ML20115F103
| ML20115F103 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/08/1985 |
| From: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| To: | Martin T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| RTR-REGGD-01.023, RTR-REGGD-1.023 NUDOCS 8504190407 | |
| Download: ML20115F103 (5) | |
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BALTIMORE G AS AND ELECTRIC COMPANY P.O. B OX 147 5 B ALTIMORE. M ARYLAND 212o3 ARTHUR c. LUNOVALL,.JR.
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February 8,1985 U. S. Nuclear Regulatory Commisstion Docket Nos. 50-317 Region I 50-318 631 Park Avenue King of Prussia, PA 19406 License Nos. DPR-53 DPR-69 ATTENTION:
Mr. T. T. Martin, Director Division of Engineering & Technical Programs
SUBJECT:
Calvert Cliffs Nuclear Power Plant Radiological Dose Assessment Capability During Emergencies
REFERENCES:
(a) I&E Inspection Report 50-317/83-35; 50-318/83-35, Inspector Open Items 83-35-04 and 83-35-07 (b) Letter from A.
E.
- Lundvall, Jr.,
to T.. T.
Martin dated June 29,1984, Radiological Dose Assessment Capability During Emergencies Gentlemen:
Reference (a) requested information regarding the radiological dose assessment capability during emergencies at the Calvert Cliffs facility. This letter responds, in part, to the remaining Open items 83-35-04,83-35-05, and 83-35-07 from that report.
Item 83-35-04 requested written documentation on the technical bases and justification used for selection of the MIDAS dose assessment system. Attached as Enclosure (1) is the response to this item.
Concerning item 83-35-05, in part, we have determined that the use of strip chart recorders in the Control Room for the primary meteorological instruments is not required to meet the intent of Regulatory Guide 1.23, Rev.1 (proposed).
Item 83-35-07 requested a statement as to whether the primary and backup monitoring systems used in meteorological njonitoring conform to the guidelines established in Regulatory Guide 1.23, Rev.1 (proposed) and justification for any exceptions. This item was answered, in part, by reference (b) which addressed the primary meterological instruments. Attached as Enclosure (2) is our response to this item concerning the backup meteorological instrument,s.
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Mr. T. T. Martin
- February 8,1985
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- Should you have any further questions regarding this reply, we will be pleased to discuss
. them with you.
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- Very truly yours, AEL/MTF/ tim Enclosures-cc:.
D. A. Brune, Esquire G. F. Trowbridge, Esquire D. H. Jaffe, NRC T. Foley, NRC ih
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ENCLOSURE (1)
REPLY TO OPEN ITEM 83-35-04 OF 1&E INSPECTION REPORT 50-317/83-35; 50-318/83-35 NRC REQUEST A'ND BG&E RESPONSE Provide documentation to NRC Region I on the technical bases and justification used for selection of the MIDAS dose assessment system, as required by Appendix E to 10 CFR Part 50.
To address this requirement verify that:
REQUEST 1: Mesoscale transport of effluents from ground level and/or elevated releases can be adequately modeled. using the meteorological data available onsite,in the vicinity (up to 10 miles) of the plant.
RESPONSE 1:Mesoscale transport and diffusion of effluents are modeled using a straight-line, Gaussian plume dispersion model as described in NRC Regulatory Guide 1.145 (with the exception that the plume meander algorithm is not used). Ground level releases are made into the building wake. Initial dispersion due to wake effects is modeled using a virtual source correction model. The main vents at Calvert Cliffs (Units 1 and 2) are treated as mixed mode releases since they release from above the facade of the containments.
They also use Briggs jet plume rise to determine the final height of the plume. The associated entrainment factor is computed as described in NRC Regulatory Guide 1.111. MIDAS currently utilizes near real-time data (last 15-minute average) from either of two onsite meteorological towers in dose calculations. The primary tower has instrumentation at the 10 meter and 60 meter levels. The height of release from Unit I and 2 is about 48.1 meters. At Calvert Cliffs, using a mixed mode release the ground portion utilizes the 10 meter instrumentation and elevated portion of the 60 meter for dose calculation. Wind speed from the 60 meter level is extrapolated by the Power Law to the height of release (48.1 meters).
