ML082320765
Text
NKLE
~ELAUR aDISSON_
OFFICE OF ULE EC IULAT ION
..SHINT*
1
, D.C. 205550001
.anuary, 1995 NRC INFOUIATION NOTICE 866-1061, SUPENENT 3:
OE6RADATWN OF REACTOR COOLANT A
SYSTEM PRESSURE 8OUNDMRY RESULTING FROM BORIC ACID CORROSION All holders of operating licenses or construction permits for pressurized water reactors (PURs).
Puoose be U.S. Nuclear Regulatory Comission (NRC) is issuing this information notice supplement to alert addressees to two recent significant incidents of boric acid-induced corrosion of ferritic steel components on the pressure boundary of pressurized water reactors.
These incidents Indicate that there may st il be a general lack of awareness of the ambient conditions that can lead to boric acid attack. It Is expected that recipients will review the information for applicability to their facilities and consider actions, as aproprItato, to avoid similar problems. However, suggestions contained in t"Is information notice are not NRC requiremnts; therefore, no specific action or written response Is required.
Oescriotion of Circumstances In February 1994, the licensee personnel at Calvert Cliffs Unit I found three nuts on an incore instrumentation flange that were corroded by boric acid, leaking past the flange gasket.
The Calvert Cliffs reactors each has eight such flange assemblies. Each assembly is held together by eight carbon steel studs that are 33 cm [13 In.) long and have a diameter of 4.45 cm [1-3/4 in.).
During a subsequent inspection, the licensee found three more nuts on another incore instrumentation flange that were also corroded by the sam mechanism.
One of these nuts had failed completely, and the mating stud had dropped out of the flange. The two adjacent nuts had been significantly damaged.
On March 7, 1994, the licensee personnel at Three Nile Island Unit I were attempting to stop a small leak across the body-to-bonnet gasket of the pressurizer spray valve by tightening a bonnet stud, when the leak suddenly increased to 11 L/min [3 gpm]. The reactor was at 100 percent power at the time of the event. After reducing the power to 75 percent to reduce potential ressure surge: that could occur without the aid of pressurizer spray, the icenseo was Wbe to isolate the leaking valve by closing other valves in the pressurizer spray tine. When the workers continued to try to tighten the studs, one of the studs, with its nut still attached, came cut in a worker's hand. The workers then found two more studs on the same side of the bonnet 9412290318--.
- that had completely failed and a fourth one that was severly~dogra.did.
The or
" caose of.thi,s damage was corrosion by boric acid.
The,daj studs -were Amng* e
-5t/8 In. notmina studs that join the bonnet to tr odyo the' Igh-PGlU t a boy.o Tns'ulated 2.5 in. nominal motor-eperated globe valve manufactured by Vol-an.,
The body and bonnet are both made of 316 stainless steel.
However,' the studs, which are threaded into the valve body, art made of ASTM A193 Grade BY -low alloy steel c
nplte fale a dre id of ASTfo t
94 Grade 2wa low alloy stool.
The license@ kept the plant at reduced power until March 17, 1994, then shut the plant down to repair the damaged valve.
At both plants dhare the recent boric acid
.orrosion prolems occurred, there were earlier Indications of boric acid leakage from the compoets that were eventually damaged.
In March 1993, the Calvert Cliffs licensee had discovered leakage from the Unit 2 ICI flanges.
The licensee detemined that the leakage ins caused by inadequate gasket m aterial and corrected this leakage by replacing the flange gaskets mdth thicker ones and by adding washers under the stud nuts to ncrd s te ts tension on the studs.
In June 1ep3, the Calvert Catffs licensee had also discovered evidence of leakage from the samr the a gon seven of the IC flanges In Unit After revAteng the problem, the licensee b
oncluded that any corrosion from thes leakage earler cceptablt low and elected to defer the corrective actions for the Untt 2
flanges until the 1994 refueling outage.
This conclusion eas based on the assudptaon that the flange temperatures would be epproxiately 260 "C [SO0 "F].
At this temperature, any, boric acid present would boil dry, and result In corrosion rates of about 0.04 me/month 11.6 oil/manth].
