electron capture area

[wlrun3@aol.com]

   
   ...are there any other plants besides limerick that post electron capture areas (standard insert in a standard pocketed placard...very straight forward...very basic)...

[TENN-1]

We wrestled with the EC issue at Cook a few years back. It was a challenge on the best days. The posting was simple enough, we made our own laminated and engraved inserts for existing signs. Enforcement was difficult. We recalculated the efficiency on our instrumentation and made everyone wait until the technicians did their thing. If memory serves we did a characterization study of the rooms associated with the effected unit and only posted those rooms with significant problems. The upside was that our problem was Cr-51 and we only had to fight the battle for six months - the half life equation took care of the rest. We only had the problem for one cycle - not sure why, but I can ask if you like.

[wlrun3@aol.com]

We wrestled with the EC issue at Cook a few years back. It was a challenge on the best days. The posting was simple enough, we made our own laminated and engraved inserts for existing signs. Enforcement was difficult. We recalculated the efficiency on our instrumentation and made everyone wait until the technicians did their thing. If memory serves we did a characterization study of the rooms associated with the effected unit and only posted those rooms with significant problems. The upside was that our problem was Cr-51 and we only had to fight the battle for six months - the half life equation took care of the rest. We only had the problem for one cycle - not sure why, but I can ask if you like.

   ...yes, please ask...
   
   ...is the origin of the hard to detect nuclides (htdn) soley undepleted zinc...is there some general explanation for both bwr's (limerick) and pwr's (cook)...

[Chimera]

Okay, I'll bite: What makes electron capture an area of unique concern?  As I understand the process, the x-ray emitted following the k-capture process should be readily detectable using our standard instrumentation.

[RDTroja]

Okay, I'll bite: What makes electron capture an area of unique concern?  As I understand the process, the x-ray emitted following the k-capture process should be readily detectable using our standard instrumentation.

Unfortunately, friskers do a particularly poor job of finding electron capture isotopes. You can take a smear, check it on a frisker, declare the area clean, put the smear in a SAM and it sounds like the Gendarmes are coming (high contam alarm.)

HP-210 probes are nominally about 2% efficient for gamma and x-ray and seem to be less than that in practice -- at least at the energies we saw at Limerick when we lost the refuel floor in... I think it was 2004. Before we got a good handle on what we were dealing with it was very confusing. Count room instrumentation is a lot better, unless you are using a MS-2/HP-210 combination. There really isn't a problem (other than nuisance) if you are aware of the presence, but it is easy to come out of an area, frisk and go on on your merry way contaminating everything until you come to a portal monitor or PCM. So, posting areas is a good idea to make sure people know that frisking is not good enough when exiting.

[Khak-Hater]

I have a friend that used to be the RPM at one of those PA/NJ power plants.  He said that one of his pump rooms always had ridiculously disproportionate levels of Fe-55, which is very hard to detect with a standard GM-pancake probe.  I'm not familiar with specifying areas as "electron capture" areas to identify areas with disproportionate quantities of "hard-to-detect" isotopes, but it makes sense, especially if you have specific processes that result in inadvertent isotopic separation.  In the commercial waste processing industry [where we see waste from practically every plant at one time or another], we historically used scaling factors, based on the plant's waste stream isotopic data, to account for isotopes with considerably worse efficiencies than our standard beta calibrations.  Typical bad actors (i.e., "hard-to-detect" MAFP) that we see from most plants are Fe-55, Ni-63, C-14, and H-3.  Of course, at the plant itself, it would make sense to post areas where your normal detection limits or instrumentation would need to be different [kind of like the DOE boys posting Tc-99 or TRU areas].  It sounds like a valid way to run a program, as long as everyone understands the requirements and bases.

Thanks,

mgm

[RDTroja]

...I'm not familiar with specifying areas as "electron capture" areas to identify areas with disproportionate quantities of "hard-to-detect" isotopes, but it makes sense, especially if you have specific processes that result in inadvertent isotopic separation.

