Information Notice No. 81-26: Compilation of Health Physics Related Information Items

                                                            SSINS No.: 6835 
                                                            Accession No.: 
                                                            IN 81-26       

                                UNITED STATES
                           WASHINGTON, D. C. 20555
                               August 28, 1981

                                   INFORMATION ITEMS 

Part 1:   Use of Recirculating-Mode (Closed-Circuit) Self-Contained 
          Breathing Apparatus (Rebreathers) 
Part 2:   Use of the Chemical "DOP" 
Part 3:   Placement of Personnel Monitoring Devices for External Radiation 
Part 4:   Personnel Entry into Inerted Containment 
Part 5:   Evaluation of Instrument Characteristics When Using Portable 
          Radiation Survey Instruments 
                                                          IN 81-26, Part 1 
                                                          August 28, 1981  
                                                          Page 1 of 3      

Information Notice No. 81-26, PART 1:     USE OF RECIRCULATING-MODE 
                                             (CLOSED- CIRCUIT) 
                                             BREATHING  APPARATUS 

Description of Circumstances: 

This notice updates information in Information Notice No. 80-19 issued on
May 6, 1980 that informed licensees of a National Institute for Occupational
Safety and Health (NIOSH) "stop-sales-and-recall" order of the BioPak-60P 
(60P) recirculating-mode (closed-circuit) self-contained breathing apparatus
(rebreathers) identified as SCBA-R. It also provides updated guidelines for 
the use of SCBA-R. 

NIOSH rescinded its stop-sales-and-recall order (NIOSH Users Notice of July 
11, 1980) after the original problem was satisfactorily resolved. The Los 
Alamos National Laboratory (LANL) has retested the equipment, as approved 
since the rescinding of the recall, to assure that recommendations on use 
are based on the performance of devices tested and certified by NIOSH. 


Current regulatory guidance (Regulatory Guide 8.15, "Acceptable Practices 
for Respiratory Protection") recognizes only a "demand" mode of operation 
for rebreathers (i.e., a mode in which there is some negative pressure in 
the facepiece during at least part of the breathing cycle). The protection 
factor permitted for such devices with full facepieces is 50. 

The recently developed 60P rebreather operates in the positive-pressure mode
(i.e., pressure in the facepiece remains positive throughout the breathing 
cycle). This device has been issued NIOSH test and certification number 
TC-13F-85. Therefore, under the provisions of 10 CFR 20.103 and Regulatory 
Guide 8.15, Section C, NRC licensees may make allowances for the use of the 
60P in estimating exposures of individuals to airborne radioactive 
materials. However, the NIOSH certification tests do not differentiate this 
new class of positive-pressure rebreathers from the demand-mode rebreathers, 
and no quantitative information on efficacy (protection factors) is 


The Los Alamos National Laboratory has tested the new devices as part of its
ongoing program for NRC. LANL has developed sufficient information for NRC 
to provide authorization for the use of these rebreathers with an assigned 
protection factor of 5,000. In addition to the existing regulatory position 
presented in Regulatory Guide 8.15, the following guidance pertains to the 
use of positive-pressure rebreathers and should be followed by licensees who
use the rebreathers. Some of the discussion deals specifically with the 60P 
rebreather that, at present, is the only available NIOSH 
tested-and-certified device of this type. 
                                                           IN 81-26, Part 1 
                                                           August 28, 1981 
                                                           Page 2 of 3     

1.   For work in which very high protection factors are required, the 
     positive-pressure (pressure-demand), open-circuit, self-contained 
     breathing apparatus (SCBA) is still the apparatus of choice, unless the
     advantage of increased working time provided by a positive-pressure 
     rebreather is necessary. The nominal "30-minute" open-circuit SCBA will
     provide air for only 15 or 20 minutes under fairly heavy working 
     conditions. A recent report presents data indicating that, under very 
     heavy working rates, standard air cylinders can be exhausted in as 
     little as 10 minutes (L. G. Myhre, et al., "Physiological Limits of 
     Firefighters," ESL-TR-79-06, Final Report, Air Force School of 
     Aerospace Medicine, October 1977-January 1979). The 60P, which was 
     tested at LANL under moderate working rates, provided at least a full 
     60 minutes of service; it also weighs less than most open-circuit SCBA. 

