ML19318C874

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Forwards Response to United Kingdom Nuclear Installations Inspectorate Request for Technical Info on Reactor Pressurizer Water Level Instrumentation
ML19318C874
Person / Time
Site: Crane Constellation icon.png
Issue date: 06/24/1980
From: Harold Denton
Office of Nuclear Reactor Regulation
To: Lafleur J
NRC OFFICE OF INTERNATIONAL PROGRAMS (OIP)
References
NUDOCS 8007020399
Download: ML19318C874 (8)
v • d • e


Text

{{#Wiki_filter:DISTRIBUTION: Docket No. 50-320 NRC PDR w/ incoming Lo jc ] PDR w/ incoming jTERA w/ incoming TMI:P0 w/ incoming TMI Site r/f w/ incoming 1 0.i ~ ,30N 2 41980 JTCollins r BJSnyder HRDenton EGCase Dock:t No. 50-320 ~ PPAS BGrimes DEisenhut ~..O 1 ~ RHVollmer Dross SHanauer RMattson ~ MDuncan HThompson w/ incoming MEMORANDUM FOR: Joseph D. LaFleur Jr., Deputy Director Office of International Programs FROM: Harold R. Denton, U! rector i Office of Nuclear Rentor Regulation

SUBJECT:

RESPONSE TO BRITISH TECH!;ICAL QUESTIONS ON THI-2 Enclosed is NRR's response to the UK Nuclear Installations Inspectorate request for technical information on TMI-2 reactor pressurizer water level instrumentation, s. This submittal has been prepared per your letter request dated April 28, 1980.. j ,@:Isig::d tf H. R. Dentan u i Harold R.'Denton, Director Office of Nuclear Reactor Regulatio~n,

Enclosure:

Staff Response to British Technical Questions cc: R. S. Senseney, IP q B. J. Snyder J. T. Collins g \\; R1 ller d " ' ~ " 8007020 6//2/80, ( l % Y' s s, .. O Lo .h R/ ,D. R ,,,g,,,,,,,,, hS.:?0 O FF.Cc k .ERCa .H enton.........'h,.... suRNavEh. nis/hnt.. JSnyder.. 6/,,10 80,, 6d/80 ,6/,h,80, ,,,,,,,9, oATe k. 6//,(/80 , 6,g,80 / NRC FOT.M 318 (9-76) NRCM 0240 DU.S. GOVERNMENT PRINTING OFFICER 1979-289 369 ,a

M d RESPONSE'T0' BRITISH ~ TECHNICAL INQUIRY (A) Is the upper tapping from the pressurizer steam space filled by design with condensate (in normal operation) to a fiduciary level? ANSWER Yes it is. During pre-startup the entire reference leg is filled with water. A figure depicting the TMI-2 pressurizer level instrumentation is provided in Enclosure 1. (B) What are the approximate temperatures of the condensate at the pressurizer and DP cell ends of the tapping during normal operation? ANSWER Based on the data from the TMI-1 Power Escalation Testing with the pressurizer temperature at 645 F, the following temperature profile was obtained: Elevation Ambient Temp (UF) Surface Temp (U ) F 5 Upper TAP 349'6" 110 151.6 Lower TAP 316' 93 110 Since the instrumentation tubing is of stain!ess steel schedule 160 material and uninsulated, the temperature gradient across the tubing wall would' be small (on the order of 100F or less). Therefore, the condensate temperatures could be slightly higher than the surface temperatures indicated above. The differential pressure cell -- mounted in the instrument rack is located behind the shield wall. The ambient temperature in this area is estimated to be in the range of 75 F to 80 F. Please note that the TMI-1 information U also applies to TMI-2. I 1 1 t

(C) How long are the upper and lower tappings? ANSWER As shown in Enclosure 1 the distance between the upper and lower tappings is 33.5 feet. From the 316' elevation level (lower tap), the tubing length of the reference leg and the lower sensing nozzle in the vertical direction is another 30 feet. The continuing horizontal run to the instrunent racks #424 and #426 is not well known. However, judging from the enclosed general area _ drawings (Enclosure 2), this distance may be in the range of 30 to 60 feet. Also, it should be noted that the location of pressurizer water level instrumention taps described for the TMI units are not typical when compared to other B&W plant designs. The differences among the B&W 177 Fuel Assembly Plants are described below. 400 Inch Level System 320 Inch Level System s Oconee - 1 Arkansas Nuclear - 1 Oconee - 2 Rancho Seco TMI-l Crystal River-3 TMI-2 Davis-Besse 1 (0) Is there any feature of the tapnings/ condensate which causes the pressurizer level instrumentation to be regarded as unreliable in the presence of a leak at the top of the pressurizer? If so, what? ANSWER The staff has performed a study on pressurizer level instrument accuracy following a depressurization event. (Internal letter from R.M. Satterfield, ICSB, CJS to R. Tedesco, AD for RS, DSS, dated April 11,1979.) 'O h' _ ~ r qq

The factors assessed which could affect instrument accuracy were: (1) a rapid reduction in pressurizer pressure that may cause the liquid to flash in the reference leg, (2) degassing of the liquid in the reference leg, and (3) rapid depressurization causing a venturi effect at the point where the reference leg joins the pressurizer vessel. It was concluded that for all of the above cases the resulting errors in the level instrument readout would be negligible. Calculations show a reduction of the water level in the reference leg due to flashing to be less than one foot. Since, the distance between the taps is 33.5 feet, the ef'fect of this reduction would be small. Very little of the dissolved hydrogen in the water of the reference leg would escape during depressurization. B&W supported the above conclusions by performing tests on a simulated reference leg subjected to LOCA conditions. (Babcock & Wilcox Report BW-4689, Pressurizer Reference Leg Effervescence Test, dated March 1,1977.) 6

b RELIEF VALVE N0ZZLE (TYP OF 3) VENT N0ZZLE 4.75" MIN. i SPRAY LINE N0ZZLE [ LEVEL SENSING N0ZZLE f SPRAY N0ZZLE M 3" + { M 6" 1" PIPE l ELEV. 348'5* ~ STEAM SPACE 1/2" TU8ING (REFERENCE LEG) 84" 1.0. ~ .$.188" MIN NORMAL WATER LEVEL 6" INSUL ATION g s VESSEL SUPPORTS ( ) _) THERM 0WELL -__q HEATER BUNOLE __d / _J ,? _ _ _ _, w e SHIELO WALL ROTATED E LEVEL SENSING N0ZZLE mu 4 ./ - ELEV-t 272'8" ELEV. 316* ELEV.= 31r INST R. - [2[V, gg g /jff ELEV. RACK 287 l SURGE LINE N0ZZLE FIGURE 11-25. The Pressurizer R E M M M.: p o g g y gn, A4 g,g g j g,

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