INTERNATIONAL ACCELERATOR RADIOLOGICAL PROTECTION E-MAIL (IARPE) NEWSLETTER "The Official Publication of the Accelerator Section of the Health Physics Society" (with Contributions from International Correspondents) --------------------------------------------------------------------------- July/August 1997 Circulation: 185 Vol.6, #4 --------------------------------------------------------------------------- OFFICERS President: Vashek Vylet, SLAC President-Elect: Steve Musolino, BNL Past President: Lutz Moritz, TRIUMF Secretary: Scott Walker, LANL Treasurer: Gerry Fallon, MIT Newsletter Editor: Scott Schwahn, Jefferson Lab Directors: Jeff Leavey, IBM (1998) Tracy Tipping, KSU (1998) Wes M. Dunn, Texas Department of Health (1999) Henry Kahnhauser, BNL (1999) Bob May, Jefferson Lab (2000) Keith Welch, Jefferson Lab (2000) --------------------------------------------------------------------------- CONTENTS * From the Editor * From the President * Feature Article * Radiation Matters: Lessons Learned * News from correspondents: o CERN o Fermilab o Jefferson Lab * How to subscribe or update subscription * Closing thought ========================================================================== From the Editor Scott Schwahn ========================================================================== I'm thrilled to get the chance to write to you for the first time as Editor of the Newsletter. It's been a challenge to get the Newsletter out for the first time since I took over. I learned a little HTML (Web language) to spruce up the web version , and I hope you can see a dramatic difference. I could still use many more pictures from correspondents - virtually any format (jpeg, gif, tif, pcx, etc.) will do. Come to think of it, I could just plain use more correspondents! Many thanks to continuing Associate Editor Ted deCastro, new Associate Editor Kristin Erickson, and to the previous Newsletter Editor, James Liu for the smooth transition. I am pleased with the contributions made in this Newsletter. First, you will find an update of section activities from our new President, Vashek Vylet. Next, we have the feature article from Manfred Hoefert, which discusses quantities and units in radiation protection. You will want to read this one - it is not the usual run-of-the-mill discussion on S.I. versus traditional units. A new section in the Newsletter has been initiated by Kristin Erickson called "Radiation Matters: Lessons Learned." This will be a regular submission, one which I hope will inspire more of you to write similar articles (hint, hint).News from correspondents include CERN, Fermilab, and Jefferson Lab. I hope you will take note of the new Accelerator Section Officers as noted above and congratulate them when you get the chance. ========================================================================== From the President Vashek Vylet ========================================================================== Dear colleagues, With fresh memories of the Accelerator Section meeting in San Antonio, I would like to congratulate all our newly elected Section Officers and wish them success in accomplishing our common goals. Additional help will come from Section Committees. Taking into account tasks that came from discussions in San Antonio, I am in the process of contacting Section members and reviewing the need for creating new committees or reinstating old ones. This process is not yet finished, but I would like to inform you about the current status. Rules Committee: Carter Ficklen will be joined by the new President-Elect, Steve Musolino. The Committee will follow up on Section efforts to get recently proposed changes to our Bylaws approved by the HPS Rules Committee and the HPS Board of Directors. Contact with Program Committee: Steve Musolino will contact the Program Committee for the next HPS Annual Meeting and explore the possibility of involving Section members in organizing the Technical Program for the Accelerator Session. Scientific Panel: Ken Kase and Don Cossairt. This panel was originally set up to investigate the possibilities of establishing a facility for high energy neutron calibrations in the U.S. Such efforts obviously depend on good will in the higher spheres and availability of funding, but our Section should not give up and continue these efforts. Some other scientific issues might also arise in the future. Summer School Committee: Bob May and Paula Trinoskey. This committee will follow up on the proposal of organizing, perhaps as part of the HPS CEC courses, a summer school on Accelerator Health Physics. This committee will help with suggesting topics, finding/proposing lecturers and coordinating with other committees or organizations. One of the recent salient successes of our Section is the work of the CASOG committee, summarized in the feature article from the last IARPE issue. I would like to explore with the Section Board (and anybody else interested) appropriate ways of keeping our Section actively involved in regulatory issues. In view of the upcoming '98 Midyear Meeting in Mobile, Alabama, Lorraine Day proposed to organize a technical tour/workshop at her facility, the Center for Advanced Microstructures and Devices (CAMD), at Louisiana State University in Baton Rouge. This event could take place on Saturday