Concerned Citizens of Renfrew County
Regulation and monitoring of radioactive waste incineration at the Chalk River Nuclear Laboratories
O.Q. Hendrickson
Abstract
The federal Atomic Energy Control Board (AECB) is the licensing agency for regulation of radioactive emissions to air and water from the Chalk River Nuclear Laboratories (CRNL), run by Atomic Energy of Canada, Ltd. (a Canadian crown corporation). A nuclear waste incinerator has operated at CRNL since 1983, releasing gases containing radioactive isotopes of hydrogen, carbon, iodine and other elements to the environment. An AECB license gives CRNL "the maximum degree of freedom in operating the facility". Release limits are derived from individual doses at the upriver boundary of the facility, 6 km distant from the stack. This allows CRNL to include a half billion fold dilution factor in their calculations of release limits. Collective doses of radiation, persistence of radionuclides for more than one year, and releases of radionuclides from other CRNL facilities are not considered in setting release limits for the incinerator. Measured H-3 (tritium) releases from the incinerator stack have ranged from 3.1 to 15.6 TBq/yr since 1983, well under the permitted off-site release of 570,000 TBq/yr. Measured I-131 releases of 0.11 GBq in 1988 and 0.12 GBq in 1989 were less than the permitted 11,000 GBq/yr. Other airborne isotopes (C-14, noble gases, I-129, etc.) were not monitored. The current regulatory framework reflects a "dilution is the solution to pollution" philosophy and does not ensure protection of public health in surrounding areas.
Introduction
An incinerator operated by Atomic Energy of Canada, Ltd. (AECL) in Chalk River, Ontario, burned about 80 tons of solid radioactive waste yearly from 1983-1988 plus an unspecified amount of liquid radioactive waste (Le et al. 1988). This incinerator is designed to trap particulate materials, but emits radioactive hydrogen, carbon, and iodine gases to the atmosphere.
On 28 February 1990, the Atomic Energy Control Board (AECB) issued a 1-year license to AECL. In the letter accompanying this license, D.H. Sykes, Project Officer for the Atomic Energy Control Board, expressed the Board's concerns about the adequacy of management controls, and the lack of assignment of clear responsibility for operation and safety of the AECL facilities, known as the Chalk River Nuclear Laboratories (CRNL). He said that the Board was looking forward to being informed of the steps taken to resolve these problems.
The AECB license cites another document (Nuclear Safety Advisory Committee 1988) governing the operation of facilities at the CRNL. The section on "Principles and General Rules for the Operation of the Waste Treatment Centre at CRNL" gives operating principles for the incinerator. It states that "The owner or his designate is to be granted the maximum degree of freedom in operating the facility...", "The owner or his designate is free to make, without prior approval... any changes in operational procedures...", and "...releases of radioactive material to the environment...will be as low as reasonably achievable (ALARA), social and economic factors being considered".
Allowable incinerator releases
The AECB license refers to another AECL document (Palmer 1981) which further describes the regulatory framework. It contains limits for airborne releases from the incinerator and other facilities at the CRNL.
After discussing radiological dose limits for individuals, Palmer (1981) noted that "The question remains whether limits on total population dose (collective dose) should also be established to limit the total detriment to the exposed population to an acceptable level." He answered in the negative: "a limit on collective dose is inappropriate."
Palmer (1981) also noted that "the radionuclides persist in the environment and hence the true dose delivered in any one year is the sum of the doses arising from that year's release and from all previous years' releases corrected for radioactive decay and for any other process which removes them from interaction with humans". However, while recognizing that this creates a problem, he declined to take this into account.
Following the principles that population doses should not be limited to an acceptable level, and that persistence of radionuclides can be ignored, Palmer (1981) calculated limits for releases of different radioisotopes from the CRNL. He provided two sets of figures, one for on-site releases and another for releases to the general public (off-site). The on-site releases were assumed to come from roof vents, and the off-site releases from a tall stack. Some of these are reproduced in Table 1.
| Maximum Ci (Curies) | Maximum Bq (Becquerels) | |||
| Radionuclide | in one week | in one week | ||
| on-site | off-site | on-site | off-site | |
| Hydrogen-3 (HTO) | 2,100 | 300,000 | 7.8 x 10 to the13 | 1.1 x 10 to the16 |
| Carbon-14 (CO2) | 4,600 | 4,600 | 1.7 x 10 to the14 | 1.7 x 10 to the14 |
| Iodine-131 | 2 | 6 | 7.0 x 10 to the10 | 2.1 x 10 to the11 |
* Data are from Palmer (1981).
The limits, given in Curies, are converted into Becquerels (1 Ci = 3.7 x 1010 Bq). A Becquerel is defined as one nuclear disintegration per second. For example, the CRNL are permitted to release an amount of tritium (Hydrogen-3) to the environment each week that would give off 11 million billion disintegrations (as beta particles) every second. The general population may receive over 100 times more tritium than plant workers, as it is assumed that gases are diluted by a factor of 5 x 10-8 as they travel to the upriver boundary of the CRNL, 6 km from the stack.
Limits for isotopes of iodine are much stricter than for other elements. Radioiodines are particularly dangerous, as they accumulate in the thyroid gland if inhaled and can cause cancer or other thyroid problems. Iodine-129 has the lowest limit of the iodine isotopes (1.8 x 1010 Bq/week); it has a billion-fold longer half-life (6.2 x 109 d) than the more common I-131 (8 d).