     However, all rebreathers have an inherent problem; should contaminants 
     enter the system, such as through a temporary facepiece leak, they 
     would generally circulate through the breathing bags and be breathed 
     repeatedly. Open-circuit devices, on the other hand, clear themselves 
     of contaminants much more quickly because breath is exhaled to 
     atmosphere and clean air is supplied with each inhalation. 

2.   Perceptible outward leakage of air from SCBA-R at any time is 
     unacceptable because service life will be reduced to only a few 
     minutes. The rebreather makeup air supply comes from a small bottle of 
     oxygen that will be quickly exhausted if the facial seal of the mask is 
     not maintained. Wearers of positive-pressure SCBA-R have to be trained 
     to immediately leave the area where the respirator is required if such 
     outward leakage is detected. 

3.   It is important that each person who is to use the rebreather be 
     quantitatively fit tested. To the extent that the test hood or chamber 
     will allow, many different body and head movements should be included 
     in these tests to simulate actual work movements while protection 
     factors are measured. A satisfactory fit is provided when a protection 
     factor of at least 5,000 is achieved (no more than 0.02%. leakage). 
     These devices, when well-fitted, can provide protection factors of 
     20,000 or greater. Therefore, a factor of less than 5,000 indicates an 
     unacceptably poor fit for the situations in which such equipment is 
     designed for use. There is also the practical consideration that many 
     licensees use quantitative fit test equipment (e.g., with sodium 
     chloride aerosol) that cannot generally measure protection factors much
     greater than 5,000. 

     The mask supplied with the 60P is manufactured by AGA (Swedish Company)
     and comes in only one size. It is a relatively wide mask that will stay
     well sealed to the face for good protection for those users who have 
     wider faces. People with narrow faces, particularly those with narrow 
     and short faces, might be unable to achieve a satisfactory fit (i.e., 
     a fit with a protection factor of at least 5,000). 

4.   Special training is essential for people who will use rebreathers. The 
     operation of rebreathers is very different from that of open-circuit 
     SCBA with which many workers are familiar. Training should include, in 
     addition to the usual information on the construction and operation of 
     the unit, 
                                                           IN 81-26, Part 1 
                                                           August 28, 1981 
                                                           Page 3 of 3     

     hands-on refilling of the carbon-dioxide-removing sorbent and 
     replacement of the oxygen supply bottle (even though maintenance will 
     not be performed by the wearer). Training should also include 
     instruction in the function of the anti-anoxia valve (the wearer will 
     experience difficulty in exhaling as a warning that the oxygen supply 
     is shut off). Trainees should wear the unit while exercising (e.g., 
     jogging, calisthenics, simulated work movements) to learn of any 
     restrictions experienced in breathing or in movement. They should use 
     the unit to end-of-service air supply to become familiar with the 
     behavior of the unit as it runs down and to recognize the 
     end-of-service whistle that sounds for only a brief time. Training 
     should be sufficiently extensive for wearers to be thoroughly familiar 
     with and confident in the use of the apparatus. 

5.   An anti-fogging solution should be applied to the facepiece lens before
     each use since there is much more fogging in rebreathers than in 
     open-circuit equipment. Some of the first samples of anti-fogging 
     solution supplied to LANL by Biomarine Industries were defective. 
     Licensees who have purchased this solution should check with the 
     manufacturer about the need for replacement chemicals. Part of the 
     training should prepare wearers to expect more fogging than they have 
     experienced with open-circuit apparatus. 

