ML20246N106
| ML20246N106 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 01/25/1989 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Lear G NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation |
| References | |
| CON-NRC-87-12 OLA-A-005, OLA-A-5, VPNPD-87-48, NUDOCS 8903270301 | |
| Download: ML20246N106 (27) | |
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,IU NRC-87-12 00CK!],m' February 11, 1987 Document Control Desk U.S. NUCLEAR REGULATORY-COMMISSION Washington, D.C. 20555 Attention: Mr. George Lear, Director PWR Project Directorate No. 1 Gentlemen:
9 DOCKET NOS. 50-266 AND 50-301 AESULTF0F6"" **""M REMOVED TRON. Tns. Erzws ruso ETwsWWs5. RAC345 POINT ='"_r= ="'r== v' = - r - umrra -1. aun . -
_.p3 Our July 23, 1986 letter advised you of our intent to remove two poison insert assemblies from the spent fuel storage racks and examine them. In that letter, we also committed to provi-ding you the results of our examination. Our report, "Results of Boraflex Examination, Point Beach Nuclear Plant" is enclosed -
with this letter and provides the examination results and our conclusions.
In the enclosure, we note that the f"11-1 .g;. ....e . in-t W sp= a t -- f"-1 f'3=' *=-k= - e i n ,.. 1 1 . .. w .4 a l i i e n . The full-length Boraflex inserts have behaved largely as predicted for the gamma exposure received, experiencing embrittlement and .,
some dimensional shrinkage. Overall, the nnrmfl., insert -were-found suitable for ps e fn emi n er their intended fun-*4mn On the other hand, th 2" x-?" : ;1 : i- ^"- -"rua4M.ancg progr== h="e zeer5M = atmen wh-** tha h-=--
4=
f ri abM anskaasily-defeeded,- The neutron attenuation properties of the samples were confirmed by testing at the Georgia Institute of Technology. However, tgirphysicalintegrityshoweddeteri-oration at doses of 1 x 10 rac.s gamma and greater.
8903270301 PDR ADOCK QM PDR 35 l
'1] .i 4' Document Control Desk February 11, 1987 l
, Page 2 i
-)
.. 1 Currently, the average spent fuel rack position has accumulated _
a gamma dose equivalent to six years exposure or 3 x 10 rads gamma. {
Theg gamples have been irradiated to gamma exposures up 1 to 1.6 x 10 rads gamma. The full-length Boraflex insert ygich was examined received accelerated gamma exposures of 1 x 10 rads, because it was adjacent to the sample location. This dose is equivalent to 20 years'for the average spent fuel rack loca-tion.
We have concluded from-the comparison of the~two programs that the samples are not representative of the-full-length Boraflex inserts. The differences observed between the physical condi- !
tions of the full-length sheets and' smaller samples are possibly 1 attributable to differences in methods of encapsulation, Boraflex geometry, and handling frequency. We do believe, however, that permention of acidic spent fuel pool (SFP) water into Boraflex has a role in diminishing the integrity of the Boraflex material.
It further appears that the extent of SFP water permeation into Boraflex is a function of gamma dose received. Our report pro-vides additional information to support these conclusions.
To monitor the condition of boraflex in the Point Beach spent fuel rccks, we intend to modify future s3,rveillance as follows:
- 1. Since the samples do not appear representative of the full length Boraflex sheets and have limited value in predicting the onset of Boraflex degrada- 1 tion in the spent fuel racks, we will terminate the Point Beach surveillance program in REI-25, " Spent Fuel Rack Neutron Absorbing Material Surveillance Specimen Program." This includes eliminating the requirement to place freshly discharged spent fuel adjacent to the sample location every six months.
- 2. In the place of the current surveillance program, we will examine another full-length Boraflex sheet in approximately 5 years from the present. The recom- ,
i mendedinsert-isatposit{gnSN-40/41,asitcurrently has exposures of 1.5 x 10 rads gamma.
- 3. Subsequent examinations will be performed'at locations and intervals to be determined after the next inspection.
- 4. We will continue to follow the industry's development of data regarding Boraflex.
s
s . . '.
Document Control Desk February 11, 1987 Page 3 I
Overall,webelieveourexaminatdonhasconfirmedthecontinued serviceability of the full-length Boraflex inserts in the Point Beach spent fuel racks. If you have questions concerning our report, please do not hesitate to contact us.
