ML19221A595
| ML19221A595 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/16/1979 |
| From: | Novak T Office of Nuclear Reactor Regulation |
| To: | Mattson R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19221A596 | List: |
| References | |
| NUDOCS 7905230281 | |
| Download: ML19221A595 (44) | |
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s UNITED STATES 4
NUCLEAR REGULATORY COMMISSION j
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April 16, 1979 m-L
- MEMORANDUM FOR:
R. J. Mattson
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NRR Technical Review Group mq.+..'-
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SUBJECT:
UPDATED STATUS OF PROPOSALS FOR ACHIEVING
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COLD SHUTDOWN FOR TMI-2
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The NRC Technical Review Group has been interfacing with
- 1) General
. _ _9 Public Utilities and Burns and Roe to review and assess the 3)i4.*
feasibility of achieving cold shutdown by going water solid on the E_--+,...
- 2) Westinghouse to review and assess the feasi-
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bility of upgrading the existing decay heat removal systems and T6Lc U-.
building a new (third train) decay heat removal system, 3) Burns F.A.:. 7.
Utilities and Burns and Roe on Primary Makeup and Pressure Control.
-N and Roe for spent ft.el pool modi fications and 4) General Public 4
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The attached enclosures identified below provide an update of the
- -21 status of these proposals.
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. - Cold Shutdown of TMI-2 Usin9 Vater Solid o,..
Seco +da ry St eam Gene ra tors.
. - Decay Heat Remova l System
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-..; - Comments on Fossible OTSG Design Limitations
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Relating to Vater So' lid Operation - Assessment of Radiological Consequences of r-Steam Generator B in Short Term Mode
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-.? - Summary of Br,v Submittal of April 10, '979 P-1 Regarding Natural Circulation J'".
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NRC TECHNICAL REVI G DJP
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i sd, ENCLOSURE 1 f~
COLD SHUTDOWN OF TMI-2 USING WATER SOLID SECONDARY IN __ STEAM GENERATORS 1.
Short Term St am Generator "B" (Approach 1)
A.
Deslan Conc g S
This concept will utilize a balance of plant cooling water w =.
. system to effect cooling of steam generator "B" during water.,
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solid operation of the secondary sIfe of the steam generator
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Water will be circulated by the secondary services cooling water pumps through the main feedwater line and into the steam generator.
It will exit the steam generator through the main steam line and will flow to the secondary service cooling water heat exchangers where it will be cooleo and returned to the steam generato. by the secondary service cool-
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-W ing water pumps.
The secondary services cooling water heat exchanger will be cooled by the nuclear services river water 7
system.
Refer to Figure 2 for a schematic of this flowpath.
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Modification This scheme will involve installation of a jumper pipe be-tween the discharge of the secondary services cooling water 165 204 u
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pumps and the feedwater line just downstream of the feed-57 ]
water control valve.
This pipe routing will be between 500 feet to 600 feet long located in the turbine building. A jumper pipe will also be installed between the main steam gge-turbine bypass line and the supply line to the secondary ser-vices cooling water heat exchangers.
This pipe routing will be approximately 20 feet long also located in,the turbine
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building.
These jumper pipes will include connections for 1
the long term sdheme.
Provisions will also be made for
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demineralization of a portion,f the fl owrate.
These pip-ing modifications will be run along the floor and attached
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to railroad ties and existing steel beams in the turbine building where feasible.
These modifications establish the flowpath for the secondary side of steam generator "B".
Additional jumper pipes will be installed between the nuclear M
services river water system and secondary services river water system to cool the secondary services cooling water heat ex-changer.
The safety classification of the nuclear services river water system will be maintained.
This water flows to the mechani al draf t cooling tower basin.
This modi fication es-tablishes the flowpath fo r cooling the secondary side of the
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secondary services cooling water heat exchanger. All piping connections will be welded.
These mod i fi ca,t i ons a re ex-pected to be comoteted in early May.
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During the meeting with Burns & Roe on April 13, 1979, 2.,
3 several shortcomings of the short term steam generator B Sr 7,-[
(Approach #1) modification were brought out.
These were:
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The secondary services cooling water heat exchangers
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The heat exchanger manu facture r would expect that 200 F water would
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be acceptable for a short period of time, however, the
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this occurrence, provisions will have to be incorporated into the design to limit this temperature.
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Since the tubes are not welded into the tube sheets, there will always be some leakage between the prirsary and secondary side of the secondary services cooling water heat exchangers.
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The pressure is higher on the steam generator side of 5b-
'57 the secondary services cooling water heat exchangers, therefore leakage is always out.