6.   The manufacturer of the BioPak-60P has alerted purchasers of the 
     equipment to attach a special accessory hood (the "BioShield") to the 
     60P when it is used in fire fighting. The hood consists of a flexible 
     "Beta Glass" covering that stretch-fits around the visor and covers the
     head, facemask, and hoses to the wearer's shoulders. The purpose of the
     hood is to keep flames or falling embers from igniting combustible 
     materials (such as hair) that might be close to a leak of concentrated 
     oxygen from the equipment (e.g., out of the facepiece). NIOSH 
     certification permits the use of this accessory hood. Licensees who use
     the 60P for firefighting, or near open flames or falling sparks or 
     embers, should also use this special fire resistant accessory hood to 
     prevent serious or fatal burns that could result from an oxygen-fed 

This Information Notice No. is provided to notify licensees of the authorized
use of the BioPak-60P and the interim regulatory positions. When Regulatory 
Guide 8.15, "Acceptable Programs for Respiratory Protection," is revised, 
the revision will reflect NIOSH certification and LANL testing of 
rebreathers. In the interim, NRC Inspectors will use. the specific guidance 
provided above in addition to the regulatory positions given in Regulatory 
Guide 8.15 for evaluating the acceptability of licensee respiratory 
protection programs. 

No written response to this information notice is required. If you need 
additional information with regard to this matter, please contact the 
appropriate NRC regional office. 
                                                           IN 81-26, Part 2 
                                                           August 28, 1981 
                                                           Page 1 of 3     

Information Notice No. 81-26, PART 2: USE OF THE CHEMICAL "DOP" 


This information notice contains preliminary information dealing with the 
potential toxicity of the chemical di-sec, octyl phthalate (DOP) as shown by
animal testing conducted by the National Cancer Institute/National 
Toxicology Program (NTP). Further guidance will be issued when more 
definitive information is developed about DOP and its applications and use. 


DOP, also called di(2-ethylhexyl) phthalate (DEHP), is used in many 
facilities, including those of some NRC licensees, for quality assurance 
testing and in-place testing of high-efficiency particulate air (HEPA) 
filters and for recommended quantitative facepiece fit testing of 

DOP is also a plasticizer commonly added to give flexibility to polymers 
(e.g., polyvinyl chloride). As such, it is used in natural and synthetic 
rubbers, lacquers, cellulose compounds, and as a pump fluid for 
oil-diffusion pumps. Because it is produced and used in very large amounts 
(almost 400 million pounds in the United States in 1977), exposure of the 
general population to products containing DOP is widespread. The U.S. Food 
and Drug Administration (FDA) approved DOP for use in polymers in 
food-contact items, and it is used in vinyl tubing to transfer blood, 
intravenous fluids, and milk. DOP has been found in blood stored in vinyl 
bags and transferred through vinyl tubing (up to 66 mg/l of blood and 250 
mg/l in bagged plasma). It has been found in the tissues of patients 
transfused with blood or blood products stored in flexible polyvinyl 
chloride containers. DOP has also been found in neo-natal tissues after 
umbilical catheterization. Children who are given multiple transfusions of 
blood to treat serious blood diseases might, in a year, receive as much as 
1500 mg (about 28 mg/kg) of DOP. 

Hazard Assessments: 

DOP has, until recently, been considered to be a substance of low toxicity 
by all routes of intake. The recommended time-weighted average threshold 
limit value (TLV) for the work environment that is adopted by the 
Occupational Safety and Health Administration (OSHA) is 5 mg/m3 in air--the 
same as that for certain nuisance dusts. 

However, the National Cancer Institute/National Toxicology Program recently 
conducted carcinogenesis bioassay tests on DOP/DEHP. One strain of mouse and
one strain of rat in a lifetime feeding study were fed relatively large 
amounts of DOP (3,000 to 12,000 ppm) in dosed feed. No inhalation study was 

A draft NTP report of this study, which has been reviewed and approved with 
slight changes by the NTP Peer-Review Panel of Experts, finds that DOP is 
carcinogenic in B6C3Fl mice and in F344 rats (hepatocellular carcinomas in 
mice and hepatocellular carcinomas and neoplastic nodules in female rats). 
The report makes no determination of risk to humans. 
                                                            IN 81-26       
                                                            August 28, 1981 
                                                            Page 2 of 3    

Current Considerations: 

The National Institute for Occupational Safety and Health (NIOSH) has not 
yet issued final revised new recommendations on the suitability of DOP for 
various uses. However, on April 30, 1981, NIOSH issued for comment a draft 
special report on DEHP toxicity. The draft report recommends corn oil as the
best alternative from a toxicological viewpoint, for the time being, as a 
substitute aerosol for quantitative facepiece fitting of respirators. Final 
recommendations are expected within a few months. 

