ML20085D871

Requests Approval for Disposal of Dredged Sands & Sediments from Discharge Canal by Transferring Matl to Onsite Spoil Pond Located Adjacent to & Draining Into Discharge Canal

ML20085D871
Person / Time
Site:	Brunswick
Issue date:	10/09/1991
From:	Vaughn G CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NLS-91-222, NUDOCS 9110170242
Download: ML20085D871 (13)

Text

.

Carolina Power & Light Company P O Bou 1%1 e Hateigh. N C F7607 SERIAL: NLS 91-222 10 CFR 20.302(a)

G E VAUGHN Vece Presedent Nuclear services Depanment United Statos Nuclear Regulatory Commission ATIENTION.' Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS 1 AND 2 DOCKET NOS. 50-325 & 50 324/ LICENCE NOS. DPR 71 & DPR-62 DISPOSAL OF DREDGED CANAL SANDS AND SEDIMENTS Gnntlemon:

In accordance with tho Code of Fodoral Regulations, Title 10, Part 20.302(a), Carolina Power & Light Company (CP&L) hereby roquests approval for the disposal of dredgod sands and sediments from the disc'targe canal of the Brunswick Steam Electric Plant, Units 1 and 2. CP&L plans to dispose of this material by transferring it to an on sito spoil pond located adjacent to and draining into tho dischargo canal. Moro detailed information supporting this request is provided in the enclosure to this letter.

After consideration of alternato disposal methods, procedures to minim!20 unexpected exposures, environmental effects, and radiation exposure risks, CP&L has concluded that the requested mothA dredging and disposal of these sodimonts represents the most acceptablo and appropriato method currently available.

CP&L has tontatively scheduled this dredging work to begin during March,1992, and estimates that this work will require 2-3 months to comploto. CP&L requests the NRC to provido approval of this request by January 15,1992, in order to allow sufficient timo subsequent to NRC approval of this request for the issuance of contracts necessary to implomont this dredging work.

This loformation is being submitted to the North Carolina Division of Radiation Protection in order to facilitate the concurrence and approval of this roquest with tho Stato of Nurth Carolina.

Pleaso refer any questions regarding this submittal to Mr. J. C. Presley at (919) 546 6132.

Yours very truly.

,pl

,/

WhD

.y kn G.E.Vaughn JCP/WRM/jcp (canal.wpf)

Enclosure cc:

Mr. Dayne Brown Mr. S. D. Ebneter Mr. N. B. Le Mr. R. L Provatto 3h l

911017n242 911009 4

POR noccu osooo m l

P eos

o ENCLOSURE 1 BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKETS 50 325 & SO424 OPERATING LICENSES DPR 71 & DPel 62 DIST'OSAL OF DREDGED CANAL SANDE AND SEDIMENTS P R EQ 1A kBg p g,$1:

In accordanco with the Code of Federal Regulations. Title 10, Part 20 302(a), Carolina Power & Light Company hereby toquests approval for the disposal of drodged sary.is and sodiments from the discharge canal of the Brunswick Steam Electric Plant, Units 1 and 2. The Company plans to dispose of this matorial by transferring the material to an on-sito spoil pond located adjacent to the disefarge canal.

Tho spoil pond will drain into the disefwgo canal, pjSCR!PTIQN OF CIRQktMSTANFS:

The Brunswick Steam Electric Plant, Units 1 and 2 consist of two 821 MWo bolling water reactors.

Thoso units discharge cooling water through a 5 25 milo canal to a basin whero the water is pumpod underground to a releaso point in the Atlantic Ocean approximately 2000 feet off shoto. Since the initiation of operation of the two units, the basin from which the ocean dischargo pumps tako suction has fillod with sedimonts and sand, thereby reducing the offective volume and adversely affectlng the operation of the ocoan dischargo pumps, wh!ch in turn has resultod in pork)dic pump cavitation and flow rostriction requiremento. The sodiment deposition has occurred at the end of the dischargo canal whero tho water losos velocity prior to being pumpod to the ocean. In addition to sedimentation, some cavo-in and crosion from the sides of the canal have added to the accumulation along the northorn half of the basin.

