ML20097F383

Proposed Findings of Fact & Conclusions of Law Re Contention 1 Concerning Asiatic Clams (Corbicula).Related Correspondence

ML20097F383
Person / Time
Site:	River Bend
Issue date:	09/17/1984
From:	GULF STATES UTILITIES CO.
To:
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ML20097F363	List: ML20097F360 ML20097F366 ML20097F380 ML20097F383 ML20097F395
References
OL, NUDOCS 8409180503
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Text

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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION l

Before the Atomic Safety and Licensing Board In the Matter of )

)

Gulf States Utilities Company, ) Docket No. 50-458 et al. )

)

(River Bend Station) )

APPLICANTS' PROPOSED FINDINGS OF FACT AND CONCLUSIONS OF LAW RELATED TO CONTENTION 1 (ASIATIC CLAMS (CORBICULA))

Findings of Fact

1. The Asiatic clam is a type of small shellfish introduced to the northwest corner of the Unites States O

Q during the late 19th century, Conner, et al., ff. Tr.

at 2, 15.

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'. 2. Most American experts believe that a single high-ly-variable species of the Asiatic clam is present in the United States, and that its most appropriate technical name is Corbicula fluminea, Conner, et _al., ff. Tr. at 2-3, 15.

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3. Corbicula is now known to inhabit 35 of the contig-uous United States, Conner, et al., ff. Tr. _ at 3, 16.

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4. In the early 1960's, the Asiatic clam was noticed in the lower Mississippi - River in the. State of Louisiana,

., Conner, et al., ff..Tr.- at.3, 16.

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5. Asiatic clams are robust, thick-shelled bivalve

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mollusks that are roughly triangular.when viewed from the side (i.e., their least outside dimension is only slightly smaller than the greatest) . They . are quite variable in color; usually they appear coppery, greenish-yellow, or brownish-yellow, and tend to become darker with age. The primary mode of feeding for Corbicula is by filtration, Conner, et al., ff. Tr. at 3-4, 18.

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6. Because Corbicula are capable of surviving only in 4

.O low to moderate salinities (up to 22 parts per thousand),

the species is generally considered to be freshwater form, Conner, et al., ff. Tr. at 4, 19.

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7. In freshwater, Asiatic clams are able to adapt to a

. O. wide variety of natural and manmade environments, although i they seem to be more successful in moving water than in quiet water, Conner, et al., ff. Tr. 'at 4, 19.

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8. Corbicula are typically "infaunal" ,or burrowing in habit. Although reported from many ' types of substrates, they appear to prefer' sands and gravels in streams, Conner,

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9. Physical barriers such as drainage divides,

. . O. saltwater, and an intolerance of low. winter temperatures all

limit the natural spread of.Corbicula in North America. An absolute lower thermal limit for Corbicula fluminea is 2' C (36' F), Conner, et al., ff. Tr. at 4, 111.

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10.- Most Corbicula grow to ab'out 25-35 mm (1.0-1.3 i

inches) shell' lengths (SL) , Conner, g al. , f f. Tr. at 1

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, 11. . Sexual maturity is achieved EP 7.5 mm SL (3/8 inch)

LO in some individuals, although about 10 mm SL (7/16 inch) appears to be the more typical size at initial maturity, l Conner, ej al_. , Conner, --et al. , ff. Tr. at 4, M12.

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12. . Growth of Corbuicula during early life is fairly rapid, and most Corbicula (especially in southern U.S. '

I Populations) seem to reach a size at which sexual maturity is anatomically possible during their first calendar year of

life,. Conner, et al., ff. Tr. at 4-5, 112.

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. 13. Occasional individuals may live up to four years, i

l but the normal life span of Asiatic clams in southern rivers i.

, is about two years, Conner, et al., ff. Tr. at 5, 112.

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14. 'Corbicula flhminea is monoecious (hermaphroditic).

