ML20198G644
| ML20198G644 | |
| Person / Time | |
|---|---|
| Site: | Idaho State University |
| Issue date: | 08/14/1997 |
| From: | Bennion J IDAHO STATE UNIV., POCATELLO, ID |
| To: | Mendonca M NRC |
| References | |
| NUDOCS 9709040233 | |
| Download: ML20198G644 (11) | |
Text
- _ _ _ _ _ _ _ _ _ _ _ - _ _ _
August 14,1997 t
Mr. Marvin M. Mendonca orn ( rno U.S. Nuclear Regulatory Commission 0 llil D PDNP UNIVERSITY M.S. Il-B-20 Washington, D.C. 20555
Subject:
Transmittal of facility status report following the 7/97 reportable occurrence at Idaho State University AGN-201 reactor facility.
C dese d im Pocatello, Idaho
Dear Mr. Mendonca:
83209 806o Enclosed please find a copy of the facility status report regarding the July 1997 reportable occurrence at the ISU AGN-201 nuclear reactor, License No. R-110, Docket No. 50-284, involving the abnormal degradation of a primary fission-product barrier. As requested, the report discusses the current status of the facility and actions taken and planned to recover from the event and allow recommencement of normal reactor operations. I apologize for any inconvenience that the delay in submitting this report may have caused you or your staff.
A copy of this report was transmitted to your office by facsimile this aftemoon, August 14th, at approximately 2:10 p.m. MST. As we discussed during our telephone conversation earlier today,I understand that you will deliver a copy of the repoit to the NRC Document Control Center. Your assistance is greatly appreciated.
Pi ase call me at (208) 236-3351 regarding any questions you may have concerning this mater.
Sincerely yours, John S. Bennion ^
Reactor Administrater
'[
Enclosures:
(1) Facility Status Report to the US NRC Regarding the Control Element Chalding Failure at the ISU AGN-201 Nuclear Reactor (2) Envelope containing original photographs.
\
\
m cs:05 tillgy"'BIE!llllilll .
(208) 236 2902 2C 236-4538 g [hg LN b 9709040233 970814 PDR ADOCK 05000284
- #8 * ** U##'*"* "####'
hf //1 D m_ _ __ Ll_ . PDR , ,
J
FACILITY STATUS REPORT TO THE U.S. NUCLEAR REGULATORY COMMISSION REGARDING THE CONTROL ELEMENT CLADDING FAILURE AT THE IDAHO STATE UNIVERSITY AGN 201 NUCLEAR REACTOR Introduction This repon provides a brief summary of the current status of the Idaho S, e University (ISU)
AGN-201 reactor, License No. R-110, Docket No. 50-284, following the discovery of a breach in the control element capsule on July 3,1997. The failed element, Safety Rod No. 2 (SR-2), contains fuel material in the form of 20%-enriched UO2homogeneously dispersed in a radiation stabilized polyethylene matrix. The failure of the aluminum capsule, which is
,_ - cons;dered a primary fission product barrier, exposed a small portion of the fuel material. As required by AGN Technical Specification 6.9.2.a.(3) of the operating license, this event was classified as a reponable occurrence and was promptly reported to the U.S. Nuclear Regulatory Commissia with a written follow-up report, dated July 21,1997, which was transmitted to the NRC by facsimile July 18,1997.
Immediately foPowing discovery of the cladding failure, facility personnel with the assistance of the personnel from the ISU Technical Safety Office performed surveillance for radioactive contamination, radiatiw fields, and airborne radioactive particulates. Surveyed areas included p the region beneath the reactor core near the control element access, the general vicinity of the reactor, affected components, and the reactor laboratory room. Contamination surveys of the affected components showed only low levels (barely above background, net <100 cpm /100 cm2 except for the inside of the capsule) of removable contamination on surfaces that were in direct contact with the fuel material; specifically, on the extemal surface of the SR-2 capsule adjacent to the failed weld and on the interior surface of the detached end cap. Analysis of the filter media from the air particulate sampler showed no evidence of airborne radioactive particulates beyond what would be expected from, and consistent with, short lived radon progeny.