This could result in
.eleasing radioactive coolant into the mechanical,
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draft cooling towers basin by way of the nuclear
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services river water system if steam generator B leaks.
Bl owdown from the cooling tower would carry poten-
..fjE{[ tially radioactive water to the river. -~.n.- LL 72J Based on the shortcomings oF the steam generate-3 short term C., 2e Aoproach #1 modifications identified and the relatively short
- E' difference in time to fabricate Approach #2, it appears
'= T_., that it may be possible to go directly to a more leak , 7-tight modi fication with little compromise in completion time. a-2. Short Term Steam Generator "B" (Acoroach 2) A. Desien Concept 493 This approach will utilize a new high pressure loop to effect cooling of the secondary side of steam generator T~ "B" during water solid operation and ul timately under natural circulation of the primary water. The advantages of this system would be
- 1) poten-tial leakage would either be into the primary sy:-
t em instead of out or less than expected in Approach 1 a nd 2) high reliability for long term operation. if thi< approach is used the long term modifications to steam generator 8 described in section 3 would probably hq5 5 2 0 7 eliminated. Whether approach I or 2 for short term -:a Il .m. .m
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steam generator 8 modifications is used is dependent c- - = - _ '
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~ 2. }:-- on the schedule for completion of the modifications. If the time difference is small, which is expected, then '. ~. '. - approach 2 is obviously preferrable. .p er.9 r-Water will be circulated through a new heat exchanger
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^ ~ The secondary side of this new heat exchanger will be . -; ~ cooled by water from other the nuclear services river
- ==a m.n water cr; secondary services river water systems.
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~.I to Figure 3 for a schematic of this flowpath. =~- : ] B. Modi #ication ~ This scheme will involve instal'ation of a new train con-5isting of a pump, nest exchanger and piping. The loop will be connected to the main steam bypass line and the f eedwa te r line just downstream of the feedwater control N salve. This pipe routing will be between 550 feet to 650 feet long located in the turbine building. Provisions will be made for system surge and expansion and for de-mineralization of a po tion of the fl ow r a t e. The piping modification will prebably be run along the floor ar.d attached to railroad ties and existing steel beams in the turbine building in a manner similar to that for Short Term S.G. "B" Approach 1. This modification establishes the f1wpath for the secondary side of steam generator "B". 4 165 208 ~' s. --~?-. ---~v.:~---, --~,--*--.-?-- .~e; ~ ~_ -f., F.,,1,., r-je., 5 ,.j
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k Jumper pipes will oe installed between the nuclear services
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([ ~ river water system or secondary services river wa er sys- }' tem to cool tN secondary side of the new heat exchanger. --f The safety classification of the nuclear services river water system will be maintained if it ir "tilized in this -7 scheme. Nuclear services river water flows to the mech- ,i ~ anical draft cooling tower basin, and secondary services ~ river water is discharged directly to the river. This modification establishes the flowpath for cooling the secondary side of the new heat exchanger. All pioing connections will be welded. These modi fications a re ex- {,} pected to be completed in early Hay. a.-- Short Term Steam Generator "A" 3, A. Desion Concent-l t i This concept will utilize the normal flow path through steam generator "A" during water solid operation of the secondary side of the steam generator and ultimately under natural. circulation of the primary water. l .i t Vater will be circulated by the condensate pum through the condensate booster pump, fee'dwater pump and nain f ee d-l water line into the steam generator. It will exit the steam generator th ough the main steam line and will fl os ~ 165 209 m 9 V0 W' b' 4 O " -R.: a s.. 1 ^_ #e Na 4.** amuse. Sere ^^ D ^ ^
e t -~ * .'T :. A7 to the condenser..In order to achieve adequat.e heat ~T' transfer in the condenser, the water will enter through ~ the makeup line. This line consists of a spray header which will spray the water over the condenser tubes there- = ? by utilizing the majority of the tube surface area for ' ~ ~ cooling. Normal water, level will be mair.tained in the con-denser hotwell. The water will be returned 'by the conden-sate pump from the condenser hotwell to the steam generator. Normal circulating water will cool the condenser. Refer to Figure 1 for a schematic of this flowpath. 8. Modification This scheme will involve installation of only one jumper pipe between the main steam turbine bypass line and the condenser makeup line. A separate Independent cooler will sswp be provided-for the ccndensate pump motor bearing oil and the impellers of the condensate booster pump and feedwater pump will either be removed o-blocked. Other than the '.. + above modifications, the flowpath for the secondary side of steam generator "A" is the same as during normal plant [ ope ra t i on. All piping connections will be welded. These modi fications are expected to take 2 days fo'l l ov i ng isolation and cooldown of Steam Generator 'A. 165 210 e d5 ..~....a..... Q..... ~. -. *... ?.<... , *~ .L 1 .., _' ? I # a -,e _ _ _._ e_a.m _. _
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E.if A. Desion Conceot ~ :.5 a The long term steam generator A and B modifications have not t,een designed, however, the concept entails instal- &1.1
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ling a high pressure loop with a heat exchanger and
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pump between the turbine by-pass line and the feedwater -= Inlet. I t should be noted that Approach #2 to short term Steam Generator #8 is very similar "to the long term concept. The advantages of this system would be: ,g
- 1) potential leakage through steam generator tuves D
would be into the primary system instead of out and - -} '4
- 2) high reliabilf'y for long term operation.
