ML20004D599
| ML20004D599 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/22/1981 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| A01645, A1645, IEB-81-03, IEB-81-3, NUDOCS 8106090564 | |
| Download: ML20004D599 (17) | |
Text
_ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
4 NORTHEAST UTILmES 1
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May 22, 1981 h.((.a 0o, g5c[./
Docket Nos. 50-245
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4 Mr. Boyce H. Grier, Director U.S. Nuclear Regulatory Commission Region 1 Office of Inspection and Enforcement 631 Park Avenue King of Prussia, Pennsylvania 19406
Reference:
(1)
- 3. H. Grier letter to W. G. Counsil, dated April 10, 1981, transmitting I&E Sulletin No. 81-03.
Gentlemen:
Millstone Nuclear Power Station, Unit Nos.1, 2 and 3 Resconse to I&E Bulletin No. 81-03 In Reference (1), the NRC staff requested that Northeast Nuclear Energy Company (NNECO) provide infornation with respect to flow blockage of cooling water to safety system components by Corbicula sp. (Asiatic Clam) and Mvtilus sp. (Mussel) at Millstone Unit Nos.1, 2 and 3.
In response to the Reference (1) requests, NNECO hereby provides the following informaeion.
Item 1 - Millstone Unit Nos. 1, 2 and 3 Determine whether Corbicula sp. or Mvtilus sp. is present in the vicinity of the station (local environment) in either the source or receiving water body.
If the results of current field =onitoring programs provide reasonable evidence that neither of these species is present in the local environment, no further action is necessary except for items 4 and 5 in this section for holders of operating licenses.
Response
NNECO is aware of the existence of Mytilus sp. (Mussels) in the vicinity of the Millstone Nuclear Power Station site.
Substantial consideration was given to the problem of =arine fouling prior to construction of Millstone Unit No. 1.
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-t-Corbicula sp. (Asiatic Clam) is a fresh water mollusk and, as such, is not found in the source or receiving water body for Millstone Unit No.
1, 2 and 3.
NNECO has contacted the purveyor of the station domestic water supply which among other uses, is the water source for fire protection systems. There is no evidence of the existence of Corbicula sp. in the domestic water supplied to the Millstone Nuclear Power Station.
Item 2 - Millstone Unit Nos.1 and 2 If it is unknown whether either of these species is present in the local environment or is confirmed that either is present, determine whether fire protection or safety-related systems that directly circulate water from the station source or receiving water body are fouled by clams or mussels or debris consisting of their shells. An acceptable method of confirming the absence of organisms or shell debris consists of opening and visually examining a representative sample of components in potentially affected safety systems and a sample of locations in potentially affected fire protection systems. The sample shall have included a distribution of components with supply and return piping of various diameters which exist in the potentially affected systems. This inspection shall have been conducted since the last clam or mussel spawning season or within the nine month period preceding the date of this bulletin.
If the absence of organisms or shell debris has been confirmed by such an inspection or another method which the licensee shall describe in the response (subject to NRC evaluation and acceptance), no further action is necessary except for items 4 and 5 of actions applicable to holders of an operating license.
Item 3 - Millstone Unit No s. I and 2 If clams, mussels or shells were found in potentially affected systems or their absence was not confirmed by action in item 2 above, measure the flow rates through individual co=ponents in potentially affected systems to confirm adequate flow rates i.e., flow blockage or degradation to an unacceptably low flow rate has not occurred.
To be acceptable for this determination, these measurements shall have been made within six months of the date of this bulletin using calibrated flow instruments.
Differential pressere (DP) measurements between supply and return lines for an individual omponent and DF or flow measurements for parallel connected individual coolers or components are not accaptable if flow blockage or degradation could cause the observed DP or be masked in parallel flow paths.
Other methods may be used which give conclusive evidence that flow blockage or degradation to unacceptably low flow rates has not occurred.
If another =ethod is used, the basis of its acceptance for this determination shall be included in the response to this bulletin.
