ML090910462
| ML090910462 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 04/01/2009 |
| From: | Wang A Plant Licensing Branch IV |
| To: | David Bice, Brooke Clark Entergy Operations |
| Wang, A B, NRR/DORL/LPLIV, 415-1445 | |
| References | |
| TAC ME0125 | |
| Download: ML090910462 (3) | |
Text
From:
Alan Wang Sent:
Wednesday, April 01, 2009 1:23 PM To:
David Bice; Bob Clark Cc:
Susan Lent; Janet Burkhardt; Summer Sun
Subject:
ANO-2 Request for Additional Information Regarding RCS Flow Verification License Amendment Request (ME0125)
By letter dated November 13, 2008, Entergy requested an amendment to the Arkansas Nuclear One, Unit 2 (ANO-2) technical specifications (TS). The proposed change would modify TS 3.3.1.1, "Reactor Protective Instrumentation," specifically Table 4.3-1 and associated noteds 7 and 8 to clarify and streamline reactor coolant system flow verification requirements associated with departure from nucleate boiling ratio (DNBR) reactor trip signal. The NRC staff has reviewed the November 13, 2008, request and has determined that we require additional information to complete our review. A request for additional information is enclosed. This request was discussed with Robert Clark of your staff on April 1, 2009, and it was agreed that a response would be provided within 60 days of receipt of this email.
- 1. Paragraph 4 on page 2 to Attachment 1 of letter dated November 13, 2008, indicates that the calorimetric method can be susceptible to the effects of temperature stratification of fluid in the reactor coolant system (RCS) hot-leg. It claims that these effects will result in calorimetric flow measurements being overly conservative as compared with the COLSS indicated flow rate.
(a) Discuss the RCS hot-leg temperature measurements that are used for determining the calorimetric flow rate. The information should include a discussion of locations and numbers of temperature probes for hot-leg temperature measurements, and method of the hot-leg temperature determination.
(b) Provide a discussion with applicable temperature measurement data to substantiate the claim that the calorimetric measured flow rate is overly conservative as compared with the COLSS indicated flow rate. The information should include a typical set of hot-leg temperature measurements that show temperature stratification, and a discussion to distinguish effects of uncertainties of RCS hot-leg temperature measurements and temperature stratification phenomena on the calorimetric flow rate determination. Also, quantify the conservatism in terms of a power level reduction in meeting the safety limit DNBR at a lowest value of the measured calorimetric flow rate.
- 2. Paragraph 4 on page 3 indicates that the licensee has performed for ANO-2 validation of the calibration constants using manufactures reactor coolant pump (RCP) head curves, and validated calorimetric flow measurements (from early cycles less affected by flow streaming). It claims that the validation can be used as a one-time effort to qualify the COLSS indicated flow as a wholly independent calibration standard.
(a) Explain the term, validated calorimetric flow measurements (from early cycles less affected by flow streaming). Does the term imply that the flow streaming effects will increase as fuel cycles increase? How is it determined that the calorimetric flow measurements are less or more affected by flow streaming phenomena? Discuss the validation steps and provide the results of validation with information used for validation, including RCP head curves
with derivations of the associated uncertainties that define the RCP head curve bands, and calorimetric flow measurements with rationale to support that the measurements used are those of less affected by flow streaming at early fuel cycles.
(b) Justify that the validation performed for ANO-2 is adequate to support the licensees claim that the COLSS indicated flow can be used as a wholly independent calibration standard over the entire operating temperature and pressure range for an extended period of RCP operating time. In addition, the licensee should satisfactorily address the following concerns - (i) the COLSS indicated flow rate is determined using the RCP head curves, which are developed on a specific testing configuration, temperature and pressure condition.
The RCP curves may be changes for plant configurations, temperature and pressure conditions that are different from that used in determining the RCP head curves, (ii) the other parameter used to determine the COLSS indicated flow rate is the RCP differential pressure (delta-P), which may be a very sensitive parameter to the RCP flow rate in a certain range of RCP head curves, i.e., a small uncertainty in the delta-P measurement may introduce a significant uncertainty in predicting RCP flow rate, and (iii) the RCP heads may be degraded through a long period of operating time.
(3) Describe the uncertainty analysis and provide the associated results that account for process uncertainties, instrumentation uncertainties and the uncertainty associated with the onetime adjustment of the COLSS flow algorithm constants indicated in paragraph 4 on page 3.
Justify that the determined uncertainties are bounding values that adequately include the uncertainties discussed in above RAI 2.(2), and are applicable to the entire operating temperature and pressure range for an extended period of RCP operating time.
E-mail Properties Mail Envelope Properties (419623E8C7444444BF132DA3AE69EDA219B9C51EC3)
Subject:
ANO-2 Request for Additional Information Regarding RCS Flow Verification License Amendment Request (ME0125)
Sent Date: 4/1/2009 1:22:48 PM Received Date: 4/1/2009 1:22:48 PM From: Alan Wang Created By: Alan.Wang@nrc.gov Recipients:
DBICE@entergy.com (David Bice)
Tracking Status: None RClark@Entergy.com (Bob Clark)
Tracking Status: None Susan.Lent@nrc.gov (Susan Lent)
Tracking Status: None Janet.Burkhardt@nrc.gov (Janet Burkhardt)
Tracking Status: None Summer.Sun@nrc.gov (Summer Sun)
Tracking Status: None Post Office:
HQCLSTR02.nrc.gov Files Size Date & Time MESSAGE 13377 4/1/2009 Options Expiration Date:
Priority: olImportanceNormal ReplyRequested: False Return Notification: False Sensitivity: olNormal Recipients received: