NOC-AE-04001704, Response to NRC Request for Additional Information Regarding a Proposed Exigent Change to Technical Specification 3/4.7.7

Response to NRC Request for Additional Information Regarding a Proposed Exigent Change to Technical Specification 3/4.7.7

ML041040392
Person / Time
Site:	South Texas
Issue date:	04/07/2004
From:	Jordan T South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-04001704, STI:31718582
Download: ML041040392 (12)

Text

Nuclear Operating Company South TcwsItcdEkCbkaGnertiSbta0on POQ2os bur2sch sZ7 483 VaA April 7, 2004 NOC-AE-04001704 10CFR50.90 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Units 1 and 2 Docket Nos. 50-498 and 50-499 Response to NRC Request for Additional Information Regarding a Proposed Exigent Change to Technical Specification 3/4.7.7

Reference:

Letter from T. J. Jordan, STPNOC, to NRC Document Control Desk, dated March 18, 2004, "Proposed Exigent Change to Technical Specification 3/4.7.7" (NOC-AE-04001697)

STP Nuclear Operating Company (STPNOC) is submitting the attached information in response to NRC staff questions regarding the referenced proposed change to the STP Technical Specifications.

If there are any questions regarding the responses, please contact Mr. S. M. Head at (361) 972-7136 or me at (361) 972-7902.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on A-r;f -7 izoo+.

date

. Jran Vice President Engineering & Technical Services awh/

Attachments:

1. Response to Request For Additional Information Regarding Proposed Amendment To Technical Specification 3/4.7.7

2. Bases Inserts l ( b I 04001704 (RAI-exigent TS CRH).doc STI:31718582

NOC-AEO-04001704 Page 2 cc:

(paper copy) (electronic copy)

Bruce S. Mallett A. H. Gutterman, Esquire Regional Administrator, Region IV Morgan, Lewis & Bockius LLP U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 L. D. Blaylock Arlington, Texas 76011-8064 City Public Service U. S. Nuclear Regulatory Commission Michael K. Webb Attention: Document Control Desk U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike R. L. Balcom Rockville, MD 20852 Texas Genco, LP Richard A. Ratliff A. Ramirez Bureau of Radiation Control City of Austin Texas Department of Health 1100 West 49th Street C. A. Johnson Austin, TX 78756-3189 AEP Texas Central Company Jeffrey Cruz Jon C. Wood U. S. Nuclear Regulatory Commission Matthews & Branscomb P. 0. Box 289, Mail Code: MN116 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704

NOC-AEO-04001 704 Attachment 1 Attachment 1 Response to NRC Staff Questions

NOC-AE-04001704 Attachment 1 Page I of 6 Response to Request For Additional Information Regarding Proposed Amendment To Technical Specification 3/4.7.7 By letter dated March 18, 2004, STP Nuclear Operating Company (STPNOC) submitted a proposed amendment to the Technical Specifications (TSs) for the South Texas Project (STP)

Units 1 and 2. The Nuclear Regulatory Commission (NRC) staff has reviewed the information the licensee provided that supports the proposed TS changes. In order for the staff to complete its evaluation, the following additional information is requested:

1. The current licensing bases for the control room as described in the STP Technical Specifications and UFSAR states that the control room envelope is maintained at a minimum 0.125-inch positive water gauge with respect to adjacent areas. The proposed technical specification would allow positive pressure less than 0.125-inch water gauge with "appropriate compensatory measures." This proposed change represents a decrease in the pressure margin used to assure that unfiltered inleakage is minimized. In light that this decreased positive pressure condition may exist for approximately 18 months, there are no provisions to compensate for possible boundary degradation or variances in pressure conditions external to the control room boundary. The staff believes that compensatory measures are necessary to offset this decreased margin.

Please specify and justify the "appropriate compensatory measures" to be taken to offset this decrease in the pressure margin (for example, increased surveillance frequency, potassium iodide and/or self-contained breathing apparatus (SCBA)). If potassium iodide and SCBA are deemed appropriate measures to insure that GDC 19 is maintained, Regulatory Position 2.7.3 of NRC Regulatory Guide, 1.196, "Control Room Habitability at Light-Water Nuclear Power Reactors" provides a method for crediting these compensatory measures. If Regulatory Guide 1.196 is used please verify if these provisions are met. The staff believes that inclusion of these compensatory measures in the bases is necessary to provide reasonable assurance that these compensatory measures are "appropriate."

NOC-AE-04001 704 Attachment 1 Page 2 of 6 STPNOC Response:

The proposed technical specification change will allow STPNOC to operate under a degraded condition where the control room in not maintained at least 1/8 inches water gauge (in-wg) positive relative to adjacent areas. STPNOC will implement increased testing to provide assurance against further degradation of the boundary and variances in pressure conditions external to the control room boundary.

