ML20090L751
| ML20090L751 | |
| Person / Time | |
|---|---|
| Site: | University of Missouri-Columbia |
| Issue date: | 03/13/1992 |
| From: | Langhorst S, Mckibben J MISSOURI, UNIV. OF, COLUMBIA, MO |
| To: | Gregor R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 9203230165 | |
| Download: ML20090L751 (6) | |
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Reevh %v!nr Gwmtv 11 Research Park Columora. %ssoun 65211 ea2 UNIVERSITY OF MISSOURl COLUMBIA
- P$*iQ3 March 13,1992 US Nuclear Regulatory Commission Region Ill 799 Roosevelt Road Glen Ellyn, IL 60137 ATTN: Mr. L. Robert Gregor, Chief Docket No. 50-186 Reactor Programs Branch
Dear Mr. Gregor:
This refers to the request made in your cover letter accompanying Inspection Report No.
50-186/91000(DRSS). You asked that we address the concern expressed in the inspection in regard to our external exposure control program and two higher than normal extremity exposures for a pneumatic tube operator. Your original request was to advise you in writing within thirty days of the corrective actions we have taken er pian to take on this matter. On January 29,1992, Mr. C.
McKibben, Associate Director, and Dr. S. Langhorst, MURR Health Physics Manager, discussed with you by phone our desire to have additional time in which to reply to your request. Our reason for making this request was that during this time we would be finalizing MURR's appiication for a broad scope materials license. This additional time gave us the opportunity to make our long term corrective actions for this type of reseanh under the reactor license (R 103) consistent with
. how we proposed to handle similar urk under the requested materials license. You agreed to our request for additional time and asked that we refer to this phone discussion in our reply.
l' First, we would like to correct a few minor items contained in the Inspection Report No.
50186/91006(DRSS) to prevent future misunderstanding. Dr. James Rhyne is the Director of MURR, a position he has held since joining the University in December 1990, and not the Interim Director. Under the Environmental Monitoring Program section (5.d.), semiannual sampling of vegetatic,n, utu and soil are gathered at predetermined locations. Milk is not sampled.
During the inspartion referenced above, an NRC inspector reviewed the monthly MURR ALARA eports. In the May 1931 and Sepember 1991 ALARA reports, the extremity 6,ses received by a senior experimenter in the MURR Nuclear Analysis Program (NAP Group) w< re reviewed l These extremity doses for May and September were 4390 mrem and 3600 mrem, re3pectively. This j individual's extremity dose for the second calendar quarter was 4710 mrem (25% of quarterly l - limic) and for third calendar quarter was 3630 mrem (197c of quarterly limit). In investigating
- L the circumstances of these two exposures, the inspector raised questions concerning the prejob evaluation of the irradiations resulting in the two exposures and the velics . ;i
- n.ea un the more Ii than twenty years of experience of this senior experimenter in performing pneumati: tube l irradiations. Generic questions were also raised in regard to the extent of administrative and L monitoring check's in place to contiol personnel exposures associated with MURR pneunatic tube t
irradiations.
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e-o hir, L. Robert Gregor Chief hiarch 13,1992 Page 2 Backcround _ hiformation A pneamatic tube system (p-tube)is utilized at h1URR for the purpose of providing short neutroa iiraciatians (typically G hr) of small samples, primarily for neutron activation analysis (NAA). The laboratory p-tube dispatch terminals are located within ventilated hoods '
with the irradiation position of the system located 150 mm below the reactor core center line near the region of maximum Oux in the reflector, The system is operated at a negative pressure with the exhaust air being released through the facility stack. The outer irradiation containers, or
" rabbits," are high density poly-thylene capsules having an inside diameter of 23.8 mm and a -
usable length of 79 mm. Samples are typically sealed into a second high density polyethylene container and placed at a Oxed position inside the rabbit, hiinimum travel tinm from the p tube irradiation position to the laboratory terminal is 4 seconds, allowing for detection of short halflife activity in the samples, The irradiations in question are controlled under Reactor Utilization Request (RUR) No.
i- 254 which allow experimenterr. 'o irradiate small samples using the p-tube for times ranging from
. a few seconds to a maximum of one hour, provided activity limits are not exceeded. Procedures and limits governing the use of the p-tube reside in the h1URR Standard Operating Procedures 1(SOP Section VIH.3.). While the experimenter has the control over setting irradiation times and for sample insertion and retrieval, the cor.irol of the blower system lies with the control room operators. Prior to irradiation, the experimenter must contact the control room, provide
.information on the irradiation (s) they will be performing and request that the operators allow the irradiation by initiating the blower system.
