Radiation Safety

Regulations and Hierarchy
The CAMD Safety Officer reports to two separate individuals regarding safety. These are the Radiation Safety Officer for the University, and the Campus Safety Officer in all other matters. Thus safety is independent from the CAMD administration. This permits the CAMD safety office to make decisions regarding the safe operation of the facility in an unencumbered manner.

The CAMD safety officer reports to the campus Radiation Safety Officer for the university in all matters pertaining to radiation safety. When the CAMD safety officer is unavailable, this office is in charge of radiation safety at CAMD.

Whenever changes in operation are made or alterations which might affect the overall radiation safety of CAMD personnel, these changes are discussed and approved by the LSU (Baton Rouge Campus) Radiation Safety Committee. In cases where no decision is reached or an event has occurred then the matter will be forwarded to the LSU System Radiation Safety Committee.

Louisiana is what is termed an "agreement state" in that is does not report directly to the Nuclear Regulatory Commission. Thus the DEQ or Department of Environmental Quality is the highest level of authority for matters pertaining to radiological protection. It is this body which gives CAMD its license to operate the accelerators. If at any time you feel that CAMD safety is not doing everything possible to protect its workers from radiation, you may call the state department of environmental quality - radiation protection division at the following telephone number: (504) 765-0160.

Our license to operate stipulates that all persons working at CAMD will receive radiation safety training and that said persons shall be re-trained yearly. Persons not attending the annual refresher training course will be denied access to the experimental hall and will lose their badge until such time as they have received re-training from the CAMD safety office.

CAMD Access
The CAMD facility is opened from approximately 6:30 AM until 6 PM in the evening. Access during these times may occur through either the gray door facing the parking lot or via the double glass doors facing the park area.

Access to the experimental hall requires that the person have an active security card. Such cards may be obtained only after radiation safety training and approval of your CAMD contact person. A sheet signed by the CAMD safety officer is supplied to a trained individual. This sheet is then transferred to the CAMD Facility Manger who will issue the security access card. Radiation safety badges are also ordered following this training. A person may remain as a guest of the CAMD facility for up to one week without a badge provided they are always accompanied by a badged individual.

Individuals who are not members of a state supported institution, must sign an indemnification agreement as part of their radiation training. It is the responsibility of the person being trained to inform the CAMD safety officer if he/she is not a member of a state-supported institution.

Some individuals may request after hours access to the building. Such access requires approval by the CAMD director who must sign the access sheet. Additionally, the individual must apply to receive a key to the gate and an access code to the building. Normally such privileges are reserved for CAMD staff or faculty.

Persons wishing to receive radiation safety training should contact their CAMD contact person (i.e. the person with whom you will be working while at CAMD). The contact person will then contact CAMD safety to set up a training schedule. The information requested will include, name, date of birth and social security number. The date of birth is required to ascertain that persons working in the CAMD laboratory are at least 18 years of age. Exceptions have been made and can be made for minors under 18 years of age.

Once a radiation badge has been issued from the LSU radiation safety office, you will be requested to sign a form stating that you have never been exposed above the allowable limit. If you have been exposed, then your radiation records must be retrieved before you can begin work at CAMD.

The Security Access Card
The security access card is obtained from the facility manager after he/she has received proof of radiation safety training and an active radiation badge has been assigned to that individual.

The security access card is a tiered computer level card as follows. Upon completion of radiation safety training, the card is issued which permits entrance to the experimental hall only. Those individuals who wish to access the facility after normal operating hours must obtain prior written permission from the CAMD director.

Security access cards are coded for the experimental hall, for after hours access and for cleanroom access. Cleanroom access requires separate training following radiation safety training. Further, your project must be approved by the CAMD director before access to the cleanroom is obtained.

After radiation safety training testing (computer based), print out your results and bring them to the CAMD Facility Manager. You must receive a minimum of 80% on the radiation safety test before you can obtain your security access card. You will be asked to sign for this card before it can be activated. Further, when you leave CAMD, this card should be returned to the Facility Manager or to your CAMD contact person.