1. Within 60 days of approval of the proposed Technical Specification change and on a quarterly frequency thereafter, each train combination (e.g., A-B, B-C, or A-C) will be tested on a staggered test basis in the pressurization and recirculation cleanup mode of operation (i.e., the emergency mode).

2. If all test points for a train combination are greater than or equal to 1/8 in-wg positive pressure relative to adjacent areas, that train combination will be removed from the increased testing. However, retest of the removed combination will be required if rebalancing is performed on one of the other train combinations.

During the period where increased testing is required because some test points are positive but are not greater than or equal to 1/8 in-wg positive pressure relative to adjacent areas, the following personnel protective compensatory measures will be in place.

1. For degraded conditions across walls with sealed penetrations where the likelihood of any inleakage condition resulting from changing conditions between testing would be minimal (i.e., a few cfm), potassium iodide (KI) tablets will be credited as the compensatory measure.

2. For degraded conditions across doors where seals have the potential for degradation and the inleakage condition resulting from changing conditions between testing would likely be more than minimal, self-contained breathing apparatus (SCBA) will be credited as the compensatory measure.

In both cases, crediting the compensatory action will only be required until the surveillance demonstrates that the differential pressure is greater than or equal to 1/8 in-wg. Conditions with positive differential pressure, but less than 1/8 in-wg will be addressed in the Corrective Action Program.

The personnel protective measures of KI and SCBAs are deemed appropriate measures to insure that GDC 19 is maintained. The provisions of Regulatory Position 2.7.3 of NRC Regulatory Guide, 1.196 will be met.

The compensatory action will be incorporated into the Bases for TS 3.7.7 as shown in .

NOC-AE-04001704 Attachment 1 Page 3 of 6 Justification for compensatory measures Surveillance testing history demonstrates that control room pressure relative to adjacent areas does not significantly vary during 18-month surveillance intervals. Increased testing further compensates for the degraded differential pressure conditions across the control room boundary to provide assurance that further degradation would be detected in a timely manner.

The 1/8 in-wg relative pressure has provided adequate margin over an 18-month surveillance interval to compensate for possible boundary degradation or variances in pressure conditions external to the control room boundary. For areas such as walls where penetrations are sealed, any inleakage into the control room is expected to only be a few cfm. For areas that contain doors where the seals have the potential for degradation, the inleakage is expected to be greater than a few cfm.

The spectrum of postulated accidents in UFSAR Chapter 15 has been reviewed and the LOCA accident is the limiting operational accident with regards to unfiltered in-leakage effects on the dose to the control room operators. However, during an outage the fuel handling accident (FHA) is the limiting event.

A general revision of the LOCA analysis was recently performed and the ICRP-30 dose conversion factors were incorporated into the analysis. This revised analysis was applied to the dose and unfiltered in-leakage analysis pertinent to this TS change application.

For the LOCA, STP performed calculations to determine thyroid dose at various levels of inleakage. The estimated results are:

Unfiltered inleakage Estimated Radiological thbroid dose 30 cfm 30 rem 710 cfm 30 rem*

• Credit taken for use of KI tablets using a personnel protection factor of 10 Note these unfiltered in-leakage values do not include the 10 cfm assumed for door pumping action.

STP Technical Specification 3.9.4 allows fuel movement in the reactor containment building (RCB), with the personnel airlock (PAL) open and being capable of being closed within 30 minutes, after the fuel has decayed 95 hours0.0011 days <br />0.0264 hours <br />1.570767e-4 weeks <br />3.61475e-5 months <br />. After 165 hours0.00191 days <br />0.0458 hours <br />2.728175e-4 weeks <br />6.27825e-5 months <br /> of decay, fuel movement may occur with the personnel airlock and the equipment hatch open and being capable of being closed within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

NOC-AE-04001704 Attachment I Page 4 of 6 Additional analyses were performed to quantify the protection afforded by the use of KI during a fuel handling accident. The results are provided below.

Fuel Decay Dose Limit Allowable Unfiltered In-Time (hrs) Scenario (rem) leakage with KI (cfm) 95 FHA in FHB 17.5 5702 FHA in RCB 95 (30 minute PAL 27 3 920 closure) 165 FHA in FHB 17.5 775 FHA in RCB 165 (2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> PAL 273 920 closure)

1. 17.5 rem is used as a limit to keep the LOCA as the limiting control room accident. If the dose limit is increased to 30 rem, the allowable unfiltered inleakage with KI would increase.

2. If the dose limit were to be increased to 30 rem, the allowable unfiltered inleakage with KI would be greater than 710 cfm.