Subsequent measurements 5 weeks later showed the same radon results, in addition, all personnel present at the time of the initial dashpot failure and during the later reinoval of SR-2 underwent in vivo counting of the thyroid gland for uptake of 1-131. Results from the thyroid counting did not show any positive indication of elevated emissions from the thyroid glands of any of the personnel surveyed.
ISU AGN 20t Reactor Facility Status Report August 14,1997 page I
_ __ Y
The Intemal incident Assessment Committee (IIAC), which was summarily formed to determine the cause and assess the consequences of the event, concluded that the failure of the SR-2 capsule was caused directly by the failure of the dashpot mounted beneath the control element. This dashpot serves to decelerate the element following ejection from the core as a result of either a scram or the normal shutdown sequence. Without the damping action of the dashpot to absorb the energy of the ejected element, the abrupt and unattenuated impact of SR-2 against the steel frame of the drive assembly was sufficient to fracture the weld joining the end cap to the capsule tube, it is also possible that normal aging of the aluminum components may have contributed to the capsule failure. The IIAC also concluded that the radiological consequences of event were negligible and had no adverse impact on the health and safety of facility personnel, the public, or the environment.
Enclosed with this report are eight photographs of the SR-2 components that were taken to document the extent of damage incurred by the capsule as a result of this event.
Figure i shows the SR-2 drive assembly and the complete SR-2 control element assembly subsequent to removal from the reactor. Note the black tip of the control element assembly at the left of the photograph. As may be seen in more detail in Figure 2, this black tip is the distal UO 2polyethylene fuel disk / cylinder protmding approximately 2 cm out of the element capsule as a result of the complete fracture of the weld joining the end cap to the capsule tube and the consequent loss of the end cap. The undamaged CCR (Coarse Control Rod) is juxtaposed with SR-2 for con.parison.
Figure 3 shows a close-up view of the end portion of SR-2 with the protmding fuel disk / cylinder. Also shown in this figure are the detached SR-2 end cap and the CCR. Note the jagged edge of the capsule tube where the weldjoining the end cap failed. In Figure 4, the SR-2 has been disassembled and its component parts have been arranged for display. Starting from the bottom of the photograph is the SR-2 capsule. Above the capsule, from left to right, are the compression spring, washer,9-cm-high graphite reflector disk / cylinder, and four 4-cm-high fuel disks / cylinders. Above the internal SR-2 components is the extension shaft which connects the fueled portion of the element to the drive carriage. The entire control element assembly is created by loading into the capsule, in sequence, the four fuel disks, the graphite disk, the compression spring, and the washer, which is then screwed onto the threaded extension shaft. A gas-tight seal for the control element is obtained by tightening the capsule to ISU AGN-201 Reactor Facility Status Report August 14. 1997 page 2
_ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ - _ _ _ ]
compress the seated o-ring that is visible in the photograph at the right end of the extension shaft,just to the left of the t :rew threads.
Figure 5 gives a close-up view of the end of the SR-2 capsule and the detached end cap showing the fractured weld. Figure 6 shows the failed dashpot next to the threaded flange with attsched mounting studs which are used to secure the dashpot to the control element drive assembly. The intemal components of the dashpot are visible through the transparrnt cylinder tube. Figure 7 gives a close-up view of the broken dashpot. The broken pieces of the graphite piston are visible within the dashpot cylinder.
c Figure 8 shows one of the new replacement dashpots obtained from Airpot, Inc. The cylinder of the new dashpot is made of a black, opaque plastic instead of a transparent material and conceals the internal graphite piston from view.
As discussed in the July 18,1997, report to the NRC, three options are available for replacing the SR-2 capsule to make the reactor operable so that the facility may resume normal operations.
The first option involves attempting to repair the failed capsule. This option would require decontamination ofinterior surfaces, expert welding of the delicate components, and finally, pressure testing to ensure that the capsule is air-tight. The second option entails fabrication of a new capsule. The third option is to locate and transfer toISU a replacement capsule from a decommissioned AGN-201 reactor. After a careful consideration of these options, we concluded that the only viable option is to acquire salvaged units from a decommissioned facility.