AECL personnel appear to have been concerned about the potential hazards of radioactive iodine, although they were slow to act upon these concerns. Prior to incineration of radioactive wastes, Beamer (1981) stated that "Although the waste is not expected to contain significant radioiodine, stack effluent will also be checked periodically for radioiodine release". After several years of operation with radioactive wastes, Beamer (1984) again stated that "The waste is not expected to contain significant radioiodine, and to date none has been detected in the stack effluent". Barrington (1988) stated that "Sampling the incinerator off-gas for I-131 is difficult due to the high temperature of the gas stream", and added that "... the effluent from the Waste Treatment Centre is now monitored routinely for iodine-131 and these results will be reported in subsequent annual safety reviews." Thus, it is highly likely that radioiodine was released during the early years of incineration, albeit in unknown amounts.
It should be noted that other facilities at the CRNL (such as the NRX, NRU, PTR, and ZED-2 reactors) also release radionuclides, but these additional radiation sources are not considered in calculating permitted release limits for the incinerator.
Actual incinerator releases
The annual safety reviews (McAuley 1985, 1986; Barrington 1987, 1988, 1989, 1990) provided limited data on actual incinerator effluents, some of which are reproduced in Table 2.
| Isotope | 1983 | 1984 | 1985 | 1986 | 1987 | 1988 | 1989 |
| H-3, TBq | 15.6 | 11.8 | 12 | 8.3 | 10.8 | 6.3 | 3.1 |
| C-14 | ND | ND | ND | ND | ND | ND | ND |
| I-131, MBq | ND | ND | ND | ND | ND | 111 | 115 |
*Data from McAuley (1986) and Barrington (1990). ND = No data,
MBq = 1 million Becquerels, and TBq = 1 million million Becquerels.
Yearly releases of tritium (H-3) appear to be declining, while it is not possible to establish trends for other gases. No monitoring data are given for carbon-14, nor for the radioactive noble gases. Tritium and I-131 releases are well within permitted limits (Table 1), whether off-site limits are used (McAuley 1985, 1986), or on-site limits are used (Barrington 1987, 1988, 1989, 1990).
No details are given concerning the methods used to calculate releases of I-131. For tritium, a continuous isokinetic sample from the stack is drawn through a centre-line probe and two tritium detection bubblers in series (Beamer 1984). According to McAuley (1985), the tritium bubbler samples are analyzed three times per week (the incinerator averages one burn per week).
Discussion
In a 17 January 1991 letter to Mr. I. Theilheimer
of Killaloe, Ontario, Mr. Leo P. Buckley of the CRNL states that
the incinerator has been shut down for more than one year because
it is uneconomical to operate. He adds, "We do intend to
bring it back into operation later this year to destroy a backlog
of waste oils we have accumulated". There appear to be no
regulations for the burning of liquid organic wastes in the incinerator.
A permit for incineration of organic wastes would be issued by
the Ontario Ministry of the Environment, but no mention of such
a permit is made in the AECL documents. The accumulation of waste
oils at CRNL includes 90,000 liters of uranium contaminated oils,
and 10,000 liters of oils contaminated with polychlorinated biphenyls
(PCBs).
There has not been consistent and thorough monitoring of waste
gases from the incinerator. For example, there are no data for
C-14, and none for I-131 prior to 1988. Furthermore, the derived
release limits appear to be excessively high. Written in 1981,
they do not reflect new findings and recommendations of international
authorities that set radiation protection standards. They fail
to consider population dose, or accumulation of radionuclides
in the environment. There is no analysis of H-3, C-14, or I-131
prior to incineration, so any monitoring of these radionuclides
is done "after the fact".
Conclusions
The regulatory framework for the incinerator does not appear to adequately address public health and environmental concerns. Ineffective regulation and monitoring of releases of radioactive waste gases from facilities at the CRNL has created the potential for serious public health problems. A review of the situation by independent experts is needed.
Acknowledgement
References
Barrington, D.A. 1987. Review of the operations
of the waste treatment centre during 1986. AECL-MISC-304-86.
Barrington, D.A. 1988. Annual safety review of the low level waste
treatment center, 1987. AECL-MISC-304-87.
Barrington, D.A. 1989. Annual safety review of the low level waste
treatment centre, 1988. AECL-MISC-304-88.
Barrington, D.A. 1990. Annual safety review of the low level waste
treatment center, 1989. AECL-MISC-304-89.
Beamer, N.V. 1981. Radwaste incineration at CRNL. AECL-7437.
Beamer, N.V. 1984. Experience with low-level waste incineration
at Chalk River Nuclear Laboratories. AECL-8187.
Le, V.T., Beamer, N.V., and Buckley, L.P. 1988. Experience with
radioactive waste incineration at Chalk River Nuclear Laboratories.
AECL-9722.
McAuley, S.J. 1985. Review of the operations of the waste treatment
centre building 570 during 1984. AECL-MISC-304-84.
McAuley, S.J. 1986. Review of the operations of the waste treatment
centre building 570 during 1985. AECL-MISC-304-85.
Nuclear Safety Advisory Committee. 1988. Principles and general
rules for the operation of the waste treatment centre at CRNL.
AECL-MISC-191.
Palmer, J.F. 1981. Derived release limits (DRL's) for airborne
and liquid effluents from the Chalk River Nuclear Labor