IR 05000128/1982001

IE Insp Rept 50-128/82-01 on 820604.No Noncompliance Noted. Major Areas Inspected:Facts & Circumstances Re Reported Beta/Gamma Radiation Exposure of 180 Rem to Right Hand TLD for Reactor Operator.Max Exposure Approx 2.5 Rem

ML20054M405
Person / Time
Site:	05000128
Issue date:	07/06/1982
From:	Murray B, Wilborn L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
Shared Package
ML20054M402	List: IR 05000128/1982001 ML20054M401
References
50-178-82-01, 50-178-82-1, NUDOCS 8207130156
Download: ML20054M405 (6)

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U. S. NUCLEAR REGULATORY COMMISSION

REGION IV

Report: 50-128/82-01 Docket: 50-128 License: R-83 Licensee: Texas A&M University College Station, Texas 77843 Facility Name: Nuclear Science Center, Texas A&M TRIGA (1 mw)

Inspection at: Nuclear Science Center, Texas A&M University Inspection conducted: June 4, 1982 Inspector: 7!d[2.-

orenzo WflAorn, Ra~diation Specialist Date Faciliti W Radiation Protection Section Approved: !8@ '[MM2/k7 Blaine Murray, Chief, Fact 7ities Radiation Protection 7///8L D' ate Section Inspection Summary Inspection conducted June 4, 1982 (Report 50-128/82-01)

Area Inspected: Special inspection of the facts and circumstances surrounding a reported beta /ganna radiation exposure of 180 Rem to the right hand thermoluminescence dosimeter (TLD) for a reactor operator. This special inspection involved four inspector-hours by an NRC inspecto Results: The inspection disclosed that, by reenactment of the reactor operator's actions and movements during the wear period, the maximum radiation exposure to the right hand was approximately 2.5~ Rem.

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DETAILS Persons Contacted D. Feltz, Acting Director

• R. Neff, Radiological Safety Officer

• H. Diegl, Senior Health Physicist W. Sims, Reactor Operator

• Denotes those present at exit intervie . Introduction On May 18, 1982, NRC Region IV received telephone notification from the Texas A&M University's Radiation Safety Officer that they were informed by their dosimetry vendor that a finger badge designated for the right hand of a reactor operator indicated a beta /ganina radiation exposure of 180 Rem for the month of April, while the radiation exposures for the designated left hand and whole body badges were well within the NRC regulatory limit During April, the reactor operator to whom this badge was assigned pur-portedly worked on a part time basis in the material handling area (MHA)

during 12 days. The work performed in the MHA involved the routine handling of activation products from the reactor except foul transfer procedures involving germanium-77. These transfer procedures involved vials containing irradiated germanium-77 powder being cut open in a lead brick and poured into a 250 ml beaker where 60 cc's of methyl nepthlene was added and the mixture heated on a hot plate. The procedures were done in a fume hood behind at least 2 inches of lead shielding. The mixture was poured from the beaker through a funnel into a lead shielded shipping container using the left hand. The right hand was about 6_ inches from the ,

mixture in the funnel for about 10 minutes during each procedure, while tamping in the funnel with a glass rod to cause the mixture to proceed into the shipping containe There were purportedly no circumstances or a specific incident that would cause one to suspect an exposure of the magnitude of 180 Rem to th'e right hand. Therefore, the reactor operator's actions and movements, during the month of April, associated with routine procedures in the MHA in addition to procedures involving the transfer of germanium-77 were evaluated during this inspectio _ _ . _ - ._ _ _ _

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3. Discussions with Licensee Representatives Discussions with licensee representatives revealed that because of the licensee's complexity of work schedules and continuing operations with a small staff, the reactor operators work in the MHA on a rotational basi Several reactor operators and operations personnel worked in the MHA at least 12 days or more during the month of April. Except for the 180 Rem exposure, the maximum dose reported by the TLD vendor to any extremities was 1940 mrem. The actions and movements of the reactor operators performing routine handling of activation products during April did not deviate to any significant degree.