Very truly yours, 2, g C. w. Fay Vice President Nuclear Power Enclosure Copy to NRC Resident Inspector NRC Regional Administrator, Region III 0
l
. February 11, 1987-F RESULTS OF BORAFLEX EXAMINATION POINT BEACH NUCLEAR PLANT-l Background -
~
Our license amendment application to inc'rease the spent fuel storage capacity at Point Beach Nuclear Plant (PBNP) was submitted to NRC on March 21, 1978.
In response to NRC requests for additional information, we described a surveillance program to verify the continued integrity of the Boraflex material contained in the spent fuel storage racks. This program utilized l
30 standard, 2" x 2" Boraflex squares per pool that were control checked and placed in a surveillance train (See Figure 1). These samples were then suspended in a poison box location in the spent fuel pool-(SFP) such that freshly discharged spent fuel assemblies could be placed next to the surveil-lance sample location,.thus providing maximum irradiation to the samples.
Tes+= m -+ t: M perforsakaftar_twctyears avaa="e= '4" y::r: spner;, _
and tea-yeero-::;:: r:. Additionat testilfcFehanges w ui. i. .,tr:; c' testing.could.bt_specifi-d f r--din r;:r *'" c"*^^+4^^ ^' spar.insa w remaued-dur4ag-the-eeelp portion-abtha progr== ___ _
BISCO Report No. 1047-1, "Boraflex I Suitability Report", Revision 1, dated May 5,1978 provides information on the testing done to qualify Boraflex for use in the radiation and borated water environment found in the SFP.
Inthesegests,Bgraflexwasirradiatedtointegratedgammadosesofapprox-mately 10 and 10 rads. At these dose levels, testing was done to measure changes in tensile strength, elongation, elastic modulus, dimensions, weight, and hardness. Additionally, a study of gases evolved in the test chamber -
was conducted. The qualification study also immersed Boraflex in 3,000 ppm borated water for a period in excess of 4,700 hArs. The water temperature-was 240'F, and the water pH was adjusted by the addition of NaOH'to a range of 9.0 to 9.5. <
In BISCO Report No. 748-10-1, " Irradiation Study of Boraflex Neutron Shielding Materials", dated July 25, 1979, the test program further checked the stability oftheBoraflexandtheneutrggattenuationcapabilityoftheboraflexata cummulative gamma level of 10 rads.
The qualification c+nd47- -----ally indiented Enraflax to A. -+- 4- + ha_
hi gh + ^ r--= + "ea wa+ae = ^ = l< med *adiggjen envd ronment found ingsptat, fu W peol. The data gdicated that Boraflex wi'1 generaWgas up to irradia-tion levels of 1 x 10 rads gamma. The "! " *i c-t i r .... ;;di-"-d that.
alth e m m- eraflex embrit.tleLwith irradiation; thmen 4e'14++1= inne gi a' '----
neutrababooep64empaaparlias_su radi a tei h"+ 4 aa Boraflex Use in Point Beach Spent Fuel Racks Borallax.was chose ntee-wee-es-th: ;- L ... Mr ::txt:'. % tha.Jaint Beach. spent fuel TachLWitiLa_INgnitiaa a' i+" " =" = + i =9 s . For example, because.Sorallet.becomes smbr.ittled.And a"- 'r:-- ^^-- di-ansjonaldegse due..te ;- r dietteny bonding-of-L anem in iim ey.n. f_:' racks was -
elimia2+=dfra=_+ha Paint.Saash d--i r r d n . 2 .7 ;n -d"-=. Instead" the ,
_ _ _ _ _ . . _ . _ _ _ _ _ _ ____m___._______.________._______
tha Becaflem-sheet. wee simply. placad-within stainless.stambcled theb.
essenti. ally forme a p a'=+a.snyalopa?aroundethe-Sereflowe This arrangement also elimlnatabany loading to bo transmitted,to ths.&orafias. .To prevent i poison assembly swelling due to offgassing, the tight-fitting stainless steel envelope was also vented at the top and made open to the SFP water environment. t Elimination of the potential for galvanic corrosion was an important onsid- 1'
.eration in the selection of Boraflex over alternative metallic or metal-con-taining materials.
The sample test program has confirmed some of the known limitations, but the-overall behavior of Boraflex in the racks is within expectations. Neverthe-less, in4the-Pe4+Besetr spenkfwokrash das;laa + ' ;r' n inserts"aren.
