ML20245F772
| ML20245F772 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 04/24/1989 |
| From: | Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 89-242, NUDOCS 8905020489 | |
| Download: ML20245F772 (8) | |
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VIHOINIA 15LECTHIC AND l'OWER OOMi%NY HICIIM ON D, VI H OINI A 2 0 2 61 '
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April 24, 1989 y
NUCLEAR United States Nuclear Regulatory Commission Serial No.89-242 Attention: Document Control Desk N0/SAH/acmR1 Washington, D.C. 20555 Docket Nos.
50-338 50-339-License Nos. NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 RESPONSE TO INSPECTION REPORTS 50-338,339/89-02 The pucpose of this letter is to provide to you a written statament detailing the ac'cion plan and estimated dates of. completion regarding reso.ution of ERF Appraisal findings referenced in Inspection Reports 50-338,339/89-02 dated March 24, 1989. This is being submitted in accordance with your request contained in the above inspection report.
The attachment provides the current status of 'each item in the subject inspection report requiring a response.. Section 1 of the attachment provides a -
description of those items which have been completed.
Section 2 describes those items which will be completed in the near-tenn, and Section 3 includes those areas requiring long-term corrective action.
Should you have any further questions regarding this matter, please contact us immediately.
V ry tru o
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/P df W. R. Cartwri t
Attachment cc:
U.S. Nuclear Regulatory Commission 101 Marietta Street, N.W.
Suite 2900 Atlanta, GA 30323 Mr. J. L. Caldwell g
NRC Senior Resident Inspector North Anna Power Station
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-l ATTACHMENT VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS'1 AND 2 DOCKET NUMBERS 50-338 and 50-339 IMPLEMENTATION STATUS OF REMAINING ERF APPRAISAL FINDINGS l
l APRIL 24, 1989 i
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IMPLEMENTATION STATUS OF REMAINING ERF APPRAISAL FINDINGS SECTION 1: COMPLETED ITEMS 1
Item 50-338,339/89-02-01:
Protecting the meteorological tower instrument power supplies from the effects of power surges caused by lightning strike.
RESPONSE
Required Engineering Work Requests have been completed to provide meteorological tower lightning protection.
2.
Item 50-338,339/89-02-02:
Repleeing the instantaneous meteorological data values available through the SPDS with time-averaged data, except where there is specific need for instantaneous or spot data.
RESPONSE
During t' e North Anna Power Station ERF Appraisal (NRC Inspect'in Report h
50-338,339/88-14, dated August 22, 1988),
the NRC recommended, as an enhancement item, that meteorological inputs regarding wind speed and direction be time averaged in order to facilitate reading of these values by plant operators directly from CRT displays.
An engineering. study has been performed which determined that the best method of performing this function is by using the filter factor function available on the ERFCS.
The filter factor changes recommended in this study have been implemented at North Anna. A 50% filter factor has been established for wind speed and direction related meteorological inputs, thereby minimizing the frequency of instantaneous changes and evenly displaying indications over time.
3.
Item 50-338,339/89-02-04:
Providing a preventive maintenance (PM) program for key emergency ventilation system components.
RESPONSE
Preventive Maintenance Procedures M-10-HV/M-1 and M-10-HV/M-4 have been revised to include periodic inspection and maintenance of the components in the LE0F and TSC HVAC systems.
I In addition, a system walkdown was performed to identi fy and correct improperly labeled equipment and provide local labeling of damper positions.
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.SECTION 2:
ITEMS TO BE COMPLETED NEAR-TERM 1.
Item 50-338,339/88-14-01:
Completion of resolution of differences in dose calculations between the RAD / MET Model and manual method defined in the' EPIPs.
RESPONSE
The differences between dose calculations performed by the RAD / MET model and EPIPs have been addressed by software changes in the RAD / MET model and currently reside on a " developmental" system.
As a result of these software
- upgrades, source code documentation is being revised and 1
independent verification and validation will be performed.
In addition, the applicable EPIPs will require revision and the EPIP reference document-will also be revised to reflect these changes.
Completion of these actions is scheduled for July 31, 1989.
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'l Additional dose assessment inconsistencies between the EPIPs and RAD / MET model were noted during the software upgrade.
These additional discrepancies, coupled with the enhancements and other deficiencies noted j
during the North Anna ERF Appraisal as well as an overview evaluation of j
the model through comparison of state-of-the-art Class A models, has i
resul ted in an alternate long-term approach to resolving the radiological i
dose assessment problems. This approach is further described in Section 3 (Long-Term Corrective Actions) of this' attachment.
2.
Item 50-338,339/88-14-02:
Completion of evaluation of validity of use of j
field monitoring data for calculating a source term and use of same in the protective action decision
- process, or in determining emergency classifications.
RESPONRE.
The source term (Ci/sec) calculations for Xe-133 and I-131 based upon field monitoring data were evaluated in EPIP 4.13, Offsite Release Assessment With Environmental Data.
This derivation is non-conservative because it algebraically inverts the Gaussian diffusion equation used to generate the X/Q which is then used to estimate the dose rate and dose calculations.
In addition, it is recognized that there is a degree of uncertainty in the use of field monitoring data to derive the source term during the early stages of an accident.
EPIP 4.13 will be revised to delete the back calculation of source term using environmental data.
