ML20023B931

Forwards Responses to NRC 830406 Request for Addl Info Re Use of Radcal Gamma Thermometer (Rgt) for Inadequate Core Cooling Instrumentation.Rgt Consists of Sheathed Thermocouples,Heater Rod,Core Tube & Jacket Tube

ML20023B931
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/04/1983
From:	John Marshall ARKANSAS POWER & LIGHT CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
0CAN058301, CAN58301, NUDOCS 8305090333
Download: ML20023B931 (8)

Text

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ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 LITTLE ROCK. ARKANSAS 72203 (501)371-4000 May 4, 1983 BCAN058301 Mr. Darrell G. Eisenhut, Director Division of Licensing Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, DC 20555

SUBJECT:

Arkansas Nuclear One - Units 1 & 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6 Additional Information Regarding ICC Submittals Gentlemen:

Our letters dated April 15, 1983, (1CAN048308 and 2CAN048306) provided AP&L's response to your December 10, 1982 " Order for Modification of Licenses" regarding Inadequate Core Cooling (ICC) instrumentation. Our proposed systems utilize an approach based on the RADCAL gamma thermometer (RGT).

The proposed systems were presented to members of the NRC staff in Bethesda on March 31, 1983. On April 6, 1983, a list of eight questions regarding our proposal was received from the staff via telecon. The attachment to this letter addresses each of these items as appropriate.

ery truly yours, ohn R. Marshall Manager, Licensing JRM:JK: sc Attachment 9 0k A

8305090333 830504 PDR ADOCK 05000313 p PDR MEMBE A MiOOLE SOUTH UTtLITIES SYSTEM

STATE OF ARKANSAS )

) SS COUNTY OF PULASKI )

I, John R. Marshall, being duly sworn, subscribe to and say that I am Manager, Licensing for Arkansas Power & Light Company; that I have full authority to execute this oath; that I have read the document numbered OCAN058301 and know the contents thereof; and that to the best of my knowledge, information and belief the statements in it are true.

I John R. Marshall SUBSCRIBED AND SWORN T0 before me, a Notary Public in and for the County and State above named, this h day of I d(A - ,

1983.

.dddttI% OAQ. dig Notary Public My Commission Expires:

My commholen Sqess Sits 64 i

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ATTACHMENT 1 RESPONSES TO STAFF CONCERNS REGARDING USE OF RGTs FOR ICC INSTRUMENTATION

1. A description of the approach to development of a separator tube; e.g.

discuss its design, design parameters, and fluid dynamics to achieve a collapsed level.

A RGT rod consists of the following basic components:

a. Sheathed thermocouples

1. Stainless steel cladding

2. Aluminum oxide insulation

b. Heater rod

1. Hot section - Nichrome

2. Cold section - Copper plug

3. Insulation - Aluminum oxide

c. Core tube - stainless steel

d. Jacket tube - stainless steel Figure 1 shows the basic components of an RGT rod and the sequence of assembly. By selectively swaging the jacket tube to the core tube, a unitized sensor-manometer is fabricated as shown in Fig. 2. This design approach will be used for above core monitoring in AN0-1 (B&W).

A fully swaged RGT rod will be inserted into the in-core instrument guide tube in AN0-2 (CE). In this case the manometer is formed by the gap between the RGT rod and the inside diameter of the guide tube. The confirmatory test program will test configurations which are representative of the ANO-1 and ANO-2 designs. The bare RGT rod will be tested to get baseline data for the sensor response. With the sensor installed in the manometer (separator tube), tests will be performed to determine the optimum porting arrangement. Voiding tests will demonstrate the adequacy of the instrument to sense level in the manometer annulus while a frothy mixture is present on the outside.

When considering the hydraulic performance of the separator tube, it is important to consider also the inherent stability of the RGT probe.

The sensors are embedded in a stainless steel monolith which acts as a heat sink and one sensor is somewhat insulated by the internal gas chamber. This results in a relatively slow time response. The RGT, then, is relatively insensitive to unstable two phase conditions and passing voids. The stability of the sensors will provide the ability to faithfully track changing level conditions and furnish the operator with unambiguous level indication.

2. Discuss the planned test program in detail, including operational parameters and evaluation of heater power effects on the thermodynamic response.

Our test program was discussed in the two April 15, 1983, submittals 1CAN048308 and 2CAN348306. The heater rod can be powered such that a range of heating can be applied to the sensors. The test program will be designed to test a variety of heater powers and to establish an optimum power for ICC level applications. Heater power versus measured signal strength, transient as well as steady state, will be used as one criteria for final specification of heater power.

3. Discuss the effects of thermal transients on the gamma thermometer sensor integrity and performance.

Scandpower submitted a topical report (ScP-01) to the NRC describing the use of RGTs as power measuring devices. Section 3.5 describes a thermal cycling test that was performed on prototype RGT. The specimen was cycled more than 50 times from room temperature to 550 C. During the test, no thermocouple signal was lost and destructive examinations revealed no positional disturbance of the RGT components.'