If the above flow ratas cannot be measured or indicate significant flow degradation, potentially affected systems shall be inspected according to item 2 above or by an acceptable alternative method and cleaned as necessary. This action shall be taken within the time period prescribed for submittal of the report to the NRC.
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' Response to Items 2'and 3 The site fire protection system utilizes locally supplied domestic water as its source.
As was reported above, it has been determined that Asiatic Clams do not exist in this water source. With respect to mussels, the plant specific responses to Items 2 and 3 for. Millstone Unit Nos.1 and 2 are provided below.
Millstone Unit No.1 Millstone Unit No. I has experienced flow blockage of service water heat exchangers, cooled with sea water, by mussels. The service water system provides cooling to the following safety related systems:
o Diesel Generator o
Reactor Building Closed Cooling Water (R3CCW)
Turbine Building Secondary Closed Cooling Water (T3SCCW) o o
Emergency Service Water (ESW)
Flow blockage is routinely detected by monitoring heat exchanger cooling performance or through surveillance testing.
The ESW system flow is verified quarterly by a surveillance procedure.
The thermal performance of the RBCCW and T3SCCW systems are monitored on normal operator rounds. These heat exchangers are cleaned based upon their ability to maintain the cooling water at the desired temperature.
Variables include the number of service water pumps in operation, the heat load and the sea water inlet temperature. The thermal performance of the diesel generator heat exchanger is checked weekly during a one hour full load surveillance run.
Heat exchanger thermal performance criteria has been utilized satisfactorily at Millstone Unit No.1 to determine cleaning and inspection schedules for heat exchangers cooled by the service water system.
Millstone Unit No. 2 The service water system at Millstone Unit No. 2 supplies sea water cooling to the following safety related systems:
Reactor Building Closed Cooling Water (R3CCW) o o
Vital Switchgear Room Coolers o
Diesel Generator Heat Exchangers The RBCCW heat exchangers are monitored for blockage by measuring the differential pressures across the heat exchangers. The differential pressures are monitored on a shift bases by plant equipment operators.
Design flow is measured quarterly during in-service inspection testing.
The vital switchgear room coolers consisting of six heat exchangers were opened and inspected for mussels in accordance with Reference (1). One mussel was found in one heat exchanger. Flow through these coolers is not normally monitored.
Flow is investigated when a noted temperature rise occurs in the switchgear rooms.
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The diesel generator heat exchanger service water supply was modified during the past refuel outage. There now exists a full flow bypass around the heat exchangers.
Studies have shown that mussels do not attach themselves in high-flow pipes, therefore, the bypass line helps to minimize any mussel growth. Also installed during the modification was 'a duplex strainer which will capture any mussels prior to reaching the heat exchangers.
Flow through the heat exchangers is regulated by a flow control valve.
Low flow is annunciated both in the diesel room and through a common diesel alarm in the control room.
Therefore, an adequate flow rate is confirmed during each diesel run. The diesel generators are operated weekly.
Item 2 - Millstone Unit No. 3 If these organisms are present in the local environment and potencially affected systems have been filled from the station source or receiving water body, determine whether infestation has occurred.
Response
Systems which could potentially be affected by mussels at Millstone Unit No. 3 have not yet been filled with source or receiving water.
Item 4 - Millstone Unit No s. 1, 2 and 3 Describe methods either in use or planned (including implementation date) for preventing and detecting future flow blockage or degradation due to clams or mussels or shell debris.
Include the following information in this description:
a.
Evaluation of the potential for intrusion of the organisms into these systems due to low water level and high velocities
' L2 the intake structure expected during vorst case conditions.
b.
Evaluation of effectiveness of prevention and detection methods used in the past or present or planned for futur( use.
Response
The Millstone Environmental Lab has conducted extensive studies of mussels in the vicinity of the Millstone Nuclear Power Station.
The
=ussel program is discussed in detail in Attachment 1 and is applicable to Millstone Unit No s. 1, 2 and 3.
I Specific respones to Items 4a and b for the operating units are provided below.
Ar Millstone Unit No. 3 is not operational, Items 4a and b are not applicable.
