ML20126C213

Forwards Comments from Review of Draft Rept of EPA Plume at Plant

ML20126C213
Person / Time
Site:	Monticello
Issue date:	03/19/1976
From:	Grimes B Office of Nuclear Reactor Regulation
To:	Higginbotham L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
References
NUDOCS 9212220423
Download: ML20126C213 (4)

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i Leo B. HiEgiubotham, Chief, Safety and Environmental Programs, 07&E 4

COMMNIS ON EPA PLUME STUDY AT HONTICELLO As requested in your March 4,1976 inemo, the Environmental Evaluation Branch has reviewed the draft report of the EPA plume study at Monticello.

Our commento are enclosed. We note that EPA does not address dose effects from turbine shine and that their implied dose conversion factors differ i by orders of magnitudo from NRC's values.

I This review was performed by S. Block, EEB.

i B. K. Grimes Chief g Environmental Evaluation Branch Division of Operating Reactors y N Office of Nuclear Reactor Regulation Encioaure:

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EPA PLUME STUDY AT MONTICELLO (1) Page 8 Reference is made in the' draft report to the noble gas Bottom of page releases from operating reactors. Table 2 of the report is a breakdown of the fractional abundance of the gaseous radionuclides and the resultant fractional ground level exposure rate at 2 Km. Note that the 89 Kr (T1 /2 = 1.3 Hrs) with fractional abundance of 0.159, and 88 Kr (T1/2 = 2.8 hrs) with about the same fractional abundance have a factor of

• about 200 in their relative exposure rate. This is incorrect.

The gamma dose factors for these radi nuclides currently used by NRC for exposure calculations for total body ex-posure from routine effluents are as follows:

87Kr = 5.3 x 10 mrem 5

/hr per uCi/cc 88Kr = 1.33 x 106 mrcm/hr per pCi/cc.

These dose factors differ by a factor of 2.5. Thus the statement, on page 8, that "approximately 90% of the ex-posure rate was due to the two nuclides 00 Kr and 135 Xe" is incorrect.- Also, the last three nuclides in the table were inadvertently labeled as "Kr" instead of "Xe."

(2) Page 11 The statement "The natural background measurements were First paragraph subtracted from the. total exposure measurements'to yield the net exposure shovn'in Table 5. . ." is somewhat mis-leading if one were to use the data in table 4 '" Total Exposure." _For example, at: Site A in table 4, the period .

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i - 2- l (2) Page 11 for the background measurement for both PIC and TLD '

) (continued) i detectors is given as the data collected during 03/18 -

.I 05/13. Howevet, only the TLD data is used to subtract

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this background in order to obtain the TLD net' readings 5

1 1 in Table 5 as this instrument recorded the background 4

5 continuously and "the plant contribution was determined i

t

! by integrating only the peak or additional exposure" I '

(Quote from page 18, 8th line from bottom). The back-

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ground measurement for the PIC was not constant and .a 1

therefore the background value in table 4 was not the 4' ,

value used to find the net results shown in table 5 as j the text-on page 11 infers.-

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4 It should be noted that one approach that EPA could take I for subtracting TLD background radiation exposure from I

the total exposure

• on a more continuous basis is to t I locate some TLD's suf ficiently remote from Moniicello-b so that the background can be measured without radio- ,

nuclide ef fluent' release interference from the plant.

4 Thus one could correct for diurnal and seasonal varia-

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tions in dose rate.- It would be assumed that the back-i b

4 ground at the remote location would be equal to the i

background of the-TLD at the measuring station. By so I doing, EPA's conclusion that. the ability of TLD to i- I accurately measure 5 mrem /yr above natural background

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I would be less. questionable (see page 20).

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Some discussion relevant to the contribution of turbine shine on the net exposure would be useful in the report I

as measurements of this source of radiation are being conducted at several plant sites.

(3) Page 16 There is a large difference between NRC's exposure rate Second paragraph ~

conversion factor for noble gases and EPA's as given 1n the draft report. EPA's concentration of 0.034 pCi/M 3 *

(average between 0.032 and 0.036 given on page 16) yields their calculated dose rate of 102 pRem/hr (value given on same page. This gives a dose factor of 102 pRem/hr J 1

, X 10-3 MREM ,

0.034 Pci 10-6 M3 10-6 pCi UKER K3 CC PCi 3 x 1012 MREM /hr pC1/cc 00 Kr (the largest calculated fraction NRC's value for of ground level exposure given in table 2) is 1.33 x 10 6 MREM /hr (see (1) above) pCi/cc Consequently there is ; factor of 106 difference between

, these values. Perhaps EPA meant 0.034 301. If so, MJ table 8 should also be corrected.

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