ML19253C591

Forwards Response to 791026 Request for Addl Info Re Review of WCAP-91-57.Includes Info Re Qualification of Resistance Temp Detectors & Remote Bellows Sensing Containment Pressure Transmitters

ML19253C591
Person / Time
Site:	Sequoyah
Issue date:	12/04/1979
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	Rubenstein L Office of Nuclear Reactor Regulation
References
NUDOCS 7912060522
Download: ML19253C591 (7)

Text

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. s TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374o1 400 Chestnut Street Tower II December 4, 1979 Director of Nuclear Reactor Regulation .

Attention: Mr. L. S. Rubenstein, Acting Chief Light Water Reactors Branch No. 4 Division of Project Management U.S. Nuclear Regulatory Comission Washington, DC 20555

Dear Mr. Rubenstein:

In the Matter of the Application of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 Enclosed is the additional information requested in your letter to H. G. Parris dated Octooec 26, 1979, concerning qualification of resistance temperature detectors (RID's), field connections for RID's, and remote bellows . sensing contarment pressure transmitters. This information should assist your review of Westinghouse WCAP-9157,

" Environmental Qualification of Safety-Related Class IE Process Instrumentation."

Very truly yours, TENNESSEE VALLEY AUTHORITY d y wcm L. M. Mi]1s, Manager Nuclear hegulation and Safety Enclosure 1506 271 7912000 5a4 0 OI

$5 An Ecual Cecertunity Employer

ENCLOSURE f RESPONSES TO NRC CONCERNS TRANSMITTED BY L. S. RUBENSTEIN'S LETTER TO H. G. PARRIS DATED OCTOBER 26, 1979 THE QUALIFIED LIFE OF RESISTANCE TEMPERATURE DETECTORS (RID'S) TO BE USED TO MEASURE THE TEMPERATURE OF REACTOR COOLANT In an effort to avoid retesting the resistance temperature detectors (RTD's) to the new NRC requirements, TVA requested Westinghouse to inves-tigate the possibility of showing that the radiation deses used in the tests reported in WCAP 9157 were adequate for 100 days post-LOCA. While such a demonstration is possible for the radiation dose used, the two-week post accident thermal aging simulation could not be extended in a similar manner. The attached calculation separately derives the gamma dose applicable to those parts of the RTD external and internal to the RCS pressure boundary.

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I ATTACFF,NT SEQUOYAH NUCLEAR PLANT RADIATION JOSE CALCULATIONS FOR RTD'S The object of the following calculations is to est.imate the plant speci-fic inservice life that, when taken in conjunction with assuming the RTD's operate for 100 days in a post-LOCA environ =ent, yields a total dose equal to 1 x 10 8Rads as employed by Westinghouse fe.r the testing reported in WCAP-9157.

External Environment WCAP-8587, Figure 6-4, indicates a containment accosphere dose of 1 x 108 Rads for 100 days post-LOCA. This value is based on a TID calcula-6 3 tion for a 4100 MW reactor and a containment volume of 1.1 x 10 gt ,

The Westinghouse calculated dose can be approximately scaled for applica-tion to Sequoyah by the formulae:

D = 1.0 x 10 Rads

, 41 0 Inserting a value of 3565 MW (P) and 1.1 x 106 (V) as applicable to Sequoyah yields a post-LOCA 100 day integrated dose of 8.7 x 10 Rads for the RTD external connection. Since the narrow range RID is only required for a short time after the event, this calculation only applies to the wide range ceasurement. The external dose for the narrow range 6

RTD is on the order of 10 Rads and is insignificant compared to the test condition.

The remaining doce available to cover inservice effects is the difference between the total dose employed in the Westinghouse test reported in WCAP-9157 (i.e., 1 x 10 8Rads) and the above calculated post-LOCA dose for the wide range (i.e., 8.7 x 10 Rads), which is 1.3 x 10 Rads. The dose rate during normal operation appropriate to the external connection is taken as 165 R/hr (T ble 6-2, WCAP-8587). Thus, assuming an 80 per-cent load factor, the time required to attain this remaining dose is:

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Wide Range 1.3 x 10 #

= 11.2 years 165x24x365x0.8 0

Narrow Range 1.0 x 10 = 86 years 165x24x365r.0.8 The Westinghouse calculated doses post-LOCA presented in WCAP-8587, Figure 6-4, for the post-LOCA containment environment are conservative with respect to the doses recommended by the Staff in NUREG-0588. From Appendix D of this document a conservative 100 day dose post-LOCA is 7 6 2 x 10 Rads for a containment volume of 2.52 x 10 ft 3and a power of 4000 MW. Repeating the calculation 'above using this data yields an equivalent inservice life of approximately 50 years for the wide range RTD external connections.

Internal Environment WCAP-8587, Figure 6-8, indicates a RCS internal pipe dose of 1.8 x 10 Rads for 100 days post-LOCA. Without considering any reduction in this value by scaling for Sequoyah, the remaining dose available to cover inservice radiation effects on the RTD is 8.2 x 10 Rads. The dose rate during normal operation for wide range RTD's installed directly in the reactor coolant system is conservatively taken as 820 R/hr as defined for the RCL pipe center in Table 6-2, WCAP-8587. For the bypass line, narrow range RTD's, the dose rate is conservatively taken as 165 R/hr as defined for the RCL outside surface. Thus, assuming an 80 per-cent load factor the time required for the internal part of the RTD to attain the remaining dose is:

Narrow Range 8.2 x 10 = 70.9 years 165x24x365x0.8 Wide Range 8.2 x 10 = 14.3 years 820x24x365x0.8 Summary Using Westinghouse dose estimates from WCAP-8587 scaled for Sequoyah, 8

the shortest demonstrated life equivalent to the 1 x 10 Rads used in 1506 274

~i the RTD tests (WCAP-9157) is defined by the external connections and is conservatively esti=ated to be 11 years for the wide range RTD's. The demonstrated life of the narrow range RTD's exceeds 40 years. Using the post-LOCA doses recommended by the NRC in NUREG-0538 scaled for Sequoych, the shortest life for the wide range RTD is 14.3 years and greater than 40 years for the narrow range RTD.

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i QUALIFICATION OF FIELD CONNECT 1C?tS FOR THE RID'S The resistance temperature detectors (RTD's) are furnished with a calibrated length of cable. The conductors of the RID cables are interfaced with field wiring on terminal blocks located in a junction

'ou x . Terminations are needed to accoc=odate RTD calibration check-point, maintenance, and/or replacement.

At most, only two RID cables interface in a junction box. The covers of the junction boxes are gasketed and the cable entries into the boxes are sealed with room temperature vulcanizing (RTV) silicone rubber to restrict moisture entry and chemical exposure to terminations in the event of a loss of coolant accident (LOCA).

To ensure the field connections are protected for post-LOCA condition, the RTD terminations have been coated with Dow Corning 3140 RTV Silicone Coating. Information from the manufacturer indicates that this protective coating has a temperature range of -65 C to 250 C and is effective after a radiation exposure of 100 megarads. Also, it is electrically non-conductive, has good insulation properties, and provides protection against corrosion. From this analyses TVA considers the installed configuration of the RID ficld connections to be acceptable for measur-ing the reactor coolant temperature under a post-LOCA environment.

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QUALIFICATION OF REMOTE BELLOUS SENSING PRESSURE TRANSMITTEhS TO'BE USED TO MEASURE PRESSURE OF THE CONTAINMENT ATMOSPHERE Sequoyah does not use remote bellows sensors for containment pressure sensing, therefore TVA does not have a concern for the phenomenon observed during the bellows tdsting reported in WCAP-9157.

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