The Los Alamos National Laboratory (LANL) is investigating potential 
substitutes for DOP (in quantitative fit testing) for both NRC and the 
Department of Energy (DOE). LANL has successfully used di-2 (ethylhexyl) 
sebacate (DEHS, "Octoil-S") as a substitute test agent that seems to be of 
acceptably low toxicity according, to current data. The draft NIOSH report 
also examines the suitability of DEHS as a substitute for DOP in generating 
quantitative fit test aerosols. The report does not rule out such use of 
DEHS at this time, but it indicates that more toxicity tests are needed 
before NIOSH can make a more definitive recommendation on such use of DEHS. 

Manufacturers of quantitative fit test equipment have recommended the use of
corn oil as an interim substitute test agent for DOP. A satisfactory test 
aerosol can be generated from corn oil for making the measurements. There 
may be some disadvantages, however, in odor (described as that of french 
fries or popcorn) from oxidation of the oil, potential for mold growth on 
test chamber exit-air filters, and housekeeping problems from the need for 
more frequent and more difficult cleaning. 


A forthcoming final NTP report may find that DOP/DEHP is a weak carcinogen 
in two strains of mice and rats as indicated by feeding studies. DOP is 
present in many products in common use, and human exposures to it are 
widespread. NIOSH and OSHA have not yet had time to fully evaluate and make 
recommendations on the health significance of exposures to and uses of DOP. 
Until such information is available, the following interim guidance is 
suggested for licensees: 

1.   For quantitative respirator fit testing, even though human exposures 
     are very small during these tests, it would be prudent, at least for 
     now, to discontinue the use of DOP and to substitute an available, less 
     potentially hazardous test agent for these tests. Corn oil, as 
     recommended by the test equipment manufacturers, is acceptable for this 
     use. Licensees should check with manufacturers for detailed 
     instructions on the use of corn oil and on how to avoid or minimize 
     potential problems with odor, mold growth, and cleaning. Di-2 
     (ethylhexyl) sebacate ("Octoil-S") may also be used if manufacturers 
     deem it compatible with the operation of their equipment. 

2.   For quality assurance or in-place testing of HEPA filters, DOP may be 
     used where required. However, emissions of DOP from generating and test
     equipment should be controlled by containment and ventilation to avoid 
     unnecessary exposures of personnel. Exposures of personnel to DOP 
     should be individually assessed and minimized by well-planned work 
     practices. Respiratory protective equipment should be used if 
                                                           IN 81-26, Part 2 
                                                           August 28, 1981 
                                                           Page 3 of 3 

Several different agencies are continuing to clarify and resolve the 
questions that arise with respect to the use of DOP. Licensees will be 
further informed as more definite information is developed about DOP, 
suitable substitutes, or recommendations on permissible applications and 

No written response to this information notice is required. If you have any 
questions regarding this matter, please contact the appropriate NRC Regional
                                                           IN 81-26, Part 3 
                                                           August 28, 1981 
                                                           Page 1 of 2     

Information Notice No. 81-26, PART 3:     PLACEMENT OF PERSONNEL 
                                             MONITORING DEVICES FOR EXTERNAL
                                             RADIATION EXPOSURE 

Description of Circumstances: 

A recent inspection at a nuclear power plant revealed a situation in which 
inappropriate placement of personnel monitoring devices resulted in under-
estimating the radiation dose received by the workers. In this case, the 
heads and lenses of the workers' eyes were exposed to about 50% more 
radiation than was measured by their chest-worn film badges and self-reading
pocket dosimeters. Such a nonuniform radiation field resulted during repair 
work in a steam generator when the principal source of radiation came from 
overhead. Conservative re-evaluation by the licensee of the dose received by
these individuals revealed that sixty-six workers may have exceeded their 3 
rem per calendar quarter  exposure limit specified in 10 CFR 20.101. 

On a regular basis, NRC inspectors observe other situations where sufficient
attention has not been given to the placement of personnel dosimeters. Many 
of these involve situations where significant extremity (hand) exposure 
occurs and extremity dosimeters are not supplied to workers by the licensee.
In many cases, the licensee has not made the necessary surveys and/or 
calculations to adequately evaluate the need to supply extremity dosimeters 
to the workers. In other cases, the evaluations may have been conducted, but
no evaluation records are available. 


