[ RadSafe ]" EPA Tritium Risk Plan May Force Tighter Nuclear Plant Controls "

[Philippe J. Duport]

Radsafers

Follow-up on John Johnson’s comments:

Carcinogenesis following HTO intake appears to be strongly dependent upon dose rate.  Yamamoto et al exposed mice to chronic ingestion of HTO starting at 10 weeks of age.  They show fairly clear thresholds at or below 12 mGy/day.  I think Myers et al conducted their experiments at doses total doses of about 1 to 3 Gy, delivered in one intraperitoneal injection; the total dose was delivered in a few days and the dose rate was fairly high immediately after the injection.  The difference in dose rates may explain the difference between Yamamoto's and Myers's results.   

Reference:  Yamamoto, O., Seyama, T., Itoh, H., and Fujimoto, N. (1998) Oral administration of tritiated water (HTO) in mouse. III: Low dose-rate irradiation and threshold dose-rate for radiation risk.  Int J Radiat Biol, 73:535-541.

Philippe Duport

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf Of John R Johnson
Sent: June 20, 2007 10:13
To: Franta, Jaroslav; Radsafe (E-mail)
Subject: Re: [ RadSafe ]" EPA Tritium Risk Plan May Force Tighter Nuclear Plant Controls "

Radsafers

It is "well known" that tritium and other radionuclides that emit low energy 
electrons and photons have a higher risk per unit dose than the "standard" 
250 kVp X-rays, but than so does lower energy X-rays, and higher energy 
electons and photons have lower risks. We did a large animal experiment at 
CRNL to test this.

See

INDUCTION OF MAMMARY TUMOURS IN RATS BY X‑RAYS AND TRITIUM BETA‑RAYS

D.K. Myers, N.J. Gragtmans, J. R. Johnson, L.D. Johnson, and A.R. Jones

Published in the proceedings of an international symposium on The Effects of 
Low‑Level Radiation with Special Regard to Stochastic and Non‑Stochastic 
Effects, jointly organized by the International Atomic Energy Agency and the 
World Health Organization, IAEA‑SM‑266/12P (1983) 653.

and

AN EXPERIMENT DESIGNED TO MEASURE THE RBE OF TRITIUM FOR THE INDUCTION OF 
MYELOID LEUKEMIA IN ANIMALS

J. R. Johnson, D.K. Myers, and N.J. Gragtmans

Radiation Protection Dosimetry 16 Nos. 1‑2 (1986) 161‑164, AECL‑9339.


The ICRP, NCRP, etc have decided that a single radiation weighting factor of 
unity is adaquate to represnt the risk from all this radiation, given the 
large uncertainty in the risk.

Is there new information that is "leading" the EPA to change this titium 
weighting factor?

***************
John R Johnson, PhD
CEO, IDIAS, Inc.
Vancouver, B. C.
Canada
(604) 222-9840
idias at interchange.ubc.ca



----- Original Message ----- 
From: "Franta, Jaroslav" <frantaj at aecl.ca>
To: "Radsafe (E-mail)" <radsafe at radlab.nl>
Sent: Wednesday, June 20, 2007 6:10 AM
Subject: [ RadSafe ] " EPA Tritium Risk Plan May Force Tighter Nuclear Plant 
Controls "