.- 1 individu4 Libra 91Acaable should lengstarm .nanteaa a*****=h 24 Momm.
develek insths Saraflaa--
Surveillance Specimen Prograni - March 1985 Testino and Results In accordance with the Point Beach Nuclear Plant Boraflex sample surveillance program, six Boraflex specimens (North Pool - N7, N8, & N9; South Pool - 54, ;
l 55, & 56) were cut from their respective sample trains and shipped to the 1 1 Georgia Institute of Technology in March of 1985 for testing. This testing I program included neutron radiography of the samples, neutron attenuation testing utilizing a thermal beam of neutrons at an energy of .037 eV, weight a and thickness measurements, hardness testing in a Shore A durometer, and isotopic analysis of the boraflex.
The specimens were dried.out in an attempt to decontaminate and reduce the radiation levels of the specimens prior to shipment to Georgia Tech. i Contact radiation readings of the samples at PBNP, averaged 35-45 mrad i beta gamma per hour. Subsequent isotopic analysts of the samples at Georgia Tech determined that these radiation levels resulted principally from Cobalt-60, Cesium-134, and Silvar-110. In effect, +" ":r:f'r ---'- had acte Lat.,.Lspongg_,pnd had absorbed sa== en--+ < " ' =aai --+- _
In packaging for shipment, the Boraflex samples were retained inside the original clad channels that were cut from the sample trains. The stainless steel clad was then inserted in a snug fit between lead shielding designed for a 2-2.5 inch pipe. This was then banded, wrapped, and placed in a 55 gallon shipping drum. When the drum was opened at Georgia Tech, it was observed that the stainless clad had bent somewhat and was applying a slight force to the Boraflex samples contained therein. This torsion may have contributed to some breakage of the already brittle samples.
At Georgia Tech the Boraflex specimens were observed to have broken into multiple smaller chips. These chips were friable with a small amount of graphite-like particulate matter loosely covering them. Ti. 0. . . G ., C ';
wertolargoc - " : " ' r_ ^. . . . C ^.. . ... ^.1. . . .. ^.. , . .. . . . . . 221. oh some.,0f thS,,thicknatt da+= e-a"*"+-d 4a +A ***=+ 9eaa**=- However, width and weight measurements could not be obtained as specified in the test program due to the crumbled state of the specimens.
l Hardness of the specimens in the Shore A durometer was 100 or fully hard.
This is higher than the original material qualification studies projected.
Neutron attenuation capability of the Boraflex was about 99%, slightly
.g.
~, .
higher than projected. Sample thickness averaged about 0.1No inch and had decre~ased roughly as the qualification studies projected. conclusions could be drawn concerning the change in weight and width of the specimens duetotheirbrokensgte. Thetotalgammadosetothenorthandsouthtrainswas 3
R, respectively.
estimated at 1.4 x 10 R and 1.0 x 10 p In reviewing the specimen degradation problems, several factors,'alone or in combination, were thought to have contributed:
I
- The specimens were thoroughly dried out prior to shipping.
- Shipping and handling, although accomplished carefully, did apply some torsion and shocks to the specimens.
- The PBNP Boraflex specimens may have been exposed to an environment outside of BISCO's original material qualification envelope. In other words, the Boraflex immersion tests in. BISCO's qualification study were done in a borated solution of 3,000 parts per million boron in the form of boric acid that was, however, pH adjusted by the addition of sodium hydroxide to a pH range of 9.0 to 9.5. This differs from the Point Beach SFP environment in which the pH ranges from 4.5 to 4.9. See Attachment 1 for typical chem-istry in the Point Beach SFP. J As initial resolution of the problems of specimen degradation and ensuing testing, several actions were taken.
- Point Beach, Reactor Engineering Instruction REI-25, " Spent Fuel Rack Neutron Absorbing Material Surveillance Specimen Program," was revised to test additional Boraflex specimens immediately and in mid-1987. This was in addition to the testing scheduled for 1990, the ten year test date.
i
- In preparing the Boraflex samples for shipment, they would be braced and shipped in a moist condition, with no loose water in the shipping package.
- Chemical analysis would be included in future Botaflex testing to deter-mine if the Boraflex may be undergoing a chemical reaction in the SFP environment.
