ML20059C375

Safety Evaluation Granting Exemption & Approving Alternative DAC Values for Use in Place of Generic Value for Radionuclides Specified in App B to 10CFR20.1001 - 20.2402

ML20059C375
Person / Time
Site:	Pilgrim
Issue date:	12/29/1993
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20059C370	List: ML20059C367 ML20059C372 ML20059C375
References
NUDOCS 9401050139
Download: ML20059C375 (6)

Text

P o

ja atc

. [ Ft UNITED STATES

(('"

"j NUCLEAR REGULATORY COMMISSION

, f WASHINGTON. D.C. 20555 0001

%..,...)

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION EXEMPTION FROM APPENDIX B. TABLE 1. FOR DERIVED AIR ,

CONCENTRATION VALUES FOR KRYPTON-89 AND XENON-137 PILGRIM NUCLEAR POWER STATION DOCKET NO. 50-293

1.0 INTRODUCTION

By letter dated September 13, 1993, Boston Edison Company (BECo) requested an exemption from Title 10 of the Code of Federal Regulations (10 CFR) Section 20.1902(d), " Posting of airborne radioactivity areas," which requires that the licensee shall post each airborne radioactivity area with a conspicuous sign or signs bearing the radiation symbol and the word as, " CAUTION, AIRBORNE RADI0 ACTIVITY AREA" OR " DANGER, AIRBORNE RADI0 ACTIVITY AREA."

Section 20.1003 defines " airborne radioactivity areas" as "a room, enclosure, or area in which airborne radioactive materials, composed wholly or partly of licensed material, exist in concentrations --

(1) In excess of the derived air concentrations (DACs) specified in appendix B, to f5 20.1001 - 20.2401, or ....."

Some airborne radionuclides, in particular the noble gases (such as argon, krypton and xenon) are not metabolized to an appreciable extent by the body. .

The methodology for calculating the DAC for these radionuclides is based on consideration of the external dose due to submersion in air containing the <

radionuclide. The DAC for a particular radionuclide is the maximum.

concentration of that radionuclide in air that, for a 2,000-hour exposure, will result in a dose that is equal to or less than each of the applicable  :

limits in 10 CFR 20.1201 for occupational dose. These applicable limits are- l 5-rem effective dose equivalent (H ),15-rem eye dose equivalent, 50-rem dose equivalent to other organs or tiss,ues, and shallow dose equivalent of 50-rem to the skin.

The radionuclides Kr-89 and Xe-137 are not listed individually in . Appendix B to 10 CFR 20.1001 - 20.2402. Both of these noble gas radionuclides decay by j beta emission and have half-lives (3.16 minutes for_ Kr-89 and 3.83 minutes for  !

Xe-137) of less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />; therefore, the DAC, calculated for submersion, l for both Kr-89 and Xe-137 is 10'7 pCi/ml (in accordance with the' provision at  !

the end of Appendix B to 10 CFR 20.1001 - 20.2402 for "any single radionuclide i not listed above with decay mode other than alpha emission or spontaneous l fission.") j 9401050139 931229 4 PDR ADOCK 05000293 P PDR \

l Section 20.2301 provides that the Commission may, upon application by a licensee or upon its own initiative, grant an exemption from the requirements of the regulations in 10 CFR Part 20 if it determines the exemption is authorized by law and would not result in undue hazard to life or property.

By their submittal dated September 13, 1993, the BECo requested an exemption, pursuant to 10 CFR 20.2301, to use derived air concentrations (DACs) of 10' yCi/ml for Kr-89 and 10-5 pCi/ml for Xe-137 instead of using the generic (default) value of 10~7 pCi/ml for these radionuclides, which is provided in Appendix B to 10 CFR 20.1001 - 20.2402. In this request proposes to use the DACs of 10 pCi/ml for Kr-89 and 10'gdpCi/ml exemption, BECoat for Xe-137 the Pilgrim Nuclear Power Station when determining whether an area is, and requires posting as, an airborne radioactivity area.

2.0 DISCUSSION AND EVALUATION Criteria and background information used for this evaluation include the following:

1. 10 CFR Part 20, Standards for Protection Against Radiation, 5%

20.1003, 20.1902(d), and Appendix B to ES 20.1001 - 20.2402.

