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atw Vol. 63 (2018) | Issue 1 ı January 46 AMNT 2017 Key Topic | Enhanced Safety & Operation Excellence Focus Session: Radiation Protection Erik Baumann and Angelika Bohnstedt The objectives of radiation protection are to minimize the negative health effects due to radiation. Over many past decades, the regulatory environment, i.e. the various international and national codes and standards but also recommendations issued by IAEA and IRCP, was always subject to continuous development reflecting up to date knowledge and experience. Currently, discussions focus on “new” areas of human activities like decommissioning and on “new radioactive substances” and potential threats associated with their handling (handling and treatment of substances containing naturally occurring radioactive materials). Latter already became subject to regulations issued by EURATOM. For topics like decommissioning, statement can be found doubting that the existing regulations address radiation protection in a sufficient manner. Authors Erik Bauman New NP GmbH Paul-Gossen-Str. 100 91052 Erlangen, Germany Dr. Angelika Bohnstedt Karlsruhe Institute of Technology (KIT) Programm Nukleare Entsorgung, Sicherheit und Strahlenforschung (NUSAFE) Hermann-von- Helmholtz-Platz 1 76344 Eggenstein- Leopoldshafen, Germany In the Focus Session Radiation Protection – What about the basic principles and objectives in the current regulatory environment? three presentations (a forth one had to be cancelled on short term for personal reasons) directed the view on different aspects. This gave the occasion to the 25 to 30 participants for interesting questions and a fruitful exchange of opinion not only with the lecturer but also among each other. Especially the presentation dealing in a somewhat provocative way with the subject ‘Hormesis’ led to a motivated discussion in the audience about different point of views. In the first presentation Hormesis – a Miracle in reality? Discussion Required Jan-Christian Lewitz (LTZ- Consulting GmbH) started with from literature compiled controversial conclusions about the amount of harmed people by the Chernobyl accident. This was followed by a provocative statement about the hormesis principle in the way “when unhealthy things become healthy” and “it is just depending on the right dose”. He quoted the explanation for hormesis as “biopositive reaction of biological systems” but also restricted that there are “no general mechanism known for the different hormetic effects” and indicated that hormesis is not con sidered for risk assessment. Then Mr. Lewitz showed curves about the dose/effect relation and the LNT model and remarked that little scientific evidence of any measurable adverse health effects at radiation doses below about 100 mSv is at the moment available. As a discussible example for another effect he shortly gave an overview of an incident in Taiwan in the eighties of the last century where buildings, used by about 10,000 people, were constructed with Co-60 contaminated steel. Higher-than-normal radiation levels were discovered after 9 years and therefor surveys for cancer and birth defects in this group of persons, some lived up to 20 years in the building, where executed. Mr. Lewitz presented the result of the survey with a lower mortality in the examined group than in the normal average public. He ended his presentation with the questions “What should be looked after and be obeyed?” and “Is Optimization below 100 mSv/y justified in regard to limited resources?” and encouraged the audience to discuss with him his challenging point of view. The second lecture Radiation Instrumentation and Measurement Technologies for High Radiation Fields was given by Dr. Marina Sokcic- Kostic (NUKEM Technologies Engineering Services GmbH) who talked about the possibility to monitor radioactive materials in high dose-rate environments where common types of gamma detectors reach their limits. The first instrument she presented was a Geiger- Mueller-Counter where by switching on and off the counting tube dead-times can be avoided. Next Ms. Sokcic-Kostic remarked that measurement of particle radiation in the presence of high gamma fields is quite challenging. She explained a fission chamber, operable for gamma radiation up to 50 to 100 Sv/h, where ionization efficiency is set very low, so that mainly the fission products are measured and additionally by adjusting the pulse heights neutrons can be separated from gammas. Afterwards she presented some applications of this chamber. One device with several chambers is used to characterize irradiated fuel assemblies in a storage pond by passive neutron and passive gamma counting. Another one she explained where the chamber is combined with other measurement instruments works with active neutron detection monitors using external neutron or ion sources. Ms. Sokcic-Kostic conclude her pre sentation with a Gamma camera which is able to localize hot spots in waste packages and some information about Cherenkov detectors. With the final talk Predictions of Expected Dose Rates by validated Activation Calculations as Input for a step-wise Decommissioning and Dismantling of a Nuclear Power Plant Dr. L. Schlömer (together with Dr. S. Tittelbach and Prof. P.-W. Phlippen; all WTI Wissenschaftlich- Tech nische Ingenieurberatung GmbH) changed the subject to Monte-Carlo modelling. He listed the specific requirements for decommissioning like licensing, planning of packaging, probing and of course cost estimation. Then he showed that Monte-Carlo code coupled with modern variance reduced techniques (ADVANTG) is a good solution for radiological characterization while reducing number of samples and related costs. Mr. Schlömer commented that even more detailed calculations are able with an activation and decay module (ORIGEN-S). With an example for a BWR (same for a PWR) he explained the steps which have to be performed for the calculation procedure to get from a technical drawing of a reactor to a detailed MCNP-model. To validate the method a comparison of measured and calculated dose rates is necessary. Therefore, Mr. Schlömer continued, dose rate measurements have to be executed on defined places between RPV and biological shield. He concluded his presentation with the outcome that the methods of validation show good results for the BWR and the PWR. AMNT 2017 Focus Session: Radiation Protection ı Erik Baumann and Angelika Bohnstedt
The International Expert Conference on Nuclear Technology Estrel Convention Center Berlin 29 – 30 May 2018 Germany AMNT 2018 Key Topics Outstanding Know-How & Sustainable Innovations Enhanced Safety & Operation Excellence Decommissioning Experience & Waste Management Solutions Preliminary Programme December 15, 2017 Subject to change. www.nucleartech-meeting.com
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