ML18004B953

Submits Results of Followup at Hb Robinson from Commitment for Further Action in Util Response to Insp Rept 50-400/87-22 Re Exposure to Noble Gas.Potential Unassigned Skin Dose to 11 Personnel Found Insignificant

ML18004B953
Person / Time
Site:	Harris, Robinson, 05000000
Issue date:	09/30/1987
From:	Morgan R CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RNPD-87-4842, NUDOCS 8710080098
Download: ML18004B953 (5)

Text

REGULATORY jFORMATION DISTRIBUTION SY M (RIDS)

ACCESSION NBR: 8710080098 DOC. DATE: 87/09/30 NOTARIZED: NO DOCKET FAC IL: 50-000 Generic Do c k e t 05000000 50-261 H. B. Robinson Plant> Unit 2a Carolina Poeer 0 Light C 05000261

~~0-400 Shear on Harris Nuclear Poaar Plant Unit 1 Carolina AUTHOR AFFILIATION

~ 05000400 AUTFI. NAME MORGANl R. E. Carolina Power 0 Light Co.

RECIP. NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Submits results of folloeup at HB Robinson from commitment for further action in util response to Insp Rept 50-400/87-22 re exposure to noble gas. Potential unassigned DISTRIBUTION CODE: IE01D COPIES RECEIVED: LTR ENCL SIZE:

TITLE: General (50 Dkt)-Insp Rept/Notice of Violation Response NOTES: Application for permit renewal filed. 05000400 REC IP IENT COPIES RECIPIENT COP IES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-1 PD ECCLESTONa K BUCKLEYl B INTERNAL: AEOD DEDRO NRR MOR ISSEAUa D NRR/DOEA DIR 1 NRR/DREP/EPB NRR/DREP/RPB 2 NRR/DR IS DIR NRR/PMAS/ILRB 1 1 ERMANs J OGC/HDS1 1 1 REG FILE RES DEPY GI 1 LE 01 EXTERNAL: LPDR 2 NRC PDR NSIC 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 23 ENCL

Form 244 CML Carolina Power 8 Light Company Company Correspondence ROBINSON NUCLEAR PROJECT DEPARTMENT POST OFFICE BOX 790 HARTSVILLE, SOUTH CAROLINA 29550 Robinson File No: 13510C Serial: RNPD/87-4842 Harris File No. SHF/10-13510E (10CFR2.201)

United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Ho B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261 LICENSE NO. DPR-23 RCrb FOLLOW-UP REPORT FOR IE REPORT RII: 50~/87-22

REFERENCE:

CPSL Letter NRC-571 of August 21, 1987; McDuffie/NRC;

Subject:

IE REPORT RII: 50-40/87-22 Gentlemen'.

The Carolina Power 6 Light Company (CP&L) letter of August 21, 1987, submitted in response to the NRC inspection of the Shearon Harris Nuclear Plant Project as reported in IE Report RII: 50-40/87-22 included a commitment for further action by the H. B. Robinson staff. The response stated the following.'The potential for 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-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 individual, in one quarter, was calculated to be 185 mrem. The potential skin doses to the vast majority of individuals who entered containment during this time period are much smaller. In the first quarter of 1986, less than 1X of all individuals who entered containment could have received more than 100 mrem. Additional follow-up regarding these individuals (ll total) is being conducted. During the subsequent five quarters (through June 1987), no individuals received greater than 100 mrem. Results of the follow-up to the ll 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 September 30, 1987."

8710080098 870930 ggo I PDR ADQCK 05000261 G PDR lP

Serial: RNPD/87-4842 Page 2 The purpose of this submittal is to provide the results of the follow-up.

The highest exposures to noble gases at the H. B. Robinson Plant occurred during the first quarter of 1986 when concentrations ranged from .01 times to 60 times the Maximum Permissible Concentration (MPC) for Xe-133 in containment. Follow-up has been performed for the 11 individuals who had the greatest potential for unassigned skin doses, ranging from 108 to 185 mrem.

