ML20033D366
| ML20033D366 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 11/30/1981 |
| From: | Johnston W Office of Nuclear Reactor Regulation |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML082410577 | List: |
| References | |
| FOIA-92-463 NUDOCS 8112170335 | |
| Download: ML20033D366 (6) | |
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Docket Hos. 50-352 i
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S0-353 S
'e'/Th MEMDRANDUM FOR: Robert L. Tedesco, Assistant Director 8 01g3IA 'I for Licensing L
Division of Licensing h "* 4:u, D
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William V. Johnston, Assistant Director Q/
FROM:
9 for Materials & Qualifications Engineering f
G Division of Encinesrina SU3 JECT:
PliE STORAGE PRACTICES AT LIMERICK i
i GENERATIIG STATI0'l SITE in response to your renarandum of July 8,1981, the Corrosion Engineering Sec-tion of the Chemical Engineering Branch, with consultation from Bmokhaven l
National Laboratory, has evaluated the carbon steel pipe storage practices at Limerick Generating Station.
l We find that, on the basis of the Icw corrosion rates and the inspections perfomed and witnessed by the NRC inspectors, that the piping is acceptable fcr use.
At other plant construction sites, however, especially those on coastal locations where chloride contanination is probable, pipes should be placed such that natural drainage will occur with the upper ends capped to prevent significant ingress of chlorides.
l William V. Johnston, Assistant Director for Materials 8 Qualifications Engineering Division of Engineering i
Enclos ure:
Safety Evaluation Report for Linerick
Contact:
D. Tumvlin X28556 j
cc: !; ext pa;,e 8112170335 811130 l.
CF ADOCk 03000352 a
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Philadelphia Electric Cumpany i
Limerick Generating Station, Units 1 &2 Corrosion Engineering Section Chemical Engineering Dranch i
Site Pipe Storage Practices
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Dackground Information
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Oy Amendment 17 to Appendix A,
the applicant requested' permission j
1 to store carbon steel pipes outside without end caps.
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The justification for supporting this amendment consisted c1 l
L imit ed corrosien data, and was questioned by the Chief, Reactor Construction and Engineering Support Dranch, NRC:1 i n March 1977 l
t and has been an item of active controversy to date.
Eva!uation l
j In order to evaluate the utitity's pipe storage practicese we i
j ct,cpared the susceptibility of capped and uncapped pipe to the corrosion process and the limiting factors of availability of 4
n oxygen and presence of aggressive species in the aqueous M
environment, such as.htorides.
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Most pipe spools are not capped with a pressure tight seat but rather with plastic and caps, which in nornal circunstances allow water vapor intrusion (and eventual condensatien) as a result of I
the espansion and contraction cycle of the pipe on warm days s
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relatively cooter evening hours, thi; c oriden s e d moisture through s
would tend to accumulate and provide the aqueous solution f
necessary to cause localized ccirrosion.
The oxygen supply would j
also !<e rejuvenated on the inside of the pipe spool during the f
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contraction cycle and therefore available to sustain the corrosion process.
The condensed water may also contain 4
dissolved tonic species which mi Dht further concentrate locally on the pipe surface and accelerate the corrosion roter by repeat ed evaporat ions and rewet t ing.
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The licensee's alternative to topped pipe spool storage consists of three steps:
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a) removal of sealant tape, end caps, and dessicant from the pipe spoolse i
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b) location of all spools in storage such that they are free l
l draining and not in contact with the grounds
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i c) inst allat ion of rain hoods on open ends protruding upward, where spools are impossible to situate in storage without leaving a " rocket" in which water may be trapped.
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This method of pipe storage would clietnate the problem of n
standing water.
The conted angle of the pipe would also help l
to wash off any water soluble contaninants on the pipe's inside t
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, surface during periods of rain.
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' Lither acthod of storage would term 19 :'6 5nac a sufficisr.t sepunt i
of caygen to promote sont corrosions if the slett is in contact with vattro regsidLts: of tsps bring prestnte j
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Mlld steel Is not generstly susceptible to the sees type of intergranuter attack as art sustenitte stainless stetts in the I
presence of chlorldts, sulf at es, nit rates of carbonates tacept j
l st elevated itsperatures, thest contaninants in verlous trate amounts are assuard to be the c onst lturnt s of the rain la the j
Llatrick sres,
!!nte Intergranular corrosion can be esfely
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ruled outs the prioary concern would then center on s thlnning j
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l of the pipe watt thickness below ASMC Codt required Levels by W
tither o generat totrosion or perhaps e pittlng et tsch, a
j tither of the se prottssts would rety on onyf tn sys tlablLily
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and the chtnistry of the aqueous ardlus, which in both casts
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appear to kt comparsklee the rstes of neither are tellskly i
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i sessured by weight lost technicurs.
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fcterhone convernstions vlth the Llatttch sitt resident tst Inspector confirard (bst the withdrsynt of pipt f rom tutdter
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storsgt is governed by site procedures which rt4ulte a grit i
blasting operation and a thorough (LeJnlIntst inspectlen prier f
a to Instat tst len.
this inspect ion would include the rejectlen of pitso gougese had other delet t so shith wov\\d entresth on ihe Pipt's mininus Codt allowed wall thltkness.
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d The avsfleble test dets show the overstl watt thinning in I
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ettner case to be relativet, saalt.
This together with i t.r i
utility's practist of prit blasting the pipe and then l
i perferaing a visvat inspestien of the inside surface for l
l stesallness and defects prior te Installation gives assurante j
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that the evtsidt storage of the pipe without end caps will 1
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not pese say serious hasards to the paterials intended service l
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On the basis of the low serres ten rates and the inspection perferase sad ultnessed by the Est lastatters, we conclude i
j tble piping 13 agssplable for the Lirtrick statten.
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