The proposed plan for recovery, therefore, is as follows:
Submit a comprehensive report to the RSC for review, a
Transfer replacement control elements to ISU from the Oregon State University nuclear facility.
- Install replacement SR-2 control element in the ISU reactor.
Replace the SR-2 dashpot on the drive assembly.
- Perfonn all required surveillance procedures, e.g., measurement of scram time and rod worth.
Submit a final recovery report to the RSC for review and seek approva! to resume normal reactor operations Submit a courtesy copy of the final recovery report to the NRC.
ISU AGN 201 Reactor l'acility Status Report August 14,1997 page 3
4 Current Status of the Facility The reactor facility remains shutdown, as it has since discovery of the failed dashpot and the subsequent discovery of the failed SR-2 capsule.
The Reactor Safety Committee (RSC) has been notified of the event and is expecting a report for review at the next scheduled meeting. The RSC will review the event, including actions taken to correct the problem and to prevent its recurrence, and may advise on any further actions deemed appropriate. Once the required repairs have been made to the affected control element (which will effectively entail the replacement of the control element), the facility will submit a final recovery report to the RSC and request approval to resume reactor operations.
Following the initial surveillance of the SR 2 components, the element was disassembled and the various components were packaged to prevent the dispersal of radioactive material. The fuel disks / cylinders were scaled in a polyethylene package and stored in the appropriate location.
The aluminum capsule and end cap have been surveyed and sealed in polyethylene pending final disposition. All other internal components contaminated by fuel and/or fission product radionuclides have been surveyed and scaled in polyethylene pending final disposition. These materials are currently being stored within the facility boundaries.
All control rods have been removed from the reactor, surveyed, and inspected for signs of possible abnormal degradation around the end cap of the fuel capsule. All of the capsules were found to be in good condition with no evidence of weld deterioration. Contamination surveys of the capsules showed no evidence of leakage of fuel material or fission product radionuclides.
An application for an amendment to the operating license has been submitted to the NRC which would allow the facility to possess additional fissile material and enable the transfer of salvaged control elements to ISU from the Oregon State University AGN-201 reactor. This reactor (License No R-51, Docket No. 50-106) was decommissioned from 1978-1980. The NRC terminated the operating license November 10,1981. OSU has retained all of the AGN fuel, including the complete core and the three fueled control elements, having transferred the fuel material to OSU's TRIGA NRC license. Discussions for transferring these control elements to ISU have been initiated with Dr. Brian Dodd, Director of the OSU Radiation Center, arai with representatives of the U.S. Department of Energy, which owns the fuel. Dr. Dodd fully supports the transfer of the three intact control elements and the DOE has indicated that they will ISU AGN 201 Reactor Facility Status Report August 14. 1997 page 4
provide financial assistance and transfer casks as necessary for transponing the control elements to ISU. OSU personnel have initiated the transfer process and are awaiting notification of approval of the ISU license amendment application to proceed with the transfer.
Three new replacement dashpots have been obtained from Airpot,Inc., manufacturers of the failed SR-2 dashpot. A new dashpot will be installed on the drive assembly for each of the scrammable elements as discussed in the next section of this report. A repon is being prepared as a counesy for submittal to Airpot,Inc., describing the dashpot failure complete with some of the photographs included in this report that may help them determine the cause of disintegration of the graphite piston for quality control purposes.
Future Actions The following actions will be proposed to the RSC to prevent recurrence of this event.
All existing dashpots will be replaced with new units. The existing dashpots that are in good working condition will be retained as spare components in case of failure or deterioration of the new units. Once installed, should one of the new units fail or otherwise deteriorate to the extent that failure is probable, it shall be replaced temporarily by one of the existing units and another equivalent unit shall be purchased from the manufacturer for immediate installation.
Future annual inspections of the control elements will be aggressively perfarmed. In particular, inspections will focus on the end region of the capsule for any evidence of weld cracking or other signs of deterioration and on the dashpot for evidence of excessive wear of the seal or excessive play in the piston which might indicate impending failure. Any evidence of degradation of either the capsule or the dashpot will be sufficient reason for immediate replacement.
We plan to modify the safety rod drive logic circuits to allow the safety rods to be manually withdrawn at the conclusion of reactor operation instead of scramming the reactor. This modification will reduce the number of scram cycles on the scrammable control elements.
Currently both safety rods must be fully inserted or " cocked" before either of the two control rods can be driven for reactor startup. Once the safety rods are cocked, the only method for lowering the safety rods and hence to tenninate reactor operation is to scram the control ISU AGN 201 Reactor Facility Status Report August 14,1997 page 5
elements. The control element drive logic will be modified to pennit manual withdrawal of all control elements while retaining the original design feature requiring th.it the safety rods must be cocked before insenion of the remaining control rods can occur. This modification would not, of course, interfere with any of the reactor safety systems, nor the scramming function of the control elements. The primary benefit from the proposed modification would be a significant reduction in the number of scram cycles and subsequent stresses exened on the scrammable control elements and dashpots and would vinually eliminate the possibility of another capsule failure.
Additional actions to be determined by the RSC may also be implemented.
ISU AGN-201 Reactor Facility Status Report August 14, 997 pge 6
.. - _ - - _ _ _ _ _ _ _ - _ _ - - _ - - - _ _ _ _ _ . _. .a
M f QY
,- ~ f' }R QE
~M$% .} 4[ Q - -% :
V27x?f,tL*lDfL%i%C251u:dC $>L[, . ' ..;Q.uf.v-QQ-l-[t 4
j y , ' ' x.ygt r- %:
FlG. UHE 1 ' 1* A: *$m, - +x>;r.a n - -
3
-m N' "d! '"QN Y 0?-?hk j
$ ped..hg@w v yg g%nery;
'M b glyajf. T%# ' ..;,J/$q p.JT aAu@gdd Y. ,C pm~, m
'::;nesMnd GQ9 %$
%;@pHQQAAegy y
m + = 4 t ge . m elk i ) n .1.e mmw x i a.e.u.+i n,.. m. i , a s , .w,.% u .. . v e 4 j.n . 4 4 , o.,%.o . 4 2 a ,as 9 &s i e w .a. ,
V-'-_ , ;
. w.c ,0 ,. & 9 3., z . .g g, q,.
- y. ,
i kk$ [ '
b$hfkg e g
w a.
a R** e,w. aq w w&
9;~.,;mmad ;i.N w%swv%m;g#
% w mk- smar :
nwn .
n.
my:esyj}& .~ 41D% s an
+
3:.s ,1 -
~
hk: yk NY A YM*~ ) 58 -
N-
~
- &&G&-@w&&
-wwmsGW duiame -*O
.;Le_ my. ,
aom
n. .y; ,
- th . '
'" '1 .
- is '
- g. .e, qg :-- i t' . - -
,,.1
....mm, . . . .
xwamww, em. .. .mmansu, , _mm_. .wang, .s.. . . .
,s., , .
i.pn.f. ,p,n._,, g.uy. _ .,
FIGURE 2
.a-0 ISU AGN-201 Reactor Facility Status Report August 14.1997 page 7
'r
. .; g '
'g :p 1
-< M c4 ' -
g:9 n .- gev g V 'y ff']g!j;% :.. y N, " r +p m'kk: , e a
- x-NyjOM.%',~,7 %ra(? ,7:%
', :,g. :g ;;; c a 4}. b 4 , 34 ~ . . k$
v.
(gg .+e
..,c-w.n,. Qig
gg,
. ;p.
u n w ;
?_,.+ f.9 'p!pg A (: p pr.y
. . < . , , . c.:
4 p.
.'N{h% 4 .- j. k:kl.$:: N' $'. :S' ,'?.
s,> 9.4- g :n 4 y.; ,' Yr - - , >
~
v . e.w e
>bg, 'u * ^ j'[ ;&::' ; _. e , ) .
b v'Y,',:'j
': {d, $-$ 7'fN E ,:pN /
L;> ,8,.
w e s.,.
rg ;,
- A.. u.s .
ftT . i Q.i
.: .j ry 3:;? .u E'[Ok;;
- f. .9%. [r m m'N.5,lio , :[g$. , e' a'
- M sy,A#w w;,?wwe FIGURE 3
-s _ ___
maam.mgyp.g "O 5 > J,, 3y:5_yf .5:1_.'L.1 1-- J. 3. -.