It is fairly standard practice to wear personnel dosimeters on the trunk, 
most frequently at the chest or waist position. This is acceptable practice 
when workers are exposed to relatively uniform fields of radiation. However,
it is important to evaluate all nonstandard and unusual situations, 
particularly where high dose rates are possible, to determine if trunk-worn 
dosimeters are appropriate. In the majority of the cases, the dose limit of 
interest is the one that applies to the whole body, head and trunk, active 
blood-forming organs, lenses of eyes, and gonads. Since the same limit 
applies to all of these body locations, the potential dose to each should be
considered. The objective should be to place the dosimeter in a position 
where it will measure the highest dose to the areas of interest. 

Therefore, if the principal source of radiation is overhead, the dosimeter 
should probably be placed on the head. If the principal source of radiation 
is from underfoot, the appropriate location for the dosimeter might be on 
the lower leg just above the ankle, since long bones of the lower leg 
contain active blood-forming marrow. If a worker is sitting on or straddling 
the source of radiation, the dosimeter should be positioned to record the 
radiation dose to the gonads. If the source of radiation is predominantly 
behind the workers, the dosimeter should be worn on the back rather than on 
the front of the body. To be explicit, the dosimeter should be worn at the 
location of highest entry dose. 

The other situation that occurs regularly is significantly higher exposure 
to the hands, forearms, feet, or ankles. These situations occur most 
frequently during direct handling or manipulation of radioactive items or 
while working 
                                                           IN 81-26, Part 3 
                                                           August 28, 1981 
                                                           Page 2 of 2     

from behind a partial shield. In many of these cases, NRC regulations would 
require wearing dosimeters to record what might be termed the "whole body 
dose" and dosimeters to record the dose to the extremities. 

NRC Regulation 10 CFR 20.202 requires that an appropriate personnel 
monitoring device be worn if an individual receives or is likely to receive 
a dose in a calendar quarter in excess of 25% of the values specified in 
paragraph (a) of 10 CFR 20.101. Thus, a "whole body badge" is required if 
300 mrem per quarter is likely to be received by those portions of the body 
with a limit of 1.25 rem per quarter. In addition, an extremity badge is 
required if an extremity is likely to receive about 4.7 rem in a quarter. 
Dosimetry for the only other limit, skin of whole body, is normally 
accommodated by the beta capability of most personnel dosimeters. 

All of the discussions above apply to situations in which the NRC 
regulations require that dosimeters be worn by radiation workers. There are 
many cases hen an employer may choose to supply dosimeters to workers above 
and beyond the NRC requirements. This may be done for administrative, 
information gathering, or other purposes. In some special situations, a 
worker may be seen wearing several dosimeters. Such conservative safety 
practices are encouraged. 

Some discussion of requirements for radiation surveys and evaluations may be
in order. Because 10 CFR Part 20 requires each licensee to supply personnel 
dosimeters to workers under certain conditions, there is the companion 
requirement that the licensee make such surveys and evaluations necessary to
comply with that requirement. For example, if significant hand exposure is 
likely to occur and a licensee chooses not to supply extremity dosimeters, 
the potential dose to the hands must have been evaluated by instrument 
surveys, calculations, or by other means to support the position that 
extremity monitoring is not required. Records of such surveys and 
evaluations must be maintained for inspection. 


No written response to this notice is required. Licensees should review 
their radiation survey and evaluation practices to ensure personnel 
monioring requirements are met. Special attention should be given to 
nonuniform radiation fields. 