2. Federal Guidance Report No. 11, Limiting Values of Radionuclide Intake and  !

Air Concentration and Dose Conversion Factors for Inhalation, Submersion, I and Ingestion, 1988.

3. David C. Kocher, Radioactive Decay Data Tables - A Handbook of Decay Data for Application to Radiation Dosimetry and Radiological Assessments, U.S.  ;

Department of Energy Report DOE / TIC-Il026, 1981.

l

4. Letter from Keith Eckerman, Oak Ridge National Laboratory, to John Buchanan, U.S. NRC, November 1, 1993.

In its September 13, 1993 letter, BEco states that the requested exemption is i needed because Kr-89 and Xe-137 are a significant fraction of the noble gas '

radioactivity in a boiling water reactor and the DAC of 10' pCi/ml provided in Appendix B to 10 CFR 20.1001 - 20.2402 is too small for these particular radionuclides. BECo notes that the " maximum permissible concentration (MPC)"

for Kr-89 and Xe-137 given in Appendix B to 10 CFR 20.1 - 20.3 (which is is 10 Ci/ml rather applicable than at theBEco 10-7 pCi/ml. Pilgrim plant states until that the January use of the1,1994) 10' pCi/ml value for the Kr-89 and Xe-137 DACs would cause over posting of airborne radioactivity  !

areas, which erodes the significance of the posting and consumes resources. j BECo also states that the use of the 10'7 pCi/ml value for the Kr-89 and -

Xe-137 DACs would result in undue hardship and would overburden operational staff by posting areas that are normally not required to be posted while providing little to no benefit.

l l

BEco further states that: (1) the exemption request does not decrease any safety measures employed at the plant and does not invalidate previous commitments or requirements to comply with regulation, (2) the exemption request relates to occupational radiation exposure, and (3) the exemption ,

request is authorized by law, will not present undue risk to public health and safety, and is consistent with common defense and security.

To determine the radiation dose equivalent values corresponding to the BEco-requested values of the DACs for Kr-89 and Xe-137, the NRC staff used dose conversion factors calculated by Dr. Keith Eckerman, Group Leader, Radiation Dosimetry Research Group, Oak Ridge National Laboratory (ORNL), which were provided in his letter dated November 1. 'Q93. In performing these calculations, Dr. Eckerman used nuclea m . data for Kr-89 and Xe-137 taken from the report by D. C. Kocher. Dr. __ a and his group at ORNL calculated the DACs and other quantities contained in Appendix B to 10 CFR Parts 20.1001 - 20.2402 and in Federal Guidance Report No.11. Dr. Eckerman '

provided the dose equivalent rate conversion factors for Kr-89 and Xe-137 in the SI units of [(sieverts/second) per (bequerel/ cubic meter)]. These factors were converted to factors with conventional units of [(rem / hour) per (microcurie / cubic centimeter)] by multiplying by a factor of 1.332 x 10".

These dose equivalent rate conversion factors are listed in Table 1. In this table, the H is the dose "effe,ctive dose equivalent" equivalent to asthe remaining defined in 10 organs or tissues and Hand Federal , is CFR 20.1003 Guidance Report No. 11.

The dose equivalent rate conversion factors from Table I were use to calculate thedoseequivalent,inunitsofrem,tpatcorrespondstoanexpopureof2,000 3 3 i

hours at the BEco-requested DACs of 10' pCi/cm for Kr-89 and 10' pCi/cm for Xe-137. The results of these calculations, together with the corresponding Part 20 dose limits, are shown in Table 2.

All of the calculated doses in Table 2 are below the corresponding Part 20 limits and, therefore, are acceptable.

l l

l l

I Y

}:?

i Table 1. Dose Conversion Factors for Krypton-89 and Xenon-137 Krvoton-89 (Sv/s) Der (Ba/m3 ) 3 (rem /h) oer (uCi/cm ) i Gonad 9.19 x 10"' l.224 x 10*' 1 Breast 1.03 x 103 1.372 x 10 3 '

Lung 9. 29 x 10 1.237 x 10 3 Red Harrow 9.22 x 10 1.228 x 10 3 Bone Surface 1.34 x 103 1.785 x 10 3  :