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In addition to the routine handling of activation products during April, there were four similar procedures involving the transfer of germanium-7 One reactor operator, referred to as operator A, performed two transfer procedures involving one germanium-77 sample each and received a reported beta / gamma radiation exposure of 140 mrem to the right hand. Another reactor operator, referred to as operator B, who was assigned the TLD that indicated 180 Rem, performed two transfer procedures involving four germanium-77 samples each. Based on this, one would suspect that the exposure to the right hand of operator B should have been approximately 560 mrem, considering that each germanium-77 sample contained approxi-mately equal activity. Theoretical calculations (disclosed in the enclosed attachment to this report) for the two transfer procedures performed by operator B involving four germanium-77 samples, within the time / distance parameters agreed upon with operator B, resulted in maximum beta and gamma exposures to the right hand of 84 mrem and 412 mrem, respectivel Thus, assessing the maximum radiation exposure for routine procedures for handling of activation products of 1940 mrem and the calculated beta and gamma doses of 84 mrem and 412 mrem, respectively. The total dose to the right hand of operator B should have been approximately 2436 mrem.

l Discussions with licensee representatives revealed that when exposures of

approximately one-third the quarterly limit set forth by the NRC are i suspected, the finger and/or whole body badges are immediately sent in for processing. Operator B's badges had not been suspect because his activities during the 12 days of April had been associated with procedures that had not posed a problem in the past.

l Further discussions with licensee representatives revealed that,

, historically, an unexplainable high radiation exposure is reported approximately once a year by their vendor, however, most are still within the NRC regulatory limit . _ _

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Review of vendor reports for reactor operators and operations personnel during the past 6 to 9 months substantiated the discussions with the licensee representatives in that reported radiation exposures for the left hand badges were typically within the range of 120 mrem to 2730 mrem with a one time high of 5610 mrem for the wear period February 1-28, 1982. The reported radiation exposures for the right hand badges were typically within the range of 110 mrem to 2530 mrem and the reported radiation exposures for the whole body badges were typically 20 mrem to 30 mre . Conclusions The inspector concluded that there existed a high degree of probability that: (1) the result of the finger TLD reading was invalid, (2) time / distance parameters of operator B's actions and movements associated with handling of activation products were routine, (3) contamination of the TLD can be ruled out because operator B purportedly surveyed normally on the hand and foot monitor with the finger TLD in place, (4) the TLD was on the designated hand, and (5) the exposure to the right hand of operator 8 did nnt exceed the NRC regulatory limit No violations or deviations were identifie . Exit Interview The inspector met with those individuals denoted in paragraph 1 at the conclusion of the inspection on June 4, 1982, and discussed the nature of this inspection.

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ATTACHMENT Theoretical Calculations 1. Considerations The calculations did not consider that the mixture was being funneled into the shielded shipping container therefore decreasing the exposure to the right han The mixture in the funnel was considered a point source of radiatio . Beta dose from 2.5 mci of Germanium-77 The equation used to calculate the beta dose was taken from " Radiation Dosimetry," by Hine and Brownel Rg =0.0355 5gC Rad / min where: Rg = the be a dose rate 5g= the average beta energy per disintegration in MeV C= the concentration of the radioisotope in uCi/gm The beta energies for germanium-77 are as follows:

2.20 MeV (42%), 1.38 MeV (35%), 0.71 MeV (23%)

The average beta energy for germanium-77 from the Radiological Health Handbook is 0.637 Me The concentration was calculated as 2.5 mci of germanium-77 in approxi-mately 60 gm of methyl nepthalene, therefore:

C= 2.5 mci = 0.042 mci 60 gm gm

Rg = 0.0355x0.637x0.042x10 Rad / min

= 0.95 Rad / min The operator's right hand was approximately 15 centimeters for 20 minute Rg = 19 Rads for the 20 minutes

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Using the range equations for 8 particles from the Radiological Health Handbook:

R= 412 E1 .265-0.0954 inE

R(2.2 MeV)=1052 mg/cm

R(1.38 MeV)=613 mg/cm

R(0.71 MeV)=264 mg/cm The density of 15 cm of air is approximately 1.9x10 -2 mg/cm

therefore, we can assume that the energy is distributed according to the inverse square law out to the end of the average range, therefore

19 Rad = .084 Rads or 84 mRads 225 The dose equivalent in Rems is numerically equal to the absorbed dose in Rads 3. Gamma Dose from 2.5 mci of Germanium-77 The equation used to calculate the gamma dose was taken from " Radiation 00simetry," by Hines and Brownel Dy (t) = 1.44Tqo T (1-e -0.693t/T)

r2 where l' =the gamma ray dose-rate constant (cm2 -r/ mci-h)

go=the initial source strength (mci) .

T=the physical half-life (minutes)

r= distance (cm)

t= time (minutes)

D (20 min)=1.44x1.9x2.5x678(1-e-0.693x20/678)

=412 mrem 4. Total Dose Assessed Maximum for routine procedures 1940 mrem Calculated beta dose 84 mrem Calculated gamma dose 412 mrem Total dose to right hand 2436 mrem