Actual flange tempratures, masured during a startup after the damage was discovered, are in the range of 7o to h46 eC
[160 to 295 OF].
These tolperatures encompass the range ohere boric tcid can rgmin in solution and rbecoe concentrated by evaporation.
The tepoeratures also cover the rais fhore the hitgh corrosion rates identified by the 1iestangheuse tests (discussed below) can occur.
Workbrs had reported a body-to-bonnet leak from the pressurizer spray valve at Three Mile Island Unit thin November a
993.
A b ork request was prepared to reaair the leak.
However, the oucensee inspected the valve without rhmovAng an of the insulation and concluded that the boric actd crystals around the valve care aron the valve packing rather 1han the body-to-bonn2t joint. As a consequence the work request ias cancelled.
beclted cnenerate boyunpcat ion Boric acid coolant leaking onto hot carbon stoel surfaces has si nificantly damaged reactor pressure boundary components at a number of plants in the past.
As a result, the NRC has issued a number of generic communcations dealing with this issue.
The following are some of the more significant examples:
ag 3U4f bIM 96, Fort Calhoun personnel1 found In each of two separate pwps three E,
reactor coolant pop studs whose diameter had bee reduced from 31/2 i nominal to between 2.5 and 3.8 cm [1 and 1.5 in. I by corrosion caused by boric aitid leaking past the flange gaskets (Information Notice 80-27).
- ?:*;In 1982, the Noine Yankee 1license@ reported that 6 of the 20 primary Ianwiy closure studs on one stem generator had failed.
Five more of the studs were cracked. The studs had surface corrosion wastage caused by boric acid leaking past the studs.
The final failure mechanism was stress corrosion cracking that my have been aggravated by the Injection of Furmanite sealant and tihe additional torquing that was applied in an effort to stop the Initial boric acid leakage (information Notice 82-06).
In June 192, the NRC Office of Inspection and Enforcement issued Bulletin 80-02, which sumarized the problems with threaded fasteners in the reactor coolant pressure boundary. This bulletin gave 11 examples of boric acid corrosion of closure studs. The bulletin required licensees to establish maintenance procedures to ensure the integrity of such threaded fasteners. It also requested licensees to identify all bolted closures in the reactor coolant pressure boundary that had leaked and to describe corrective measures taken to eliminate the problems.
In October 1986, personnel at Arkansas Nuclear One Unit I discovered 1.3 cm
[1/2 in.]-deep wastage on the *A*
high pressure injection (HPI) nozzle caused by boric acid leaking from an HPI mnual isclation valve and running dwam the stainless st"e HPI lIne onto the carbon steel nozzle. The boric acid had corroded two-thirds of the way through the nozzle, which was attached to one of the four reactor cold legs (information Notice 86-108).
In March 1987, personnel at Turkey Point Unit 4 discovered over 227 kg
[500 lb] of boric acid crystals on the reactor vessel head and in the exhaust cooling ducts of the control rod drive mchanisms. The boric acid crystals had precipitated from reactor coolant that had leaked from an Instrument tube seal. The boric acid had severely corroded three of the reactor vessel head bolts, the control rod drive shroud support, and the leaking Instrument tube seal clamps. All of these items, including the entire control rod drive shroud, had to be replaced (Information Notice W-106, Supplament 1).
In August 1987, personnel at Salem Unit 2 discovered a pile of rust-colored boric acid crystals 0.9 a by 1.5 a by 0.3 m (3 ft by 5 ft by 1 ft) high on the reactor vessel head as well as a boric acid coating on other areas of the head and control rod drive mchanism.
The boric acid had precipitated from reactor coolant leaking through pinholes in a seal weld at the base of a thermocouple connection. The boric acid had corroded nine pits, ranging In depth from 0.9 to I cm (0.36 to 0.4 in.], in the surface of the reactor vessel head (Information Notice 86-108, Supplement 2).
Also in August 1967. personnel at San Onofre Unit 2 broke off the packing plate hold-down bolts of a 10-in, nominal isolation valve in the shutdown cooling system while attempting to open the stuck valve manually. The resulting leak of approxlmately 230 to 380 L/min (60 to 100 9pm) spilled 66 kl (IS k gal) of reactor coolant into the containment. Boric acid leaking from the valve had corroded the valve packing plate hold-down bolts, which were made of carbon steel (Information Notice 86-108, Supplement 2).