Individuals must have prior p-tube authorization to perform these p-tube irradiations and Reactor Operations maintains a list in the control room of approved experimenters for each RUR authorizing p-tube irradiations. The Group Leader of the Nuclear Analysis Program is a principal experimenter for_ RUR No. 254 and is responsible, along with his senior personnel, in developing and controlling the NAA research programs conducted under this RUR. Individuals-
- seeking approval to be authorized to use the p-tube must be approved by the principal experimenter, by the Health Physics hiantger, and finally by the Reactor hianager prior to being allowed to conduct any p-tube irradiations without direct supervision by an authorized individual
-Extremity Fanosures and Associated Exoerim nts
' The greatest number of p-tube irradiations performed under RUR 254 are for sel nium trace element analyses in support of epiden.iological studies on human and animal health. Each sample is encased in a small high dendty polyethylene vial and irradiated one at a time. The L typical protocolinvolves a 5 second irradiation at approximately 8x1013 n/cm2-sec,15 second decay l and 25 second gamma count in order to measure activity of the Se 77m (17 4 second halflife). This l protocol is performed by the experimenter quickly removing the sample, which is still contained -
li in its small high _ density polyethylene vial, from the peh rabbit. The majority of the activity.
produced from this irradiation is contained m the rabbit. P tube experimenters _ wear TLD ring I
badges with tF a sensitive part of the badge turned towards the inside of the hand so that the TLD faces the rabbit as the experimenter opens the rabbit and retrievc the sample vial. Over ten years L
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of experience in developing and utilizing this protocol has provided dose rate data to characterize these irradiations and the associated personnel dose data. The typical personnel exposure from this protocol has been reasonable for the work performed.
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Mr. L Robert Gregor Chief March 13,1992 Page 3 Assignment of these trace element projects involving p-tube irradiation are made by the NAP Group Leader and his senior staff with careful ecnsideration to personnel dose. Projects are usually assigned to individuals on a " start to fir.ish" basis. That is the individual prepares the samples for irrudiation, irradiates the samples while gathering the associated data, and does the data reduction associated with the assigned project. This " start to finish" assignment technique not only provides dose control by limiting the number of irradiations assigned, but also provi:' a consistency for sample / data control and gives the individual a variety of tasks. Assignment 4 600 to 700 irradiations in a month under this protocol have resulted in extremity doses of typically 250 to 300 mrem.
ladiridual's Hicher than U193] Extremity Ewpsures fer.May and Seotember 1M1
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Development of new protocols or evaluation of irradiation techniques / materials utilizing NAA experiments are conducted by the senior NAP staff who have many years experience in performing a wide variety of such irradiations. It was during two sach instances of ,
developmental work and evaluation that one of the senior members of the NAP group received higher than normal extremity exposures.
> The May extremity dose resulted from a series ofirradiations made for a preliminary "
study to determine the accuracy and precision attainable for the analysis of water and human nail specimens for fluorine (F). An analysis known as cyclic instrumental neutron actiution analysis (CINAA) was being utilized. The protocol was very similar to the selenium NAA protocol with an irradiation time of 7 seconds, decay time of 10 seconds and a 10 second count time to measure F-20 (11.03 second halflife), but slight differences in irradiation, decay and count times were not considered significant related to extremity dose. However, this protocol mvolves re-irradiation of the samples (cyclic irradiation) to maximize the signal to noise ratio in determining F content in the presence of other activation products. An initial study of this NAA method for F analysis was conducted in June 1989 when 537 rabbits were irradiated via CINAA using a 5 second irradiation time, a 10 second decay, a 10 second count time and recycle of rabbits
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after 2.5 minute decay. The resultant extremity dose from this June 1989 project was 250 mrem
. (1.5% of allowable limit).