In the Calvert Cliffs area, the effect of the terrain (generally flat to gently rolling) and effects from the Chesapeake Bay, (addressed in NRC Inspection Reports 50-317/81-19-37, 50-318/81-18-37 and the Calvert Cliffs Updated Final Safety Analysis Report, are insignificant.
At the present time, no supplemental meteorological data from areas outside of Calvert Cliffs are being used in dose calculations. Data is available from the Patuxent River Naval Air Station on an as needed basis. There are no plans to use the data since a straight-line Gaussian model can only use one set of meteorologicalinputs.
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I-ENCLOSURE (1)
REPLY TO OPEN ITEM 83-35-04 OF I&E INSPECTION REPORT 50-317/83-35; 50-318/83-35 REQUEST 2: The physical height of the mixing layer can be adequately determined from onsite measurement and model statistics and is included in the dispersion calculation RESPONSE 2: The physical height of the mixing layer is not measured nor used in the dispersion analysis.
As discussed in (1) above this is not deemed necessary.
REQUEST 3: Diffusion rates are based on the most appropriate stability indicator (s).
RESPONSE 3: Vertical temperature difference is used to determine stability classification at Calvert Cliffs. MIDAS has the capability to use either delta temperature or sigma theta to determine atmospheric stability classification. No clear determination has been made as to which method, delta temperature or sigma theta, is most appropriate at sites such as Calvert Cliffs. Studies of atmospheric stability will be reviewed in the future to determine if the use of delta temperature is still appropriate.
REQUEST 4: Source characteristics are factored into the model.
RESPONSE 4: All pertinent source characteristics are factored into the MIDAS Class A model. These characteristics include mode of release, stack diameter and exit velocity, height and location of release, and building wake effects.
Wind speed from the meteorological tower is extrapolated to the release height via the Power Law to better estimate the wind speed at release height. In addition, the height of the plant area terrain is used in the dispersion calculation.
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4 ENCLOSURE (2)
REPLY TO OPEN ITEM 83-35-07 OF IAE INSPECTION REPORT 50-317/83-35; 50-318/83-35 t
NRC REQUEST State in a letter to Region I, whether the primary and backup monitoring systems used in the meteorological monitoring conform to the guidelines established in Regulatory Guide 1.23 Rev.1 (proposed), or justify any exceptions.
BG&E RESPONSE (IN PART)
Concerning backup monitoring instruments, we have determined that these instruments
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substantially conform to and meet the intent of Regulatory Guide 1.23, Rev. 1
- (proposed). We will use wind speed, wind direction and horizontal wind deviation (sigma theta) instruments to provide the specified backup information. There are three minor deviations from the literal statements in the Regulatory Guide and these are addressed below, however, we have determined that these deviations are insignificant.
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Regulatory Guide 1.23 specifies 10 meters as the. height at which wind speed and direction should be measured. Our backup instruments are located at a height of 38 meters. These instruments, (the lower of two original wind instrument sets),
were placed at 38 meters to avoid air flow influence from nearby obstructions at 10 meters.
In addition, measurements at 38 meters are more indicative of conditions at the plant vent (48 meters) than measurements at 10. meters.
Therefore, backup instruments at 38 meters are adequate to meet the intent of Regulatory Guide 1.23.
2.
Regulatory Guide 1.23 specifies that obstructions to air flow should ideally be lower than the measuring level to a horizontal distance of 10 times the measuring level height.
The containment structures are approximately 48 meters high and 230 meter.; away from the tower. This means that the 38-meter wind measurements are not " ideal" in that they might be influenced by the containment structures. This effect is not considered significant, however, as in operation there has been no discernable change ~ in the relative difference between the 38-and 60-meter measurements as wind direction moves through northeast (from containment to tower) for a given wind speed. Therefore, the backup instruments meet the intent of Regulatory Guide 1.23 as concerns obstructions to air flow.
3.
Regulatory Guide 1.23 specifies that wind instruments be located on a boom directed into the prevailing wind at least two tower widths from the tower. The backup instrument boom extends toward the northeast a distance of approximately eight feet (tower width varies from approximately 15 to 25 feet). The instrument boom is directed toward the northeast to most accurately measure onshore winds. Onshore winds would cause a potential release to drif t toward the larger population centers.
The tower itself is an open frame structure which minimizes influence on air flow.
Therefore, the placement of the backup instruments is such that, especially for onshore wind cor.altions, air flow is adequately measured.
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