before the Midyear Meeting, i.e. on February 7th, 1998. CAMD being a synchrotron light facility, the workshop could concentrate on specific health physics issues at synchrotron facilities, but a broader topic is also considered. At this stage we would like to get your input regarding attendance and topics. If you are interested, please send e-mail to Lorraine , with a copy to me. ========================================================================== FEATURE ARTICLE QUANTITIES AND UNITS IN RADIATION PROTECTION Manfred Hoefert ========================================================================== Dilbert: "Management has decided to use sieverts in our lab." Dogbert: "Rat(d)s" At the HPS Midyear Conference in San Jose I noticed that many American colleagues are not only utterly confused but in addition are disgusted by the way ICRP and ICRU continuously seem to destabilize radiological quantities. Having followed the development in this field over the last 25 years I went through various stages of depression and confusion myself - which in fact rather disqualifies me to write this article. In order to split up the great confusion into chewable bites let us put some order in the discussion and quickly do away with radiological units. They are really not an important issue. Many colleagues still consider that the rem as the unit of dose equivalent and the curie for activity were more convenient than the SI units and cling to the former, but let's face it: the world has gone SI. In a time of decreasing doses and dose limits the unit sievert is actually not so bad as a dose rate of 10 microSv/h in a controlled radiation area is about the level where you as an operational physicist like to think about, and an effective dose of 1 mSv is roughly what we all receive from external natural radiation - excluding radon - in a year. Personally, I prefer the becquerel very much to the curie (thinking of decays per second as something everybody can easily grasp) than relating the physical quantity activity to that of one gram of radium (we had milligrams of that stuff at CERN and are happy that we got rid of it). What was the limit still for milk in those days of Chernobyl: 800 Bq of Cs-137 in a liter or roughly 1 kBq in a quarter (sic!) so the becquerel is a rather convenient measure for the environment and food stuff. Switching from units to physical quantities I shall only consider external exposure. The sievert is actually the unit of various physical quantities used in the radiation protection of external radiation. Ambient dose equivalent, personal dose equivalent and effective dose - the latter is not to be confused with the nowadays "obsolete" quantity effective dose equivalent - are the most important ones. The first two, H* and Hp, are operational or secondary quantities whilst the last two, E and Heff, are protection or primary quantities sometimes also called risk quantities. These are actually the quantities in which ICRP recommends dose limits and on which legal limits are based. Let us discuss operational quantities first. Why do we need them? They are necessary as the protection quantities are by definition not measurable. In fact, the effective dose that builds up in my body moving in an external radiation field is pp (personal and private) and quite distinct from the one that would be present in somebody else's body should he/she move around in the same field. So obviously we need quantities in which our instruments and personal dosimeters are calibrated such that we can measure dose equivalents in any radiation situation and in a defined way. It is clear that the numerical values thus determined should be a good estimator for effective dose that would have been received by people of various sizes and weights moving around in the external radiation field. The concept of having only one physical quantity for all kinds of various radiation types as the estimator for effective dose is appealing. Hey, wait a moment: there is not one but there are actually two operational quantities in radiation protection: ambient and personal dose equivalent. Unfortunately, the concept of one or two universal operational quantities in radiation protection went through several iterations that were painfully carved out between 1980 to 1996 in at least four international conferences with the participation of ICRP and ICRU representatives, sometimes just ending up in cul-de-sacs like the index quantities. Historically, ambient dose equivalent for area monitoring, and defined in the ICRU sphere, was the first useful quantity but then ICRU felt the need for an additional quantity to be used in individual monitoring. Their original definition of personal dose equivalent is somewhat weird: "The personal dose equivalent is the dose equivalent in soft tissue below a specified point on the body at an appropriate depth. The calibration of the dosimeter is generally performed under simplified condition (how much?) on an appropriate phantom." Surely the obvious idea for an appropriate phantom was the ICRU sphere itself but that would mean that a personal dosimeter must show an isotropic response. This is surely not the case for a single detector worn on the front of the body hence shielded from the back. Well, ICRU finally surrogated the person by a tissue