The study performed in May 1991 involved approximately 350 sample duplicates and rtandards. The analysis protocol was modified to allow a 7 second irradiation and to allow 2.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> decay for rabbits before reuse to minimize the extremity dose to the experimenter. A total of about 2000 irradiations were planned for the project. The total extremity dose for the project was expected to ange between 1000 - 2000 mrem and was planned to be shared between the NAP Group Leader (over 15 years experience in NAA at MURR) and this senior experimenter (over 20 years experience in NAA at MURR). Right after the start of the study, the NAP Group Lcader had to shift his attention to another major project. The senior experimenter with the knowledge of the NAP -
Group Leader decided to perform all the irradiations because of her ability to quickly retrieve the samples from the rabbits. This would result in less hand exposure than having one of ths less experienced members of the group do the job. A total of 1721 irradiations were made over a week long period at the beginning of the month. Following completion of the study, this senior experimenter reported to the IIcalth Physics Group to alert them of the higher than normal number of p-tube irradiations performed for this study and the expected higher than normal extremity dose for that individual. The senior experimenter also told IIP personnel that work had been scheduled so that she would not be doing further p-tube irradiations that month.
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Mr. L Robert Gregor Chief March 13,1992 Page 4 Dose results for the May badges indicated this senior experimenter had received 4370 mrem extremity dose, or approximately twice the upper limit of what had been expected. In reviewing the May dose report the HP manager noted this hand exposure. In discussions with the senior experimerter, the NAP Group Leader and IIP Manager investigated the cause of the higher than normal dose which was judged to be due to the higher number of rabbits handled with the short decay time and was documented in the group's May ALARA report. The IIP Manager verbally asked the senior expens nter to alert the HP Group prior to performing a future study of this type and to involve them in dose assessment. The senior experimenter reported that ar other study of
' this type was not cun ently scheduled and that tha HP Group would be consulted when one is.
In September 1991, this sen;or experimenter conducted a " rabbit test" to evahiate the integrity of two now types of rabbits, both of a slightly modified rabbit design and one made of a new high purity source of high density polyethylene. The evaluation was being made to determine
- whether these changes would improve the integrity of the rabbits and allow for an increased number of uses. NAP grcup members perform an evaluation of new high density polyethylene stock material to test for unwanted contaminants which could cause excess activation resulting in higher dose rates. They then perform a test of this type to evaluate new batches of rabbits for integrity and to check for contaminants present in the polyethylene that may have been introduced during manufacturing. The test was planned for the senior experimenter to run 20 p. tube irradiations of each of the 36 "new type" and "old type" rabbits (total of 720 irradiations). The experire:t.ter noted a slightly higher (<20% increase) than normal dose rate reading from the "old type" rabbits, but continued with the runs. Noting a higner than normal increase on the personnel pocket chamber, the experimenter thought there was a problem with the pocket chamber and <
consulted the HP Group. The HP Group did not observe a problem with the pocket chamber but asked her to closely monitor the pocket chamber reading to see if she had further problems.
Observing an increase in dose on an assistant's porlet chamber, the senior experimenter stopped the test at a total of 213 irradiations and reported this to the HP ">roup. The semor experimenter also reported to the HP Group that she expected her extremity dese to be higher than normal for that month. The resultent extremity dose for the senior experimenter was 3600 mrem.
No further icsts of this type were scheduled and an investigation by the senior experimenter was imme_diately initiated to determine the cause of this higher than normal dose rak from the "old type" rabbits. The investigation by the senior experitacuter that same day revealed these "old typo" rabbits contained higher than normal aluminum contamination, a problem that has been observed in the past for both rabbits and vials. This contamination of aluminum likely resulted from use of a mold release agent, which when irradiated produces Al.28 (2.24 minute halflife).
With this short halflife, handling of these rabbits immediately following irradiation, as needed
-in the selenium and fluorine analyses and as was done in the rabbit tests, would result in higher than normal extremity dose, especially when large numbers of samples are handled. Boxes containing these rabbits had been uncovered follawing the rearrangement of NAP supplies during a supply area housecleaning done in April 1991.
