Missing Nuclear Inventory

One of the most important requirements in planning for any situation is to have a complete set of information. It is therefore entirely appropriate that one of the requirements for the Environmental Impact Assessment is that it contain a complete list of all the chemical elements – radioactive or not – that the proposed waste contains. This not only allows proper evaluation of the plan, it also provides a rationale for excluding waste that the repository has not been planned for.
However, this is not the position that OPG is taking. For instance, the International Institute of Concern for Public Health documents the following exchange with OPG:

IR EIS-04-107: Request # 10 (IICPH): Section 8.1 General Information and Design Description
The Reference Inventory Report (page 23, Table 2.8) provides the inventory of non-radioactive components in the waste (in kg at the year 2052). OPG was asked to clarify whether some of the substances listed in the Table are stable end products of the decay of the radionuclides in the wastes.

OPG’s Response:
The list is not intended to include all stable end products of all radionuclides – only elements that are important for overall chemical composition or are otherwise important for the non-radiological safety case.
IICPH submission 89441E, p. 6

There are multiple problems with OPG’s approach. Most fundamentally, the whole point of the review process is to let people and organizations outside of OPG see what elements will be going into the repository and offer their own feedback. This purpose is defeated if OPG decides beforehand which information to show. OPG doesn’t get to decide on its own which “elements… are important” and whether the proposed design addresses them adequately – that’s the purpose of the review process.
This is especially problematic because in many cases, OPG has used its own estimates for the concentration and even the presence of important radionuclides. Frank Greening, a career radiochemist for Ontario Hydro and OPG, responding to his examination of the data provided by OPG, notes that

What is notable about these tables is the fact that much of the data are not based on direct measurements at all but rather on “scaling factors, used fuel ratios and neutron activation calculations”. Indeed, none of the data for pressure tubes, end fittings and calandria tubes is based on direct measurements and only a handful of radionuclides are reported to have been directly measured for steam generator waste.
Frank Greening, submission 98019E, p. 2

To date the NWMO has relied solely on calculated values to estimate inventories of individual radionuclides in pressure tube waste even though measured values of many species are readily available.
p. 5

As a result,

The specific activities published by OPG and the NWMO for radionuclide inventories associated with CANDU pressure tube refurbishment waste are seriously underestimated, sometimes by factors of more than 100.
p. 17

This is especially of concern when OPG has not merely underestimated the radioactive activity, but omitted important radionuclides from consideration altogether. As the IICPH notes,

Many of the radionuclides in the waste are alpha emitters. Internal exposure to alpha particles is particularly dangerous. This factor alone deserves consideration, especially for workers who may be at greatest risk of internal exposure to alpha particles. […]

The potential impact of drinking water contamination, due to the potential migration of toxic waste to groundwater, poses a threat to human health and the environment for countless future generations. Even if the level of radioactivity diminishes over time, enough will remain to cause serious harm for a million years or more. Potential geological changes over time, that may increase the chance of releasing radioactivity into the environment, have also not been adequately addressed.
IICPH submission 89441E, p. 9

The importance of listing all alpha emitters can be seen from the following table, in which Mr. Greening compares reported data from actual measurements of nuclear reactor pressure tubes to the estimated values from OPG. In the last line, he also provides real measurements for curium-244, which OPG completely left out of their EIS analysis.

Estimates vs. Actual Measured Data

Estimated Values
Measured Values
Measured Values
RadionuclideOPG/NWMO Activity (Bq/kg ZrNb)Averaged Data from Table 5 (Bq/kg ZrNb)SIMS Data for B3U11 (Bq/kg ZrNb)
Cm-244Not Reported50,000,00014,900,000

Looking at this data reveals three salient points:

• The measured activities of alpha-emitting transuranic radionuclides in irradiated pressure tubes are considerably higher than the OPG/NWMO “used fuel ratio” estimates
• Cm-244, which is not included in the OPG/NWMO’s estimates, is by far the highest alpha activity measured in irradiated pressure tube samples
• There is a high degree of variability (by up to a factor of 3), between measurements from different pressure tube samples.

A comparison of [OPG’s estimates with actual measurements] shows that the alpha-activities in Bruce samples are somewhat higher than the activities of the equivalent species in Pickering samples. Nevertheless, these measured values are consistently higher than the OPG/NWMO estimated values by a factor of at least 3. More importantly, however, the reported OPG/NWMO values imply that Cm-244 is entirely absent from irradiated pressure tubes when in fact this radionuclide accounts for more than 90% of the alpha activity in this type of waste. It is worth noting that Cm-244 is an [especially] important component of radioactive waste because it decays to another alpha-emitter, Pu-240, and is a significant neutron source through spontaneous fission and the associated (a,n) reactions with 0-17 and 0-18 in metal oxides in the waste matrix.
p. 13

But it’s not just OPG’s omission of its most potent alpha-emitter in its inventory. Note also Mr. Greening’s concern with curium’s decay products and their radioactive and chemical profile. Not including curium in their estimates also means that they leave its decay product plutonium-240 out of their estimates, and do not allow for its effects on the chemical reactions that take place around it. Likewise, plutonium-240 itself decays into (among other things) mercury, a toxic chemical in its own right. As the IICPH notes:

It is important to include all stable end-products, particularly as the composition of decay products will change over time, many of these products are hazardous, and they affect the chemical activity within the repository.

Many of the resulting stable progeny from the decay of radionuclides are heavy metals, such as mercury, lead, and thallium, which are very toxic to human health and the environment. Has OPG examined the impact of this?
p. 9

OPG can hardly make a proper plan for the DGR if it simply ignores important components of the toxic and radioactive materials that it plans to store there.

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