equivalent slab in which personal dose equivalent is calculated for various external radiation field conditions (energy and angle of incidence) relating the quantity to primary field quantities through conversion factors. For practical calibrations the conditions of the TE slab have been further simplified by introducing the ISO Plexiglas/water phantom. Personal dosimeters shall have a defined angular response which, for strongly penetrating radiation up to angles of 60 degrees, however is not very pronounced. Although there are subtle differences between the conversion factors for the ICRU sphere and the tissue equivalent slab phantom (already due to their different mass), all in all ambient dose equivalent and personal dose equivalent are both used as estimators for effective dose from external exposure. In fact, if you enter numerical values of either ambient or personal dose equivalent into your dose records and you can show that those values are well below any legal limits you have done a good job (the cream on the coffee is of course that the doses received had been ALARA). The long and painful birth of the operational quantities in radiation protection appalled many colleagues and some went so far to claim that our trade stepped backward not forward. Would it not be much better to use primary radiation field quantities that could be directly related to (an overestimation of) effective dose? This we had already and here we would just retrograde. Remember MADE, the word which to a person of German mother tongue is not really appetizing? Well, at CERN we used the MAximum Dose Equivalent a lot and somehow our rem (sic!) counters are still calibrated in MADE but as it has been pointed out several times the dose value was rather a maximum than a good estimator and in addition MADE is not an additive quantity. Anyway the basic idea that a dose can only be defined in a phantom was there in the field of neutron dosimetry and the photon people surely learned from the neutron dosimetrists. What we went through with operational quantities is nothing compared to the tale on protection quantities. Ralph Thomas wrote an article in the early 70s: "What dose equivalent?" Rightly so, as at that time a distinction between operational and protection quantities was not made. Enter ICRP Publication 74: Let's see what they have to say: We find Physical quantities (fluence, kerma, absorbed dose possibly in tissue), Operational quantities (ambient dose equivalent, directional dose equivalent and personal dose equivalent) and Protection quantities (Effective dose, organ equivalent dose and organ absorbed dose). All is nicely explained and there are conversion factors too. For those of you who like history books ICRP 74 is fascinating reading; however, beware of many trivial and a few less trivial printing errors like the legend in figure 3. As a Freudian slip we read on the ordinate: Quality of Radiation Weighting Factor. Let us forgive the proof readers as "the quality of mercy is not strained" and hope that ICRU in their parallel publication will do a better printing job. Number 5 is the best chapter with a critical but reasonable discussion on the estimator properties of the operational quantities with respect to the protection quantities. All the problems of this world arise from the fact that ICRP in their wisdom replaced effective dose equivalent (based like ambient dose equivalent on the Q-LET relationship) by the completely different concept of effective dose based on radiation weighting factors. Here the gurus went as far back as ICRP 4 where dose equivalent could be determined by multiplying tissue kerma in air with the quality factor (now weighting factor) of the external radiation field. This in spite of the fact that for intermediate neutrons the quality factor in the body is greatly reduced because of the many accompanying photons. So there are now radiation situations where ambient or personal dose equivalent are no longer over-estimators for effective dose but these are luckily only a few. With respect to this issue Graham Stevenson immediately reacted as far as the shielding provisions for the LHC are concerned. I recommend that you read: "G. R. Stevenson, The Implications of ICRP Publication 74 for the Design of the LHC shielding, CERN/TIS-RP/97-15, 1997." Exeunt ICRP Publication 74. It is quite obvious. ICRP Publication 74 will not be the final chapter of the saga on radiological quantities. Remember: "Those who don't understand anything else than dosimetry don't even grasp dosimetry properly." Aphorism copied and slightly modified from the famous messy notebooks of Georg Christoph Lichtenberg (1742-1799), Professor of Physics in Goettingen. ========================================================================== Radiation Matters: Lessons Learned Kristin Erickson ========================================================================== Developing A Radiation Safety Program at A Large Heavy Ion Accelerator Under U.S. Nuclear Regulatory Commission Regulation and Licensing The National Superconducting Cyclotron Laboratory (NSCL), located at Michigan State University in East Lansing, Michigan, operates under the NRC broad scope license and is currently in the process of being permitted by the State of Michigan. Regulatory oversight has been confusing and sometimes deficient over the years, creating a very vague and sometimes uncomfortable situation for radiation safety managers. In fact, as a NRC inspector stated "the NSCL had fallen through the cracks of regulatory oversight", leaving us to do our best with no clear set of guidelines, regulations or programmatic approach. I began working heavily with the NSCL in 1989, and in 1990, as the new MSU Radiation Safety Officer, radiation safety at the NSCL escalated significantly as a priority. It was clear that radiation safety needed significant improvement and clarification, based on previous experience and encounters with the NSCL safety issues. Practical procedures, guidelines and programs were often lacking or insufficient for the current regulatory and safety needs, and those in existence were frequently inconsistent. Similar to many radiation safety programs, whether in biological research laboratories or in accelerators, effective, efficient and user friendly radiation safety guidance was desperately needed. Programs, guidance, protocols, forms and tracking needed to be developed and implemented, and training on these items needed development and follow up. An even more difficult twist on all of this was the sweeping changes in the Federal Title 10 CFR 20 regulations which were in final comment stages in 1990, and which were promulgated to be effective January 1, 1994. We chose to "bite the bullet" and develop everything to be in accordance with these new regulations, a tough challenge. It is my opinion that one of the problems in trying to manage safety and compliance at accelerators is that institutional radiation safety officers and their staffs are unfamiliar with accelerators and the risks present, and often the physics is elusive. Another reason is the atypical and continually changing nature of the work done and people present at accelerators. Lastly, if an accelerator has its own in-house staff, there is usually a large gap in interactions between the accelerator safety staff and the institutional management staff, creating differences and lags from institutional management programs and changes. Thanks to the conscientiousness, concern and expertise of Reg Ronningen, NSCL Senior Staff Physicist and Radiation Safety Officer, a superior cooperative approach to radiation safety management was developed, and has been used throughout this eight year odyssey. We continue to work as "brothers in arms" in managing radiation safety programs and issues, running the gamut from incident response and resolution to developing new programs in accelerator safety. Our NSCL currently operates fully under U.S. NRC regulations and is now in an excellent position as we prepare to write a site specific permit with the State of Michigan under their recently revised regulations. We are in the midst of major construction as part of the K500/K1200 Coupling Project, targeted for operation in the early 2000s. Many unusual problems have already been resolved, involving complex coordination of many priorities and people. We expect to continue the fast and challenging pace for the next 10-15 years and to see many interesting and unusual radiation safety issues. We will to continue sharing our "war stories" with you as many accelerators begin preparations for changeover from Department of Energy oversight to Nuclear Regulatory Commission oversight. We also welcome inquiries and discussions with others who are experiencing or anticipating changes in accelerator radiation safety management. Coming Next: Activated Parts Radiation Identification, Measurement and Labeling * This will be a regular bimonthly feature. It will focus on some of the difficult issues we encounter and how we tackled or solved them. Articles will be brief and should be of a type that they will benefit others who have or may encounter similar situations. Please submit your articles or suggestions to: Kristin Erickson <10525kfb@msu.edu>. "Lessons Learned" is a good concept to think of when coming up with ideas. ========================================================================== News from CERN Manfred Hoefert (with contributions from Thomas Otto, Marco Silari, Graham R. Stevenson and Jan W. N. Tuyn) ========================================================================== The selection board for the new RP physicist replacing Jan Tuyn (once he is retired) was held and resulted in the recruitment of Dr. Doris Forkel-Wirth. Doris is a well known and excellent physicist in the ISOLDE Collaboration; in fact she has been the coordinator and showed that she managed to tame a whole bunch of researchers always asking the maximum beam time for their own experiment. This feature of her personality and her deep knowledge of what could go wrong in the Isotope Separator On Line made her the ideal replacement for Jan. She will take up her job in October thus assuring a good overlap period before Jan will definitively leave the Group next year. The damage caused by the fire which struck the SPS exactly three months ago and mentioned in CERN's contribution in the last IARPE Newsletter was repaired in record time. Management decided to cancel this year's heavy ion runs in favour of extending the proton period until mid-November. This step saved the about two weeks of beam time