ML20238A292

Forwards Response to NRC Re Violations Noted in Insp Rept 50-400/87-22 & Assessment of Applicability of Finding at Facility.Util Denies Violation Re TLD Concentration of Noble Gas in Containment

ML20238A292
Person / Time
Site:	Harris, Brunswick, Robinson, 05000000
Issue date:	08/21/1987
From:	Mcduffie M CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
CON-NRC-571 HO-870479, NUDOCS 8708310009
Download: ML20238A292 (5)

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i C N LL Carolina Power & Light Company AUG 211987 HARRIS NUCLEAR PROJECT P.O. Box 165 New Hill, NC 27562 File Number: SHF/10-13510E . NRC-571 Letter Number: H0-870479 -

Document Control Desk 5 United States Nuclear Regulatory Commission Washington, DC 20555 Gentlemen:

In reference to your' letter of July 8,1987, referring to I.E. Report RII: 50-40/87-22, Attachment 1 is Carolina Power & Light Company's (CP&L) reply to the violation 3 l

identified in Enclosure 1. In a telephone conversation on August 6,1987 between Mr. D. Verrelli of your staff and Mr. D. Tibbitts of our staff, CP&L requested and received a two week extension until August 21,1987 for submittal of this response. '

Your letter also requested an assessment of the applicability of this finding to CP&L's Brunswick and Robinson Plants. Attachment 2 provides this information.

It is considered that the attached response is satisfactory for resolution of this item.

Thank you for your consideration in this matter.

Yours very truly,

'b M. A. McDuffie Senior Vice President Nuclear Generation ONH:MAM:pp Attachments cc: Mr. B. C. Buckley Dr. J. Nelson Grace Mr. G. F. Maxwell 8708310009 870021._

PDR ADDCK 05000909 a PDR 411 re yettevine street . e o Box isst . naietgs N c 27602 y

r Attachment I to CP&L Letter of Response to NRC I.E. Report RII: 50-400/87-22 Reported Violation:

10CFR20.201(b) requires that each licensee make or cause to be made such surveys as may be necessary for the licensee to comply with the regulations in 10CFR20, and are reasonable under the circumstances to evaluate the extent of radiation hazards that may be present. A survey is defined in 10CFR20.201(a) as an evaluation of the radiation hazards incident to the production, use, release, disposal, or presence of radioactive materials or other sources of radiation under a specific set of conditions.

10CFR20.101(a) specifies the quarterly occupational radiation dose limits to the lens of the eyes and the skin of the whole body.

Contrary to the above, the licensee failed to perform adequate evaluations of individual exposures to noble gas in that algorithms used to convert thermoluminescent dosimeter (TLD) readings to skin and lenses of the eye dose for personnel who made containment entries on June 17,1987, and before were inappropriate for the noble gases present in containment. The licensee used no other dose assessment technique to assess doses due l to noble gases.

This is a Severity Level IV violation (Supplement IV).

Denial or Admission and Reasons for the Violation:

The violation as stated above is denied. It is the position of CP&L that adequate dose evaluations were being performed at the Shearon Harris Nuclear Power Plant (SHNPP) in accordance with 10CFR20, and that the dose evaluations were reasonable under the circumstances to evaluate the extent of radiation hazards that may have been present.

This position is based on the following: (1) the TLD dose algorithm was adequate l considering concentrations of noble gases found in containment, and (2) it was reasonable for radiation protection personnel to assume, based on the low concentrations of noble gases measured during routine monitoring and the expected MPC-hours of exposure, that i personnel dose from the noble gases would be insignificant and that further dose evaluations were not necessary. The TLD dose algorithm utilizes beta correction factors which are based on the range of beta energies most responsible for personnel exposure.

Although some noble gases emit beta particles with energies outside of this range, the resultant doses which may go unassigned are very small. Conservative calculations based on air sampling results at SHNPP show that the maximum potential unassigned dose to any individual during the first two quarters of 1987 was less than 7 mrem to the skin and 1 mrem to the lens of the eye. Such low doses are considered insignificant. Therefore, the assumption by radiation protection nersonnel that the TLD would adequately monitor the exposure of personnel entering containment was correct.

The maximum unassigned doses to the skin and lens of the eye correspond to less than 0.1% of the applicable quarterly dose limits in 10CFR20. NRC regulations do not require monitoring when exposure is not expected to exceed 25% of the quarterly limit. In addition, the unassigned doses are much less than what would be considered significant according to ICRP 35 for recording dose to individuals. ICRP 35 recommends that the minimum recording level for individual monitoring should be based on one-tenth of that fraction of the annual limit corresponding to the period of time to which the individual monitoring measurement refers, and that doses smaller than this level can be treated as zero. For a quarterly TLD badge exchange frequency as used by CP&L, this corresponds to a minimum recording level of 750 mrem for skin dose and 125 mrem for eye dose.