It isn't just that they are hard to detect. The decay mode is electron capture. One of the atom's own electrons (K- or L-shell) is captured by the nucleus in a 'inverse-beta-emission' that produces only a neutrino from the nucleus but emits a characteristic x-ray (or more) as the inner shell vacancy is filled by an outer shell electron (or a series of such events.) It isn't caused by isotopic separation but more by a significant reduction in 'regular' isotopes (the purpose of the process that created the EC isotopes) to the point where they are 'overwhelmed' by the EC isotopes. The waste stream is altered by replacing the more common isotopes with EC isotopes... an unintended consequence of an attempt to reduce overall RCS activity. Simply replaced one problem with another.

[wlrun3@aol.com]

Okay, I'll bite: What makes electron capture an area of unique concern?  As I understand the process, the x-ray emitted following the k-capture process should be readily detectable using our standard instrumentation.

  ...as i understand it, obviously not well enough, the pcm's and the portal's can't see these "hard to detect nuclides" so we are releasing licensed material in a non-detectable release criterion regulatory environment...

   ...i need to know where they come from...

   ...this is what i think i know..

      ...they are corrosion products...

      ...different sites have different mixes and quantities of them...

      ...their locations within the systems differ from plant to plant...

      ...their locations differ under different operating conditions...

      ...some come from corroding pipes...

      ...some come from material introduced into the system...

   ...relevant topics are zinc, noble metals, crud burst, oxygenation, hydrogen peroxide, primary system chemical decon, intergranular stress corrosion cracking,
antimony...

[wlrun3@aol.com]

I have a friend that used to be the RPM at one of those PA/NJ power plants.  He said that one of his pump rooms always had ridiculously disproportionate levels of Fe-55, which is very hard to detect with a standard GM-pancake probe.  I'm not familiar with specifying areas as "electron capture" areas to identify areas with disproportionate quantities of "hard-to-detect" isotopes, but it makes sense, especially if you have specific processes that result in inadvertent isotopic separation.  In the commercial waste processing industry [where we see waste from practically every plant at one time or another], we historically used scaling factors, based on the plant's waste stream isotopic data, to account for isotopes with considerably worse efficiencies than our standard beta calibrations.  Typical bad actors (i.e., "hard-to-detect" MAFP) that we see from most plants are Fe-55, Ni-63, C-14, and H-3.  Of course, at the plant itself, it would make sense to post areas where your normal detection limits or instrumentation would need to be different [kind of like the DOE boys posting Tc-99 or TRU areas].  It sounds like a valid way to run a program, as long as everyone understands the requirements and bases.

Thanks,

mgm

   ...what is MAFP...

[Khak-Hater]

RDTroja,

I understand the electron capture mechanism, but it's nothing special.  It's basically an alternative to positron emission (i.e., a proton needs to turn into a neutron), but positron emission is usually reserved to lower atomic number isotopes[? - I think].  It's just another form of decay, by isotopes that aren't otherwise a significant ALARA concern (e.g., little or no penetrating gammas).  I understand that plants may make an attempt to filter or reduce production of gamma emitting isotopes (e.g., through use of different materials) but that isn't increasing production of EC isotope, it's just reducing the other contaminants [isn't it?].  EC isotopes (e.g., Fe-55) are already present in all commercial power waste streams, but so is Ni-63, which is a very weak beta emitter which presents the same operational problems as Fe-55, so I guess my question would be "why is the EC mechanism being singled out?".

I have to believe that there are some isotopic concentrating mechanisms at work, otherwise you wouldn't have "EC Areas."  You'd just realize that EC isotopes are your primary isotopic concern and monitor accordingly (i.e., everywhere would be an EC Area, wouldn't it?).

wlrun3,

Mixed Activation and Fission Products (MAFP); your basic commercial power plant isotopic waste stream, as opposed to a NORM or Uranium or TRU waste stream or something more exotic from a research facility, hospital, or university (e.g., pure C-14 waste streams).  Sometimes you use lingo so much that you forget what lingo is standard and what's specialized for your business.

mgm

[RDTroja]

Most of the EC isotopes in plants that have problems with them come from processes used to reduce Cobalt activity in the RCS. I can't remember enough of the chemistry specifics (I am sure someone will contribute more) but it has something to do with noble metal injection to stop the corrosion of Cobalt and thus reduce Co58 and Co60 concentrations in the RCS. The change in chemistry did a good job of reducing the cobalt, but also had the effect of raising the concentration of the EC isotopes... I seem to remember Ni56 and Cr51 but that was information I didn't need to retain so I didn't once I left. I don't think it was just eliminating the Cobalt and 'unmasking' the EC isotopes... I think the concentrations went up. I could be wrong, but that is what I remember.

