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European Laboratory for Particle Physics |
The irradiation area is surrounded by concrete walls (8.4 m high and 80 cm thick) and is covered by a grid roof. Access is via a standard PPE (Personnel Protection Entry) door, with an emergency exit provided on the other side of the area. The large chambers are introduced into the zone through a gate close to the PPE door.
For the first time in CERN history, safe operation is not assured by an accelerator Division but by the Physics Division, a fact that caused many political discussions and practical considerations. The safety aspects of the GIF are indeed mainly dictated by the operation of the gamma source, the muon flux being too weak to pose any radiation hazard. A search procedure of the area is required before the zone can be locked; the same (and unique) key which gives access to the zone must be inserted in the console controlling the operation of the source, such that the source can leave its shielded position only if the area is cleared and locked up. Naturally, the operation of the source is interlocked with the operation of the beam line, as particles other than muons (e.g., electrons) could in principle be transported in the X5 beam. Radiation monitors, movement detectors, fire and gas detectors complete the safety system.
From Thomas Otto:
Two developments in the field of radiation
measurements came to a successful end in January in the Dosimetry and
Calibration Section: During his six-months stay in the Radiation Protection
Group a Technical Student from the Universität Karlsruhe designed a detector
to track down weak radioactive sources. Its principle of operation is to
observe a rise in count rate over background, indicating the presence of
activated material. The detector uses a BGO-scintillator, giving less
photoelectrons per MeV than the classical NaI(Tl)-crystal, but having for
gammas of all energies a higher interaction probability that "counts" in a
pulse-counting application. A special requirement was that the detector unit
should be coupled to a universal portable basic unit rate meter already in
wide use in our group. The device has an autonomy of 50 hours on four 1.5
Volt cells. We are now going out for tender to find a supplier for about 10
units according to the student's design.
CERN still uses films, the Kodak Type 2, for individual gamma- and beta-dosimetry. It is an individual monitor of a reasonable price and has the additional benefit of allowing to identify the radiation hardness to which a person was exposed to. At the end of January, an automated development laboratory for this type of film was installed replacing the existing equipment. A robot is now transferring baskets loaded with exposed films through the whole development process. Thus, process times are precisely controlled. Furthermore, a regeneration system injects fresh processing chemicals at the end of each development in order to keep the chemical concentrations at constant levels. The laboratory was constructed by a specialized French firm according to CERN's requirements. We are now tuning the parameters of the machine with the goal to ensure the reproducibility in the dosimeter evaluation within stricter limits than before.
From Manfred Hoefert:
STOA, but no indifference.
On 5 February I assisted in a one day workshop that had been organized by STOA . Although the invitation had come from Prof. P. A. Assimakopoulos, University of Ioannina, Greece, STOA has nothing to do with the ancient philosophical school but stands for the unit of Scientific and Technological Options Assessment of the European Parliament in Brussels. In fact, this workshop was meant to help members of Parliament in their "survey and evaluation of criticism of basic safety standards for the protection of workers and the public against ionising radiation" notably the European Directive based on ICRP Recommendation 60.
Invited oral contributions from both mainstream supporters of the present radiation protection standards and from adversaries of nuclear energy were well mixed with even some presentations by speakers making the point that current radiation protection efforts were excessive and hence too expensive. While except for a few wild i.e. unfounded statements of those who drove fundamental attacks against the existing radiation protection system these contributions repeated already well known standpoints.
However, some arguments emerged that were not easily refutable during the
generous discussion periods of an hour, following the four topics :
Although the discussion was rather intended to concentrate on the EU Directive on radiation protection it was ICRP, the originator, who was pilloried.
Should we believe the statement of Dr. R. Bertell, International Institute of Concern for Public Health, Toronto, Canada, that the original ICRP dose limit of 5 rem per year for workers was forwarded before the first dose effect estimations for the victims from Hiroshima and Nagasaki had even been made? If therefore the agreement between these estimations and the dose limit was fortuitous, what shall we then think of the remark by Dr. A. Stewart, the impressive and venerable 92 years old lady from Birmingham, that the bomb data are not representative for risk estimations as they are "strongly biased in favour of persons who were exceptionally resistant to all (early and late) effects of radiation". Is it so that persons with a weak immune system are also more sensitive to radiation such that this cohort simply died out due to infections in the years following the explosions? Does this mean that ICRP have lost their basis of risk estimations?