PROPQSFR MANNER _QF DISPOSAL:

Soundings of the basin indicato that approximately 00.000 cubic yards :A material wm!d have to be removed to retum the basin to its original dimensions. The material will bo pumped using dtarglard drodging practicos to a spoil pond located adjacent to the canal. The spoil pond is beated on property ownod and controlled by CP&L Drainago from tho spoil pond will bo to the eischar00 canal.

RESCRIPTION QF MAIffRJA1. INVOly_FA:

Sampling has indicated that the material consists primarily of sand with some smaller particulato nmtorial nearer the end of tho basin. The averago density of the material dried is 1.1 gm/cc. The material exhibits many of the inert chemical proporties typical of silicatos. Thoro appears to be a st! ht 0

adsorption, probably by tonic attraction, of cobalt and manganeso 6ons The material cannot bo reduced in volume by incineration or by any other reasonable chem cal treatment.

Ton sary clos of the material to be removed woro collected, driod, and analynxi by gamma spectros :opy. Results of those tests are presented in Table 1. Tho samplos were taken from the proposed dredge area indicated in Figure 1. Those concentrations represent very low values in comparison to the roloaso concentrations allowed by 10 CFR 20, Appendix B, Tablo II, as demonstrated in Table 2.

E1 1 l

i 4

DESCRIPTION OF DISPO)AL METHOD:

The sediments will be dredged from the bottom of the canal using standard dredging prv$tices The equipment will include an auger type dredge which wWt move the material taczgh a pipa sydem and discharge the material into the spoil pond area. The discharge will be controlled to form a berm about a pond area of approximately six acres A drain v/'l be constructed to retum sluice water to the discharge canal Figure 1 shows the location of the spoil pond on CP&L property where access by the public is limited.

f PROCEDURES TO MINIMlZE UNEXPECTED EXPOSURES:

Calculations based on the average concentrations presented in Table 2 indicate that no detectable radiation exposure will occur to workers operating the dredging equipment. Weekly surveys of the spoil area will be conducted to verify that unexpected concentrations of radionuclides are not forming If ambient radiation surveys detect general radiation levels greater than 20 SR/ hour above norrnal L

backgmund, the disposal operation will be suepended until environmental laboratory analyses and r'sessment sampling of the sediment of that area is completed and the Manager, Environmental &

Radiation Control Unit at the Brunswick Steam Electric Plant has approved resumption of the disposal operations based upon acceptable laboratory results, ho additional protection measures are planned for t

this operation.

ENVIRONMENTAL EVALUATION:

Because the disposal site for the dredged sands and sediments from the discharge canal is located adjacent to and drains into the discharge canal, topographica!, geological, meteorobgical and hydrological characteristics, including tesage of ground and surface waters in the general area will not be altered by implementation of the requested disposal plan These environmental characteristics remain as evaluated and analyzed in the " Final Environmental Statement Related to the Continued Construction and Proposed issuance of a>1 Operating Ucense for the Brunswick Steam Electric Plant Uni's 1 and 2" which v as published by the Directorate of Licensing of the United States Atomic Energy Commission in Januar).1974 (hsreafter referred to as the FES). As noted in the FES, "the applicant plans to account for shoa ing in both canals by maintenance dredging. Dredging spoil will be placed in existing spoil -

l ponds th.t have sufficient capacity. No marsh area will be used for spoil areas, nor will any spoil be deposited a the Cape Fear Estuary

• Furtner analysis of topographical, geological, meteorological, and hydrological characteristics, including usage of ground and surface waters in the general area are consequently not applicable because these characteristics will not be altered due to allowance of the requested dredging operation and disposal method.

To assess the magnitude of perceivM risks associated with disposal of the sediments, two exposure models representing conceivable exposures that might occur to members of the public were evaluated:

1 Inadvertent intrurier Exposure:

Although public access to the spoil pond area is rare and difficult, a dose model was developed-to estimate the dose an inadvertent intruder might encounter. The dose model uses the "Microshield" software package. The model assumes that an intruder stands on top of an infinite slab of the sediment, that the sediment thickness is 20 feet, and tPat the sediment contains a L

uniform average concentration of radionuclide activities as presented in Table 1. The dose rate l~

calculated at 1 meter above this plane is 1.7 pR/ hour above background. This represents the estimate of the whole body exposure rate. An inadvertent intruder present on the berm of the spoil pond for 1D hours would receive 0.17 mulirem (see Enclosure 2).

