" New ICRP guidelines to 'clarify' collective dose, Dicus says "

["Franta, Jaroslav" <frantaj@AECL.CA>]

NUCLEONICS WEEK MARCH 25, 2004

New ICRP guidelines to 'clarify'

collective dose, Dicus says

New guidelines being prepared by the International

Commission on Radiological Protection (ICRP) will "not

lead to any major changes" affecting regulators or industry

but will "clarify" the concept of collective dose, said Greta

Dicus, a member of the ICRP.

The new guidelines will be ready for distribution in draft

form at the quadrennial conference of the International

Radiation Protection Association to be held in Madrid in

May. The commission's last comprehensive recommendations

were made in ICRP-60, issued in 1990.

Dicus, a former NRC commissioner and chairman, summarized

the results of the ongoing ICRP deliberations at the

2004 Pacific Basin Nuclear Conference (PBNC) in Honolulu on March 22.

"You won't have to rewrite national radiation protection

regulations" as a result of the new guidelines, Dicus advised,

"but there will be a few clarifications."

Dicus cited some passages from the guidelines that are

being prepared, but said she could not distribute the text

because it was still confidential.

Dicus advised that the result of ICRP deliberations would

be to "still recommend" use of quantitative standards for all

sources of radiation to be controlled. But she said that the

commission had made a point to emphasize that "protection

of the individual" was the primary objective of the use

of such standards. "We want to optimize the level of protection

in the presence of a potential probability of a health

effect of even a small exposure beginning as low as 0.01

milliSievert (mSv) and up to 100 mSv," she said, suggesting

that the commission would establish recommendations

"progressing by multiples of ten."

The new guidelines were justified because ICRP has issued

10 separate documents on specific subjects such as medical

applications of standards and radiological emergencies, during

the last 14 years. "It is time to take the information in

these documents and begin to condense it," Dicus said.

Among the key tasks taken up by the ICRP for the new

guidelines were "clarification of dose limits for individuals

and developing the concept of dose constraints for single sources," she

said.

The new guidelines will include provisions for "exceptions"

for certain sources subject to regulatory control. "We

will continue to recognize the need for certain exceptions," she said.

Differing over dose

Since ICRP-60 was issued, a debate has ensued over the

apparent difference between "dose equivalent" and "equivalent

dose." This debate will "go away," she predicted, after

the commission makes clear that "effective dose" is the

"only term we will use," and the ICRP "will go to radiation-weighted

doses in tissues and organs." The weighting factor

for neutron radiation, she said, would be "increased a little"

because the new guidelines will take into account the

gamma component of neutron radiation.

Dicus said that while "effective dose is intended to be the

principal quantity to be used in radiation protection" the

commission's guidelines will spell out that "it is not appropriate

to use estimates of effective dose for epidemiological

studies or to predict the consequences of exposure. Effective

dose should not be used to estimate the consequences of a radiological

injury."

ICRP "will retain the concept of collective dose," Dicus

said, however, the commission will address criticism that "it

has been misapplied"since ICRP-60 was published. The new

guidelines "will put it into its proper context. The main

point is that (collective dose) will not be used to predict

what will happen in the future."

The basic distinction between three categories of exposure

groups-non-professionals, radiation professionals, and

those working constantly in a controlled radiation environment-

will be retained, Dicus said.

The ICRP debated "whether to regulate the medical industry,"

Dicus said, but that was "ultimately rejected," she said.

Regardless of some outside criticism, the ICRP "is not

going to abandon the concept of collective dose," Dicus

said. "But there will be more attention to protection of the individual."

The ICRP also "chose to discuss environmental protection,

a subject which had not been treated in the past."

Until now, she said, the ICRP had operated on the premise

that "if you are protecting humans, you are protecting the

environment. That might not be the case. There are places

where humans are not." Independent of the ICRP, "several

countries" were moving toward setting up guidelines for

environmental protection in radiation regulations "and the

absence of international consistency was of concern" to the

ICRP, she said. The result of the ICRP recommendations

"may be establishment of dose limits for animals. We have a

potential list, and we're working on it."

The bottom line of the new guidelines, she said, is that,

14 years after ICRP-60 was issued and drew criticism from

industry and some other professional quarters, "we can't

lower the standards" in ICRP-60. "We are very cautious

about this. We can't explain (lower standards) to the public."-

Mark Hibbs, Honolulu