Provisions are being incorporated into the short term modi fications ~' to tie in the long term when ready. Refer to Figure 4 [' for a schematic of this flowpath. B. Modifications c ~ lhe heat exchanger, pump and piping would be connected to the main steam turbine bypass line and feedwater line for e \\65 2\\\\
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-9 .~ = ~ 2.2 r_. = m. N .dj each steam generator. This will provide the flowpath for I -a _g) the secondary side of the steam generator. 7,.:- Additional ccnnections will be made to the nuclear services S river water system to provide cooling to the new heat ex-EE:- changers. This water will flow to the mechanical draf t cool-g ing tower basin. All piping connections will be welded. D _. ~. F This modification is scheduled to be completed in 45 days. -5 ; t._.rc.r.- El ect r i cal -Powe r Rec 4oi rement s 1. Short Term "B" SG System (Approach 1) W- &:t d Power system requirements for Approach #1 are limited to supplying loss-of-of fsi te-power (LOOP) back-up to the Secondary Services Cooling Pumps. Ve understand this require-ment will be satisfied by adding two new 2500 kw diesel M generators to two existing non-safety 4160 voit busses. The i primary system status has evolved to the point that quick-response fast-starting diesel. generator performance is not required., c We.m. b 165 212 .'e .n
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positioning of valves and starting pumps). The tertiary =" cooling loop for this modification (ultimate cooling) =. .Z.' utilizes the Nuclear Services River Vater Pumps which are already connected to the existing Class I E diesel generator s.
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2. Short Term "B" SG System. (Approach 2) .12 Power sy: tem requiremeqts for approach #2 include the addition of two new 700 hp pump motors that will ba powered off the two 42 W~ new 2500 kw diesel generators. We have no further information 7 on the electrical requirements at this time, it has not been
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decided whether to use the secondary services river water pumps (which requires LOOP back-up f rom the new diesel generators) or the Nuclear Services River Vater Pumps (which al ready receive Class IE power) for ultimate cooling. W.$ 3 Short Term "A" SG System Power system requirements to support this modification in-clude supplying LOOP back-up protection for the Condensate Pumps and the Circulating Vater Pumps. We understand that the LOOP back-up requirement for the condensate pumps will n e n,- 165 213 .'.( ~-. q + s ' ~ a=- M ww w.a me.sm.Av.i.am.1' " ean.sm ee w4% e hlm - * "-v.=,orm ' M E - - ^*
e ~~ * .} ........x... . s.. t 57.1 - ~ ::.: ,c '7 be satisfied by connecting these pumps to the new 2500 kw diesel ~ generators. Consideration has been given to using a construc-tion poser line that comes into the site for supplying LOOP back-up to the circulating water pumps (2250 hp each). The use of this-13.8 kv line will not provide total LOOP protection '-^ 1211 7-- If the entire grid in the area of the plant should experience -~ ~ a black out. '! mever, we have approved this design concept on the followirj bases: a) the time window for needing the circulating water pumps is limited to the time in which the steam cenerator A short term system will be in operation, b) the starting rqquirements of the circulating water pumps fig emar.ds a diesel generator much larger than has been located to da te, c) Burns and Roe has stated that this back-up can b e coerational within 3 days of the approval, and d) this line will have remote connections to the 230 kv system and four 115 kv system lines Avhich gives a reasonable degree of station blackout protection. The-re,ainder of the system is all manua; and primary sys-tem conditions are such that no prompt response is required given system interruption due to such occurrences 'ds LOOP. 4 Long Te rn '%" and "B" SG Sys tems Long te m modifications for each steam generator are proposed to be the same. The design calls for all new equipment 165 214 h.& .[. _,., _ y, z _ _ _ _ _. r ~ c-. .. s.'.'d * '. 2. ' U. ., ? w.