- '#\'" -'"'""%
'- 'IN FIGURE 4 e'- %
% s. . .
"'f
- kn 7
- . 3.m
- m.Syg~.
.: ~ . . ..
, ,.z,
. 44 .0. : ,. . i ..p.t{6: m...:tN . m. :~
.. f ) ;'rc E... . .. ." . . . .lz . 3.gb*lt eW.e.-> --
~.3:,
.n .
g_ . 4 4
n.~,.
~ m. g. J. y n.- -
ys 1 gs . h[.g' .
3 QQ 'lW* y QQg ::;
ID= .
E-(pit _ j ww.-awcw: g w g 9 .
f . .- .
jsy; : u@y , % .$
3
,,, MW4 mm, ea:: .- +4Jg.
A .a: ~ L ,
5,y m t m:d, l .p @ :
y,,.p p p3.t 3 -;
X ' %. . a D.l"D }'}QQ::dag4hRh?
m 'W nEin %*
x SQOT f&- >
%d3 ISU AGN-201 Reactor Facility Status Report August 14,1997 page 8
. %, s s ,:.s N k_w r* +. .
't'
-n ;- %
lin IJN@M y .b M +
@;7 h v '
j,$
h w:JR O G %g %Qn. > - '
t .QW s
.w@~
u **
.; .>- d ;#$ , :.-i:ap -3 pg,;
bn t
e%
O +
p&
w ,p%Q&:p y.Q-., ,
JL px XQ a,
T?
[E ok,8 b..- n:
M n w'**" D ( _ , n s
[
- b. .w,k.h.n,.; h d@_ 4 hy i;;$h t n
,'f.
p, 9 Y~ -
-.: Yc '
- q. I
- h. Y 5 ., g 05:2[')[ , g $ . .' , V ) *
^-4 [
, - u.m p#'4' h1- ==# Q ' *>? :.Q m,, y 4:tf
'p k ,u;:!+. .km.m ,J $ & $ t m ga:
~:,, - r s w.y
, e,{ CQ x
c>
~
~mg.w M Y,- . 9. ;N. -
w T'. .
- f. Q' f.hk:p & W [l ;
'. g
&l'5 d.9yb,_ , _h. .u N . 7- **
(L. -
-4 7
.qmww ridn sa-4 d Mk idhi p
, s %L W}
c m .f ' A qW, s g'
M. '
m, e.g#,4., ..3 y,.
,t 1
s s s r.
,p y .
. cw \E'k; s
- 1
" 4s -
+) 3 4
, ,,, & *' D*'* ], p.;;p ba y ^
i
- pb s a ;e '@
43.,4 4 y W(
M.
\
'a1
- L.,. n;&&;, ,9 v A,::.M&:nw,: 4: Y r ais:J. :42 D; ,_. ,
J FIGURE 5 .
,4 8%sT( '
j
[W T@i W Tf @ tI:S$T3FEf 7 @ @lE i $t _
MMSW.
s5@' % WAR NQ$$e
.A; u Mmnd "'e i.G"QWWAM0W W id W* $n@MNME#!$$N' % @O'!ruw%pt N MF60 Vw i
g -
14
. , g#g#'pNg h~ {;
b.s [$ ad a d, %' 'Nd@efcM'
~
-m
,.9 .;.rMMb
&- 9' %[,.aW4 WW;.;9MQg[hh@d4MiQ hpk?- 7 4 . # ===== -
%fk g ygg agp:e s .
gu.yuT,M ,w. , ,,bpasce s
Ap :~4.
% _ ? :g y' a 3 s
hh a y+ ' W. ;,& %%. 4, Agpa
':' :K n a g (. -3;.9yw& gg ' ' g
.m .
hg . ' .# a ph. .