The Experimental Hall
When you enter the experimental hall, you will observe that there is a utility distribution bridge. This is an eight-sided structure. In the middle of each of these spans is a single red light. This is also a display of our interlock system. When the light is illuminated, either beam is in the machine or the potential for beam exists. To confirm the status of the beam, you may walk to any beamline which houses an identical monitor to the one outside the experimental hall door.

Additionally, there is a 7 foot concrete shield wall in the experimental wall which houses the CAMD storage ring. Obviously , one may not scale the shield wall nor can any work above 7 feet in height be done in the CAMD experimental hall during injection or stored beam. Thus, it is clear that no ladders are permitted on the experimental hall while the accelerator is in operation. Conversely, if a ladder is brought into the experimental hall when the accelerators are turned off, the person bringing the ladder in is responsible for removing the ladder prior to operation of the synchrotron.

Injection is preceded by a verbal announcement" Prepare for injection" followed by the following: "Injection. Injection, Injection". When injection is terminated you will hear one of the following announcements: " Injection is complete" or "Injection has been aborted due to a technical failure, stand by for further instructions". Radiation falls off as 1/distance squared increases as the 4th power of the energy.

Experimental Hall Door
At the entrance to the experimental hall , a computer monitor and several signs are posted. Most noticeable of these is the computer monitor which is located to the right of the door at about 7 feet above the floor. This monitor displays the mode of operation of the machine. Two main screens are possible. The first displays the exponential decay of stored beam with time. The monitor also displays the number of mA circulating in the ring and the energy of operation, either 1.5 or 1.3 GeV. Each day the ring must be re-filled. At this time (approximately 3-5 times per day), the display changes to the yellow graphic which models the injection of electrons from the linac into the ring. Some 95% of all the radiation that is produced in the facility occurs during the injection mode. Fortunately, injection only takes about 1 minute. However, the display will remain yellow until the electrons have been ramped from 200 MeV to the operating energy of at least 1.3 GeV.

Above the experimental hall door is a flashing red and white sign which says. " Caution Radiation, Authorized Personnel Only". This sign represents a terminal display of our interlock system, such that the accelerators may not be turned on unless this interlock system has been set. A flashing sign here indicates that there is either potential for beam in the machine or that there is beam in the machine. To determine the status of the machine just turn to the computer monitor to assess the situation.

The door also holds two signs: the international symbol for radiation which must be visible when we are operating and the danger Nd-Yag laser sign. The laser is located on the experimental hall floor, 90o clockwise from the experimental hall door behind some blue welding screen. Because of the potential for serious eye injury, this area can not be entered without proper eye protection. We bring it to your attention for your own protection. Knowledge reduces risk.

Radiation Production at CAMD
Whenever relativistic electrons are bent, usually by a magnetic field, they produce the entire electromagnet spectrum, from infra-red rays (long wave lengths) to X-rays. The CAMD synchrotron light source (storage ring) is optimized for soft X-rays, up to 4 KeV. To achieve this goal, 8 magnets, each weighing 12 tons, with a 45o bending radius are installed in the CAMD ring. It is from each of these 1.7 Tesla magnets that synchrotron radiation is given off tangentially. The normal operating energy is either 1.3 GeV or 1.5 GeV. The CAMD electrons achieve speeds approaching 99.9997% of the speed of light.

The threshold for neutron production is somewhere between 6 and 10 MeV, Normally the hardest X-ray coming down a beamline is around 22 KeV at 1.5 GeV. When an insertion device is in operation, this may increase to 60 KeV. Thus, any photons on the experimental hall are below the energy threshold for neutron production. However, inside the ring, it is possible to exceed this threshold. Neutrons are produced when electrons or photons hit high Z materials such as lead, tungsten, or iron. These collisions cause excess neutrons to be released from these heavy Z materials. Eventually sufficient neutrons are removed so that the remaining materials become unstable and remain radioactive (activated) even after the storage ring energy has been removed. Activation is a function of the energy of operation of the accelerators, the efficiency of the machine during injection and the materials bombarded by the electrons and photons. For this reason, personnel dosimeters (badges) should be worn at all times when at CAMD, especially if working in a front end or other work in the ring while the machine is turned off.