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e -g. e incteding motor merated valves and high pressure pumps. These loads will :e assigned to the two new diesel generators busses to assure LOOP back-up protection. This system will Save the provision for remote operation but will not rec.:i re prompt response to such events as y,q LOOP. Ultimate :ooling will utilize the Class IE Nuclear Services River *'ater Pumps which are al ready on the exist-ing plant IE diesels. 165 215 ...h i.i. '} \\ ~ ' ' r..-- r w..u w.- 'md-12 . ad ~
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~.. 'i., ENCLOSURE 2 DECAY HEAT REMOVAL SYSTEM ~ I. SCPE estinghouse has been given the responsibility for direct decay heat removal from the primary system. Their work will be done in two parts as follows: Un ra d i ng Existing Decay Heat Remova_1 System Vestinghouse will make provisions for ar:d conduct a preopera-ti nal test of each loop of the existing DHR system. Locations of system leakage will be identi fied using television cameras installed at key locations. Once leakage paths are identified, thev will be corrected if possible, thereby providing as leak ti nt a system es practical. Leakage collection capability will also be added to the system where feasible (i.e. collection .w m of leakage around valves), instrumentation to detect pump vi: ration will also be installed. 4 165 220 .z ..:::f L. .a. . " \\,. P' ~.. ;*.~- j ' '. ~~ ' - - ~
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This will involve a tie in to the decay heat re- ..M . ' *,1 moval system dror line downstream of valve DH-V-3 located in the 2. ,[,j fuel handling building (Aux. Building) and tie ins to the two rN. _ 4;.] return lines to the cold legs also located in the fuel handling -? building (See Figure 1). New lines will be run through the penetr.ation room to an opening cut in the fuel handling luilding wall and out to a skid located outside the building a*. grade !? level (304'-6"). This skid will contain a new decay heat removal heat exchanger and two pumps. The discharge line for the heat ex-changer will return through tht; opening in the fuel handling building to the return line penetrations. The tie in to ti:e decay heat removal drop line will be made by welding an 3 inch waldolet to the pioe with a full penetration weld, dye penetrate t esting the weld, then cutting t!e hole in the pipe using a ??? plasma ar cutting process to minimize debris and finally welding the new pipe to the wel dolet. A similar procedure would be used ~ for the tie-ins to the two return lines. This procedure should minimize the time that the decay heat removal system will be out of operation. All valves will have two seals with pro-visions for collecting leakage and will be electric motor operated. Additional connections will be provided in the new piping out-165 221
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? .a--- , u i s.'. ,N side the fuel handling building for future use in the instal- -T:. y lation of a long life, hardened structure which will contal.: -b heat exchangert, pumps, demineralizers and filters for long term decay t eat removal and cleanup of primary water. The secondare side of the new decay heat removal heat exchanger m will be cooled by a new separate decay heat closed cooling water system with its own pump, piping and valves (See Figure 2). I...; This sys tern in turn will be cooled by a new decay heat service ~ 1 n.-' cooler. This cooler will be cooled by water f rom the nuclear -3 services river water system. New connections will be made to this sys te:n. ~~ 4 ' 7-The design of this new decay heat removal system will require that the pressurizer level be maintained half full at all times. Alter-atively, a backup makeup and pressure con; il system as des:ribed in Enclosure 8 would serve to satisfy this requi re ent. 2. Structural Fuel Handlinc ?alldino Wall Penetration (Aux. Blda) Penet ration w;uld have to be made through the west wall of the Fuel Ha i: ling Bldg., between column lines AC and AF and _a 165 22z ,7,.4. -.... ~..... -.... ~. _ _ _ _ _. ~- - ?. ,~ ;. t-a . ~.. m uw__ -. _ = .__,._.._.4 ,v.-~- ,-~. raw m m.