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self-fertilization (and, if so, to what degree) has been the t

subject of debate, but the capability to do so has been

, amply demonstrated, Conner, et al., ff. Tr. at 5, 113. l 1

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15. Once fertilized, 'the developing embryos and early

) - larval' stages are incubated (brooded) inside special pouches in the adult clam's inner gill, Conner, et al., ff. Tr.

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16. Development and growth proceed inside the parent i

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have acquired their bivalved shell and a muscular organ

) known as the " foot." Corbicula larvae at this stage are l

4 technically known as pediveligers, Conner, et al., 5, 114.  !

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By virtue of its foot, a pediveliger is capable of f">O crawling, and presumably burrowing, as are the older indi-4 viduals. It is unlikely that this larvae is capable of intrinsically-directed locomotion when not in contact with a surface, Conner, et al., ff. Tr. at 6, 115.

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• 19. 'When subjected to ' turbulence, pediveligers can be

' j carried great distances by currents before settling.out on substrates, Conner, et al., ff. Tr. at 5, 115.

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20. The drifting of pediveligers, and of juveniles up  !

.O. to 5 mm SL (3/16 inch) given sufficient turbulence, is t

generally accepted to-be the basis for the extensive and rapid downstream dispersal of Corbicula populations in rivers and is also the primary mechanism whereby Asiatic clams gain access to industrial cooling and service water systems, Conner, et al., ff. Tr. at 6, 115.

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21. The young clams are considered " juveniles" from about 0.5 mm SL (0. 0'2 ' inch) until attainment of sexual i

maturity, Conner, et al.,.ff. Tr. at 6, 116.

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22. Juvenile Corbicula can produce "byssal threads," or

.O holdfast organs. The byssal thread, muscular foot, and r

ability to burrow in substrates all enable young Corbicula to rapidly assume a benthonic existence, even in moving J

water, Conner, et al., ff. Tr. at 6-7, 116.

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23. Reproduction of Corbicula in the U.S. appears to be

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closely . - related to temperature, with spawning essentially limited to those periods when the water is over 16' C (60*

F) , Conner, et al., ff. Tr. at 7, 117.

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4 a breeding . season of . 9-10 .. months , ' Conner, et al., ff. Tr.  ;

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25. -In the . lower Mississippi River, however,. tempera-  ;

i tures ordinarily remain below 16* C from November through l March, Conner, et al., ff. Tr. :at 7, 117.

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26. Although some reproduction occurs throughout -the

, period encompassing appropriate temperatures, many U.S.

Populations of Corbicula exhibit a bimodal pattern of 4

spawning. .There are two pronounced peaks of larval release (late spring /early summer and late summer /early autumn),

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27. During spawning peaks, an individual' clam may

.- O release several ' hundred pediveligers per day, Conner, et -

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. 28. Corbicula (living and/or dead shells) cause prob-lems by obstructing water flow. Flow is impeded by the clogging of orifices and/or by increased friction on sur-faces that would ideally be smooth, Conner, et al., ff. Tr.  ;

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29. Attachment of clams to surfaces, or the passive

- accumulation of living Corbicula and/or their shell debris,

i. can interfere with heat-transfer processes, Conner, et al.,

ff. Tr. at'7, 118.

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30. Historical data for Corbicula in the river near the i ..

site exist from' Louisiana State University (LSU) studies performed for Gulf States Utilities Company (GSU). Twelve years of data exist for substrate-associated juveniles and adults. Eleven years of data exist on drifting juveniles in these same areas, Conner, et al. , ff. Tr. at 7-8, 119.

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31. Benthic (substrate-associated) Asiatic clams have

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been encountered somewhat less frequently, and in generally lower numbers per unit area, in . the late-1970's and ear-ly-1980's than duri g the baseline studies of the early- and mid-1970's, Conner, et al., ff. Tr. at 8, 119.