E1-2 i

~-

Neares! Resuent E>Dg3m:

I The nearest resident to the prumsod spoil pond is located approximately 900 feet south of the area, en :epresentoa h Figure 1. The dose model uses tho *Microshield" software package. The modo! sasumes the resident is exposed to a pile of the sodiment measuring 36 feet by 60 'eet by 1000 feet. Using a soll density of 1.1 gm/cc and a untform averago concentration of radionuclide activities as presented in Tat /s 1, the doso rate to the resident is estimated at 2.27E 2 R/ hour (see Enclosure 3). An exposure time of one year would yield an estimated resident doso of 0.P millirom.

SUMMARY

$;nce initiation of operation of the BSEP, the basin from wlilch the ocean discha ge pumps take suction has filled with sodiments and sand, thereby reducing the effectivo volamo and adversely affecting operation of the ocean discharge pumps. The Company proposes to drodge the sand and sodiments from the basin of the discharge canal snd dispose of the material by transferring it to an on slte spoll pond located tdjacent to the discharge canal. Spectroscopy analysis of samples of the material InJeates the material is of a radioactive concentration which is very low in value in compgrison to rotease concentrations allowed by 10 CFR 20. Appendix B. After consideration of alternate Jisposal methods, procedures to miniml20 unexpected exposures, environmental effects, and radiation exposure riska, CP&L has concludod that the requestod methM of dredging and disposal of these sediments represents the most acceptablo and appropriate method currently available. Consequently, CP&L requests approval for the disposal of drodged sands and sediments as described heroin.

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TABLE 1 I

SEDIMENT RADIOLOGICAL CHARACTERISTICS Cobalt 60 Manganeso54 Cosium 137 Sample No.

pCl/gm pCl/gm pCl/gm i

1 1.07 1.90E 1 2

1.57E-1 4.76E 2 3

1.21E 1 4.49E 2 2.4GE 2 4

1.79E 1 9.31E 2 5

8.71f! 2 6

9.01E 2 7

1.34E 1 4 63E 2 8

1.53E 1 5.73E 2 9

1.80 3.42E 1 10 1.20 2.49E 1 1.87 Average 5.00E 1 1.10E 1 1.34E 1 El-4

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i TABLE 2 COMPARISON TO 10 CFR 20, APPENDIX D. TABLE 11 OF RA0lOACTIVITY CONCENTRATIONS IN CANAL SE0lMEllTS Observed Sodiment Appendix B.

versus Average Table il Regulatory Concentration Column 2 Valoo Radionuclide (yCl/ce)

( C;/ml)

(Ptsrcont of)

Manganese-54 1,1E 7 1 E-4 0.11 Cobalt 40 5.0E 7 3E 5 1.7 Coslum 137 1.3E 7 4E 5 0.32 E1-5

f FIGURE t

x x

1.fROJEQT SITE x

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vi 3 :

! ! N v

MARSH o

s u.

o 3 :

J w/

O y

w DISPOSAL e

o Q

AREA x

x

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M / /v D

x x

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DREDGE

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AREA y

y. 4 'Alj kY1'$MMg s,f i

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PUMPitlG gggigy STATION L.J4 E

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4 NEAREST IPESIDEt1T i

OCEAN i

I Y DIScil ARGE

- ~....

9 ENCLOSURE 2 BRUNSWICK STEAM ELECTPIC PLANT, UNITS 1 AND ?

NRC DOCKETS 50 325 & 50 324 OPERATING UCENSES DPR 71 & DPR 02 DISPOSAL OF DREDGED CANAL SANDS AND SEDIMENTS i

l i

I I

t liX!'Q1Vff_flEEV.kIS 1!LADVERTENT INTRUCER EXPOSURE MOD %

i h

1 i

i r

F l

i.

l E21 1

P k

-w w a,2-'+,

,4.e-,,,--r,,,,,,em.r w

r-,.v+=

<e---c--ww----=---iam

_.____m__,_

i Microchield 3.11

..a r....;. ; aa r...:n t v5}s Face

~

Tile Ref:

Tile Dato:

?.un dato: Decer.cer 19, 1990

~

F.un tine: '0:13 a.m.