> Comments welcome:
>
>
> EPA Tritium Risk Plan May Force Tighter Nuclear Plant Controls
> Energy Washington Week, Vol. 4, No. 25, 20 June 2007
>
> EPA is considering a substantial increase in its estimates of the risks
> posed by human exposure to tritium, a controversial byproduct of nuclear
> power generation, in a move that could prompt nuclear regulatory agencies 
> to
> tighten their risk-based approaches for regulating radiological releases
> from nuclear power plants.
>
> However, sources say any effort by EPA to tighten the risk estimates for
> tritium would likely prompt opposition from the industry and nuclear
> regulators, who fear it would complicate industry efforts to present 
> nuclear
> power as an alternative to coal-fired generation under any future climate
> change regime.
>
> Informed sources say EPA is weighing whether to double the effectiveness
> factor it assigns for tritium, a risk estimate figure used in setting
> contamination and cleanup standards that represents a given radionuclide's
> potential to damage the human body. EPA and other federal regulators
> generally set this factor at 1.7 for tritium and similar radionuclides.
>
> However, recent scientific findings from the International Commission on
> Radiological Protection and evidence accumulated by the National Institute
> for Occupational Safety and Health (NIOSH) have led some EPA regulators to
> consider increasing that factor to 2 or higher, the sources say.
>
> Tritium is an isotope of hydrogen that produces relatively low levels of
> radiation. Nuclear power plants release tritium in water and steam
> discharges. Regulators in several instances have also dealt with tritium
> leaks from nuclear facilities in the form of contaminated water.
> Consequently the task of estimating the health risks associated with 
> tritium
> is a highly contentious issue among nuclear experts, industry and
> environmentalists.
>
> Observers say increasing the effectiveness factor for tritium could result
> in risk assessments that suggest human exposure to tritium is more 
> harmful,
> thereby giving federal regulators grounds to tighten tritium containment 
> and
> release standards at nuclear power plants, research laboratories and 
> places
> where nuclear fuel is stored. Additionally, a key activist source says the
> increased risk figures could encourage more severe federal enforcement
> actions should regulators discover tritium leaking at a nuclear facility.
>
> Increasing the effectiveness factor for tritium would have little to no
> impact on EPA's radiation standards because the risk associated with 
> tritium
> would still be within already regulated levels, which are based on
> calculated doses, the sources add. Nevertheless, the move could spur
> regulators in other agencies -- such as the NRC and the DOE-- to adopt a
> similar risk assessment approach, the sources say.
>
> Sources say EPA efforts to tighten its risk estimates would likely prompt
> opposition from NRC and the industry, in part because it could stifle
> efforts to build as many as 27 new nuclear reactors in the United States
> over the next few years.
>
> Nuclear industry officials are hoping for a so-called "renaissance" for
> nuclear power nationwide, arguing in part that the plants provide 
> increased
> energy supplies without increasing harmful greenhouse gas emissions that
> contribute to climate change.
>
> However, environmentalists and Democrats are calling for stricter safety 
> and
> environmental controls on the industry before new plants can be built.
>
> News that EPA is eyeing an increase in the tritium effectiveness factor
> could bolster anti-nuclear activists and prompt opposition from NRC and
> industry.
>
> The expected growth in the nuclear energy sector, an informed federal 
> source
> says, is one reason NRC would likely resist any effort to increase the 
> risk
> factors connected to tritium. "The other agencies would try to stop it," 
> the
> source says. "Not under this administration, it'll never make it through."
>
> A radiological protection expert agrees, saying such an increase in 
> tritium
> effectiveness factor could "make the NRC mad."
>
> An NRC source downplays the significance of increasing the effectiveness
> factor for tritium, saying the agency would have to formulate its own
> technical opinion on the factor before adopting it. The source also takes
> issue with the suggestion that the factor could impact power plant
> standards, noting that new plants tend to use the most current methods to
> ensure radiation exposures remain well below regulated levels. A nuclear
> industry source agrees, noting that the deliberative nature of setting
> radiation standards could mean that any regulatory change may be years in
> the making.
>
> One informed source cautions that it is "not a foregone conclusion" that
> increasing the factor will lead to stricter tritium regulations because
> those rules are most often based on specific dose calculations. However, 
> an
> expert with a nuclear watchdog group suggests the increased factor would
> translate into tougher standards and regulators "would have to do 
> something
> to undercut that" in their risk calculations for it to not have a
> significant impact.
>
> But despite potential efforts to block tighter risk factors for tritium, 
> the
> federal source notes that EPA is slated to begin a review of its water
> contaminant limits for radionuclides in 2009. Increasing the effectiveness
> factor, the source adds, could encourage agency regulators to impose
> stricter maximum contaminant level (MCL) limits, which the agency also 
> uses
> to set cleanup standards, during this review. The tritium MCL is currently
> set at 20,000 picocuries per liter of water, roughly 4 millirems of 
> exposure
> per year.
>
> EPA has already seen pressure from nuclear watchdog groups to impose
> significantly stricter water standards for plutonium in the pending 
> review.
>
> EPA is also in the midst of a Science Advisory Board panel review 
> examining
> the agency's risk approach to radiation that will likely prompt the agency
> to adjust its risk calculations for many radionuclides. A nuclear watchdog
> group has repeatedly urged the panel to increase the effectiveness factor
> for tritium to 3 or higher, citing several studies arguing it should be
> raised. A source with one group says the panel will soon receive formal
> written comments advocating such an increase.
>
> The panel's most recent draft report, released Feb. 23, says tritium is
> among several issues the National Academy of Sciences most recent report
> evaluating radiation risks, which is the basis on the panel's work, did 
> not
> address. EPA has a "need to derive a basis for risk estimates" for it, the
> report says.
>
> The report also suggests EPA's effectiveness factor for tritium could be
> increased as the agency adopts its proposed radiation risk methods based 
> on
> the NAS report. In its discussion of the risks associated with low-energy
> photons and electrons, the report says "an effectiveness factor for these
> low energy radiations in the range of 2 to 2.5 seems reasonable." The 
> report
> includes the chemical symbol for tritium, 3H, among the particles that 
> would
> fall within that category.
>
> Additionally, tritium will likely be at issue in a June 21 meeting between
> officials with the NRC and the nuclear industry focused on a voluntary
> industry initiative begun last year to boost groundwater protection
> standards at power plants. The initiative was prompted by concerns over
> tritium leaks at several nuclear facilities.
>
> However, the nuclear industry contends such leaks are not dangerous to
> public health and are generally contained within the facility in question.
> The radiological protection expert adds that concerns over tritium leaks
> would be better addressed by ensuring it is contained at a site, rather 
> than
> increasing the risk factors associated with it. The source points out that
> NRC and the nuclear industry itself closely monitor tritium to ensure 
> leaks
> and other unintentional releases are prevented.
>
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