If you require additional information regarding this subject, please contact
the appropriate NRC Regional Office. 
                                                       IN 81-26, Part 4 
                                                       August 28, 1981 
                                                       Page 1 of 3     

Information Notice No. 81-26, PART 4:     PERSONNEL ENTRY INTO INERTED 


The information provided below deals with personnel safety issues that are 
outside the scope of the NRC's nuclear safety requirements; as such no 
action or response to this information notice is required. However, this 
information notice provides useful information that will be helpful to 
licensees in their efforts to maintain safe working conditions for their 

Description of Circumstances: 

On February 24, 1981, a boiling water reactor (BWR) licensee dispatched 
three workers, who were fitted with self-contained breathing apparatus 
(SCBA), into the primary containment (drywell) with the reactor at 30% power 
and the drywell fully nitrogen-inerted to approximately 3% oxygen by volume. 
The purpose of this drywell entry was to determine the source of 
unidentified, primary system leakage into the drywell. 

An inerted drywell constitutes an atmosphere immediately dangerous to life 
and health (IDLH). Personnel safety provisions for the February 24 entry 
included verbally restricting the areas where the personnel should travel in
the containment; providing two other persons with SCBA equipment on standby 
outside the containment airlock for rescue, if necessary; and preparing for 
ventilating the containment if a problem arose. The entry lasted 7 minutes 
and the plant page system was used occasionally to verify the status of the 
work party. Upon completion of the activity, the work party left the 
containment with no reported problems. Licensee management reportedly 
authorized the entry for the purpose of maintaining the plant at power, 
rather than shutting down. 


Had an individual's air supply failed while in the inerted drywell, the 
planned deinerting in the event of a problem would not have prevented severe
personnel injury. Unprotected exposure to an atmosphere containing less than
6% oxygen by volume causes spasmodic breathing, convulsive movements, and 
death in minutes. In atmosphere with oxygen content in the 8-12% by volume 
range, unconsciousness can be immediate and without warning upon loss of air
supply (SCBA failure). Title 29, Code of Federal Regulations, Part 1910.34 
provides certain regulatory requirements for the safe use of respirators in 
dangerous atmospheres. It states, in part, "Communications (visual, voice or
signal line) shall be maintained between both or all individuals 
present...," e.g., for this situation the working party in the drywell and 
the rescue party outside the containment airlock. Given the logistics of the 
situation and available communications equipment, the use of signal line or 
voice communications was physically impossible. The licensee used the plant 
pager system intermittently, and thus communications were not maintained on 
a continual basis. Discussion with the licensee management revealed a lack 
of awareness of the above-cited Title 29 requirement. 

Other airborne-toxic/oxygen-deficient are as can exist at nuclear power 
plants. Some examples include unventilated tanks or voids; inerted primary 
                                                       IN 81-26, Part 4 
                                                       August 28, 1981 
                                                       Page 2 of 3 

such as steam generators or portions of primary loop piping; areas affected 
by oxygen displacement fire suppression systems; confined spaces affected by
decaying marine growth, such as circulating water cooling systems; and areas
affected by leakage of chlorination systems or accidental mixing of caustic 
and acid chemicals for makeup water treatment. 

Subatmospheric containments can constitute oxygen-deficient areas, to 
varying degrees, depending on the containment air pressure. At sea level, 
for example, if the containment air pressure is 11.1 lb/in.2, then the 
partial pressure of oxygen is approximately 120 mm of mercury; 30 CFR 11 
defines an oxygen-deficient atmosphere as " atmosphere which contains 
an oxygen partial pressure of less than 148 millimeters of mercury (19.5 
percent by volume at sea level). 

Another potential nonradiological hazard can exist for personnel making BWR 
drywell entries. In some earlier designed plants, the primary safety valves 
discharge directly to the drywell atmosphere. In the event of safety valve 
activation, personnel could be severely injured or killed. 


IDLH areas, such as an inerted BWR drywell, should not be entered. In fully 
inerted areas, assuming SCBA failure, physical incapacitation occurs in 
seconds and death occurs in minutes. If entry into inerted areas is required
under certain extreme emergency conditions and timely deinerting is not 
possible, then carefully planned and controlled personnel entries can be 

Even after purging and ventilating, a deinerted area can present a personnel
hazard. Pockets of the inerting gas can remain in localized low-lying areas 
of the space. Before the deinerted area is opened for unrestricted worker 
access, a thorough sampling inspection should be performed by personnel 
equipped with SCBA. 