.Ioformation Notice 06-1B, Spplement 2 also discussed a seriesof tests performed by Nestlnghuise tht shined that high concentrations (.(15
-to 25 percent) of wate.d or dripping boric acid could corrod*e a sb"ostel surfaces at rates as high as 10 r/month (400 oil/month]
n193 to 90 -%
[200 to 210 OF) environments.
In Narch 1908, the NRC staff issued Generic Letter I8-05 in which It requested licensees to institute a systematic program to monitor locations Wre boric acid leakage could occur and to provide measures to prevent degradation of the reactor coolant pressure boundary by boric acid corrosion.
The latest two incidents of boric aci'-induced corrosion indicate that, although M licensees have generally become sensitive to the possibility damage from boric acid leakage, there my still be a lack of awareness of the conditions that can lead to boric acid attack. The wide range of ambient conditions around reactor primary coolant leak-sites with the resulting wide variation in boric acid corrosion rates make it difficult to predict the likelihood of corrosion damage when a leak is present. This is particularly true of components such as insulated flanges and valve bonnets that are somewhat isolated from the areas of heat input from the reactor coolant and may experience large temperature variations.
The primary defense against boric acid corrosion, previously discussed in Information Notice 86-lO0, remains the sam; i.e., minimize leakage, detect and stop leaks soon after they start, and promptly clean up any boric acid residue.
This Information notice requires no specific action or written response. If you have any questions about the information In this notice, please contact one of the terhnical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRN) project manager.
1~ar K.
- irimes, ere or Division of Project Support Office of Nuclear Reactor Regulation Technical contacts: Nichael Nodes, RI (215) 337-51" Donald Kirkpatrick, NR (301) 504-1849
Attachment:
List of Recently Issued NRC Information Notices
V.
IN i
ft. 3 lanuary '5 19 Paopl of I LIST OF RECENTLY ISSUED NRC INFOUSATION NOTICES
-.JIformation Date of Nfottce No.
Subject Issuanie Issued to 95-01 94-90 94-N9 94-88 94-87 94-M 94-I5 94-40.
Supp I OOT Safety Advisory:
High Pressure Aluminum Semless and Aluminum Composite Hoop-Wrapped Cylinders Transient Resulting in a Reactor Trip and Multiple Safety Injection System Actuations at Salem Equipment Failures at Irradiator Facilities Inservice Inspection Deficiencies Result in Severely Degraded Steam Generator Tubes Unanticipated Crack in a Particular Heat of Alloy 600 Used for Westinghouse mechanical Plugs for Steam Generator Tubes Legal Actions Against Thermal Science, Inc.,.
Manufacturer of Thermt-Lag Problems with the Latching Mechanism in Potter and drumfield R10-C3286-2 Relays Failure of a Rod Control Cluster Assembly to Fully Insert Following a Reactor Trip at Braidwood Unit 2 All U.S. Nuclear Regulatory Comission licensees.
All holders of OLs or CPs for nuclear power reactors.
All U.S. Nuclear Regulatory Commission Irradiator lIcensees.
All holders of OLs or CPs for pressurized watev reactors.
All holders of OLs or CPs for nuclear power reactors.
01/04/95 12/30/94 12/28/94 12/23194 12/22/94 12/22/94 12/21/94 12/15/94 of OLs or CPs power reactors.
All holders of OLs or CPs for nuclear power reactors.
All holders for nuclear of OLs or CPs power reacto's.
