How is hydrogen generated and managed in Hanford's double-shell tanks?

[CFDFEAGURU]

Hello all,

I have been reading about the hydrogen problem at the Hanford Vitrification Plant site. Hydrogen and/or other flammable gasses are being generated in the double shell vessels.

Excerpt below is from :

http://www.komonews.com/news/local/Nuclear-board-warns-of-Hanford-tank-explosion-risk-201128721.html

In addition to the leaks, the board noted concerns about the potential for hydrogen gas buildup within a tank, in particular those with a double wall, which contain deadly waste that was previously pumped out of the leaking single-shell tanks.

"All the double-shell tanks contain waste that continuously generates some flammable gas," the board said. "This gas will eventually reach flammable conditions if adequate ventilation is not provided."

END OF EXCERPT

I know that in an operating LWR there is the Zircaloy-Water Reaction (among other reactions). This reaction generates hydrogen. However, in a vessel containing an unknown mixture of nuclear materials, how is the hydrogen being generated and how could one determine to a certain accuracy the amount of hydrogen being produced?

Just because hydrogen is there doesn't mean an explosion is imminent and there are methods to make the atmosphere containing the hydrogen to be non-explosive.

Thanks
Matt

 

[NUCENG]

Here is a link to an analysis from 2008 indicating 2 weeks to a month to reach a specific level below the LFL (Lower Flammability Level) after loss of ventilation for tanks with active ventilation or Passive HEPA filtration. The reference you provided and similar liinks from a Google search seems to indicate a new analysis from DOE, but I haven't found it.

There are some equations in the report that may help determine the generation chemistry.

http://www.osti.gov/bridge/purl.cover.jsp?purl=/967370-ygCUcv/

 

[CFDFEAGURU]

Thanks for the information. The paper is pretty thorough and gives good insight into how quickly a couple of the tanks can reach the lower level.

Thanks
Matt

 

[nikkkom]

I'd expect tanks' atmosphere to be inerted by periodic injections of e.g. nitrogen or argon, making explosions impossible. Is something like this done, and if not, why not?

 

[NUCENG]

I'd expect tanks' atmosphere to be inerted by periodic injections of e.g. nitrogen or argon, making explosions impossible. Is something like this done, and if not, why not?

Based on the discussion in the report it appears they use active ventilation on some of the tanks, not inerting. The basic problem is that tanks can leak and are leaking and need to be cleaned up. That would also eliminate issue with hydrogen.

 

[CFDFEAGURU]

Based on the discussion in the report it appears they use active ventilation on some of the tanks, not inerting. The basic problem is that tanks can leak and are leaking and need to be cleaned up. That would also eliminate issue with hydrogen.

Yes, the site needs cleaned up. It is such a complex process and requires a tremendous engineering effort to bring the Vit plant to operation. Hopefully, in this decade the cleanup will start.

 

[etudiant]

I had heard that several of the most urgently threatening sites were treated fairly quickly by freezing the entire volume and then excavating the material. However, I've not found any reference to such an action.
What would be a useful overall source record for Hanford cleanup activities? Right now, it seems the process is going nowhere at great expense and it would be nice to know if anything had gotten done.

 

[aquitaine]

Yes, the site needs cleaned up. It is such a complex process and requires a tremendous engineering effort to bring the Vit plant to operation. Hopefully, in this decade the cleanup will start.

It makes me ask why they didn't start this much earlier, like 20 years ago?

 

[CFDFEAGURU]

It makes me ask why they didn't start this much earlier, like 20 years ago?

The process was started years ago. Fabrication/erection of the plant started 11 years ago.

The link doesn't give the start date of construction but it does give the completion date.

http://www.hanford.gov/page.cfm/WTP

Some more digging yielded these dates. Taken from a Hanford Fact Sheet.

"The WTP will cover 65 acres with four nuclear facilities –
Pretreatment, High-Level Waste Vitrification, Low-Activity Waste
Vitrification and an Analytical Laboratory – as well as operations
and maintenance buildings, utilities and office space. Site
preparation began in October 2001, and the concrete for the first
nuclear facility’s foundation was placed in July 2002. WTP will
reach commissioning in 2019 and full operations in 2022."

 

[nikkkom]

It is such a complex process and requires a tremendous engineering effort to bring the Vit plant to operation. Hopefully, in this decade the cleanup will start.

Or US could simply (gasp) contract French to build a vitrification plant for them.

France has the immence experience in vitrifying nuclear waste. IIRC they went through three evolutionary steps - they had two older reprocessing plants in operation and now they run a third one, with improvements from past experience.
According to their website, in this latest plant, workers exposure is exceptionally low.