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32. . Sampling of drifting larvae and early juveniles has suggested that, in some years at least, there are two peaks of abundance (early and late summer). This presumably reflects a bimodal spawning pattern such as has been ob-

served in other streams of the southern U.S., Conner, ej i al., ff. Tr. at 8, 119.

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Adult and larger juvenile clams appear to be more v., .

j abundant along the west side of the river, Conner, el al . ,

ff. Tr. at 8, 119.

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34. Based on observations taken since 1980, the sub-O' strate in the immediate vicinity of the proposed intake (and i

of the intake embayment in general) has so far been i .

colonized by extremely low numbers of Corbicula, Conner, et a_1_., ff. Tr. at 8, 120.

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.. 35. Routine monthly Petersen grab samples have yielded

. density estimates ranging from 0-5 per' square meter with an

. overall mean of 1 per square meter at this location, Conner, et al., ff. Tr. at 8, 120.

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I p 36. Two years of samples of microzooplankton exist which include Corbicula larvae. Preliminary indications are

.that, relative to the river channel, densities of drifting

, larvae in the intake embayment are quite low, Conner, g al. , f f. Tr. at 8, 120.

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37. Big' Cajun, a power plant directly across the river, has had no fouling problems, Conner, et al., ff. Tr. l 1

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38. Crown-Zellerbach, a paper mill located on the east O. shore two miles downstream of the River Bend Station intake, generates'its own electricity, Conner, et al., ff. Tr.

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39. Crown-Zellerbach circulates more river water through its plant than does River Bend Station, with makeup j water suction taken from a position in the river nearer.the 1

1 bottom where Corbicula would be more likely to be found, '

Conner, et al., ff. Tr. at 9, 122.

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!- 40. In 17 years, Crown-Zellerbach has never observed a t <

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7 If Crown-Zellerbach entrains pediveligers, their t

clarifiers (very much like those at River Bend Station)  !

, and/or continuous low-level chlorination must be entirely effective, Conner, et al., ff. Tr. at 9, 122. '

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42. Considering the River Bend Station intake design j

O and . clarification equipment, the only possible means by i

which Corbicula could enter River Bend Station would be by

j. entrainment of pediveligers, Conner, el al., ff. Tr. j j at 9-10, 123.  ;

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Adult class could not pass through the intake 43.

o screens'or clarifiers, conner, ,e_t,al,., t ff. Tr. at 10, 4 .

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., 44. There are three systems at River Bend Station that i

could potentially be affected by Asiatic Clams, inasmuch as i

they use water from the river, the Cooling Tower Makeup l Water System, the Circulating Water System, and the Normal Service Water System, Conner, g al,., ff. Tr. at 10, i .

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45. The Codling Tower Makeup Water System could poten-

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46. . Of . the three systems that could potentially be affected by the Asiatic clam, there are safety-related components only within the Normal Service Water System, l ' Conner, et al., ff.-Tr. at 10, 124.-

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. 47. Asiatic clam infestation is a safety concern only j in the Normal Service Water System , Conner,.et al., ff. Tr.

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48. The Normal Service Water System provides cooling lO ~

water to remove heat from turbine and reactor plant auxilia-ry systems and components during all modes of normal plant operation, Conner, et al., ff. Tr. at 12, 129.

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,~...--,-,-....--,.n, . , - , - , , , , .,-,-.-_,n.n,,- n.n, . ~ . , , - , .

f i 49. During a loss of.the Normal Service Water System, t

O the Standby Service Water System goes into operation supply-ing safety-related components which normally use normal-service water, Conner, et al.' ff* Tr- -

at 12, 129.

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50. The Normal Service Water System consists of three

'O' 50% pumps which take suction from the circulating water flume. Design flow for the Normal Service Water System is approximately 51,000 gpm, Conner, et al., ff. - Tr. at 12, 129.

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51.. The Normal Service Water . pumps discharge into a  !

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common header where~the system is continuously chlorinated 7

to prevent biofouling, Conner, e._t _al., ff. Tr. at 12,

[ 129.