Also at this time, the geometry of poison inserts and lead-in guides in the l spent fuel racks was carefully reviewed. It was determined that the nominally _
O.11 inch thick Boraflex sheets were closely retained by the clad such that
" slumping" of the Boraflex material could not occur even if it should crack. [
The Boraflex material is sandwiched between two pieces of stainless steel /
sheet that are completely seam-welded on three sides and seam-welded on the /
top with intermittent fusion to allow gases to escape. f Supplemental Surveillance - October 1985 Testing and Results ,
In October of 1985, three more boraflex samples (N10, Nil, & N12) were shipped toGeorgiaTechforasimilartegingprogram. The total gamma dose received
.by the test samples was 1.6 x 10 rads. The samples were shipped to Georgia Tech in a container of SFP water that was further packed,in a shipping drum.
Upon unpacking the samples at Georgia Tech, it was observed that the water
. used to ship the samples was black. .
4 Subsequent inspection and testing of the samples revealed that the corners In fact, of the Botaflex samples were rounded and the edges were eroded. ,,
sample thickness, width, and weight for these samples decreased an average of 30%, 15%, and 50%,~respectively.Boraflex samples, however, was projections. Hardness measurements in the Shore A durometer indjcated Chemical compo-one sample to be 100 and the other two only slightly less.
sition testing (spectrographic analysis and gas chromatograph mass spectro-scopy) on a Boraflex sample and the surrounding graphite-like powder had ill been specified but could not be performed due to the contamination level of l the samples.
While the water in the shipping container was black with graphite-like particulate shed from the samples, the Boraflex color itself w darkened the water, but each time to a lesser extent.When a sample of this rinsed Borafl in turn, lightened to a whitish gray.
was placed in a beaker and magnetically stirred for 36Nohours, the water additional stayed clear and only " crumbs" from the sample came off.It should be noted that
" sooty" black material appeared.
particulate material shed from the Beraflex did not appear to dissolve to any extent, but eventually settled to the bottom of the beakers.
Again, transportation was suspected as having caused degradation of the bora-flex samples. It was hypothesized that agitation of the Boraflex container
' during shipping caused erosion and wear on the Boraflex, much like might occur in a moving stream.
Supplemental Surveillance - April 1986 Testino and Results !
l To further investigate sample thinning and degradation, an additional ;
sample, N-13, was removed from the SFP in April 1986 and examined at PBNP. i Again, the decrease in sample thickness, width, and weight was '
50%, respectively.in the SFP environment and was not resulting primarily from trans as suspected previously.
In summary, the neutron attenuating capability of the Botaflex was confirmed by the recent testing, but the Boraflex samples were found to be fragile and easily broken. The following summarizes the doses the samples received:
Gamma Dose
~1.44 x 10 rads .,
Boraflex Test Samples: N-7, 8, & 9 ~1.0 x 10 rads S-4, 5, & 6 (Tested at Georgia Tech in March 1985) 10 rads Boraflex Test Samples: N-10, 11 & 12 +1.55 x 10 (Tested at Georgia Tech in November 1985) ,
10
~1.6 x 10 rads Boraflex Test Sample: N-13 (Examined at PBNP in April 1986)
- Full-length Boraflex Sheet Examination - August 1986 Since there are significant differences in the geometry and encapsulation
c - ,
_. y methods between the Boraflex samples and the actual fell-length sheets in the spent fuel storage racks, we decided to remove two full-length Boraflex sheets from the SFP and examine them on-site.
On August 18-20, 1986 twoBoraflexpoisoninsertandlead-inguipeassemblies After each assembly was re-were removed from the SFP at PBNP and examined.
moveo from the spent fuel storage racks, a replacement poison assembly, manu-factured to original material and dimensional specifications, was immediately installed. The poison inserts were chosen for examination based on the gamma exposure received. One poison insert was highly irradiated; the other was not. This combination was intended to identify whether the SFP water was affecting the Boraflex, apart from known radiation embrittlement.
The location of these poison inserts in the SFP and their exposures were as follows:
SFP LOCATION Gamma Dese SX-47 (West) .