Item 4a Millstone Unit No. 1 The intrusion of organisms into sea water cooling systems is currently under investigation by the Millstone Environmental Lab.
Millstone Unit No. 2 The location of the service water pump suction precludes the intrusion of organisms into the service water system during low water level and high velocities.
Item 4b Millstone Unit Nos.1 and 2 NNECO has determined that the current methods of detection of flow blockage by mussels are effective at Millstone Unit Nos.1 and 2.
An evaluation of the effectiveness of prevention methods is provided in.
Item 5 - Millstone Unit No.1 and 2 Describe the actions taken in items 1 through 3 above and include the following information:
a.
Applicable porrions of the environmental monitoring program including last sample date and results.
b.
Components and systems affected.
c.
Extent of fouling if any existed.
d.
How and when fouling was discovered.
e.
Corrective and preventive actions.
Item 3 - Millstone Unic No. 3 Describe the actions taken in items 1 and 2 above for construction permit holders and include the following information:
a.
Applicable portions of the environmental monitoring program including last sample date and results.
b.
Components and systems affected.
c.
Extent of fouling if any existed.
d.
How and when fouling was discovered.
e.
Corrective and preventive actions.
Response
The actions taken in items 1 through 3 for unit Nos.1 and 2 sud items 1 and 2 for unit NC 3 are provided in Attachment 1 and the resconses to items 1 through 4 above.
As requested in Reference (1) to assist the NRC in evaluatint the value/ impact of this bulletin, NNECO has determined that 150 man-hours wete expended in conduct of the review and preparation of the report required by the bulletin.
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We trust you find this information satisfactory to disposition the l
Reference (1) concerns.
E Very truly yours, e
NORTHEAST !!JCLEAR ENERGY COMPANY s
I sf1f$.A W. 'G. C6uns'i'l b
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Docket No s. 50-245 50-336 50--423 A01645 Millstone Nuclear Power Station, Unit Nos.1, 2 and 3 Mussel Program May, 1981
ATTACHttENT_ Page 1 of 10 MILLSTONE NUCLEAR POWER STATION - MUSSEL PROGRAM i
Prior to the construction of Millstone Nuclear Power Station (MNPS)
Unit 1, consideration was given to the problem of marine fouling.
This consideration emphasized:
1) recognition of the problem.
Based on past histories of thennal power plant water systems, control of bicfouling organisms was needed.
2) incorporation of control features in initial design and construction.
These features included provisions for chlorination and thennal back-washing, design of intake and discharge structures to minimize regions of stagnation and reduced water flow, and application of protective coatings to affected structures.
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3) proper equipment operation by plant personnel.
This was primarily a matter of establishing schedules and procedures for back-washing and chlorination, based on plant operating characteristics and the ecology and physiology of the fouling organisms.
On the basis of the pre-operation recommendations and the literature, by 1977 a schedule was established that called for intennittent chlorination of Units 1 & 2 and monthly thermal back-washing.
A NPDES permit allowed for continuous chlorination when ambient water temperature was between 45-55 F (ca. 7-13 C), presumably the period of maximum mussel settlement in Long Island Sound (Engle and Loosanoff 1944).
Despite the recommended schedule, the anti-fouling procedures were not totally effective; appreciable iussel growth occurred, necessitating manual cleaning operations.
Part of tha problem was that the procedures were established to reduce the settlement and growth of young post-larval stages, presumably the phase at which they are most vulnerable.
However, divers observed large clumps of adult mussels carried into the screenhouse by waves; these mussels could reattach themselves, and cause extensive fouling. Additional studies by the Millstone Environmental Lab of NUSCo concerning larval entrainment, plantigrade settlement, chlorine effectivuness, and h situ observations made by divers, as well as more recent literature pertaining to biofouling (see Bayne 1976 for review),
led to a reassessment of the biofouling program.
ATTACHMENT.
Page 2 of 10 The primary objectives of the mussel program were to monitor the abundance of mussel larvae in the water column throughout the year, to establish critical periods for settling, to detemine growth rates of mussels, and to assess the effectiveness of the MNPS anti-fouling procedures (in laboratory experiments and in, situ).
n Infomation on temporal and spatial distribution of mussel larvae in the water column has been collected primarily from entrainment and off-shore plankton samples collected by NUSCo biologists.