Thyroid 9. 51 x 10 1.267 x 10 3 l H' 8.99 x 10 l.198 x 1033

• H 9.45 x 10' 1.259 x 10 Skin 1.99 x 103 2.651 x 10 3 <

Eye 1.31 x 103 1.745 x 103 '

Xenon-137 (Sv/s) per (Bo/m 3) 3 (rem /h) Der (uCi/cm )

Gonad 8.75 x 10 l.166 x 10'2 Breast 1.02 x 10 1.359 x 10 i Lung 8.94 x 103 1.191 x 10 2 ,

Red Harrow 8.66 x 105 1.154 x 10 2 Bone Surface 1.54 x 10' 2.051 x 10 2  ;

Thyroid 9.16 x 105 1.220 x 10 2 H' 8.56 x 105 1.140 x 10 2 H 9.20 x 105 1.225 x 10 2 Skin 1.35 x 103 1.798 x 10 32 -;

Eye 5.04 x 10 6.71 x 10 _j l

i i

a:

Table 2. Dose Equivalent Values (ren hours at the BEco-Requested DACs (10 ) ACi/cmCorreggondingtoanExposure'pf2,000 for Krypton-89 and.10' #Ci/cm3 -

for Xenon-137) Together with the Corresponding Part 20 Dose Limits (rem)

Krypton-89 Xenon-137 - Part 20 Limit Gonad 2.45 2.33 50.

Breast 2.74 2.72 50.

Lung 2.47 2'38

. 50.

Red Harrow 2.46 2.31 50.

3one Surface 3.57 4.10 50.

Thyroid 2.53 2.44 50. _

2.39 H, 2.28 50.

H 2.52 2.45 5.

Skin 5.30 36. 50.

Eye 3.49 13.4 15, i 1

'I d

-1 5

, 9 7 .wr.. e a m e--- ,- J

} .

I BEco, in its exemption request, included skin dose and whole-body dose values for Kr-89 and Xe-139 calculated using dose conversion factors from Regulatory '

Guide 1.109. These values (in units of rea) are as follows:

Krvoton-89 Xenon-137 "Whole Body" 3.8 3.2 Skin 6.1 31.

These doses appear to be in reasonable agreement with the corresponding doses calculated by Dr. Eckerman, considering that the "whole body dose" used in RG '

l.109 is not the same dose quantity as the " effective dose equivalent" as defined in 10 CFR 20.1003 and that computational models used by Dr. Eckerman to obtain the dose conversion factors reported above are not the models that were used to obtain the dose conversion factors for RG 1.109. BEco did not provide calculated doses for organs or tissues other than the skin. BECo did state that the eye dose is even less restrictive for these two radionuclides than the skin dose and the whole body dose; however, BECo provided no basis for that statement, and the validity of the statement appeared to be questionable for Xe-137 considering the relative magnitudes of the BECo values for the Xe-137 "whole body" and skin doses and the high energy (4.3 MeV maximum, 1.77 MeV average) of the beta radiation emitted in the decay of Xenon-137. The results of the dose calculations by Dr. Eckerman show that the eye dose is limiting in the case of Xe-137; nevertheless, as shown in Table 2, theeyedosegorrespondingtoa2,000-hourexposureattheBECo-requestedDAC of 10-5 yCi/cm is below the limiting dose-equivalent value of 15 rem.

3.0 SAFETY

SUMMARY

The submersion doses corresponding to a 2,000-hour exposure at a DAC of ,

10 for Kr-89 or at a DAC of 10'5 for Xe-137 are below the limiting dose values used for determining the radionuclide-specific DAC values in Appendix B to 10 CFR Part 20.1001 - 20.2402 (and in Federal Guidance Report No.11).

Therefore, these DAC values are ac,ceptable alternatives for use in place of the generic (default) value of 10' yCi/ml for these radionuclides (that is specified in of Appendix B to 10 CFR 20.1001 - 20.2402) when determining whether an area is, and requires postii.g as, an airborne radioactivity area.

4.0 CQNCLUSION The staff has concluded, based on the considerations discussed above, that:

(1) there is a reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) the issuance of this exemption is authorized by law and will not result in undue hazard to life or property.

Principal Contributor: John D. Buchanan Dated: December 29, 1993 m