- ?g. p:: .,e Q s s.J{yb$e s.p%~Q d 7 h-?yk M " s%% ' #dMbe:ZM ? . we:w.
.[jf:::* * * @c-M ~"yU *s Q (Np$.; g
. w%
sg M FIGURE 6 F h #/ cy u$4E n s y y ?' gxx' 7Q%ye$lC'@f m4 ya g.u a .n rmy ,;q y,ym% mmm (pppfp'Jk" a s 4:dg QW
- i. n A .. . v iq@m;p:: yes g;g pNmpR; af ;"d? ;
g Q ;ggW n .w wa w - -
a yw+ c
,s y a --
, . . .v .. .
' R,'u 9 u.a
,: , xp. va:.
- s y% y M h. n. .,.. . a (Nh_. i .. 5 f~n4p$NN 7,, u . r [w$rMihhdi
.: % :y
. _ . % : y
,r;
- p. '..s; fds>.., ?%hY:$:
y 7. g j;-. gs .
- pg::g g ,st. 4. . v:.. .w.y p;g c. >y ;; ,q< .:spys;p gd,p.1sy Ja is.,, _N:y g %.
y Awv;p g .- gos. yy , -
g
$ A., .y f.g t.\
l l '
h*;N b ;lg '
@LSw, .'
.:. _: e-
.y w .
g y;h <;8- bh bMAk$ :- zAjc Mb:M aI %. _
~e.?g mg*yl% :n>
-s%
. L < r "
d3 ISU AGN-201 Reactor Facility Status Report August 14.1997 page 9 1
=
yogy 93 7*9=+' T
- 1 - ?pwvy may.y1_p .-&.*t.y 'yy?r ,y:. q-y et y
,C
- <*3_ W&sp y *1 +.yPQ,' Ctw\.p" v>
r .qt : * '- ' % AM'
'f; Aih.dMMA Juis.AA edLJaLJZL,i tw9 JA) '+
khjh . s >. > ~
+ %Q :~ v. %MQ
![k kl .r I .- 'iM%N 1:M NNk 2 d y'r g m a.onggyy:g.m
- m , yg -
ug3,_y _ e n n v er S <><>1 +
& " \iNQ l;fw & %M3Wg.g $ t W5I M k;k ) b y; " ;~
k ..3 .y A f -
n :< w,p h g g g Q ._; g~- .4a N =
W L, gy**myrge.4$,t e
g9
.~- ,
-4#' *t .
p a w,%9 L
1 7,,
h.,'f,:- M
_
- bl(&
b.-
(c-Ys % W kt:J15 ) MW s., s ,
gp 4 N
- {;; g 1"[7l4 .s s J : . y '_ .. . :.N}'f'.. . : . b- '; 4 , ; L. ]- = < ,
(j['[q)([;)] 3 f M) k M )fQ #{ MJ),Q 8 h.IL) D 3 N,,
6 Y _Y :tN' y ,
=
- , , ,.,..: ., AA y y
'l $ '. b
~
.,l.' ,
.- - % @' :gj O
~
yssm,nw , +g s.,pc. . ,
us y ~ y **-
mr- - ,. - 1 --
.< W $ _. ,, o Jam g : -
y%; .g:[.j; ;_ y . y yy y;.;. fy
_M.f ; .'
g . ,4 . s.
3 ;
w
^!Q -
yQQ ;? " ' :& :
' (%Q Q. .. ps..)gji%..,
.; :.A * - t . ..
.l
~
L%& ,'
i;% : ..
- Qhf.f . ;;;;
Msp e A .%Q'\ I gm .
- s. ,. .
}f s1
$% nh..
a %.fht
& g. .; 7 ,fw;[
1
,q p,_i.;$4%.
- w, -
Vf 1.: E f ,
fb .# ': , c.m -
Nf ew. . .M:, V$ ) ' '-
j(y;; $m.w ::
lk:l
, .a
$F l r .-
d.
l llk ISU AGN 201 Reactor Facihty Status Report August 14,19'M page 10
- _ _ _ _ _ _ _ _ _ _ - ._ )