M ~ + '., y.. - : M. g across column line A68, at elevation 297'-0". (See ST,R OrawJng 2075). This is approxima ely seven feet below grade. Excavation outside of the structure will be done by pick and shoven to minimize a possibility of m-s, % 'a 'I damaging any piping or electrical conduit. The outside wall i M N-- at that location is reinforced concrete, 5'0" thick. The com- ~" pressive strength of concrete in this wall is 5000 psi. The o pening will be rectangular in shape, 3' horizontal by 4' vertical. The reinforcing t,ars will be cut on each side of ,[. the opening providing sufficient length exposed to install
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-:= Cadwell type splices with the new reinforcing after the in-s:.. stallation of the new pipe is completed. A concrete pour to reclose the penetration will occur following installation of piping runs. Possible Problems Because we have not had access to structural as-built drawings m w e have not been able to arrive at a definite conclusion re-garding the _ ept of penetrat ton of the wall, however, s ome problems can be foreseen. These are outlined below: 1. The exposed reinforcing ends must be of sufficient length to enable splices to be instelled. 165 223 r. s O --r- ' -6= ~. m s- ,-a.,a;--- . man & w.s w o.n e wa mmm _-n%'M-> ... +,,;
~ ~ 5 1.4 ,w:., s 2. The exposed surface of concrete inside of the opening must be preperly cleaned and prepared to receive the new con- \\ crete to fill the opening after Installation of the new t piping is completed, so that the joint between the new and the existing concrete remains leak-tight. EN9 1 ~ ~ 3. 7,e safety margin of the structure af ter the wall is restored should be examined. 3 Electrical Power Reop[reme ts This new system will have motor operated 480 volt valves arranged f gg,:s in such a manner that therelwill be two sets of isolation valves 12 -~~ on each of the three DHR lines that will be tapped. These valves will be assigned power sources in a manner that assures isola-tion capability given a single power source failure. The rema in-ing motor operated valves will be arranged on a "per loop" basis %i ~ to al l ow scicction of ei of the two new 4160 vol't pumps. These valves and the associt e; .,p s w i l l be powe r ed f rom dif ferent busses to assure system function given a single power i source railure. d ~
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e , r. wi f*k -b- ~ e s7= s The two busses : at will be selected for powering this system are to receive diese: generator back-up power f rom the two new 2500 kw diesel genera: ors, tIestinghouse will also provide two 480 volt motor control :e: te rs. All electric powered equipxnt (valves, g ,. ~ pumps, moto. co rol centers and cabling) will be Class 1E system quality. System installation and pewer sources preclude this systen F on seing a fully qualified Class IE system. Sys-tem functional equirements of the prinary reactor coolant sys-tem precluce the.,eed for a fully qualified Class 1E system 7,=s. due to the. l.o wing conside.at. ions: T. / U 1. There are tw-existing DHR systems that are fully Class IE. 2. Because of t e low decay heat levels, it is ex:ected that sufficie-t time would be available for riar::a1 -+2 operator act* n. W h. Mechanical I cio ent Desion Pumo and Heat Ex-ance r ASME Section 111
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~ -7 r S Picinq t Mixture of ' Type 304 and 31610" Sch. 40 Stainless Steel sections. Ed 17. Edi ASTM Material Certification m -- J All welds *,. ly radiographed except for weld-o-let connections ~ to existing DHR ip*ng. Desion C r i t e r i,,=, E Loads N sidere? No. mal oles OBE ~: T j M, Normat st. II.al ts will be met for all piping and components including losos f rc.n 08E. i Design Stress Limits Used: s. Pumps, Valves, Heat Exchangers - as soecified in ASME, Section Ill for applicable Code Class. .w w I Piping - Stress limits per ANSI B-31.7. Valves including operators have been seismically qualified for worse seismic environment than would be experienced at TMI site in an SSE. 165 226 . mal < 1 -_9 . h-_l, 3,_j. ,, _ _ g,._j c..: ..~......, - . w s _ _ _.. _ _
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r Pumps and Heat Exchanger - V to review BTW supplied Design .f, ' 5peci fica t ion for specific seismic qualification and advise NRC. = Desion information: Soccific For System to Existing DHR Pioing, Weld-o-let Connection 0-Reinforcement area of fitting provides a 240 percent margin ~ l' over the area of DHR piping it replaces. ~~ "~ ~ ' ' ~ W Pipe supports will be arranged so maximum stress levels from the normal plus OBE load combination at the weld-o-let to DHR }'s pipe interaction will be held to about one thi rd of the B-31.7 .7 stress limit for normal loads. 9. Veld-o-let to DHR pipe welds will be made using a qualified c-procedure and by welders qualified on weld-o-let to pipe con-nec t i on mockups. I ~ Because of time constraints, the weld-o-let to pipe welds will m not be radiographed; however, the root of the weld will be ground and dye penetrate inspected and the final surface will be dye penetrant inspected. Additionally, the design is being qualified by hydrostatic pressure tests and bending moment tests which apply loads until the simulated DHR pipe exceeds its yield strength. 165 227 m... n ..,....._-.c s.