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52. 'Outside of the turbine building, the common header l' branches into two headers, one to the turbine and radwaste buildings, the other to the auxiliary, diesel generator, control, and reactor buildings. The second branch supplies

all safety-related components of the system as well as certain non-safety systems which would be isolated during SS" operation if required, Conner, et al., ff. Tr. at 12, 129.

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53. Automatic isolation of the Normal . Service Water O. - System supply and return headers allows standby service i i

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water to supply the auxilia.ry , control, diesel generator, and' reactor buildings, Conner, et al., ff. Tr. at 12,

, i 129.

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.. .. . . . . . - . . ..~ . - . . . .~ . . - . . -. ..

54. .The Standby Service Water - System consists of the 4-standby service water cooling tower and four 50% capacity pumps, Conner, et al.,.ff. Tr. at 12-13, 130.

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. . , 55. The Standby Service Water pumps take suction from

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the standby cooling tower and supply well water from the

, basin to all safety-related service water components as well as some non-safety related components which are isolated, if required, Conner, et al., ff. Tr. at 13, 130.

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56. During functional testing of the Standby Service O Water System, there may be . a potential for water from the Normal Service Water System to enter the Standby Service Water System. Chlorination of the Standby Service Water System would be used to- prevent the survival of any Corbicula which may be present, Conner, et al., ff. Tr.

at 13, 130.

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57. The Cooling Tower Makeup Water System is designed

%/J to supply approximately 14,000 gym of clarified water to the circulating ' water . flume ,. Conner, et al.,

ff. Tr. at 10, 125.

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'58. Mississippi River water enters the Cooling Tower -

Makeup Water System through one of two conical-shaped wedgewire screen units which are constructed to screen all i

material greater than 1.5 X .75 inches, Conner, et al., ff.

Tr. at 10, 126.

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59. One 36 inch diameter intake line for each screen r

unit conveys water to the makeup - pumphouse. In the pump-house, the intake lines join' at a c"amon header to two i makeup water pumps, Conner, et al., ff. Tr. at 10, 126.

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60. A makeup water pump supplies the raw river water to

- O, a clarifier which is sized.to handle makeup water flow. The clarifier is a Graver solids-contact type treatment unit.

Raw water is mixed with a polyelectrolyte and a recirculated 1

floc and enters the clarifier unit, Conner, et al., ff. Tr.

at 11, 127.

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61. The water is retained in the clarifier to permit the chemical and colloidal process to proceed to completion

-so that by the time the water passes into the outer settling zone, floc particles have. formed and separated cleanly. The clear water rises and is uniformly collected over a substantial portion of the surface. Water from the clarifier is supplied to the flume from which the circulat-ing water and service water pumps take suction, Conner, ej a_1_., ff. Tr. at 11, 127.

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- 63. - Any adult clams which reach the clarifier will be O trapped within the clarifier along with suspended solids and .

4 transferred back to the Mississippi River. The clarifier will also be effective in removing most, if not all, larvae, Conner, et al., ff. Tr. at 11, 127.

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64. The Circulating Water System dissipates heat from the main condenser and provides the necessary heat sink for the . Normal Service Water System, Conner, et al., ff. Tr.

at 11, 128.

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, J,q 65. The Circulating Water System consists - of four V

multicell cooling towers, four 25% capacity circulating  ;

i water . pumps, and associated piping. Design flow for the 'l Circulating Water System is approximately 510,000 gpm, Conner, et al., ff. Tr. at 11, 128.

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66. The water chemistry for the Circulating Water System is controlled in order to minimize biofouling by the 1

injection of sodium hypochlorite solution periodically into I

J the discharge of the circulating' water pumps downstream of the blowdown header to the Mississippi River, Conner, et M ., ff. Tr. at 11, 128.

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67. Blowdown from the Circulating Water System is approximately 2,200 gpm, Conner, et al., ff. Tr. at 12, 128..