0L - Operating License CP a Construction Permit All holders for nuclear
~>1
r Technical contacts:
Michael Modes, RI (215) 337-5198 Donald Kirkpatrick, NRR (301) 50-1849
Attachment:
List of Recently Issued NRC Information Notices DOCUNENT NAME: 86108SP3.IN SW )revious concurrences OECB:DOPS*
PUB:ADM*
C/ENCB:DE*
DRS:RI*
0Ktrkpatrick Ilejac (Tech Ed) JStror-,der MKodes 10 i 9410/19/94 11019 11/29/9 D/DRS:RI*
SC/OECB:DOPS' OECB:DOPS*
C/OECB:DOPS*
JAivoins EGoodwin Wkiessel AChaffee 11 29 12/19/94 12/12/94 01 122194
-IfWmat'on Sotce 86-108, Supplement 2 also discussed a series of tests p
eri'o d by Westinghouse that sAwed that high concentrations 15 to
,25 0percent) of aerated or drippiog boric acid could corrode carbon steel surfaces at rates as high as 10 mn/month 1400 mil/month] in 9V' to 99 *C
[200 to 210 "F] environments.
Page 4 of 4-~
- 1 In Narch 19M8, the NRC staff issued Generic Lettr 88-05 In whi:h it requested licensees to institute a systematic program to monitor Jocatiors where boric acid leakage could occur and to provide measures to prevent d.egradation of the reactor coolant pressure boundary by boric acid corrosion.
The latest two incidents of boric acid-induced corrosion indicate that, although PWR licensees have genert)lly become sensitive to the possibility damage from boric acid leakage, there my still be a lack of awareness of the conditions that can lead to boric acid attack. The wide range of ambient conditions around reactor primary coolant leak sites with the resulting wide variation in boric acid corrosion rates make it difficult to predict the likelihood of corrosion damage when a leak is present. This is particularly true of components such as insulated flanges and valve bonnets that are somewhat isolated from the areas of heat input from the reactor coolant and may experience large temperature variations.
The primary defense against boric acid corrosion, previously discussed in Information Notice 86-108, remains the same; i.e., minimize leakage, Jetect and stop leaks soon after they start, and promptly clean up any boric acid residue.
This information notice requires no specific action or written response. If you nave any questions about the information In this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Oilinal signed by BBrii I. Grimes Brian K..
Grines, Drector Division of Project Support Office of Nuclear Reactor Regulation
'Decalmbe xx, 19 1*
0 arch 1968, the NC staff Issued Generic Letter i8-05 in which it requested r icensees 6o institute a systematic progrm-to monitor locations where boric acid leakage could occur and to provide measures to prevent degradation of the raoctor coolant pressure boundary by boric acid corrosion.
The latest two incidents of boric acid-Induced corrosion Indicate that, although PWR licensees have generally become sensitive to the possibility damage from boric acid leakage, there may still be a&lack of awareness of the conditions that can lead to boric acid attack. The wide ranqes of ambient conditions around reactor primary coolant leak sites with tbt resulting wide variations in boric acid corrosion rates make it very difficult to predict the probability of corrosion damage. This is particularly true of components such as insulated flanges and valve bonnets that are somewhat isolated from the areas of heat input from the reactor coolant and may exist with large temperature variations.
The primary defense against boric acid corrosion, previously discussed in Information Notice 86-108, remains the same; i.e., minimize leakage, detect and stop leaks soon after they start, and promptly clean up any boric acid residue.
This information notice requires no specific action or written response. If you have any questions about the information in this notice, please contact oeie of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director Division of Project Support Office of Nuclear Reactot Regulation Tpr.hnical contacts: Michael No~es, RI (21S) 337-S596 Donald Kirkpatrick, NRR (301) 504-1849
Attachment:
List of Recently Issued NRC Information Notices DOCUMENT NAME: S:\\DOPS -!EC\\BORICORR.IN
- _S previous concurreices OECB:DDPS*
PUB:AOM*
C/EMCB:DE*
DRS:RI*
DKirkfatrick NfeJac (Tech Ed)
JStrosnider NModes 10=Is 94 10/19/,
1/9o2/
I D/DRS:Ri" SC/OECB:DOPS_
OECB:DOPS*
C/OECB:DOPS*_
Jtggins A
kiessel AChaffee 11 2911/29/94 '41Q94..12/12/94 12/;94 1
BGrimes
Page 4 f coolant Inaking through pinholes in a seal weld at the base &f a thermcouple coomect.i.
The boric acid had corroded nine pits, ranging In depth from 0.9 to 1 ca [0.36 to 0.4 in.], In the surface of the reactor vessel head (Information Notice W6-106, Supplement I).