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. *-~-~ ~.~.... ..:...s-.-.,.. ~ ~-- -. - - 5... =." -i..'.. r .g:Y =. J All welds and the cut into the DHR pipe will be performed U~i .g. using the plasma arc method. The plasma arc was chosen for "" 1 I-the combination of small heat-affected zone and minimum 72 [ resulting slag which can be cleaned us. I M Miscellaneous s. ' ~ ' Valves - Line valves and relief falves will have leakage l.@. or discharge fluid piped to a drain tank in the auxiliary I _--'] building. l ~. r -2.. l -. r '. - =~ =2.~ Decay Heat Closed Cooling Water Svstem Comoonents i a I _L. ASME Section iII CL.3 'I~E 2 For all components-Materials: C.S. piping ? S.S. Pumo, Valves, Heat Exchange r 4
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+ which will be flanged. 5. Instrumentation for New Decav Heat Renoval System The following identifies the instrumentation to be provided by j Vestinghouse for the third DHR System train. 3 A trailer will be used to provide remote control room ..~ operat. ion. 165 228 ~* $ L.q
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T .< ---:w.. -~. -. ...........-.--.--a.: .= ....m.....-...-... SC.. n, . _ = 2,>., z-t 1 4 DHR System Pressure Transmitters with remote control '?] .A..e. room indication. ~ Two have lown pressure alarms. ,~ = 2. 2T Sensors for each pump leg with remote control H0T room indication. W 3 2 Pressure Transmitters Upstream cf DHR cooler with remote control room Indications, 4. 2 Pressure Transmitters downstream of DHR cooler with ~~~ =. C remote control room indications. .:= 5. 2 DHR System Flow, 2 Delta P transmitters from a single d'E ori fice with remote control room indications with low flow t; : alarms. 6. 2T sensors with remote control room indication. COLD The instrumentation supplied by Vestinghouse will provide m measurements of the important system variables - nressure, flow, and temperature. The pressure measurement provides system pressure at the suction of the pumps. From the pressure measurenent, estimates of' pressurizer water level c an be made. The temperature measurements provide rear. tor values. TH0T d TC01.0 165 229 . j i ~- -' v -~~. ~ 1?-~ . ',, * * * ' ~ ' -- -'*-*'---[-~~ ~ ...f._- ~ 2 -... W b'w A s. a 7 - ),. Aga,,, d m g.~. '.. d .y, ,d m, a ea -~ W. J '
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'b ENCLOSURE 3 r COMMENTS ON POSSIBLE OTSG DESIGN I' LIMITATIONS RELATING TO VATER SOLID OPERATION -J-- Water Solid Steam Generator Flow Considerations Prior to the accident B&W had established an upper limit of 1000 gpm for secondary side fluid flow - under water solid -7 conditions. This limitation i.s apparently related to concerns P. over possible tube vibration. The steam gene rators a re com- .T pletely filled with water during normal operation of the plant ? for performing hydrostatic tests. e-- a... 3 'f Although subject to con f i rma t ion f rom B&W we bel i eve t ha'. w 'en g such tests are perfor ed the inside of the tubes are dry. When the OTSG is used water-solid for ~ core cooling, tl.3 ~ tubes will be filled. Because the water filled tubes will .k m have considerably more mass.and s tif fness, it is unlikely that vibration would be a concern in the water solid shutdown cool- ~ ing mode of operation. ~165 233 } ,g. - -. -.. ~ .,.a.. .a ..... ~, ~ e.is.;,;.- ,w s.a.m u *.,.auM\\m..% ' - -
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-. L.h '.. :-.1 ~ h.= '=. l. ~ ~' ENCL.05URE 4 -~~- ~. - - ~ - - .92~ ASSESSMENT OF RADIOLOGICAL CONSEQUENCES OF .a OPERATION OF STEAM GENERATOR 8 IN [_ SHORT TERM MODE 7.' The procedure for operation of Steam Generator 8 in the solid mode must consider radiological effects of this operation on radia-tion levels which may develcip in the turbine building as well as the possibility that some leakage may occur across the Secondary Services. Cooling Vater Heat Exchanger and be released to the 5? basin of the mechanical draft cooling tower. Calculations can L. be performed to assess the radiation levels expected assuming -jL a source term based upon the latest known water activity