(5266JDK/pp )

j ANSI N!3.ll, which is the basis for performance testing for NVLAP dosemitry  ;

accreditation, does not require dosimeters to be tested for mixtures of photon and beta '

radiation at levels less than 200 mrem.

Based on a review of the radiations emitted and the relative concentrations of the noble gases typically found at each plant, Xe-133 was determined to be the only nuclide for which underestimation cf the skin dose from beta radiation by the present TLD dose algorithm would be a concern. Other nuclides were found to either emit radiations with energies high enough to be measured accurately or too low to cause skin dose, or are not  ;

present in sufficient relative concentrations to cause significant underestimation of skin l dose by the current TLD algorithm. In a similar manner, Ar-41, Kr-87, Kr-88, and Xe-138 were determined to be the nuclides of cancern for calculating potential unassigned dose to the lens of the eye. Other noble gas nuclides were found to either emit beta radiations with energies too low to cause lens of the eye dose, or are not present in sufficient relative concentrations to cause significant underestimation of the lens of the eye dose by current TLD algorithm.

The potential unassigned dose to the skin and lens of the eye from noble gases was evaluated for SHNPP using conservative assumptions for the time period following initial criticality on January 3,1987. Calculations to determine the total skin dose from Xe- ,

133 beta exposures were performed for all individuals who entered the reactor  !

containment from initial criticality through June 30,1987. These calculations used: (1)

Radiation Work Permit log-in/ log-out times to conservatively determine the exposure period for each worker's entry, (2) the maximum Xe-133 concentration observed during the sixth month period, and (3) the beta dose conversion factor of 0.35 mrem per MPC-hour of exposure (Reference 1). The highest calculated skin dose from Xe-133 beta exposure during the entire six month period for any individual was 7 mrem. The maximum potential beta dose to the lens of the eye at SHNPP was also calculated, based on measured concentrations of Ar-41, Kr-87, Kr-88, and Xe-138 in containment, on beta dose factors for these nuclides given in Reference i for lens of the eye, and on the maximum cumulative stay time in containment for any individual during the first two quarters of 1987. The maximum beta dose rate was .011 mrem /hr, the maximum stay time was 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />, and the resultant maximum potential unassigned dose was 1 mrem. It should be emphasized that because of the conservative assumptions employed in these calculations, the actual dose to any individual would have been considerably lower.

In conclusion, the dose assessment techniques used for SHNPP were adequate to evaluate the exposure to noble gases. However, CP&L recognizes that with continued plant operation, the potential for higher noble gas levels exists. If this occurs, it will be noted during routine monitoring and appropriate actions will be taken to ensure that dose evaluations are reasonable to evaluate the extent of any radiation hazard present.

References:

1. Berger, M. J., " Beta-Ray Dose in Tissue Equivalent Material immersed in a Radioactive Cloud". Health Physics, Vol. 26,1-12.

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(5266JDK/pp )

i Attachment 2 to CP&L Letter of Response to NRC I.E. Report RII: 50-400/87-22 As further requested, CP&L has evaluated the applicability of this finding to the Brunswick and Robinson Plants. It is our conclusion that adequate dose evaluations have been performed at those plants in accordance with the requirements of 10CFR20 for substantially the same reasons as stated in Attachment 1. Estimates of the unassigned dose resulting from exposure to noble gases at these plants are likewise not significant.

Brunswick The potential for unassigned skin and lens of the eye dose at the Brunswick Plant was evaluated using data collected between January 1986 and June 1987. Airborne concentrations in the reactor and turbine buildings were derived from monthly effluent noble gas grab sample results. Only 3 of 72 samples indicated the presence of any of the noble gases of concern (Ar-41, Kr-87, Kr-88, Xe-138 and Xe-133). These measured concentrations were multiplied by a factor of two to account for possible localized higher concentrations within the buildings. Cumulative stay time was assumed to be 40 hrs / week for the entire quarter. The resultant maximum potential unassigned dose was 2.4 mrem per quarter to the skin and .02 mrem per quarter to the lens of the eye.

Robinson The potential unassigned skin and lens of the eye dose at the Robinson plant was also evaluated for the time period between January 1986 and June 1987. Airborne concentrations of Xe-133, Ar-41, Kr-87, Kr-88, and Xe-138 were obtained from containment noble gas sample results. Stay times were estimated based on RWP log-in/ log-out times, security logs of containment access, and/or conservative estimates based on work being performed. The maximum possible unassigned skin dose for any l individual, in one quarter, was calculated to be 185 mrem. The potential skin doses to l the vast majority of individuals who entered containment during this time period are much smaller, in the first quarter of 1986, less than 1% of all individuals who entered l

containment could have received more than 100 mrem. Additional follow up regarding these individuals (11 total) is being conducted. During the subsequent five quarters (through June 1987), rto individuals received greater than 100 mrem. Results of the follow up to the 11 individuals with doses to the skin of the whole body in excess of 100 mrem will be submitted in a separate report from the Robinson Plant by i September 30,1987, i

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(5266JDK/pp)

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