0 rads 10 SP-40/41 +1 x 10 rads 10 Typical Botaflex insert in 1.8-2.0 x 10 rads spent fuel racks after 40 Years The projected 40 year exposure is based on placing fresh spent fuel in a typical location in the spent fuel racks three (3) times on thirteen (13) year cycles. Hence, the recently tested samples had exposures approaching the 40 year design exposure of the Botaflex in the spent fuel racks. The poison insert from SP-40/41 received one-half of this design exposure, or in other words, an equivalent dose equal to 20 years. The Boraflex insert in since it was adjacent to the position location SP-40/41 received accelerated of the surveillance exposure,iad test samples, which recently discharged spent fuel assemblies placed next to them every six months. This compares to a poison insert in the average spent fuel rack position which has received about six (6) years exposure or about 3.0 x 10' rads gamma.
Removal / replacement of the Botaflex insert and lead-in guide assemblies in SFP positions SX-47 and SP-40/41 was performed according "to Point Beach Nuclear Plant Special Maintenance Procedure (SMP) - 72B, Examination of Bora-flex Sheets from Poison Insert Assemblies Removed from the Spent Fuel Racks."
This procedure required immediate replacement with a poison assembly manu-factured to the original material specifications after each poison insert was removed from the spent fuel storage racks.
The full length poison inserts selected for examination were chosen to contrast the effect of gamma irradiation and compare the effects of exposure to the SFP water environment on Boraflex. This cause and effect approach was adopted because the original Boraflex material qualification studies were performed by BISCO at a pH 1evel different than that of the Point Beach SFP. In addition, the actual 5 year exposure time to the SFP water environ-ment is more lengthy than that of the qualification testing.
The Boraflex inserts were inspected according to Table 1 - Boraflex Qualita-
- tive Inspection Criteria and Table 2 - Boraflex Quantitative Inspection Criteria of SMP-728. These tables are provided in Attachment 2. Attach-m
.v. ,
~
~
ment.3 is a radiological survey of the samples taken from both of the larger l Boraflex sheets. Attachment 4 consists of pictures taken to document the examination of the larger Boraflex sheets.
I It should be noted that both Boraflex' sheets were wholly intact phen initially examined. During the exam, the Boraflex was broken in many places to gauge its brittleness and hardness. The photographs of Attachment 4 document this examination and corresponding cleavage fractures, not the as-found state of the Boraflex.
The poison insert at SX-47 received a negligible gamma dose as spent fuel was not placed in this position. This assembly was selected to see if the acidic environment of the spent fuel pool water was causing the degradation observed in the surveillance specimens. In the absence of gamma radiation, this did not appear to be the case. The poison insert appeared to look brand new. Only a whitish powder govering the Boraflex where it was in contact with the stainless steel clad distinguished the SX-47 Boraflex
~
insert from new Boraflex.
10 The poison insart at SP-40/41 received accelerated irradiation to 1 x 10 rads gamma. This insert had good integrity with no pieces missing, no cracking, or other degradation observed. This is unlike the samples S4, 5, and 6 at the same dose. The thickness of the Boraflex sheet was consistent over its length, nominally 0.1 inches. Over most of the insert length, !
the Boraflex sheet was black and did not have dust or powder being shed from
. it.
There were some discolored areas along the edges of the Boraflex insert from SP-40/41. These appeared as gray scallops working into the material and typically measured 0.25 inches deep by about 2.5 inches long. The largest gray patch observed was 0.5-0.75 inches deep by about 5 inches long. l The gray discolorations were spaced randomly along the edges and probably occupied about 1-2% of the entire Boraflex sheet surface area. These gray areas when first observed were reminiscent of the color of the Boraflex samples. Further examination showed that, although the thickness of the Boraflex at the gray areas was consistent with nominal Boraflex thickness, the gray area yielded a dust or powder much like the samples when rubbed.
Overall, the insert from position SP-40/41, although brittle, had good integrity with minimal degradation.
Some additional observations on the full-length Boraflex inserts based on their radiation levels can be made. As stated previously, the Boraflex samples sent to Georgia Tech averaged 35-45 mrad / hour beta gamma, on contact.
These radiation levels were found to principally result from absorption of spent fuel water that contained cobalt and cesium.
The radiation levels of samples taken from the unirradiated Boraflex insert from position SX-47 were less than 2 mrad / hour beta gamma. This indicates the unitradiated insert hardly absorbed any spent fuel pool water.