This calculational capability will also be deleted from the RAD / MET model which is addressed in EPIP 4.27 l
for North Anna Power Station.
These procedure revisions will be implemented by July 31, 1989.
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Item 50-338,339/88-14-03:
Completion of revision to the EPIPs addressing l
dose assessment to include separate stability classes for vertical and horizontal diffusion.
I Adjunct item:
Providing support for a back-up method for estimating the j
vertical diffusion coefficient that does not involve sigma theta.
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RESPONSE
The existing methodologies for determining stability classes used in estimating diffusion coefficients are consistent with NRC staff guidance.
These include the primary method, delta T,
the vertical temperature difference, and the secondary method, sigma theta, the standard deviation of the wind direction.
Conversations with the Region II NRC staff indicated that the NRC emergency
.1 dose assessment code, referred to as RASCAL, will be available in 1989.
l The software uses the Delta T and Sigma Theta methods for determining stability classes as well as the Pasquill-Gifford-Turner (PGT) tables which 1
give stability classes as a function of wind speed and outdoor ' weather i
conditions for daytime and nighttime periods.
Based upon a review of the J
regulatory documents, the implementation of the RASCAL code for performing 1
dose assessments by the NRC, and discussions with the meteorological j
personnel in our Air Quality group, EPIP 4.10, Determination of X/Q, will d
be revised by July 31, 1989 to include the PGT tables for stability class l
determination which should be used upon failure of the Delta T and/or Sigma i
Theta system.
It has been determined that the RAD / MET model and the EPIPs do not require separate horizontal and vertical diffusion coefficients.
4.
Item 50-338,339/88-14-06: Completion of revision of TSC ventilation test procedure (1-PT-77.9)~ to test s) stem components, including system interlocks.
RESPONSE
While preparing to revise 1-PT-77.9, Technical Support Center (TSC)
Emergency Ventilation System In Place Leak Test On 1-HV-FL-100, to include testing of system components and interlocks, it was determined that discrepancies existed in applicable electrical schematic drawings. As a result, Station Design Engineering has been tasked with correcting these c'rawi ngs.
In order to provide corrected drawings, the design change that installed the TSC will be reviewed, the system will require a walkdown, and the drawings will then be revised.
The scheduled completion date for corrected drawings is June 1,1989.
1-PT-77.9 will be revised within 30 days of the completion of the corrected drawings to include testing of remaining TSC ventilation system components and interlocks.
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Item 50-338,339/89-02-03:
Developing a procedure to test the throw-over feature of the UPS buss.
RESPONSE
A periodic test procedure is currently under development to test-the throw-over feature of the TSC Uninterruptable Power Supply (UPS).
Thi s.-
,d procedure is ' scheduled to be approved by June 1,1989.
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SECTION 3:
LONG-TERM CORRECTIVE ACTIONS NOTE: A discussion of proposed corrective actions for the following four items will be provided in one overall response.
l 1.
Item 50-338,339/88-14-01:
Completion of resolution of differences in dose calculations between the RAD / MET Model and manual method defined in the EPIPs.
2.
Adjunct item to E0-338,339/88-14-02:
Modi fying the manual EPIP dose calculation method to run on a personal computer or a computer system separate from RAD / MET.
3.
Adjunct item to 50-338,339/88-14-02:
Conducting a more detailed comparison between RAD / MET and the Commonwealth of Virginia's dose assessment model j
following completion of the Commonwealth's proposed modifications of the model.
1 4.
Item 50-338,339/88-14-04:
Completion of modification of the RAD / MET model 1
to provide dose projection estimates at future plume positions.
RESPONSE
As noted in Inspection Reports 50-338,339/88-14 and 50-338,339/89-02, j
significant deficiencies have been identified regarding implementation of existing dose assessment methodology using the manual method (Emergency Plan Implementing Procedures) as well as the computerized method (RAD / MET model).
Though a number of these deficiencies have or will soon be rectified, as J
previously described in Sections 1 and 2 of this attachment, the items listed
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above have yet to be completely resolved.
While implementing programming changes to correct these deficiencies noted in i
Inspection Reports 50-338,339/88-14-01, additional inconsistencies between the EPIPs and RAD / MET model were noted.
These additional discrepancies, coupled with the enhancements and other deficiencies identified during the ERF Appraisal, prompted company management to direct the creation of a working group in November 1988.
The working group was tasked to evaluate the overall dose assessment program and recommend solutions that would make the calculations derived from either' the Emergenc (EPIPs) or Radiological / Meteorological-(RAD / MET) y Plan Implementing Procedures model essentially consistent with one another.
The following recommendations have been approved for implementation:
1.
Procure and install the Meteorological Information and Dose Assessment
" MIDAS" methodology (software and associated hardware) to l
System replace the existing RAD / MET model.
2.
Obtain EPIPs specific to the " MIDAS" methodology and reformat existing EPIPs.to reduce redundancy and closed loops, reflect implementation of I
the new system, ensure technical accuracy, provide concise instructions to the user, and automate for PC application.
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- 3. ~Upon implementation of items I and 2 above, conduct a detailed comparison between the " MIDAS" model and the Commonwealth of Virginia's dose assessment model (following completion of the Commonwealth's proposed modifications to their model).
These proposed enhancements are projected to be implemented by December 31, 1989.
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