ML14191A354

Forwards Request for Addl Info Re Resistance Temp Device (RTD) Bypass Sys Removal,Per 880726 Request & 880727 & 0913 Meetings

ML14191A354
Person / Time
Site:	Robinson
Issue date:	09/23/1988
From:	Lo R Office of Nuclear Reactor Regulation
To:	Utley E Carolina Power & Light Co
References
TAC-68988 NUDOCS 8809290267
Download: ML14191A354 (6)

Text

DISTRIBUTION NRC PDR Local PDR September 23, 1988 PD21 r/f S. Varga (14E4)

G. Lainas E. Adensam Docket No. 50-261 P. Anderson R. Lo OG C Mr. E. E. Utley E. Jordan (MNBB 3302)

Senior Executive Vice President B. Grimes (9A2)

Power Supply and Engineering &

H. Balukjian (8E23)

Construction ACRS (10)

Carolina Power & Light Company P. 0. Box 1551 Raleigh, North Carolina 27602

SUBJECT:

H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 -

RTD BYPASS SYSTEM REMOVAL (TAC NO. 68988)

Per your request by letter dated July 26, 1988 and meetings on July 27 and September 13, 1988, we are proceeding with the review of the subject issue.

In order for us to complete our review, please respond to the enclosed.

questions.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, 0MB clearance is not required under P.L.96-511.

Sincerely, Ronnie H. Lo, Senior Project Manager Project Directorate 3-1 Division of Reactor Projects I/I

Enclosure:

Questions on Bypass System cc w/enclosure:

See next page r

88309290267 860923 PDR ADOCK 05000261 OFC

LA:P R:PM:PD21:DRec:D:t PR NAME PAn

RLo:clh DATE : 9/6/889 9/0 /88 9/5/88 OFFICIAL RECORD COPY :

2:

Mr. E. E. Utley Carolina Power & Light Company H. B. Robinson 2 CC:

Mr. R. E. Jones, General Counsel Mr. Dwayne H. Brown, Chief Carolina Power & Light Company Radiation Protection Branch P. 0. Box 1551 Division of Facility Services Raleigh, North Carolina 27602 Department of Human Resources 701 Barbour Drive Raleigh, North Carolina 27603-2008 Mr. McCuen Morrell, Chairman Darlington County Board of Supervisors Mr. Robert P. Gruber County Courthouse Executive Director Darlington, South Carolina 29535 Public Staff - NCUC P.O. Box 29520 Mr. H. A. Cole Raleigh, North Carolina 27626-0520 Special Deputy Attorney General State of North Carolina Mr. C. R. Dietz P.O. Box 629 Manager, Robinson Nuclear Project Raleigh, North Carolina 27602 Department H. B. Robinson Steam Electric Plant Mr. D. E. Hollar P. 0. Box 790 Associate General Counsel Hartsville, South Carolina 29550 Carolina Power and Light Company P.O. Box 1551 Raleigh, North Carolina 27602 U.S. Nuclear Regulatory Commission Resident Inspector's Office H. B. Robinson Steam Electric Plant Route 5, Box 413 Hartsville, South Carolina 29550 Regional Administrator, Region II U.S. Nuclear Regulatory Commission 101 Marietta Street Suite 2900 Atlanta, Georgia 30323 Mr. R. Morgan General Manager H. B. Robinson Steam Electric Plant Post Office Box 790 Hartsville, South Carolina 29550 Mr. Avery Upchurch, Chairman Triangle J Council of Governments 100 Park Drive Post Office Box 12276 Research Triangle Park, NC 27709

REQUEST FOR ADDITIONAL INFORMATION H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT 2 REGARDING RTD BYPASS SYSTEM REMOVAL

1. In Table 2.1-1 of Attachment 4 (WCAP-11889) of Reference 1, the response time parameters for the RCS temperature measurement are presented for both the existing RTD bypass system (old system) and the proposed system (new system).

The new system, which has the bypass system removed, uses fast response thermowell RTDs manufactured by WEED Instruments Inc.

Adding the times given in Table 2.1-1for the components, the system response time is 5.0 seconds for the old system (Rosemont RTD) and 4.75 seconds for the new system. However, a footnote explains that you cannot simply add all the response time parameters because of transfer functions which have different forcing functions as inputs. Since it is a staff position that the RTD response time and surveillance schedule (as it affects the overtemperature delta T and overpressure delta T) needs to be addressed in the plant Technical Specifications, the following information is needed for our evaluation:

a. What RTD response time in seconds was used for the FSAR Chapter 15 accident analyses for the hot and ccld leg RTDs for transients depending on cvertemperature delta T (as performed in the ANF-88-094 report) and overpower delta T trips. What is the expected value of the RTD system response time? What data supports these response time values?

b. If total system response time data is not available, discuss the supporting data for each of the components of the total response time and how a bounding value for the total response time is derived.

Include each of the elements listed in Table 2.1-1 as well as a discussion of the effects on response time of the scoop and the gap between the scoop and the WEED RTD.

2.

You have stated that your WEED RTD is similar to other WEED RTDs installed at other plants. However, it is noted that two other plants that are using WEED RTDs have quoted "total response" times that are 1.25 to 3 seconds longer than for the H. B. Robinson plant. Their combined "RTD/thermowell" response times excluding electronics are 0.25 to 2.5 seconds longer than for the H. B. Robinson plant. How do you account for the faster response times for the H. B. Robinson plant? Does the H. B.

Robinson plant have a design difference to account for a faster RTD response time measurement than at other plants?