previously granted to the CERN European Reference radiation Facility (CERF: means in French "stag". CERN actually keeps a herd of deer in a fenced area near the CERF installation). CERF has been used for the calibration and intercomparison of dosimetric devices in high energy stray radiation since 1993 and is partially supported by the European Commission, in the framework of a research program for the assessment of radiation exposure at civil flight altitudes. The reference fields are, in fact, sufficiently similar to the cosmic ray field encountered at 10-20 km altitude such that instrumentation can be tested at CERN and subsequently be used for in-flights measurements on aircrafts. Following the measurement campaigns in the years 1993-1996, two are scheduled this year (in August and in September). Several institutions from all over Europe participate (last year we also had colleagues from Japan), using a number of different techniques, both active and passive, such as multisphere systems, different models of rem counters, different types of Tissue Equivalent Proportional Counters (TEPCs), newly developed electronic dosimeters for neutrons, nuclear emulsions, track-etch detectors, superheated drop bubble detectors, albedo dosimeters, etc. Among the users during the present campaign is a strong group from PTB (The national standards institute of Germany) testing a set of precision Bonner spheres (Drs. Wittstock and Alevra), a coincidence-anticoincidence TEPC to discriminate charged and neutral particles in the radiation field (Dr. Schrewe) and an electronic personal neutron dosemeter (Drs. Luszik-Bhadra and Matzke). Furthermore, users from GSI in Darmstadt and the Universities of Saarbruecken and Prague participate in this run in August. The facility that has been described extensively in the past so please consult a recent paper on further details [C. Birattari, A. Ferrari, M. Hoefert, T. Otto, T. Rancati and M. Silari, Recent results at the CERN-EC high energy reference field facility, Proceedings of the Third Specialists' Meeting on Shielding Aspects of Accelerators, Targets and Irradiation Facilities (SATIF3), Sendai (Japan), 12-13 May 1997 (in press)]. The results of measurements of the radiation fields with a TEPC spectrometer agree well with the latest Monte Carlo calculations performed with the FLUKA code by A. Ferrari and colleagues. Very good agreement is also found between the Monte Carlo results and experimental data taken by a set of Bonner spheres. The extension of the proton period until mid-November in the SPS will deprive us of the additional radioactive cooling from which we profited in previous years; the lead ion runs in recent years did not contribute to the activation of the machine, but caused however higher neutron doses in experimental areas. Not much progress has been made as far as RP is concerned in the LHC project. CERN is still waiting for the papers of the Environmental Impact Study (including radiation) to be distributed within France, where then they must be studied before reactions are expected. On the other hand, the answers to the queries concerning the Safety Report in the framework of the INB procedure for LEP are progressing smoothly as far as radiation protection is concerned. It appears more and more probable that INFN and CERN will build a proton target facility to send neutrinos to the Gran Sasso detectors south of Rome. This will take three times the annual rate of protons used up to now for the present West Area Neutrino Facility which has given us in the Radiation Protection Group so much trouble and heart-ache. Graham Stevenson and Marco Silari have the thankless task of ensuring that the new facility gives us less trouble than the present one. Physics at lower energies is not forgotten at CERN: Following the decision to close the LEAR antiproton program, there were strong requests from the user community to continue certain experiments with low energy antiprotons, e.g. for antihydrogen production. For this reason a simplified solution was found in the transformation of the existing AC (antiproton collector) installation into the AD (antiproton decelerator) in which antiprotons are decelerated to 100 MeV/c. Experiments will be installed inside the AC ring which caused some problems of access and shielding. The AD will be operational in 1999. ========================================================================== News from Fermilab Don Cossairt ========================================================================== The radiation protection community at Fermilab is presently busy with the conclusion of the current fixed target physics run. At the conclusion of this operational period, there will be a lengthy shutdown during which the historic Main Ring conventional accelerator will be removed from the same enclosure that houses the superconducting Tevatron. When operations resume with the Tevatron, the new Main Injector, separately housed, will supply the protons. The Main Injector will produce roughly 10 times the proton intensity of the present Main Ring. At present, several important radiation measurements are being made to properly address the control and shielding of these higher intensity beams. The current 800 GeV fixed target run has required a large number of special radiation