But not only questions arose but strong arguments against IRCP practices were voiced, like:
The concept of effective dose was another point of attack by those who consider present standards not being sufficiently conservative. This not because ICRP has fowled it up for those who must deal with neutrons for whom effective dose equivalent is a more logical quantity than effective dose. Contrary to effective dose equivalent Dr. D. Sumner, Moss park, Scotland, said that the quantity effective dose incorporates "value judgments" on issues like the quality of life for non fatal cancers. Furthermore there are uncertainties in weighting factors, the combination of doses from as varied sources as alpha, beta, gamma and neutrons is wrong and the "calibration" of effective dose with respect to radiation risk could be way off. Dr. C. Busby, Green Audit, Wales continued that effective dose is not a suitable risk quantity because of the averaging performed in space and time when radiation interacts. Hence hot particles from nuclear power are not correctly considered and may be the reason for so far unexplained local effects observed in the vicinity of nuclear installations where also high plutonium values that are 1000 times higher than natural? could be the origin.
In fact, the clusters in children's leukemia strongly came up again presented by (the now in France famous) Dr. Viel, Besançon, the man who had explained the cluster near the treatment plant in La Hague, France, by the use of nearby beaches, the local fish diet but also by residence in granite houses that are common in Brittany. At the same time he supported Gardener's hypothesis that the paternal employment in Sellafield was the reason for the increase in offspring leukemia. Alice Steward said that leukemia clusters have always been observed, more in rural areas than in cities and most of them are not explained. With respect to the leukemia in children around the nuclear power plant in Krümmel near Hamburg Dr. H. Ziggell, Physics office, Bremen, Germany, admitted that the latest models did not explain why 11 cases were observed with only one expected, but he insisted that there must be some correlation with nuclear power (any hidden parameters?).
A request for a dramatic decrease in present dose limits came from Prof. H. Kuni, University of Marburg, Germany: the annual occupational dose limit should be decreased from 50 mSv to 1 mSv and for the public doses should be lowered from 1 mSv to 20 µSv annually. One of the many arguments forwarded to support this decrease was that ICRP had always compared radiation risk with professional risk figures in safe industries but not considering that the latter had been steadily decreasing over the years. Subsequently dose limits should follow. Apparently he had overlooked that personal doses had been decreasing over the years too and that nuclear installations in Germany already limited by law with their radioactive emissions to 300 µSv/year for the surrounding population will proudly present the results of environmental measurements showing that they stayed at least one order of magnitude below the legal limit. As far as neutrons are concerned Prof. Kuni pointed out that radiobiological evidence calls for an increase in their weighting factor to 75. Would 80 or even 100 not have been a rounder figure?
On the other hand present standards in radiation protection were attacked as leading to much too expensive measures in comparison to what could be achieved with the same amount of money when invested to decrease other common daily risks. Prof. J. Jovanovich, University of Manitoba, Canada, presented the audience with the true story of a friend who had asked him whether he should rather invest Can$ 5000 in diminishing the radon concentration in his house than improving its fire safety. Knowing that the risk to die in a house fire in the States or Canada is indeed double compared with Europe the answer seemed already clear when Prof. B. Cohen, Pittsburgh University, US, presented his well known dose effect curves for radon in American houses showing a clear hormesis effect. This was supported by Prof. K. Becker, RSH Berlin, Germany who showed data on the effect of radon concentration on the lung cancer rate of non smoking women from the former Uranium mine area of Thuringia. These facts suggest that the radon risk in houses where and when the synergetic influence of dust and smoking generally experienced with miners is absent is a red herring. A correlation between all those findings and the now famous 200 mSv threshold dose in man is however audacious. In this context the official position of the Protection Office against Ionizing Radiation (OPRI) in France is fully in line with ICRP Recommendation 60. They did not retain the result of the study asked for by the French Academy of Sciences on the dose threshold hypothesis. Nevertheless the sums invested in radiation protection in particular for "cleaning up" Chernobyl in West European countries alone go into hundred of millions whereas the sums spent on radon sanitation exceed billions of dollars according to Prof. Becker. This naturally explains Prof. Jovanovich's remark that ICRP would be well advised to admit economists in its ranks.
At two occasions in the discussion the author tried to turn the discussion back to the European Directive. My remark that although exemption values for radioactive materials are common in Europe but the choice or even refusal of Clearance levels are left over to the individual member states. Such a decision hampers the free passage of goods among the EU countries and hence was against the basic treaty of the Community. My remarks found the full support of M. P. Lannoye, French member of the European Parliament and chairman of one of the sessions. Members of the European Commission's Unit DG XI present at the workshop announced improvements and the imminent publication of a paper on the recycling of weakly radioactive scrap metal that is in its final draft.
However, my other question, why the EU retained in their Directive class A
and B radiation workers although ICRP does no longer make this distinction
did not find much interest. The answer of the European Commission that
existing structures had to be retained sounds weak considering that:
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