Also In August 1967, personnel at San Onofre Unit 2 broke off the packing plate hold-down bolts of a 10 In. nominal isolation valve in the shutdown cooling system while attempting to open the stuck valve manually.
The resulting leak of approximately 230 to 380 L/min [60 to 100 gpmJ spilled 68 kl [18 k gall of reactor coolant into the containment.
Boric acui leaking from the valve had corroded the valve packing plate hold-down bolts, which were made of carbon steel (Information Notice 86-1068, Supplement 2).
Information Notice 86-106, Supplement 2 also discussed a series of tests performed by Westinghouse that showed that high concentrations (15 to 25 percent) of aerated or dripping boric acid could corrode carbon steel surfaces at rates as high as 10 rm/month [400 oil/month] in 93 to 9 "C
[200 to 210 *"] envirmawnts.
In Marckv 1988, the NRC staff issued Generic Letter 88-05 io which it requested licensees to institute a systematic program to monitor locations where boric acid leakage could occur and to provide measures to prevent degradation of the reactor coolant pressure boundary by boric acid corrosion. *_ *ft 4 A This information notice requires no specific action or written response. If you have Any questions about the information in this notice, please contact ono of the technical contacts listed below or the appropriate Office of*
Nuclear Reactor Regulation (NRR) project manager.
Dole Technical contacts:
Brian K. Grims, Director Division of Project Support Office of Nuclear Reactor Regulation Michael Modes, RI (215) 337-5196 Doald Kirkpatrick, NRR (301) 504-1849
Attachment:
List of Recently Issued NRC Information Notices DOCUMENT NAME: S:\\DOPSSEC\\SO81CORR.IN
- Se,,rvious concurrences OECB:DOPS*
PUB:AOM C/ENCS:DE'*
PRS:R1" 0Kirkpatrick feJac (Tech Ed)
JStrosnider Ngodes 1019 1/99 1/19 11129194 D/DRS:R1 SC/OECB:DOPS*
OECB:DOPS*
C/OECB:DOi JMiggns EGMoodwin RKiessel AChaffe 1/30'4 -O12/12194 121?/ 94 I6rimes Al ý j
IN W16-10, S~ip. ý3 December xx, 194 Page 4 of 4 Ibis infomation notice requires no specific action or written response. If yoo.have any questions about the information in this notice, please contact
-Oe of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation project manager.
Brian K. Grimes, Director Division of Project Support Office of Nuclear Reactor Regulation Technical contacts:
Michael Nodes, RI (215) 337-5198 Donald.irkpatrick, NRR (301) 504-1849
Attachment:
List of Recently Issued NRC Information Notices DOCUNW NAME:
G:\\DON\\BORICORR. IN
- See-previous concurrences OECB:DOPS*
PUB:AVN C/ENCB:DE*
DRS:RI*
DKirkpatrick Mfejac (Tech _d)
JStrosnider NHodes D/DRS:RI*
SC/OECB:DOPS*
OECB:DOPS*
C/O(fB:OOPS Wiggins EGoodwin Wkiessel AC f
12/94
- 11/30/94 12/'12/94 12/
Ir imes 12/ /94
IN W-1Os. u 3
Pape4 of 4 This Informmtion notice requires no specific action or written response. If you have any questions about the information In this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation project manager.
Brian K. Grimes, Director Division of Program Support Office of Nuclear Reactor Regulation Technical contacts:
Michael Nodes, RI (215) 337-5198 Donald Kirkpatrick, NRR (301) 504-1849
Attachment:
List of Recently Issued NRC Information Notices DOCUMENT NAME:
G:\\DON\\BORICORR. IN
- S e e p r v o s c o n c u r r e n c e s OECB:DOPS*
PUB:AN*
C/EMCB:DE*
DRS:RI*
OKIrkpatrick NMegac (Tech Ed)
JStrosnider mNodes 10 is 94 10/19194 11/01194 11/29-94 0/DAs:RI*
SC/OECB:OOPS*
o¢ej:,uOS
- C/OECB:DOPS JXo*q ns E~oodwin RKiessel AChaffee 11/29/94 11/30/94 12/12/94 12/ /94 D DOPS ilGrims 12 94
A, IN 86-108, Supp. 3 December xx. 1994 Page 4 of 4 This information notice requires no specific action or written response. If Y6u have any questions about the information in this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation project manager.