4. Discuss the reliability of the heater design and heater failure considerations.

The physical construction of the heater makes it very sturdy. The heater is it the form of a rod which is well supported due to the way it is housed in the center of the sensor rod. The heater is designed to produce 10 w/cm; however, during normal operation the heater is powered at only a small fraction of design (i.e. 0.5-1.5 w/cm). By operating at a level well below the design rating the heater reliability is increased.

5. Schet:ule milestones and progress criteria for a go/no go decision on continuation of the RGT program.

Our two submittals (1CAN048308 and 2CAN048306) contained a plant specific ICC Instrumentation schedule (Fig. 4 in each submittal). This schedule shows completion of a final test report on 4/13/84.

Achievement of this milestone is, of course, contingent upon timely completion of previous milestones. The submittal of the final test report will contain our final go/no go decision for continuation of the RGT program, contingent upon NRC approval; however, a "no go" decision as late as July 15, 1984, will not delay the installation of an alternate system as discussed under item 6 below.

AP&L is currently in the process of contracting with the Technology for Energy Corporation (TEC) for the design, development and testing of the RGT system. Work performed under this contract will be closely monitored by AP&L staff to ensure that the confirmatory testing program is carried out in a prompt manner using realistic criteria for testing.

This close monitoring will_ allow for early notification of situations which would necessitate termination of the RGT approach and an accelerated effort on the alternate system.

6. A description of a parallel path effort and schedules for the selected backup concept.

ANO-2 We are evaluating the results of a feasibility study for Heated Junction Thermocouple (HJTC) installation on ANO-2. This study presents AP&L with 3 options for HJTC implementation: installation in place of (1) the center control element assembly (CEA), (2) two part length CEAs, or (3) two In-Core Instruments (ICI). There are various advantages and disadvantages to each approach and we intend to evaluate each option against all relevant criteria to determine the optimum approach. This will facilitate an accelerated effort for implementation of the HJTC system should this become necessary.

Installation of the alternate system consistent with the schedule shown in our ICC submittal would require that we place an order for the hardware by July 15, 1984.

ANO-1 AP&L has investigated the feasibility of using the HJTC for ICC instrumentation for AN0-1 and has received a proposal which will allow installation of the system by removal of the center control rod. We will continue to evaluate this proposal and be in a position to commence detailed design on the HJTC system for AN0-1 head level monitoring should this become necessary. Regarding hot leg level monitoring a great deal of design work was completed for a AP system a few years ago. We will review this design for conformance to the present criteria, provide any refinements we deem necessary, and implement this system for hot leg level monitoring, if necessary.

Installation of the alternate system consistent with the schedule shown in our ICC submittal would require that we place an order for the hardware by January 1, 1985.

7. Submit a solid concept for hot leg monitoring.

A discussion of the proposed approach for hot leg level monitoring was contained in our April 15, 1983, submittal (1CAN048308).

8. A discussion of why CET's are taking so long and a discussion regarding deficiencies of the existing system.

ANO-2 Indication for each of the 44 CETs currently is provided to the control room operators via the plant computer system. The sensors, connectors,  !

and signal processing equipment are not class 1E; however, the cable inside containment is qualified and channelized.-

The existing In-Core Instruments will be depleted and must be replaced during the next refueling outage (January 1984). Because of the long lead time (approximately 12 months) AP&L initiated procurement efforts

/

for the replacement ICIs in 1982 prior to evaluation of the NRC Order on ICC. These replacement ICIs will be the same pedigree as the existing ICIs (i.e., they are not class 1E).

The new ICIs have a projected life of two to three operating cycles.

We plan to replace these new ICIs after they are depleted with class 1E ICIs as discussed in our April 15, 1983, submittal. The vendor has indicated that a class 1E ICI is similar in design and construction to a non-1E ICI. The QA program for the qualified ICI is, however, more rigorous. As previously mentioned, the ICI cable inside containment is qualified and channelized.

ANO-1 In response to NUREG 0578, the Core Exit Thermocouple (CETs) system was modified to provide indication to the control room operators for 32 CET locations. The thermocouples, cables, and associated signal processing hardware is not class 1E. The method of display is via the plant computer system.

The April 15, 1983 response to the ICC order provides details on the design and schedule for AP&L's In-Core Monitoring System.

. 1he following chart shows the compordts orid sequerice of assemoiy vi an RGT rod.

G.T. CROSS SECTION SWAGE JAW SCHEMATIC CABLE PACK

- CORE TURE 0.069" f

0.133" 0.060" @ WT=0.0370" t

WT= Wall Thickness rh WT=0.0370"  ; i 0.060" 0.131" l l I WT=0.0378" 1

0.0Q4" WT =0.0280" WT)=0.0378" 2

h 0.140"0.0564" 0.187" i JACKET TUBE f 0 188" 0.132" j l I 0.1 34" h - 0.188" 0.132" I \

                               -                 o                                              ,

0.185" o Figure 1. Fabrication Procedure Steps

r , , , , UNITIZED SENSOR-MANOMETER 1 y p ,- 1. t4j s,, E. ,. MANOMETER ANNULUS N Sp/ l/ E_Ee_ { LEVEL SENSORS N\sff f k\ s

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1: EQUALIZING PORTS N/ f \ .

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