3. 27 rem is used since it was the limit used in the analysis, and Technical Specification submittal, as a basis for the required decay times in Technical Specification 3.9.4.

Therefore, for degraded conditions such as walls with sealed penetrations, KI tablets provide reasonable personnel protective measures against a postulated LOCA or Fuel Handling Accident to demonstrate adequate margin for conditions where the worst case inleakage is expected to only be few cfm.

Managing boundaries differently provides flexibility to correct different degrees of degraded conditions. SCBA usage has a protection factor of at least 100 for thyroid dose.

However, for most boundaries, SCBA usage is not a compensatory measure that is needed to ensure GDC 19 is met. Although SCBA usage is an adequate compensatory measure for limiting operator dose, it presents an increased challenge to the operator.

The increased test frequency and personnel protective measures described above provides reasonable management of degraded control room conditions so that the operators only need to take personnel protective measures commensurate with the condition.

NOC-AE-04001704 Attachment 1 Page 5 of 6

2. With these compensatory measures available for use in case of an accident provide an estimate of the maximum unfiltered inleakage allowable to meet GDC 19.

STPNOC Response:

Estimate of the maximum unfiltered inleakage allowable to meet GDC 19 with compensatory measures is described in response to Question 1. These estimates were calculated for a Loss of Coolant Accident, which is the limiting accident at STPNOC.

The calculations also demonstrate that the 30 rem beta skin dose limits are not exceeded.

The calculations were performed using the STP TRACI models.

3. Provide the measurement uncertainty of the measurements made for Surveillance Requirement 4.7.7.e.3 and state whether this uncertainty is included in surveillance.

If the uncertainty is not included justify exclusion of the uncertainty.

STPNOC Response:

The STP UFSAR Section 6.4.5.1.3 states the following regarding acceptability requirements for the surveillance measurement:

The result of the final leak test is accepted if the control room envelope makeup airflow does not exceed 2,000 fl3/min at a positive envelope pressure of S9.125-in wg. This criterion is based on a measuring accuracy of +/-I percent of full scale on pressure reading and +1-5 percent of full scale on airflow reading.

The differential pressure is currently measured using an instrument with a reference accuracy of +/-0.02 in-wg. The test methodology is to determine the pressure on each side of the control room boundary and this whole evolution is expected to be complete within 30 minutes so that the instrument uncertainties do not appreciably affect the differential pressure value. By using this methodology, the only uncertainty term that needs to be considered is the reference accuracy of the measuring device. Other uncertainties will cancel each other out.

While this 1/8 in-wg acceptance criterion includes a measurement uncertainty as stated in the UFSAR, the 1/8 in-wg number is considered a nominal value and it is therefore acceptable to not correct for instrument uncertainties. There are no regulatory requirements for applying instrument uncertainties and the criterion is ajudgement value to establish margin. There is not a technical basis for the application of a specific instrument uncertainty for this parameter.

However, the proposed Technical Specification change to accept "positive" differential pressure would allow substantially less margin and in this case, consideration of instrument uncertainties would be appropriate in determining if a measured value is positive. To account for instrument uncertainties, STPNOCs implementing procedure will consider a measurement to be positive only if it is greater than the accuracy of the

NOC-AE-04001 704 Attachment 1 Page 6 of 6 measurement process. The "nominal" 1/8 in-wg will continue to be acceptable for the Technical Specification surveillance.

4. State whether the most limiting points measured for the Component Test will be included in future 4.7.7e.3 surveillance tests. If these limiting points will be excluded justify the exclusion of these points.

STPNOC Response:

The limiting points for the Component Test will be included in the increased testing program described in the response to Question 1.

STPNOC expects to make air balance improvements to the control room envelope so that all measured points will be greater than or equal to 1/8 in-wg relative to adjacent areas. If these improvements result in providing assurance that some measured points would not become limiting, then STPNOC may revise the scope of the surveillance. The surveillance procedure revision process requires justification of any change with respect to the surveillance points.

5. Provide a justification that the current degraded condition does not invalidate your hazardous chemical assessments.

STPNOC Response:

STPNOC's hazardous chemical analyses demonstrate that neither onsite or offsite hazardous chemical sources within the vicinity of the control room would reach toxicity limits inside the Control Room Envelope within six minutes following nasal detection by operators. This meets the NRC Regulatory Guide 1.78 requirement that states operators should be able don breathing apparatus within two minutes. The hazardous chemicals are assumed to enter the control room environment via the normal control room ventilation flow path at a rate of 4000 cfm. No credit is taken for isolation of the ventilation system although manual isolation remains available to the operators for defense-in-depth. The normal ventilation flow exceeds any unfiltered inleakage with the ventilation system in the isolation mode. Therefore, unfiltered inleakage in this mode is not measured and is not incorporated into STPNOC's hazardous chemical assessment.