Everyone working at CAMD is provided with a personal dosimeter or radiation badge. The badge is effective in recording all exposures from photons. The badges are to be kept in your assigned drawer at the CAMD facility when you are not wearing it. You must wear your badge whenever you are at the CAMD facility. Visitors staying less than one week do not normally receive a "radiation badge". Users no longer receive a neutron dosimeter since five years of monitoring showed no significant exposure to neutrons in the experimental hall.

ALARA
CAMD subscribes to ALARA. ALARA is an acronym which stands for "as low as reasonably achievable". In practice, this means that CAMD maintains an active and on-going radiation shielding program such that radiation exposures are kept as low as is reasonably possible. The ALARA is based on three guiding principles as follows:

Basically, you are not permitted to set up camp at CAMD. Theoretically, radiation falls off as 1/r2 or one over the distance squared. In practice this relationship appears to hold for distances > 100 feet from the source. This is why the badge drawers are located in the receiving area, or as far as is practical from the storage ring source. Radiation also varies to the 4th power of the energy. Thus there is a slight increase in radiation when the storage ring is operated at 1.5 GeV compared with 1.3 GeV. Nevertheless, shielding is adequate to handle these differences. The third principle of ALARA is to use the appropriate kinds of shielding. For photons, lead banding is placed in the short straight sections through which the beamlines protrude. Additional lead shielding is placed in and around the beamlines at the levels of the shield wall. The shield wall is 7 feet high and varies in thickness form 2 to 3 feet. It is reinforced with iron bars and is of a high density containing several pebbles in the mixture. All these things contribute to the overall effective photon shield. However, the bound water in the concrete is so effective against neutrons that neutron personnel dosimeters have been discontinued.

Radiation Monitoring
Constant 24 hour a day monitoring of the facility is accomplished using an ADM 610 ion chamber and a neutron detector. In addition, 25 places in the facility are equipped with TLD's (thermoluminscent dosimeters) which are changed monthly. Other TLD's are placed at the perimeter of the CAMD location. Weekly surveys are taken of both injection and stored beam cycles. Surveys are also taken after each shutdown or whenever there are significant operational changes in the machine.

Wear your badge all the time you are at CAMD! Badges must be kept in their assigned drawer when not in use. There are three reasons for this:

Radiation Exposure Units
The roentgen is named after the discoverer of X-rays, Conrad Roentgen. It is a unit of energy equivalent to 87.7 ergs per gram. An erg is equivalent to 10-7 joules. However, this value is only appropriate for the study of X-rays or gamma rays in air.

The Health Physicist is concerned with the amount of radiation deposited in the body. This is the absorbed dose. In the United States the rad is the term used to describe absorbed radiation dose. It has a value of 100 ergs / gram (of material). Most of the rest world uses a value which is 100 times larger than the rad. This is the Gray. It is abbreviated Gy and is equivalent to 1 joule of energy deposited per kilogram mass.

Since not all radiation is equivalent, quality factors assigned to each type of radiation are used to give tissue equivalent energy values. For instance the rad (100 ergs/gm) x the Quality Factor gives the Rem (roentgen equivalent man). Similarly the Gray (Gy at 1 joule of energy per kilogram) x the quality factor gives a tissue equivalent value called the Sievert (Sv). The Sievert is 100 times larger than the Rem.