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/-E levels and assuming this is in the existing inventory. The s :- calculations can then be extended to evaluate a range of primary-to-secondary leakage rates. The need to include the latest primary water activity levels should be considered. The results of these.analysc chould suggest requirements pertaining to: uwn 1. The need to address possible use or demineralizers, e.g. condensate demineralizers, to reduce secondary side contamination prior to use of secondary side of OTSG-8 This could offer a clue as to possible additional primary to secondary leakage. 2. T',e i.-d t a speci fy the inte rval s for sampi f ng secondary wa te r. 165 2M e -_s, = Q ~ m p m M Dessen.svr', - euts M k' " *"* A - ~^- 'W*#"4'****"" .s.' e.ame ? h.bM ea== =.eew %***
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q,. ' :-.. _.. ?.+L ',*Q $&.. ' " CM-i*W ' :~" ^ ~. ' M ~ : C.'*'"* ~* * - '.. " ..'T ---E- ~ ~, ~ =. =.. - -, =.. 2 m T *~ ~~M 3 The need to specify criteria for isolation of the Steam =. w.:_ Generator B and return to Steam Generator A or some other $=. mode of decay heat removal. 4 The need to specify levels of anticipated contamination '= A. In the turbine building, e.g., liquid leakage, and airborne contamination. 'h 5 The need for additional shielding of any hot piping or ~ demineralizers. -' E ./ 6. The need to control discharces of turbine sume water to a radiation controlled location for samoling ,r treatment prior to discharge. '.t. 7. The need to address locations and release ::oints of all vents, drains, traps, and pressure relief valves and mechanisms for e treatment if necessary. ' 8. The need to check valve line ups to assure a unnecessar'y con- ! tamination of " clean" areas. 9. The need to verify operability of the radiation monitoring '~ pit monitor Pfi-C7 shich reads out in Unit I control room and monitors the mechanical draf t cool ing towe r bl owdown. V 165 2*h ,,q. ....0. ,...-..w..... r-Q 84 ' 's., .4. o ~ I % ..' r.. 4. .~ m. e e...w ay m
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,. ;; g ..r.,. ,,,n.,-_,., g,.;,......... ..g.. ....,.-,s.. .s .- ^2. I -- '.. rG .:.Q' \\ ~ ~.. -. .f-2 Steam Generator "B" Tube Leakace = 'D There has been discussion about the fact that the proposed short te m cooling system loop that would utilize the B Steam Generator may be vulnerable to leakage through the steam 2" ~2 generator, it is not clear at this time how much this 1- - gene ra to r leaked during the initial portion of the transient and whether such leakage would occur at the ] lower temperatura and lower pressure dif ference conditions =. ; Z, of long term cooling. However, it is known there is now W contaminated water on the secondary side of this generator. 'r ' b B&W has suggested that there are mechanisms other than tube E:, ~ ' leakage by which the contaminated fluid could have entered the secondary side during the March 28 accident. .t Currently, there is about a factor of 10 between the pri-mary coolant iodine concentration and the OTSGB secondary s ide concentration. This means it would take 10000 gallons of clean water on the secondary side to dilute one gallon of primary coolant to current secondary side activity levels. This could be construed to imply the leakage has s topped since the iodine activity in samples taken of OTSG-B appears to be decreasing wi th decay. 165 2 % i"; %.m.. . -..... s..... .m .l;... u n.s.. a.. a.e e au*s->.*4.~ ~... ' E6a t.a J.: ..f.,.6.;. r ,.s e e
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The potential for leakage across the SSCV coolers into the river w ater appears high as these coolers are not designed for high = temperatures or pressures. Ve suggest that the possibility of pressurizing the cooling side above the shell side with the =Z secondary water be considered. If demineralizers are not used to clean up OTSG-8 secondary water and no additional primary to m ~ secondary leakage occurs, the tolerable leakage across the coolers '.'i is less than 0.1 gpm to restrict the river water outfall to Part ~.d~ 20 unrestricted area levels on iodine. This assumes dilution in the OTSG-B by flooding up to the MSIV and a mechanical draft cool-4=.i ing tower blowdown flow of 40000 gpm. ~ _ - - e .n.