Since the function of the control room pressurization system is not to mitigate against hazardous chemical sources, the degradation of the 1/8 in-wg differential margin does not impact STPNOC's hazardous chemical assessments.

NOC-AE-04001 704 Attachment 2 Bases Inserts

NOC-AE-04001 704 Attachment 2 Page l of 2 As stated in the original application, the information below will be included in the TS Bases for TS 3/4.7.7 Control Room Makeup and Cleanup Filtration System. The information in bold face has been added as noted in the response to Question I of the RAI.

Surveillance Requirement 4.7.7.e.3 verifies the integrity of the control room enclosure, and the assumed inleakage rates of the potentially contaminated air. The control room positive pressure, with respect to potentially contaminated adjacent areas, is periodically tested to verify proper functioning of the Control Room HVAC. During the emergency mode of operation, the Control Room HVAC is designed to pressurize the control room to at least 1/8 inch water gauge (in-wg) positive pressure with respect to adjacent areas in order to prevent unfiltered inleakage. The Control Room HVAC is designed to maintain this positive pressure with two trains at a makeup flow rate of 2000 cfm. The frequency of 18 months is consistent with the guidance provided in NUREG-0800. If the surveillance results are less than 1/8 in-wg and the pressure differential is not positive, the surveillance requirement is considered not met and the appropriate action of TS 3.7.7 must be applied.

The surveillance includes a footnote allowing an evaluation of conditions where the differential pressure is positive but less than 1/8 in-wg. The measured positive relative pressure condition still assures that any leakage across this boundary location would be outleakage. Therefore, the functionality of the control room HVAC system is maintained with the degraded pressure condition within the envelope. The use of the footnote for a condition where the points are less than 1/8 in-wg is intended to be a temporary application until the points are restored to the design 1/8 in-wg in accordance with the corrective action program.

Compensatory actions may be applied based on the results of the evaluation provision of SR 4.7.7.e.3. The evaluation, including appropriate compensatory actions, must demonstrate that the dose limits of GDC 19 of Appendix A of 10CFR50 are met, including a 30 rem limit to the thyroid. If compensatory measures include self-contained breathing apparatus (SCBA) and potassium iodide (KI) tablets, then the requirements of Regulatory Position 2.7.3 of NRC Regulatory Guide, 1.196, "Control Room Habitability at Light-Water Nuclear Power Reactors" must be met.

The results of the evaluation for areas with differential pressure that Is positive but less than 1/8 In-wg and the appropriate compensatory action are as described below.

STPNOC performs increased testing as a compensatory action to provide assurance against further degradation of the boundary and variances In pressure conditions external to the control room boundary.

1. Within 60 days of approval of the proposed Technical Specification change that provided for compensatory action In SR 4.7.7.e.3., and on a quarterly frequency thereafter, each train combination (e.g., A-B, B-C, or A-C) will be tested on a staggered test basis in the pressurization and recirculation cleanup mode of operation (i.e., the emergency mode).

NOC-AE-04001704 Attachment 2 Page 2 of 2

2. If all test points for a train combination are greater than or equal to 1/8 in-wg positive relative to adjacent areas, that train combination will be removed from the increased testing. However, retest of the removed combination will be required If rebalancing Is performed on one of the other train combinations.

To account for Instrument uncertainties, a measurement is considered to be positive only if it is greater than the accuracy of the measurement process. The "nominal" 1/8 in-wg Is acceptable for the Technical Specification surveillance.

During the period where Increased testing Is required because some test points are positive but are not greater than or equal to 118 in-wg positive pressure relative to adjacent areas, the following personnel protective compensatory measures will be In place.

1. For degraded conditions across walls with sealed penetrations where the likelihood of any Inleakage condition resulting from changing conditions between testing would be minimal (i.e., a few cfm), potassium Iodide (KI) tablets will be credited as the compensatory measure.

2. For degraded conditions across doors where seals have the potential for degradation and the Inleakage condition resulting from changing conditions between testing would likely be more than minimal, self-contained breathing apparatus (SCBA) will be credited as the compensatory measure.

In both cases, crediting the compensatory action will only be required until the surveillance demonstrates that the differential pressure Is greater than or equal to 1/8 in-wg. Conditions with positive differential pressure, but less than 1/8 In-wg will be addressed in the Corrective Action Program.

The procedural infrastructure to apply the compensatory actions is in place. KI is available to the Control Room crews and SCBA units are staged and ready for use by Control Room personnel. STP's emergency plan implementing procedures require that personnel radiation exposure in the control room be monitored so that appropriate personnel protective measures will be taken by the operators during accident conditions.

Reference:

CREE 04-3148-34