The radiation levels of samples taken from the irradiated insert from position SP-40/41 were approximately 2 mrad / hour gamma and 8-12 mrad / hour beta, on contact. T'ese radiation levels are less than the surveillance samples, but still indicate some absorption of spent fuel pool water. *
- r. . -
N. .
Radiation levels on contact with the discolored, " gray" area from a section of the SP-40/41 insert were approximately 2 mrad / hour gamma, 80-90 mrad / hour beta, and some detectable alpha. This perhaps indicates that' spent fuel pool water was being absorbed preferentially along the edges of the Boraflex. It also leads to the following observations about the progression qf degradation in the Boraflex: *
- 1. In the absence of gamma radiation, Boraflex appears to be inert to the SFP environment. The unirradiated insert retained "like-new" Boraflex material properties and did not appear to absorb SFP water.
- 2. With,gamme.4eredietteverthe BereMeerpo4ymere ry .. WeMRffCfP a mannan that allows,SFAwater.ta-poemoeto=the9erafftf"aTong' the eifyrs. -l Whens the" 5FP weter-does penetr-+- *k- Saraf. lex ths.sataria.bchanges.,
charseter"It" changesa meteriaFef"goetFinte w,ii.y"and*retentic'n"to~ehe that"1e friablexan6 yields-a. particulate.31'- -" ult alsa.changas,.
colon. free, black- ta' grerr= 0 nee.ft-hee reechstethedgreye stet & thinning, l weighkloserendegenecekd:;- "-theppeaa ta.fn11ag l
- 3. It' appears.S & h p '..; tie 44,wpesena4es tha.Sarmflar pn tht,,,qdgs4 1 o whers.1tuweersu6rto a.dimensien aprepaia b fan,p2 - de r : 4---
assamb 4 The=3finishode brood een h ed.themSasa G ak appaa m te.4e resistaab ter watesepoemoetion Th- 2" 2" e_;;i e, ' a the .c m * " --- ;;- n 5:d - m t'": i smal.k ,
distances h^+waaa ""+ -d;::, h;;.;; th; L"." N Iy*iaW rete !
the-s;;p b 'n e .hr t pee 4:d. - . it.wouli appaa h thab the highopm. '
gamma-radiation Jewe46 - :_'..: by th: ::g':: ::, h..,. ....'.... 4 th$p p rn.m.-
l
- 4. Insthe"casF W B6 Borefiermaf'bigfn(a,QeQxpto be susceptible to water ger eafNand"I bn ~
i y that=s-changes.inumeter$eW. ";-' *; ** -'-~+ 1 w ,n i rede g, Conclusions The BoreMeurs_...J., .ys. 76"n v. w w . , . . i n. . . .. .. ..J i.... ... e gives-gammeodesee thanethemfeHalengetPtpereMesr=9weveer Thise"--- "-* **"_ an4eseems in therpresenertf'd.m.. irisdiatTUR. It is possibly enhanced by differences in the method of encapsulation. 5 - ': "4 11 : ... -_, i: - "- - " dmteur the fact tjug,,,f_h- "-- - : 1': _ c '_ _ _ x : : ::t' r' "- ---'-- is.4argeer thas thab ofs:asase>9eMeshestem. Th4e e Meseg.._._..:... .^ .. SPP"weteP=throughs outetha 6 ages.anLaMaa361rtuid!y__. In contrast, i . ;_ .t':- H --'y =ddant.
at,thesedgmanede+'- ' ---- irradiated.Sarac em.iacost. In either case, '.
however, whefe9PP"Wege*permeetion"ei:curfthTBhrafTR"siMPftT"cMawfsom a materietroer.: _ _ ' ^ 4 '.'vte eneatheb4e ---'!y_dagradad The pe rmeaticoranh oubsegeente 8eref ter degrettetiesw eesues.reughly. la =t ' %vg4 rads gamme or-akther&,... point-tfrtMW"80raf1&deritritfrat* Peter Beacha It is believed that the chemical changes described are a second stage degradation mechanism separate from the shrinkage and embrittlement which occur initially in Boraflex in service.