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SUMMARY
OF B & W SUBMITTAL OF april 10 1979 REGAR01NG NATURAL Cl RCULAT10N .:q -:,.1 .~ .,g Comments on the B&W submittal regarding Natural Circulation: The B&W recommended primary coolant temperature for initla-tion of natural circulation core cooling is 100 F. The ~ reactor cooling system would be put into a water solid con-n:... dition and with reactor coolant system pressure b'etween 20 and 50 psia. B&W recommends both steam generators operating in a water .d solid mode at the time natural circulation is initiated with a 3000 gpm minimum '(5000 gpm preferred) flowrate provided t o each steam generatsr. .r B&W also notes that a much lower reactor coolant pressure can be maintained with solid water secondary side as opposed to m steaming on the secondary side. B&W suggested that operating both steam generators in natural circulation mode in a water solid condition provides an in-crease between 10 and 20 percent in natural circulation flow-rates. For steady-state operation two steam generators operating in natural circulation water solid would not be required. The case of transition, etc., suggests the need for.two steam genera-tors operating instead of only one generator in operation at the time when natural ci rcula tion is initiated. \\m 738 2 4 U-c. .y -~_; ~ .a L. .c -.. w >. - ink-m.-~ - w =-!L- ~-.-s= M -~'S~ ~--~ ME N ' N
'~ lp -;-h' ' r, R. -. ~:~.:= Q.. _ _, _.' 7 , _ -., _ _..,, _ _, _ _ _.... z... .. p x,-, w.. :-.,..... ,u, Q: 9.., -I. .., "..a [] B&W proposes a 100 F subcooling margin for defining accep- =.
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table natural circulation performance. C Comments un Other Natural Circulation Conditions I 2-loop operation with both steam generators,teamingat2'30( O with secondary side water level at the 95 percent level on the operating range. This mode of operation has been verified by- ~ ~ [f'J operation at the Oconee Station. .h..,- Steam Generator A steaming at 230 F and Steam Generator 8 x-I Isolated with water at the 30 foot level. Natural circula- -T. tion is estimated to be 10 to 20 percent less for this con-ditita than with both steam generators in service. ~ Single loop operation with Steam Generator A operating with a solid secondary. A minimum secondary flowrate of 3000 gpm will piovide similar natural circulation to a single loop steaming with a 30 foot secoidary side water le e 2 loop operation with both steam generators operating with solid secondary and 3000 gpm feedwater being provided to each steam generator. This is the preferred mode of operation. k O ' E. \\ 6 5 _.. -. c _.:_ _... ~ E.- ~. G.. w a.. w . Le e..- '. w ~ J - a L ' --- - -4 = - M e W _:'-.. T=. J . ~~ L.1. ~ M ?a:"w.r -.L
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~ .p ~ m. P The following B&V ccmments on the transition f rom forced ci rcula-92 tion to natural c!rculation are provided: .i I t was a ssumed that the transition would be made w!th' s.ii :-; both Steam Generator A and 3 operating in a solid mode. The B&W analyses predict a minimum core flow occurring -a about minute into the transient. Stable natural cir-culation flow is expected to occur af ter about 10 minutes Y into the transient. Hot leg temperature changes should ~ be observed at about 5 minutes into the transient. .p. N ConsiderIng the 1000F sub-cool ing cr i ter it.n, the B&W recommenda-tion is made to maintain reactor coolant system pressure as high as practicai at the time the reactor coolant pump is t. ~ t ri ppe d. For example, ooerating at 500 psig permits the 4 reactor cool nt temperature to increase 340 F before the temperature limit would be reached. The following recommendations were nade by B&W regarding the overall transition to natural circulation. 5 1. Reduce Reactor Coolant System temperature to 230 F with Steam Generator A steaming. 2. Slowly fill Steam Generator 3 solid wi th water and begin heat removal until stable temoeratures are reached in the 200-230 F range and :hm proceed to isolate Steam Generator A. 4 165 240 a
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- ENCLOSURE 6
. e.' .S.,'*. _, 4 L H.': SPENT FUEL PIT H0DIFl CATION ~ -= 05 W Figure I shows the proposed Spent Fuel Pit Modification. The pur-e pose of tre modification is to dispose of high level auxiliary building waste. Two tanks will be located at the bottom of the p it, 25,000 gal each. Their elevation will be. adjusted by means I of additional beams so that there is a clearance of approx. Ifoot .w .'. -C between the outside of the tank and the concrete structure. Four additional tanks 15.000 gal, each will be suspended from beams M (A) (See Figure 1), supported by the existing rails. The cross 1 I. bracing, consisting of structural L's will be provided to sti f fen the d s uspension structure. != - The tanks were originally intended for middle and low level waste at another nuclear plant (see Q/C discussion for further details). The w tanks will be prefabricated together with their hangers and their supporting beams and the entire assembly consisting of one 15,000 -vm gal, tank, its cross-bracing and the supporting beams will be lowered into the pool. The tanks are fabricated with their - ddles consisting of stiffened steel plates. At this time no information. is available regarding piping and electrical connections. 6 1 165 242
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