Our data indicate that spawning can occur over several months, with peaks in spring and autumn.
Larvae produced late in autumn grow very slowly through the winter, and delay metamorphosis into secondary plantigrades (final settlement stage) until the following spring, when water temperature 0
approaches 6 C (mid-April).
Larvae released as a result of the spring spawning period cMvelop more quickly, and can remain in the water column for as little as 2-3 weeks before reaching a settleable stage. Mussel plantigrades capable of settling pemanently as members of a fouling community are present in the water column throughout most of the year (Figure 1).
Data pertaining to mussel settlement patterns have been collected from a variety of sources; from reports by other researchers, and from a number of studies by NUSCo biologists, including intertidal surveys, exposure panel studies, and deployed settlement ropes.
As reported in the literature, the major settlement period varies widely between locales, and between years (Engle and Loosanoff 1944; Freeman and Dickie 1979; Kajihara and Oka 1980).
Part of the variability is due to fluctuations of planktonic larvae as noted above, and part is due to the behavior of the settling plantigrades; they are selective in their choice of settling sites, and can delay pemanent attachment for several months.
Primary settlement occurs on a variety of filamentous substrata (algae, seagrasses, etc.), and the plantigrades can detach and reattach themselves many times before secondary settlement occurs on solid substratum (Maas Geesteranus 1942; DeBlock and Geelen 1958).
In our area, the majority of secondary settlement takes place in spring and early summer but newly settled spat have been found throughout the year.
l
f ATTACH."ENT Page 3 of 10 '
f After settlement, growth is also extremely variable; other researchr.rs have reported yearly growths as high as 80 mm and as low as 1 mm/yr, depending on a variety of environmental conditions (Holmes 1970; Kajihara e t., a. l 1978).
In an attempt to relate growth rate to these environmental t
conditions, in early 1979 the NUSCo lab initiated a series of experiments.
The settlement ropes mentioned above were suspended vertically in the Unit 1 screenhouse, upstream and downstream of the traveling screens in t
two of the intake bays.
On each of the four ropes, three nylon mesh bags were tied, at each of three depths (1, 5, and 9 m below MLW); 25 young mussels of known size (around 15 mm) were placed in each bag.
Two additional sets of two mussel bags each were used as controls; one set was suspended one meter below a bouy located in Niantic Bay, in front of the Unit 1 screenhouse, the other was in Jordan Cove, from the Environmental Lab dock (1 m below MLW). The environmental parameters, qualitatively tested, were:
1) light.
Both sets of control mussels were exposed to ambient light conditions, and downstream mussels were kept in almost l
total darkness.
Light intensity in the upstream bays was intennedi ate.
2) water velocity.
Values for this parameter were high in the screenhouse (up and down stream), low at the dock (JC) and intermediate at the bouy (NB).
3) depth. Mussels in the screenhouse were obviously growing at three depths.
Additionally, mussels in the screenhouse were exposed to intennittent chlorination. The settlement ropes and mussel bags were removed prior to each themal back-wash, and replaced after measurement.
Results of the study are presented in Figures 2 & 3.
No differences in growth rates were attributed to depth (Figure 2),
growth was consistent throughout the water column. As shown in Figure 3, no difference occurred between stations exposed to low and intemediate water velocities (Jordan Cove vs Niantic Bay) or between stations with low and intennediate light levels (down vs upstream).
Overall differences between the intake and control mussels might be due to a combination of the two factors, or to a slight inhibitory effect of chlorine (Coulthard 1929; Berner 1935; White 1966; Holmes 1970).
High water velocity has
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ATTACHMENT ~ Page 4 of 10 been reported to retard growth (Harger 1970; Kastendiek unpublished),
but it is unlikely that current spee'd in the screenhouse was high enough a be deleterious.
The effect of temperature on growth rate may be inferred from the relatively high rates in summer months at all stations, and low rates in winter (Coulthard 1929; Dare 19'75).