Brian K. Grimes, Director Division of Program Support Office of Nuclear Reactor Regulation Technical contacts:
Michael Nodes, RI (215) 337-5198 Donald Kirkpatrick, NRR (301) 504-1849
Attachment:
List of Recently Issued NRC Information Notices OECB:DOPS*
PUB:ADN*
C /EMCI:DE*
DRS:RI*
DKirkpatrick MeJac (Tech Ed)
JStrosnider Modes 10o1/94, 101 19/94 11/01/94 11/29/94I D/DRS:RI*
SC/OECB:DOPS*
O C/OECB:DOPS JWigglns EGoodwin RKiessol AChaffee 11/29/9 11/30/94 12/94 121 /94 D/DOPS BGrimes 12/ 94 See previous concurrences
T*
Technical contact:
Michael Modes, RI (215) 337-5198
Attachment:
List of Receiitly Issued NRC Information Notices O3ECB:DOOPS*
IPUB: AOM*
C
/EMCB: DE*
DRS: RJ I
DKirkpatrick MMejac (Tech Ed)
JStrosnider MModes D
0 / os:RO SC/OECB : OOPS
_. OECB : DOPS C/OECB:
DOPS SJwiggins EGoodwin
'9 RKiessel AChaffee 10 i 9 94 1 /1 994 12/
/94 12/ /94 o/DoPS BGr imes 12' 94
'e previous concurrences IN 86-10Bo Supp..3 December xx, 1994 Page 4 of 4 Workers had reported a t-dy-to-bonnet. leak from the pressurizer spray valve at Three M,11 island UnitL fn November 1993.
A work request was prepared to repair the, leak.
However, the licensee made a superficial inspection of the valve wittout removing.'ll of the Insulation and concluded that the boric acid crystals awund the valve came f--om the valve packing rather than the body-to bonnet joint. As a consequence the work request was cancelled.
The wide ranges of ambient conditions around reactor primary coolant leak sites with the resulting wide variations in corrosion rates make it very difficoilt to predict the probabil ty of corrosion damage. As was previously discussed in Information Notice 86-108, the primary defense against boric acid corrosion remain-the same - minimize leakage, detect and stop leaks soon after they start, and promptly clean up any boric acid residue.
This information notice requires no specific action or written response. If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation project manager.
Brian K. Grimes, Director Division of Program Support Office of Nuclear Reactor Regulation J1
October xx, 194 Page 4 of 4 Workers had roported a body-to-bonnet leak from the pressurizer s0ray vale -at Three Nile Island Unit I in November 1993.
A work request was prepared to repair the leak NoHwater, the licen-ee made a superficial inspection of the valve without ramovtng all of the insulation and concluded that the boric acid crystals around the valve came from the valve packing rather than the body-to bonnet Joint. As a consequence the work request was cancelled.
The wide ranges of ambient conditions around reactor primary coolant leak sites with the resulting wide variations in corrosion rates make it very difficult to predict the probab'.lity of corrosion damage. As was previously discusi~ed in Information Notice 86-108,. the primary defense against boric acid corrosio3 remains the sam - minimiLe leakage, detect and stop leaks soon after they start, and proaptly clean up any boric acid residue.
This information notice requ.rcs no specific action or written response. If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation project manager.
Brian K. Grimes, Director Division of Program Support Office of Nuclear Reactor Regulation Technical contact: Michael Modes, RI (215) 337-5198
Attachment:
List of Recently Issued NRC Information Notices OECB:DOPS*
PUS:ADM*
C/EMCB:DE*
R I )
W4 DKirkpatrick IMMejac (Tech Ed)
JStrosnider MModes s &A M
10 18 94 10/19/94 11/01/94 1!/20/{94it SC/O(CB:DOPS OECB:DOPS C/OECB:DOPS D/DOPS EGoodwin RKiessel AChaffee....
_BGrmes l1/
/94 11/
o94 1n /94,r en
/94 SI prei-usocurrences