Licensees should establish and maintain a nonradiological airborne hazards 
control program. Basic elements of such a safety program should include the 

1.   Identification of potential hazard areas 
2.   Quantification of the hazard potential 
3.   Procedural controls to implement safe work practices commensurate with 
     identified hazards 
4.   Worker training program 

Such a nonradiological hazards control program could be an extension of the 
licensee's respiratory protection program established to satisfy the 
requirements of 10 CFR 20.103. NUREG-0041, "Manual of Respiratory Protection
Against Airborne Radioactive Materials," contains a summary of the OSHA 
regulations in the nonradiological airborne hazards area (Chapter 3), and 
provides a discussion of the evaluation and classification of respiratory 
hazards (Chapter 4). Another useful reference document for improving worker 
safety in nonradiological hazards areas is the DHEW (NIOSH) Publication No. 
80-106, "Criteria for a Recommended 
                                                       IN 81-26, Part 4 
                                                       August 28, 1981 
                                                       Page 3 of 3 

Standard...Working in Confined Spaces," December, 1979. This document is 
available for purchase from the Superintendent of Documents, U.S. Government
Printing Office, Washington, DC 20402. 

As discussed above, no specific actions or reports are required. If you have
any questions regarding this matter, please contact the appropriate NRC 
Regional Office. 
                                                       IN 81-26, Part 5 
                                                       August 28, 1981 
                                                       Page 1 of 2 

Information Notice No. 81-26, PART 5:     EVALUATION OF INSTRUMENT 
                                             CHARACTERISTICS WHEN USING 
                                             PORTABLE RADIATION SURVEY 

Description of Circumstances: 

The Barnwell, South Carolina, radioactive waste burial site recently 
received a shipment of radioactive waste that exceeded the radiation levels 
specified by the U.S. Department of Transportation (DOT). The power reactor 
licensee responsible for the shipment concluded that the error resulted from 
the use of a portable radiation survey instrument in an orientation other 
than that for which it was designed. ANSI N323-1978, "Radiation Protection 
Instrumentation Test and Calibration," defines geotropism as a change in 
instrument response with a change in instrument orientation as a result of 
gravitational effects. ANSI N323-1978 discusses this phenomenon as well as 
other nonradiological and radiological characteristics that should be 
considered in the routine calibration and use of portable radiation survey 

Strictly speaking, geotropism is the result of gravitational forces on the 
instrument. Almost invariably, this results from the effects of gravity on 
the moving parts of conventional meter movements. For example, if an 
instrument is calibrated in an upright orientation, a change in response may
be experienced if the instrument is used on its side with the earth's 
gravity assisting (or resisting) the movement of the meter needle or other 
meter movement parts. Additional geotropic effects can also be introduced if
instruments are not zeroed in the orientation in which the measurement will 
be made. Geotropic effects are normally not present in those instruments 
with digital readouts, since there are no moving meter parts. 

 Another instrument characteristic that is influenced by orientation is 
termed "angular dependence." This effect may be observed when a change of 
instrument response is noted or when there is a change in the direction from
which the radiation enters the detector. It is easy to visualize this effect
in an instrument with the detector mounted internally but on one side of the
instrument case. Thus, a measurement made with the side of the instrument 
where the detector is located closest to the source may be considerably 
higher than if the instrument is oriented so the radiation enters from the 
side farthest from the detector. Some of this effect results from the 
distance (geometry) effect and some may result from other parts of the 
instrument between the source and the detector (shielding effect). Even 
greater shielding effect is observed on most instruments if the radiation 
enters from the back. Angular dependence may also be observed in instruments
with cylindrical detectors, either ionization or GM type. That is, a 
different response may be obtained when the long axis of the detector is 
pointed at the source than when it is oriented at right angles to the 


Improper orientation of radiation survey instruments during calibration or 
use can cause errors in radiation measurements. All NRC licensees should 
verify that personnel calibrating or using radiation survey instruments are 
aware of this phenomenon and that controls are established to ensure that 
instruments are properly oriented during calibration and use. 
                                                       IN 81-26, Part 5 
                                                       August 28, 1981 
                                                       Page 1 of 2 

No written response to this information notice is required. If you require 
additional information regarding this matter, contact the appropriate NRC 
Regional Office. 

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