measurements to support it. As it draws to a close, the number and complexity of these measurements have continued as it is recognized that this is the last chance to operate some beams for quite some time and data is needed to support future improvements in the shielding. During the present run, Fermilab has decided to revisit the adequacy of its program and methodology for protecting groundwater resources against radioactivation. The Laboratory Director at Fermilab has always had a keen interest in this issue. This interest has recently led the Director to appoint several committees consisting of physicists, engineers, and radiation safety professionals to review both the design of the various beam absorbers and their operational histories. This "work in progress" is already leading to some lessons-learned that should eventually result in improved shielding designs and in better operational procedures to monitor and control the beams. We are in the process of carefully reviewing our methods for calculating the shielding of our beam absorbers and are critically questioning our assumptions. Some of these lessons-learned may well prove to be of interest to the larger community. The PET RFQ (Positron Emission Tomography Radiofrequency Quadrupole) accelerator at Fermilab was used for some preliminary radiochemistry studies. Beam currents were low and thus the total collective dose equivalent was easily kept small. At Fermilab, the building housing the accelerator is surrounded by concrete blocks. This will not be the case when the accelerator is relocated in Louisiana. Studies are being undertaken now to determine how to effectively shield the accelerator in Louisiana. Recently, Fermilab's activation analysis laboratory achieved a perfect score in the U. S. Department of Energy's quality assurance program administered by the DOE Environmental Measurements Laboratory. In addition to the routine analysis of a variety of samples containing radionuclides, this facility also provides support for the beam flux measurements used to calibrate the beam monitoring equipment and in some cases provides the absolute normalization of beam intensity. During the present run, we have also provided hundreds of special-use TLDs in order to support the physics research program. These TLDs are used to measure radiation levels in the high energy physics apparatus in order to monitor potential radiation damage to key components of the experiments which Fermilab hosts. The radioactive source program has now been improved so that source users can find data concerning the various radionuclides we have available as well as their present status with respect to our training requirements on an internally available World Wide Web page. ========================================================================== News from Jefferson Lab Bob May ========================================================================== Electron Polarization Transfer Measured in a Heavy Nucleus at Jefferson Lab The first phase of Jefferson Lab Experiment 89-033, "Measurement of Recoil Polarization in the 16O(e->,e' p->) Reaction with 2.4 GeV Electrons," has been completed in Hall A. This was the first measurement of polarization transfer in electron scattering from a heavy nucleus. Over 30 coulombs of polarized beam were delivered to Halls A and C at total currents of up to 100 microamperes (for a few hours, with about 70 microamperes sustained). The beam polarization was monitored using the 5 MeV Mott polarimeter in the injector and Moller polarimeters in both halls. This was the first experiment using the polarized electron source at Jefferson Lab, and the experience provided valuable information on long-term operational issues associated with its use. Parallel polarized-beam tests in both halls indicated that most helicity-correlated beam effects are already small enough to permit high-precision parity-violation experiments to be carried out at Jefferson Lab. ========================================================================== HOW TO SUBSCRIBE / UPDATE YOUR E-MAIL ADDRESS ========================================================================== To add yourself to the mailing list for the IARPE Newsletter, send an e-mail message to listserv@slac.stanford.edu The body of your message should contain the following command: subscribe iarpe-l Please don't forget to update your e-mail address if you move, change jobs or just change your computing environment. The update consists in canceling the old by 'unsubscribe' and submitting a new subscription, as illustrated below: unsubscribe iarpe-l your_old_email_address subscribe iarpe-l end If the body of your message, as in this example, contains more than a single line/command, it is good practice to finish with the 'end' command, especially if your mailer adds a signature. If you experience problems with subscribing/updating, please send me an e-mail to schwahn@jlab.org and I will do it for you. ========================================================================== Closing Thought Scott Schwahn ========================================================================== For to win one hundred victories in one hundred battles is not the acme of skill. But to win the battle without fighting is the acme of skill. Sun Tzu, The Art of War