By:

Checnod:

CASE: intruder on berm GECHETRY 14: Infinite slab sourco slab snields 21 stance to detector...............

Source slab thickness..............

......... X 864.640 cm.

Thienness of second shield..............

.... T1 764.640

.... T2 100.

H

\\

l MATERIAL DENSITIES (g/cc):

!atorial Source Shield 2 Air

.001220

.iuminu

arcon

ncreto 1.10 Hydrocen Iron

.ead-

.ithium

!!ickel Tin Titanium Tungsten Urania Uranium-Uator

'ir Onium t

[

-E2-2

?ngo 2 Tilos 7ASE: Intruder en t e rr.

BUICUP TACTOR: based on TAYLOR unthod.

'Jsing the enaracteristics of the mater 3 als in shield 1.

1NTEGRATICli PARAMETERS:

l lone - analytically integrated.

SOURCE NUCLIDES:

!Iuclide Curies Nuclido Curies tiuclido Curies Ba-137m 0.0000e+00 Co-60 5.5000c-13 Cs-137 1.4700e-13 Mn-54 1.21000-13 N-16 0.0000e+00 RESULTS:

3roup Energy Activity Dose point flux Dose rate (McV)

(photons /sec)

MeV/(sq cm)/sec (nr/hr) 1 1.3359 2.035e-02 4.685e-61 8.453e-04 2

1.1797 2.0350-02 4.043e-01 7.512e-04 3

.8359 4.476e-03 5.950e-02 1.187e-04 4

.6953 3.3*9n-06 3.794e-05 7.814e-08 5

6 7

8 9

10 11 i

12 13 14 l

15 16 17 18 19 20 TOTALS:

4.518e-02 9.323e-01 1.715e-03 l.

L

(

E2-3 l

l

ENCLOSURE 3 BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKETS60-325 & $0 374 OPERATING UCENSES DPR 71 & DPR-02

]

DISPOSAL OF DREDGED CANAL SANDS AND SEDIMENTS A

EXPOSURE RESQllS i

NEAREST RESIDENT EXPOSURE MODE t

h b

d t-E31

l Micrashield 3.11

..re....a

..:wer agn

-E>

Tile

RESIDE 2.MSH Dato:

Run date: December 18, 1990 f

By:

?.un *1=e: 3:07 p.m.

Checkoo:

CASE: resident:

GEOMETRY 11: Rectanaular solid source

- slab unields Distance to detector.........................

X

29300, Scurce V1dth.......................

W 30500.

cm.

Source length................................

L 1100.

Rectancular solid, thickness toward dose T1 1830.

Thickness of second shield...............pt..

T2 27300.

Micr0 shield inserted air gap................. air 170.

Source Volumet 61396500000 cubic contimeters MATERIAL DENSITIES (g/cc) :

'atcrial Source Shield 2 Air gap Air

.001:20

.001220 Aluminum Carton Concretc 1.10 Hydrogen Iron Lead Lithium

!!1ckel Tin Titanium Tungsten Urania Uranium Water 21r::enium e

E l

')

i n

7dC 2

File PISIDE2.MS!!

OASE: resident.

1 BUILDUP FACTOR based on TAYLOR method.

Using the characteristics of the materials in shield 1.

INTEGRATION PARAMETERS:

i Number of lateral angle segments (Ntheta).....

5 Humber of azimuthal angle segments (N 5

Nunner of radial segmentu (Nradius).. psi).....

5 SOURCE NUCLIDES:

Nuclide Curies Nuclide Curles Nuclide Curies Ba-177m 0.0000e+00 Co-60 3.3768e-02 Cs-137 9.0253e-03 Mn-54 6.7536e-03 N-16 0.0000e+00 RESULTS:

Group Energy Activity Dose point flux Dose rate 4

(MeV)

(photons /sec)

MeV/(sq cm)/sec (mi/hr) 1 1.3359 1.249e+09 6.210e-03 1.121e-05 2

1.1797 1.249e+09 5.334e-03 9.911e-06 3

.8359 2.498e+08 6.925e-04 1.382e-06 4

.6953 2.038e+05 4.805e-07 9.894e-10 5

6 7

8 9

10 11 12 13 14 15 16 17 18 19 20 TOTALS:

2.749e+09 1.224e-02 2.250s-05 E3-3

_.-