3. Regarding the problem of drift of the RTD response time identified in NUREG-0809 (Reference 2), describe (a) the method(s) for checking RTD response time after installation, (b) the frequency of checks and (c) the safety allowance or other methods to provide assurance that the response times do not drift outside acceptable limits between the required 18-month checks.

4. In Section 3 of Attachment 3 (ANF-88-094), you state that three FSAR Chapter 15 limiting DNBR events were found which trip on the over temperature delta T reactor protection feature. These are:

(1) loss of load-MDNBR case, (2) uncontrolled Control Rod Bank Withdrawal from Full PGwer; and (3) Dropped Full Length RCCA. The accompanying transient plots show a number of parameters (power, temperature, volume, etc) vs time.

Please also provide plots of DNBR vs time for these accidents. Also, discuss why overpower delta T trip related events are not impacted by the change in RTD response time.

5. In Section 1.2.1 of Attachment 4 of Reference 1 (WCAP-11889), it was stated that because of interference, one of the three RTDs in each of loops A and B will have a changed position and will be located downstream from the other RTDs. Also, as shown in Figure 1.2-3 of WCAP-11889, these RTDs are shown as not being placed in a scoop as the other RTDs are.

Please provide the dimensions that locate both the downstream and circumferential location of these displaced RTDs in relation to the others.

Will the emersion depth be the same as the others which are in scoops?. What will be the relative affect of riot having these RTDs in scoops, as the others are, on the response time and accuracy of the reading? What data supports the response time and accuracy of the RTDs for this configuration?

6. Provide the value of the latest indicated RCS flow measurement for the H.

B. Robinson Unit 2 plant in lb/hr and gpm and also the value for the thermal design flow (TDF) in lb/hr and gpm. What is the current flow measurement uncertainty value?

7. In Section 3.1 of WCAP-11889, there is reference to using standard Westinghouse methodology previously approved for the flow measurement uncertainty analysis. Please provide the reference for the methodology and also indicate if the H. B. Robinson analysis has any deviations from this methodology.

8. A flow measurement uncertainty analysis was presented in WCAP-11889 for the H. B. Robinson plant in which the uncertainties of the new WEED RTDs was factored into the analysis. However, the effect of the uncertainty due to the readings from cold leg elbow taps was omitted in arriving at the final uncertainty value. It is understood that verification is made of the RCS flow by a calorimetric heat balance performed after return to full power operation following a refueling shutdown. At that time, the cold leg elbow tap pressure drop indication is taken as the corresponding flow reading. Because the cold leg elbow tap reading is subject to additional drift and other uncertainties, it is usual (as performed for your Shearon Harris plant) to include these additional uncertainties in the flow measurement uncertainty analysis.

Please provide a flow measurement uncertainty that includes the effect of cold leg elbow tap uncertainty. Also, no mention was made of the uncertainty for feedwater venturi fouling.

It is a staff position that a 0.1% venturi fouling penalty should be added unless the venturi tubes are cleaned at each refueling before the precision heat balance is made and that the total flow measurement uncertainty should also be included in the plant Technical Specifications. The uncertainty factor can be placed either in a section addressing F delta H or a section pertaining to DNB parameters.

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9. The calibration of the RTDs is performed before the calorimetric heat balance at each refueling. It is understood that this is by a cross calibration method in which it is assumed that variation occurs in a random manner from the original calibration from the manufacturer.

Therefore, the mean value is assumed to be the correct value. However, over a 40 year life, the RTDs may drift in one direction. One manufac turer has indicated a 1F drift in five years. It is noted that several references indicate that although platiunum RTDs are quite stable, there is evidence of drift (Refs. 2. 3, and 4).

How is the original calibration accuracy of the RTD established? How will you be able to tell if there is unacceptable drift in one direction and what steps will be then taken?

10.

Your new method of obtaining the hot leg temperature differs from the previous method. In the previous method, the flow in each hot leg was sampled from the scoops in the pipe cross section.

This sampled flow was measured in a mixing plenum to obtain an average temperature value. Your present method replaces the sampled flow from a scoop with a single temperature measurement of the scoop flow which is used to be equivalent to the former sampled flow value. Please indicate how you plan to check and confirm the accuracy of this new hot leg average temperature measure ment method (new system) against the former RTD bypass system method (old.

system).

The staff should be informed of the results of such a test.

11.

In Tables 15.2.1-2, 15.4.2-2 amd 15.4.3-2 of ANF-88-094, you tabulate the sequence of times for three transient events. Please locate in these time sequences the total RTD response time as it affects the over temperature delta T trip.

12.

In WCAP-11889 you have discussed the method for detecting failed RTDs which may go offscale or fail gradually. What is the amount of tempera ture deviation in degrees that will cause T and delta T alarms? What is the frequency of channel checks?

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REFERENCES

1. Letter from L. W. Eury, Carolina Power and Light Company, to NRC, dated July 26, 1988.

2. NUREG-0890, Safety Evaluation Report, Review of Resistance Temperature Detector Time Response Characteristics, August 1981.

3. NUREG/CR-4928, Degradation of Nuclear Plant Temperature Sensors, June 1987.

4. K. R. Carr, An Evaluation of Industrial Platinum Resistance Thermometer Temperature -

Its Measurement and Control in Science and Industry, ISA Publication Vol. 4, Part 2, 1972, Pages 971-982.

5. B. W. Magnum, The stability of Small Industrial Platinum Resistance Thermometers, Journal of Research of the NBS, Vol. 89, NO. 44 July-August 1984, Pages 305-350.

6. ANF-88-094, H. B. Robinson Unit 2, Chapter 15 Overtemperature T Trip Event Analysis for Elimination of RTD Bypass Piping, July 1988.