IR 05000029/1987015

Special Insp Rept 50-029/87-15 on 871020.No Violations Noted.Major Areas Inspected:Resolution of Two Outstanding Issues Re Apparent Overexposure of Steam Generator Worker & Measurements Related to Hot Particles

ML20236W229
Person / Time
Site:	Yankee Rowe
Issue date:	12/02/1987
From:	Shanbaky M, Sherbini S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20236W222	List: IR 05000029/1987015 ML20236W221
References
50-029-87-15, 50-29-87-15, NUDOCS 8712070338
Download: ML20236W229 (4)

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  ~U. S. NUCLEAR REGULATORY COMMISSION:

REGION-I

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- ReportlN Docket No.- 50-29
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~ License No.' DPR-3-  Priority -'- . Category   C-Licensee: Yankee Atomic Electric Compan Worcester Road Framingham, Massachusetts facility Name: Yankee Rowe Inspection At: Environmental-Laboratory - Massachusetts Inspection Conducted: October 20,'1987 Inspector:  *M _ b . 65 3. Sherbini, Senior Jtfdiation Specialist,
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      ~ Date Facilities Radiatio M rotection Section Approved by: ////c/  [ f-M. ShanbiEy, Chief, Fap K ities
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Radiation Protection Section Inspection Summary: Inspection on October-20, 1987 (Report No.'50-29/87-15) Areas Inspected: Special, announced. inspection to resolve two outstanding-issues related to an apparent overexposure of.a steam generator worker and measurements related to hot particle Results: The inspection determined that the_ whole body exposure ' received by the steam generator worker was within regulatory. limits. The licensee's.-hot; particle measurement results were found to include.several' technical' inadequacies (Details, Paragraph 3.2).

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DETAILS

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1.0 Personnel Contacted

  * G; Babineau, Radiation Protection Manager,. Yankee'Rowe . .

F. Cauldwell, Dosimetry Supervisor, Environmental . Laborator .

  * D. McCurdy, Manager, Environmental Laboratory
 ' * R. Mellor, Assistant Technical Director, Yankee Row N. Panzarino, Senior Radiation. Protection Engineer R. Poeton, Manager, Analytical Services Group- _

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  * N. Scannell, Dosimetry Measurements, Environmental Laboratory
  * N. Stanford, Manager, Dosimetry Group 2.0 Purpose      j The purpose of this special inspection'was to discuss and attempt to resolve two issues related to activities at the Yankee Rowe nuclear. power l

l station. These issues were: il l An apparent whole body overexposure to one of the workers received while working inside a steam generator at Row . Measurements conducted at the Environmental Laboratory on hot j particles obtained from the power station at' Rowe'. The measurements- l appeared to indicate that the' dose rates to the' skin are substantially lower than had been estimated by calculation .0 Results 3.1 Apparent Overexposure l

  (Closed) Unresolved (50-29/87-06-01)    j Contractor workers at the Yankee Rowe nuclear power. station entered No. 2 steam generator channel head on May 22, 1987. The. entry was made to plug- ,

some degraded tubes. All the workers were issued multiple TLD dosimetry -(13 l dosimeters) because of the' expected s_ harp radiation field gradients ~in the channel head. Self reading dosimeters were also issued. Stay times: were - established for the job and were not exceede , When the TLDs were read at the end of the . job, it was found that two of the dosimeters on one of the workers indicated whole body doses.of 3.118 and' 3.399 rems, respectively. Both,these values.are in excess of the maximum NRC limit for whole body exposure' of 3.0-rems per calendar quarter, with completed exposure history. The TLDs in question were worn on the right- ' upper arm and the right thig ~ ~ u

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*       j Analysis of the incident by the licensee suggests that the high readings resulted as follows. Part of the task performed by the workers during that entry was to clean out some of the tubes. A substantial amount of crud was cleaned out and accumulated in the channel head during that operation. The worker apparently came in contact with this crud while plugging'some of the tubes. Subsequent measurements in the channel head failed to identify any unusually high fields that could. account for the observed doses. The
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licensee speculates that the crud layer that caused the exposure was dispersed as a result of personnel movements inside the channel head. .It ' may be relevant to note that the other workers who had made the steam generator entry on May 22 also showed unexpectedly higher doses on their right upper arm and right thigh dosimeters, although the doses were.not as high as those for the worker in questio ' q The licensee asked the Environmental Laboratory to evaluate' the dose- ) readings. This investigation revealed that the doses initially reported .J were doses evaluated at a depth of 300 mg/cm2, which is required practice l l if the eyes are not provided with sufficient shielding, as specified by NRC 1 i Form 5. In the case of the worker in question, the eyes were monitored by a ' separate set of dosimeters. The licensee then argued that the doses to the i arm and thigh should be evaluated at a depth of 1000 mg/cm2, a practice that is permitted as specified by NRC Form 5. Re-evaluation of the doses at , 1000 mg/cm2 rather than 300 mg/cm2 resulted in doses of 1.234 and 1.151 rems instead of 3.118 and 3.399 rem, respectivel Discussions between the inspector and the licensee, as well as a review of the relevant documents, indicated that the licensee's actions were i appropriate and acceptable. The dose record for the worker in question will therefore show a whole body dose for thct entry of 1.645 rem. This is the dose measured on the right temple at'a depth of 300 mg/cm2, and is the .l highest dose registered by the multiple whole body dosimeter ' l 3.2 Hot Particle Measurements j l ' A hot particle contamination incident at the Yankee'Rowe nuclear power station resulted in a calculated skin dose to the contaminated worker l l (based on VARSKIN) in excess of the regulatory dose limit of 7.5 rem per i calendar quarter. The licensee then performed a series of dose measurements ; l on the hot particle, and subsequently repeated 'and extended these I measurements using a more radioactive particle found at the Yankee Rowe ' station. These measurements were performed at the Environmental Laboratory, and the latest set of measurements included extrapolation chamber dose j measurements. The results indicated that the measured dose rates (45 , rem /hr) were substantially lower than the dose rates calculated using the - ! VARSKIN computer code (120 rem /hr). The purpose of this inspection was I partly to review the licensee's extrapolation chamber measurements'to-determine if they were acceptable to the NR I

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Review of the measurement data and discussions with the license'e result $df in the conclusion that the results'.are not acceptableVto;the NRC' for. the > , Mj

  'following reason .
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  .a.' The licensee had not; allowed for ths effects of, chamber currents-notL        d arising from. the source radiation. ' This.1s commonly l allowedtfor. by      ,   ?
  - repeating. the measurements with reversed ~ electrode. polarity!and-' -       M ;.

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current averaging.-- , .

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b '. .The.. series ~oftextrapolationLcha'mber measurements stopped!atia" plate: ~ / ~-

separation ofE O.4 mm.: SinceLthe dose rate is:to be, measured.atLat . . , 4 ,3 distance of:0.07- mm,- and:becauseithe' radiation- field from' the particle:

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is. axpected to be very non-uniform atisuch sma112 distances, thei

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  - process'of extrapolation to.-zero plat'e-' spacing;is 'probably;not valid        h in this case. This..is because,the rapidly. changing. field aroundithe; ..r      Y$

point. source'makes: extrapolation to zero, plate -spacing 'very uncertain; ', ' d given theLavailable dat % .1

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The. inspector: discussed these points;with'the licenseeh The licensee; stated , that'theyintendtohave:the'measurementsperformedbytheNationalLBureauL of Standards-in such a way as to eliminate the uncertainties. discussed- 4 f' i during this inspectio >

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4.0 ' Exit Interview . .  :

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The inspector met.with licensee representatives:at the. conclusion of thel T inspection on October 20.-1987. The:inspectorfsummarized the-scope of_then )d ,, inspection and-the finding ._ . p

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