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68. GSU's program of detection includes sampling for

~O. Corbicula in the intake embayment and in the river near the site, Conner, et al.,-ff. Tr. at 13, 131. l l

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69. Sampling for larger juveniles and adults will be i 1-continued monthly in the intake embayment , Conner, et al.,

i ff. Tr. at 13, 131.

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70. Sampling for planktonic early life : stages using 1 1

plankton nets will be conducted semimonthly (April through October) or monthly (November through March) in the river i

channel near the embayment, Conner, et al. , ff. Tr. at

! 13, 131.

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, 71. Sampling for plankt'onic early life stages will also i

O~ be conducted semimonthly -(April through October) or monthly (November ' through+ March) in the clarifier influent line to determine the quantities entrained in the makeup water, j _ Conner, et al., ff.,Tr. -at 13, 132.

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s i 72. Most of the sampling effort vill be devoted to i

O' weekly (April through October) or monthly (November through March) samples of the clarifier discharge using plankton nets, Conner, et al., ff. Tr. at 13-14, 132.

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Sampling for. larger - juveniles and adults will be

.. e condect'od- ~m EYinthly in various exposed portions of the Cir-1 - >~.4. ,g

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, 74. The sampling programs will begin upon start-up of

the cooling tower makeup water system (initial introduction of river water into the plant is estimated to be in-February 1985) and will continue through two complete clam reproduc-tive seasons beyond commercial operation. At the end of this period there will be data reflecting: 1) ambient densities of larvae in- the river; 2) numbers of ' larvae entrained by the plant intake water; and 3) numbers of larvae introduced into the plant service and circulating water systems (i.e., clarifier performance), Conner, et al.,

ff. Tr. at 14, 134.

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75. If, from clarifier discharge and cooling tower basin sampling, service water component performance trend-ing, and maintenance inspections, minimal or no Corbicula infestation of the plant is indicated, an appropriate reduction in intensity of the detection program will be made, Conner, et al., ff. Tr. at 14, 135.

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populations in .the river, and semimonthly or monthly sampling of the clarifier discharge will be maintained, I- Conner, et al., ff. Tr. at 14, 136.

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Lp 77. If the sampling program indicates that clams have  !

l' been introduced into the Service and Circulating Service l Water Systems, emphasis in monitoring will immediately shift i

to address: (a) the adequacy of the chlorination program

-and modifications to it, as appropriate; (b) the ecology of the clams in the plant (i.e., spatio-temporal distribution, growth, and reproduction); and (c) the relationship (s) between the numbers of clams obsel.ved and biofouling prob-lems, Conner, et al., ff. Tr. at 14-15, 137.

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78. In addition to monitoring and sampling for Corbicula, GSU will utilize instrumentation to detect the deterioration of flow (possible blockage by clams) across 4

heat exchangers in the Normal Service Water System, Conner, et al., ff. Tr. at 15, 138.

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79. The listing of the safety-related systems normally served by the Normal Service Water System, identified in Attachment 1, is correct and the instrumentation, parameters and frequency to be used - for each is - adequate, Conner, et a_1,., ff. Tr. at 15, 138.

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r l l q- 80. Operators will monitor the permanent instrumenta-(Q

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-tion daily and will record the readings on their Daily

! Operating Log. If it is determined that a particular I

reading has exceeded its prescribed limits, that reading

, will be brought to the attention of the Shift Supervisor, Conner, et al., ff. Tr. -at 15, 138.

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81. The Technical Staff . group will review the Daily Operating Logs on a periodic basis and perform trending to detect component fouling on a monthly basis for those components listed'in Attachment 1, Conner, et al., ff. Tr.

j. at 15-16, 139, 1

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j 82. Using the trending program, it will be possible to i

predict when any particular . component will. exceed its desired performance capabilities, Conner, et al., ff. Tr.

I at 16, 139.

