I was the CRS and he was the control room operator and this system malfunctioned. Needless to say it wasn't fun.
3: Spalling is a Chipping of the cladding. IIRC when Zinc Injection started the Zinc spalled the cladding. Fermi was a bit behind the industry on Zinc Injection and thus the use of Depleted Zinc was the norm by the time they entered the fray.
-
Actually you were the SM and the CRS exhibited some fine command & control and said,"You better think of something, Chuck. Were going to scram!" Luckily I thought of something. That is when I decided that I can no longer in good conscience allow someone dumber than me be my boss for the good of nuclear power.
M1Ark
1: No. Commercial PWRS use Hydrogen Overpressure on their Volume Control Tank or Make Up Tank (Nomenclature depends on Reactor Vendor. The Chargining Pumps that control pressurizer level take a suction off this tank and thus inject Hydrogen "Saturated" Water to the Primary. To change H2 Concentration you change the Overpressure. When one shuts down we change the Hydrogen blanket for Nitrogen Blanket then add Hydrazine as an Oxygen Scavenger for cold shutdown.
2: No, It's impossible, thus the BWR concern for Hydrogen Injection. At my old BWR we injected Hydrogen at a certain flowrate into the Condensate System upstream of the Feedpumps. Since Hydrogen carried over into the OffGas system we had to inject Oxygen into the Inlet to the Off Gas system in order to ensure proper recombination of the H2 so there wouldn't be an H2 buildup to an Explosive Combination. I bet M1Ark remembers a VERY interesting even he and I had in August of 1999 when I was the CRS and he was the control room operator and this system malfunctioned. Needless to say it wasn't fun.
3: Spalling is a Chipping of the cladding. IIRC when Zinc Injection started the Zinc spalled the cladding. Fermi was a bit behind the industry on Zinc Injection and thus the use of Depleted Zinc was the norm by the time they entered the fray.
-
LMAO that's right!!!
Mike
-
Besides adding H2 to the feedwater to protect the reactor welds, it scavenged the O2 added to the condensate system for the nice oxide layer.
I have also heard of adding Zinc can also affect flow by plating out in some of the tighter flow areas (small oriface, restrictor plates, etc).