Further evidence comes from observations made in the discharge quarry, where water temperatures average 10 - 15 C above ambient when the power plants are in operation.
Here, a dense settlement of plantigrades can occur in late autumn and winter (again f
indicating the presence of larvae throughout the year).
Growth is very, rapid through spring, but by early summer water temperature in the 0
quarry approaches 25 0 and growth rate decreases (ambient water temperature, O
meanwhile, is ca. IS C, and the period of maximum growth for mussels outside the discharge is beginning).
By late summer, temperature in the quarry exceeds 27 C, and total mussel mortality results; this lethal -
limit (Wells and Gray 1960; Read and Cumming 1967; Lutz and Hess 1979) is not reached in ambient water.
The mussels in the screenhouse grew more slowly. than did the controls, but mortality schedules were similar, indicating that intennittent chlorination is not an effective deterrent to mussel fouling (cf. Lewis 1964; James 1967).
This is corroborated by lab experiments, which show that intennittent chlorination does not have a significant effect on mortality, whether used alone or in conjunction with heat treatment.
p Chlorination may be useful for controlling growth of bacterial slime on surfaces (MRI 1980), but is not an effective mussel control procedure (at least in the concentrtion and schedules used here).
Present intennittent chlorination schedule for Unit 1 is:. simultaneous treatment of all five intake bays (including circulating-and service water systems), nine cycles per day,15 minutes per cycle.
For Unit 2:
sequential treatment of all four intake bays (one hour each), with separate simultaneous treatment of the service water system (four hours), three cycles per day.
For both units, injection concentration is adjusted to maintain a 0.1 mg/ liter concentration of free available chlorine residual at the condenser water box outlets.
To summarize the findings to date, average growth rate for mussels with an initial sii:e between 5 - 20 mm is ca. 30 mm/yr. with a maximum 9
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V ATTACHNENT Page 5 of 10 rate of 8 mm/mo in the summer.
On this basis, the frequency of back-washing procedures can be reduced fran 12 to 6 times per year, spaced as far as 3 months apart in winter and 6 weeks apart in summer.
On this schedule, mussels can be effectively controlled within the intake structure, wherever they can be exposed to the elevated tenperatures for a long enough time.
Present back-washing procedures for both units call for mussel cooking at 100 F (ca. 45 C) for 20 minutes, monthly for Unit 2 and six times per year for Unit 1.
This time / temperature regime has been shown to be effective in causing complete mussel mortality (Chadwick ef ;].
1950;StockandStrachan1977).
Inspections made by NUSCo divers to assess the effectiveness of anti-fouling procedures show that the necessary tenperatures can be reached in the pump bays of the circulating water system of Unit 1 (bays A-0).
The service water system cannot be thermally back-washed, so continuous chlorination and manual removal might be needed for mussel-control in E bay.
Most of the irt situ experiments and observations were made at MNPS Unit 1; the source of water is the same for Unit 2 (and for Unit 3 ar-well, under construction), so we assume that our conclusions are applicable to all three units.
Inspections of the screenhouses following back-wash procedures are scheduled, and visual inspection of other components of the water systems are made when possible.
NUSCo biologists are continuing studies into the ecology and physiology of mussels.
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Density of mussel plantigrodes in water column vs. time.
1978 - 1980 E
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MAY JUNE JULY AUG Figure 2.
Effect of depth on mussel growth, May 1979 - Aug.1980 (16ne 1 - shallow, Zone 2 - intermediate, Zone 3 deep).
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MAR MAY JUNE JULY AUG Figure 3.
Mussel growth, control and experimental stations vs. time, May 1979 - Aug. 1980.
ATTACHMEMI Page 9,of 10 REFERENCES CITED Bayne,8.L.(ed.).
1976. Marine mussels: tneir ecology and physiology.
International Biological Programme:
- 10. Cambridge University Press, Cambridge, UX.
506p.
Berner, L.
1935.
La reproduction des moules conestibles (Mytilus edulis L. et M. galloprovinciallis lmk.) et leur repartition geographique.