Quality Factor (QF)

Quality Factors
Quality factors which are assigned to a packet of radiation are determined by the biological effectiveness of a particle. For example, a packet of radiation must have sufficient energy if it is to have an effect on a liver cell of the body. This energy then is a function of the ability of the radiation to traverse the thickness of material to reach the living cell in question. The energy lost over distance travelled is the linear energy transfer or LET. In other words, if one plots the amount of energy deposited over distance traveled, you will obtain a value from which the quality factor (or biological effectiveness) may be derived. This LET is related to the cross-sectional area available for the interaction of radiation with materials, whether they be biological or not. Photons are primarily wave-functions and therefore have no mass. They can travel long distances in air without forfeiting any energy. This is because they exhibit essentially no cross-sectional area. Photons, like gamma and X-rays are assigned a quality factor of 1. Thus the rad and the rem are equivalent for photons. A beta particle is an electron ejected from the nucleus of an atom. An electron has a mass of about 1/1840th the mass of a neutron. Still this mass represents enough of a cross-sectional area, to give beta particles a quality factor of 2. Thus electrons of equivalent energy to photons are twice as damaging. Neutrons, which have a significant mass, are assigned quality factors from 2-10 depending on their energy. 2-5 MeV neutrons are most damaging because they carry sufficient energy to enter the body but do not have enough energy to travel through the body. Thus, all the energy is trapped within the body. As this energy is dissipated, cells are damaged by both direct and indirect effects. Such neutrons are assigned a quality factor of 10. Alpha particles are even more damaging. Their heavy mass (2 neutrons, 2 protons) provides a large cross-sectional area which results in their being assigned a quality factor of 20.

Risk Assessment
The Linear No Threshold Model (LNTM) is a concept that suggests that risk is directly proportional to dose. This model is derived from the high dose exposures of individuals present in Hiroshima or Nagasaki in 1945. There is no scientific basis for this model. On the other hand, there are no good studies for occupational radiation workers. Epidemiological studies have only been extensively carried out for the survivors of Hiroshima and Nagasaki.

Nevertheless, let us discuss two interesting studies. The Hanford study reported on 37,000 occupational workers and 35,000 controls who were followed for 30 years, or an average of about 1.5 generations. In conclusion, the study found that the Hanford reactor workers had a decreased incidence of cancer than did the control group. The study however, is not clear on how the controls were chosen, or if they received equivalent preventative care.

The second study is the Chernobyl study which was published in 1996. It is a mathematical model predicting an increase in the incidence of thyroid cancer in children and a concomitant rise in childhood leukemia cases. The former observation has held true, but to date, the incidence of childhood leukemia in children exposed to radiation as a result of the Chernobyl disaster has not significantly increased. This suggests that more work needs to be done to understand all of the complexities of radiation exposure and the response of biological systems to such an insult.

It is also obvious that there are few good epidemiological studies for occupational radiation workers.

A Lawrence Berkeley Laboratory mathematical model has suggested that an exposure of 1 Rem acutely (within an hour) would increase the rate of fatal cancer in the United States from 1650 /10,000+/-40 to 1651/10,000 +/-40.

Let us put this into perspective for CAMD. The background radiation in Baton Rouge is between 90 and 120 mrem per year. If you lived in Denver, it would be about 360 mrem per annum. If one builds an X-ray wing in a hospital, then one must shield the adjacent waiting area such that someone occupying the space 24 hours per day 7 days per week and 365 days per year would not receive a dose of radiation in excess of 100 mRem per annum. Thus this is the public dose limit.

With respect to CAMD, no one has received a dose in excess of 30 mRem per year, or less than one third of the public dose limit. Even though we are well below what is traditionally the public dose limit where no badges are required, the state requires us to badge those persons working at CAMD because we are radiation producing facility. The occupational worker limit is 5000 mrem / year or 500 mrem/year for a declared pregnant worker or an individual under the age of 18.

General Safety Tips
The stairs to the Linac or Storage ring are very steep. Caution should be used when using this stairs which have a 30% incline grade.

Fire extinguishers are located at every 65 feet on the outside perimeter of the experimental hall. Emergency plans are posted at each beamline as well as in the cleanroom. All CAMD telephones are equipped with a bright orange sticker displaying the emergency telephone numbers. Within the experimental hall, exits are located at every 120o. Fire alarm pull stations are also located at these doors. The fire alarm system is connected to the LSU police via a keltron system. If the emergency is not fire related, you may dial 911 to be directly connected to the LSU police. They will address the nature of the emergency and release the appropriate emergency personnel.