Hence, the higher than expected extremity dose obtained in the September 1991 rabbit tast :
- can likely b9 attributed to these "old type" rabbits manufactured in 1985. These 1985 rabbits were produced prior to the more comprehensive testing of stock material that was initiated in 1987, and prior te the NAP group requiring the manufacturer to purge the injection molding equipment of mold release agents (i.e. Al2 03), before making rabbits and vials for MURR. It is aho
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considered that these WS5 rabbits may have contributed to the extremity dose obtained in the May
' fluorine measurements.
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Mr. L. Robert Gregor Chief March 13,1992 Page 5 Areas of Concern and Corrective Actions One arco of expressed concern was the reliance placed upon the considerable experience of the NAP Group to control the radiological aspects of their experinients. Work under RUR 254 does >
allow a wide range of possible extremity doses which has been controlled by agreements made between the NAP experimenters and the IIP Manager and Reactor Manage to limit the less experienced experimenters to the routine, well established irradiation protocols, and to allow only the senior experimenters to conduct the developmental and evaluation protocols. The
-administrative structure of p tube authorizations under the various RURs is being evaluated and modified to formalize these experimenter restrictionr This will establish the types ofirradiations an individual may be approved to run and identify these individuals to the control room operators and to the HP broup. It will aln estal : the maximum number ofirradiations that can be allowed. Projects re juiring a greater number ofirradiations will require additional prejob evaluations invohing the HP Group.
The slight aluminum contamination contained in the 1985 batch of high density polyethylene rabbits raised another area of concern. New batches of rabbits can contain
- contaminants making them unaccepuble for some irradiation protocols. The September bsts conducted on the new design of high density polyethylene rabbits were in part performed to make this evaluation. This type of evaluation had been rigorously applied to sample vials and more recently applied to rabbits. Information concerning activatable contaminants in rabbits manufactured in the 1980s had not been clearly attached to the rabbit stores. Nor had the extent of
- the knowledge been well documented. The NAP Group is now clearly marking all boxes of rabbits .
.-or vil a sfta er thb e atch is tested for trace contaminants. This also pertains to the 1985 rabbits which are marked as being prohibited from use in the analysis of short halflife nuclides.
Even with this evaluation, the question remains as to how the p. tube experimenter knows during the course of p-tube irradiations when there may be a problem, especiaay with these sho-t irradiations involving short decay times. To strengthen the awareness of the p. tube e'xperime iter and to improve documentation of the irradiations, the p tube log sheet used in the laboratory to additionally record the p-tube irradiations has been modified to record such things as the checks
- made of proper dosimetry, operation of the room frisker, and periodic readings of the exp6;imenter(s) pocket chambers. Additional monitoring equipment is als_o currently being :
evaluated to provide alarm capabilities to give the experimenter indication of higher than exr- ud dose rates and/or cumulative dose received during a series ofirradiations. Evaluation is ongoing to determine the appropriate alarm levels to provide this additional " safety net" for the control of -
, reasonable extremity exposures. The evaluation of modifications to protocols, handling.
techniques and equipment also continue fer all p tube irradiation projects, it was mentioned in the inspection report that RUR 254 had not been evaluated to verifv its continued applicability to current NAA' work. Such a review was made in June 1990 with the principal experimenter and the Reactor Manager The HP Group has typically not been included -
~ in this review when no changes have been requested. This is a weakness in the overall periodic
- review of this type of work. The HP Group is now ir.cluded in the periodic review of the RURs. .
~ Also with the establishment of a MURR specific broad scope license, a more formal review criteria in evaluating radiation safety for handling radioactive material under the reactor license or materials licenses is being put into place. This is to better document the necessary controls and user responsibilities in planning and conducting procedures involving radioactive materials.
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. Mr. L. Robert Gregor Chief
' March 13,1992 -
Page 6 If you have any questions concerning this report, you may contact Dr. Sue Langhorst at .
(314)882 5227 or Mr. Charlie McKibben at (314)882-5204. '
Sincerely, M43 ~ "
Susan M. Langhorst, PhD, CI1P Manager, llcalth Physics Endorsement: -
Reviewed and Approved
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f_{,./k.
J. Charles McKibben O
Associate Director xc: Director of Nuclear Reactor Regulation, NRC /
Reactor Advisory Committee
- Reactor Safety Subcommittee
-Isotope Use Subcommittee
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