The calculations of this unassigned dose were based on actual measured concentrations of noble gases in containment; but, from January 1 to 21, 1986, accurate data on individual stay times is unavailable. Conservative estimates of the stay time in areas where exposure to noble gases might have occurred have been utilized for this time period. As a result, the dose calculations for the 11 individuals are considered to be very conservative, with a distinct probability that the actual dose received was lower than estimated. The assumptions used to estimate individual stay times have been reviewed with the individuals involved to verify they are reasonable yet conservative. Original TLD readings for these individuals prior to TLD algorithm processing have also been reviewed for any indication of significant noble gas exposure. Although the TLD algorithm does not employ a beta correction factor appropriate for Xe-133, element number 1 of the TLD is capable of detecting beta radiation with low energies quite similar to Xe-133. The beta response indicated by the readings for the 11 individuals, if any, was statistically insignificant.

Since Xe-133 also emits low energy X-ray radiation, the readings for the 11 individuals have been reviewed for any evidence of X-ray exposure. Element number 3 of the TLD is highly sensitive to this type of radiation and would be expected to show a higher response than the other TLD elements if significant exposure to Xe-133 (X-rays) had occurred. The X-ray response indicated by the readings for the ll individuals, if any, was statistically insignificant.

consistent In with fact, the predicted X-ray response on the TLD, which would be the estimated MPC-hours of exposure, was higher than that indicated by actual TLD results. Although no true estimate of Xe-133 dose can be made from these TLD readings, the results suggest that actual exposure to noble gases was less than the exposure calculated based on noble gas concentrations and personnel stay times. Full details on the dose calculations for the ll individuals have been documented in a separate technical report by the CPKL Corporate Dosimetry Group.

It is recognized that the potential for higher doses from noble gases does exist and that use of the current TLD algorithm may result in significant unassigned doses in the future. Therefore, CP&L is developing procedures for calculating and assigning beta skin dose from Xe-133 when exposure conditions could result in a significant dose. The procedures will include an Action Level at which point tracking of exposure in terms of MPC-hours will begin.

When the accumulated MPC"hours during a calendar quarter reach a specified level, the actual skin dose will be calculated using an appropriate beta dose factor for Xe-133. This calculated skin dose will be entered into the individual's official personal exposure history records as well as any skin dose as measured by the TLD. These procedures will be implemented at the H.

B. Robinson Plant by the end of the year, December 31, 1987.

Serial: RNPD/87-4842 Page 3 The dose level considered significant for the purpose of calculation of noble gas exposure will be 200 millirem per quarter. ANSI Standard N13.11, the performance testing standard for NVLAP dosimetry accreditation, does not require personnel dosimeters to be capable of measuring doses less than 200 millirem per monitoring period for mixtures of photon and beta radiation. Appendix A2 of the Standard explains that the minimum dose was established on the basis that 25 percent of the NCRP recommended annual li'mit would not be exceeded if all dosimeter readings for biweekly or longer monitoring periods were less than the specified minimum dose. Therefore, ANSI Standard N13.11 effectively allows a maximum unassigned dose of 1300 millirem per quarter based on biweekly monitoring periods. NRC regulations in 10 CFR 20 do not require monitoring when exposures are not expected to exceed 25 percent of the quarterly limits. The maximum unassigned skin dose effectively allowed by these regulations is 1875 milli'rem per quarter.

ICRP 35 defines the recording level for individual monitoring as one-tenth of the annual limit prorated for the length of the monitoring period. For quarterly monitoring periods, as utilized by CP6L, the minimum recording level recommended by ICRP 35 allows an unassigned skin dose of 750 millirem. By setting the minimum dose for Xe-133 calculations at 200 millirem per quarter, there is assurance that the maximum unassigned dose would be less than three percent of the NRC quarterly skin dose limit of 10 CFR 20. This value is conservative, since it is less than ten percent of the unassigned dose allowed by the NRC and 15 percent of that allowed by the ANSI and 27 percent of that allowed by the ICRP.

In conclusion, the potential unassigned skin dose to the 11 personnel is considered insignificant, with their calculated dose less than the minimum recording level of 200 millirem per quarter. No further action is necessary with regard to their exposure to noble gas.

If you have any questions concerning this submittal, please contact Mr. J. M. Curley.

Very truly yours, RE E. rgan General Manager H. B. Robinson S. E. Plant DAS:jch II cc: Dr. J. N. Grace Mr. H. E. P. Krug Mr. E. E. Utley