' Currently, the average spent fuel pool rack position hgs accumulated a gamma dose, equivalent to six (6) years exposure of 3.0 x 10 rads gamma. It is observed-that-a full-length-Sgaflen-4nsat has-good.,oversWintagnity.through 20 equivalent years or-1 x'10 " rads ~gemmt. Thus, the-Secefien inserts in, the racks _ ara-expected..to-ratain their sarvicaahi.ldty. far_ami.u r 10-24-yea,rsp
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. ATTACHMENT 1 TYPICAL CHEMISTRY f
Parameter Range
~
pH 4.5 - 4.8 l C1 <.05 ppm F1- <.05 ppm Boron $2000 ppm (TS Lower Limit - 1800 ppm)I 0
4-5 ppm 2 -
Si $5 ppm 1
Gross B y 8x164 pC/cc f
Temperature of the SFP water is controlled between 70'F and 90'F, and it I l typically runs in the eighties (80's) high in the SFP. At the lower levels i
in the vicinity of the fuel, temperatures are considerably hotter.
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~
ATTACHMENT 2 TABLE I BORAFLEX QUANTITATIVE INSPECTION CRITERIA F
Poison insert and lead-in guide assembly: j SFP Location SP-40/41 Total Gamma Dose 1 x'10 10 Rads Gamma
~
Location Along Length of Boraflex Sheet Average Values of Top Middle Bottom
- 1. Thickness @ center (inches) .095 .101 .096 (nom. = 0.11")
- 2. Thickness @ edges (inches) .094 .111 .102
- 3. Width (inches) 7.75 7.75 7.75 (nom. = 8.0")
i
- 4. Weight: IDEAL vs ACTUAL (gms) Ideal 17.9 17.7 17.2 l (Assume pboraflex = 3.69 gm/cc) Actual > 19.7 18.9 17.3 1 1
s S
l ATTACHMENT 2 TABLE 2 BORAFLEX QUALITATIVE INSPECTION CRITERIA r Poison insert and lead-in guide assembik:
SFP Location SP-40/41 Total Gamma Dose 1 x 10 10 Rads Gamma -
1 criteria Comments (Location, Extent, etc.)
1 l
- 1. White milky substance present Yellow staining on entire length where in contact with stainless sheet, like some sort of dried powder.
- 2. Missing pieces No
- 3. Cracking Yes - Some observed from cutting !
and handling; otherwise had good -:
integrity. j
^
- 4. Powdery substance accumulation in bottom of cladding No , j
- 5. Slumping of boraflex None
- 6. Thinning on edges / fraying, l strings on edge of boraflex Not occurring l 1
1
- 7. Surface porosity and pitting None 1
- 8. Color: gray vs. black Some gray patches.on edges, which seems to " powder" like the samples l did.
- 9. Friability Does not crumble, rather it snaps in brittle fashion.
1
- 10. Brittleness / flexibility Brittle, yet will bend over length.
l i
ATTACHMENT 2 TABLE 1 F
BORAFLEX QUALITATIVE INSPECTION CRITERIA Poison insert and lead-in guide assembly: .
SFP Location SX-47 West Total Gamma Dose ~0 Criteria Comments (Location, Extent, etc.)
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- 1. White milkey substance present White stain entire. length, where in contact with the stainless sheet,
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mostly in middle of ladder fashion.
- 2. Missing pieces No
- 3. Cracking No I 4. Powdery substance accumulation in bottom of cladding No 1
- 5. Slumping of boraflex- No l 6. Thinning on edges / fraying, >
strings on edge of boraflex No
- 7. Surface porosity and pitting No
- 8. Color: gray vs. black All black q 1
- 9. Friability No
- 10. Brittleness / flexibility Very flexible and bends well; breaks when pinched hard over. 1 l
, , l ATTACHMENT 2 TABLE 2 BORAFLEX QUANTITATIVE INSPECTION CRITERIA f
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1 Poison insert and lead-in guide assembly: )
SFP Location SX-47 West Total Gamma Dose "" 0 1
, Location Along Length I
of Boraflex Sheet Average Values of Top. Middle Bottom 1
- 1. Thickness @ center (inches) .093 .094 .099 (nom. = 0.11") ,
- 2. Thickness @ edges (inches) .091 .104 .096-
- 3. Width (inches) 7.88 7,88 7,88 (nom. = 8.0") {
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- 4. Weight: IDEAL vs ACTUAL (gms) Ideal 23.9 27.2 21.1 i (Assume pboraflex = 1.69 gm/cc) /.:tual 22.6 25.7 20.4 )
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f ATTACHMENT 4 PHOTOGRAPHS OF FULL-LENGTH BORAFLEX INSERTS TAKEN DURING EXAMINATION ON AUGUST 18-20. 1986 o
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