The EC mechanism is 'singled out' because there are very few pure soft beta emitters in concentrations of concern in commercial nukes so they are not a problem. We make some Tritium, but not enough to be be an issue. Also there are not many pure gamma emitters, either -- Tc99 is used in hospitals, but we don't make much in a light water reactor. EC is not a problem except at the plants that purposely altered their chemistry with the metal injections. These plants all had the classic mix (Cobalt, Iron, Manganese, etc.) and the workers were used to friskers finding whatever they got contaminated with. Now the friskers don't find it. It is an issue only in some areas because most of the isotopes are shorter lived and don't last long in non-RCS systems (such as radwaste systems.) So, you have a combination of a relatively new phenomenon, not being consistent in all areas of the plant and not being able to spot with 'traditional' methods. If the plants suddenly developed a Tritium problem, I am sure it would also garner a lot of attention. But so far, not a problem... but EC isotopes are, for some.

[Khak-Hater]

Interesting.

Thanks man,

mgm

[RDTroja]

No charge.

[TENN-1]

Some questions at work yielded these theories:

The EC problem we experienced at Cook may have been the product of new generators, specifically, new diaphragm coatings, two cycles previous. The time frame also coincides with the introduction of the new PRC-1 resins. It is possible that the isotopic profile switched, not because we were producing more Cr-51 & Mn-54, but rather. we were screening the balance of the isotopes out with the new resin, throwing the profile towards what was left. In this case the EC producers.

We too experienced the workers able to clear the Aptec and PCM-1B (remember this was eons ago) but could not clear the gamma-40s. A direct frisk of components would yield ND but the Sam-11 jumped into next week. It's not so much the hard to detect isotope but the lack of beta production with the associated gamma. We didn't know what we had until a very sharp contract tech, (now house at a competitor up the road), shared his experiences with an ex-Navy technician, and the questions were born.

I'll keep asking about the resin vs. the diaphragm stories and see what comes up.  I'd like to tell you how smart I am on this stuff, but the truth is, I'm not the swiftest opossum on the highway. My info is personal OE married to information from our department smart-guys. I'll keep working on it.

[wlrun3@aol.com]

Some questions at work yielded these theories:

The EC problem we experienced at Cook may have been the product of new generators, specifically, new diaphragm coatings, two cycles previous. The time frame also coincides with the introduction of the new PRC-1 resins. It is possible that the isotopic profile switched, not because we were producing more Cr-51 & Mn-54, but rather. we were screening the balance of the isotopes out with the new resin, throwing the profile towards what was left. In this case the EC producers.

We too experienced the workers able to clear the Aptec and PCM-1B (remember this was eons ago) but could not clear the gamma-40s. A direct frisk of components would yield ND but the Sam-11 jumped into next week. It's not so much the hard to detect isotope but the lack of beta production with the associated gamma. We didn't know what we had until a very sharp contract tech, (now house at a competitor up the road), shared his experiences with an ex-Navy technician, and the questions were born.

I'll keep asking about the resin vs. the diaphragm stories and see what comes up.  I'd like to tell you how smart I am on this stuff, but the truth is, I'm not the swiftest opossum on the highway. My info is personal OE married to information from our department smart-guys. I'll keep working on it.

   ...this kind of forum post is exactly why Nukeworker is such a powerful tool...

   ...congratulations and thankyou...

   ...would you agree with my assumptions about what i think i know...

   ...do you think that i'll be able to conclude this topic with a generalized understanding of all the hard to detect nuclides at all the operating power plants, have a generally accurate idea of how they were produced and how, when and where they are encountered...

   ...what i'm after is site to site variations...

   ...i think asa was the contract tech...

[TENN-1]

Thanks for the accolades on the post - as you know I can't comment on the contract technicians name, due to NW rules and regs. Both technicians were very sharp individuals indeed - and the fact they came from different backgrounds strengthened the end result discussion.