T Bulletin de I Institute Oceanographique, Monaco.
680:1-8.
Chadwick, W.L., F.S. Clark, and D.L. Fox.
1950.
Thennal control of marine fouling at Redondo Stream Station of the Southern California Edison Company.
Trans. Amer. Soc. Mech. Eng.
72:127-131.
Coulthard H.S.
1929. Growth of the sea mussel.
Contr. Can. Biol.
Fish. 4:123-136.
Dare, P.J.
1976.
Settlement, growth and production of the mussel, Mytilus edulis L., in Morecambe Bay, England.
Fish. Invest. Series II.
28; l-23.
DeBlock, J. W. and H. J. Geelen.
1958.
The substratum required for the settling of mussels (Mytilus edulis L.) Archs. neerl. Zool. Jubilee volume:
446-460.
Engle, J.B. and V.L. Loosanoff.
1944 On season of attachment of Mytilus edulis L. Ecology, 25:433-440.
Freeman, X.R. and L.M. Dickie.
1979. Growth and mortality of the Blue Mussel (Mytilus edulis) in relation to environmental indexing.
J.
Fish. Res. Board Can. 36:1238-1249.
Harger. J.R.E.
1970.
The effect of wave impact on some aspects of the biology of sea mussels.
- Veliger, 12:401-414 Holmes, N.
1970. Mussel fouling in chlorinated cooling systems.
Chem.
& Ind.
1970:1244-1247.
James, W.G.
1967. Mussel fouling and use of exomotive chlorination.
Chem. & Ind.
1967:994-996.
Kajihara, T. and M. Oka.
1980.
Seasonal occurrence of marine mussel plantigrades in Tokyo Harbor. Bull. Japan.
Soc. Sci. Fish.
46:145-148.
- Kajihara, T., Y. Ura and N. Ito.
1978.
The settlement, growth and mortality of mussel in the intertidal zone of Tokyo Bay.
Bull.
Japan. Soc. Sci. Fish.
44:949-953.
Xastendiek, J. unpublished.
Detection of plant (nuclear generating station) induced effects as detected by experimental benthic populations.
6
ATTACHMENT, Paga 10 of 10 Lewis, B.G.
1964 Water flow and marine fouling in culverts; a review of the literature up to 1962. Central Electricity Generating Board Research and Development Department. Laboratory Memo.
RD/L/M60/64.
Lutz, R.A. and C.T. Hess.
1979.
Biological and radiological analysis of the potential of nuclear power plant effluent waters for shellfish cultu re. pp. 109-138.
in:
Power Plant Waste Heat Utilization in Aquaculture (eds. B.L. Godfriaux, A.F. Eble, A. Famanfamaian, C.R. Guerra and C.A. Stevens). Allenheld, Osmun and Co., Montclair, N.J.
266p.
Maas Geesteranus, R. A.
1942. On the fomation of banks by Mytilus edulis L. Archs. neerl.Zool.
6;283-325.
l Marine Research, Inc.1980.
Selected Alternatives to Conventional L
Chlorination.
Electric Power Research Institute, Inc. 97p.
Read, K.R.H. and K.B. Cumming.
1967.
Themal tolerance of the bivalve molluscs Modfolus modiolus L., Mytilus edulis L. and Branchidontes demissus Dillwyn.
Comp. Bioenen. Physiol.
22:149-155.
Stock, J.N. and A.R. Strachan.
1977.
Heat as a marine fouling control program at coastal electric gener3 ting stations, pp. 55-62.
in:
L. Jensen (ed.)
Biofouling Control Procedures. Dekker Inc., New York.
Il3p.
Wells, H.W. and I.E. Gray, 1960 The seasonal occurrence of Mytilus edulis on the Carolina coast as a result of transport around Cape Hat'. eras. Biol.
[
Bull., Mar. Biol. Lab. Woods Hole, Mass.
119:550-559.
[
White, W.R.
1966.
Effect of low-level chlorination on mussels at Poole Power Station. Central Electricity Generating Board Research and Development j
Department Laboratorf Note RD/L/N17/66.
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