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, 83. Upon receipt of an excessive in::trument reading or i

indication from the trending program of a component's degraded heat exchange capability, the component will be removed from service, opened, and visually inspected for evidence of Corbicula fouling, Conner, et al., ff. Tr.

, at 16, 139.

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-.,.,s,.---______..,,,--,_-,m,__e_....~,-,,_wmm--,.....,. ....e___.--.r.4r ,+- .- , , . - . , _ - , _ _ _ - , . ~ - . _ _ _ - . -

84. The tubesheets and water box dividers of the safe-ty-related heat exchangers within the service water system

. are generally not of copper-nickel material composition.

The exceptions, the RHR heat exchangers and the emergency diesel generator coolers, do not rely on differential pressure across the inlet and outlet water boxes for de-termining fouling, Conner, et al., ff. Tr. at 16, 140.

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85. The trending program utilizes a heat balance calculation to determine heat exchanger efficiency for these components, precluding a false indication of cooling water flow through the heat exchanger tubes upon flow blockage by Corbicula, Conner, et al., ff. Tr. at 16, 140.

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86. If evidence of fouling is noted, the system will be  !

, -flushed and the clams and clam debris will be removed prior to putting the component back in service, Conner, et al.,

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87. If any component is found to contain adult clams large enough to foul heat exchangers, the performance testing of all other components served by the service water system and listed in Attachment 1 will be conducted within i

seven days, Conner, ej g ., ff. Tr. at 17, 142.

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88. If performance parameters exceed their prescribed .

limits, the component (s) will be opened for inspection.

Additionally, the trending frequency will be increased, Conner, et al., ff. Tr. at 17, 142.

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89. Most adult clams will be excluded from entrainment f~ in the makeup water by wedge wire screens mounted on each suction pipeline, Conner, et al., ff. Tr. at 17, 143, 4

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4 90.

The clarifier for the removal of suspended matter 4

from the makeup water is expected to remove a majority,.if not all, of the Corbicula, Conner, et al., ff. Tr. at  !

17, 143.  !

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i 91. The continuous chlorination at the normal service O

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water pump discharge header will serve as yet another level i of prevention of infestation- by Corbicula, Conner, et al.,

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. 92. Operating experience will determine the appropriate

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chlorine feed rates. A total residual chlorine concen-tration of 0.6 to'O.8 ppm is initially targeted, Conner, ej

, M., ff. Tr. at 17, 143.

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93. The residual chlorine concentration will be  ;

O measured by instrumentation at the outlet of the service water system prior to mixing with the condenser circulating water flow to the cooling towers, Conner, et al., ff. Tr. *

at 17, 143.

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94. The monthly rotation of normally-operating redun-i dant safety-related components into service will ensure that the contained water will be periodically exchanged with freshly chlorinated water. Operation of intermittent flow

systems in this manner will prevent Corbicula from surviving and growing to fouling size, Conner, et al., ff. Tr.

at 17-18, 144.

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95. To avoid fouling problems following initial intro-duction of river water or following outages, the Normal a

I service Water System will be operated such that adequate i i

chlorine levels are maintained continuously during these periods, Conner, ej al., ff. Tr. at 18, 145.

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96. The monthly rotation of normally-operating redun-1.

dant safety-related components into service will further i assure that the plant will not be started (or restarted) with existing fouling unknown to the operators, Conner, et 4

al. , f f . T r . at 18, 145.

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Conclusions of Law O 1. These detection and prevention programs and the j J l facility's design provide reasonable assurance that GSU will l 1

be effective in controlling biofouling problems by Corbicula. i 1

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2. The issuance of an operating license to the Appli-2

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cants will not be inimical to the common defense and securi-

ty or to the health and safety of the public.

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3. Pursuant to 10 C.F.R. 52.760a and 10 C.F.R. 550.57,

.O the Director of Nuclear Reactor Regulation should be au-thorized to issue to the Applicants, upon making requisite findings with respect to matters not embraced in the Initial l i Decision, a license authorizing operation of River Bend  ;

. Station.

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