IR 05000528/1986008
| ML17300B188 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 01/25/1988 |
| From: | Wenslawski F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Liza Cunningham, Knighton G Office of Nuclear Reactor Regulation |
| References | |
| TAC-67105, NUDOCS 8802090593 | |
| Download: ML17300B188 (11) | |
Text
REGULATQRY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCFSS ION NBR: 88020'7059 DOC. DATE: 88/01/25 NOTARIZED:
NO FACIL:STN-50-528 Palo Verde Nuclear Stations Unit ii Arizona Publi
AUTH. NAME AUTHOR AFFILIATION JENSLAMSKI F. A.
Region Si Qfc of the Director REC IP. NAME REC IP IENT AFFILIATION NIGHTONi G. W.
ProJect Directorate V
CUNNINGHAM'.S.
Radiation Protection Branch DOCKET 0 05000528 SUBJECT:
Informs of signficant radiological problems encountered in field oF'eactor coolant pump stel lite contents per Insp Rept 50-528/86-08.
DISTRIBUTION CODE:
IE06D COPIES RECEIVED: LTR ENCL SIZE:
TITLE: Environ 5 Radiological (50 DKT>-Insp Rept/Notice of Violation Respons NOTES: Standardized plant.
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MEMORANDUM FOR:
G.
W. Knighton, Director, Project Directorate V,
Division of Reactor Project III, IV, V and Special Projects L. J.
Cunningha'm, Chief, Radiation Protection Branch, NRR/PRPB FROM:
F.
A. Wenslawski, Chief Emergency Preparedness and Radiological Protection Branch, Region V
SUBJECT:
REFERENCE:
PALO VERDE REACTOR COOLANT PUMP STELLITE CONTENT INSPECTION REPORT NO. 50-528/86-08, SECTION 3, WASTE SYSTEMS, LIQUID, INSPECTION OF MARCH 3-7, 1986 The referenced Inspection Report documented the first report of licensee's concerns related to the antimony content of reactor coolant pump (RCP)
bearings and RCP stellite wear rings.
Subsequent reports document increasing primary system contamination with Sb-122/124 and licensee's efforts to remove the contaminants.
Modified bearings were obtained and installed in Unit 3 before initial criticality and in Unit 1 during the first refueling outage.
Unit 2 RCP bearings will be replaced during the first refueling outage.
During the Unit 1 refueling (October 1987 - January 1988), the RCP impellers were removed for antimony decontamination prior to shaft removal because of the shaft cracking problem.
Concurrent with the opening of the primary system, the licensee found a significant increase in the number of Co-60 particles identified during surveys.
Some of the particles contained mi llicurie quantities of Co-60.
Examination of the impellers disclosed significant damage to the stellite wear rings or surfaces (see attached Attachment 1).
The licensee reported that the stellite had been plasma arc deposited on the impeller base metal in a layer approximately 0. 012 inches thick.
The upper surface was 12 inches in diameter and 4 inches wide.
The lower surface was 28 inches in diameter and about 4 inches wide.
The licensee described the damage as follows:
The complete loss of the upper wear surface on one pump.
The loss of 3 or 4, 1-inch diameter blisters in another area.
The loss of a 4-inch strip, 3/4 to 1 inch wide.
The loss of small chunks or chips from one of the lower surfaces.
Seven of the eight impellers* in service in Units 1 and 2 were coated with stellite by KSB, the RCP manufacturer.
One of the Unit 1 and all the Unit 3 pumps were coated with stellite by Cleveland Hardfacing.
The Unit 1 impeller which lost all of the upper stellite surface was the unit coated by Cleveland Hardfacing.
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JAN 2 5 198S-2" During the Unit 1 outage, it was determined that the upper stellite wear ring/surface was not required and it was removed from all the Unit 1 impellers.
In addition, the'idth of the lower wear ring/surface was reduced to approximately 2 inches.
A project is presently underway to identify a suitable replacement surfacing material to be used on the impellers.
It is believed that this project will permit corrective action to be taken on the Unit 2 impellers during the first refueling presently scheduled for February-March 1988.
When the presence of stellite on the impellers first became known to the licensee's radiation protection staff, they requested but did not press for prompt corrective action in the belief that the stellite would adhere to the base metal and not contribute a significant source of cobalt target material.
Experience has shown that the stellite is a significant source for the production of Co-60.
One particle, recovered from a steam generator, was 9 millicuries.
This one particle exhibited a contact dose rate of approximately 4500 rad/hr (See Attachment 2).
The licensee's radiation protection staff has notified their management that they believe that these particles present a potential threat to the health and safety of plant workers.
Management responded by noting the previously mentioned partial removal of the stellite from Unit 1 impellers, stated that replacement surfacing was being investigated and establishing a schedule for stellite removal:
Unit 1 Next time impellers are removed Unit 2 - Refueling - February 1988 Unit 3 - Refueling - 1989 Licensee management concluded that the stellite removal was desirable but not feasible at this time.
Licensee management has agreed to submit a report on the stellite problem to the Region V office following the inspection of the Unit 2 impellers during the February-March 1988 refueling outage.
The purpose of this memorandum is to keep you informed of significant radiological problems encountered in the field.
In addition, if there are other instances of degraded stellite applications, an Information Notice or vendor inspection involvement might be appropriate.
t Attachments:
As Stated.
F.
A. Qenslawski, Chief Emergency Preparedness and Radiological Protection Branch
JANzs 1sSs-3-cc w/attachments:
E. Licitra, NRR/PD5 P-302 R.
R. Bellamy, Chief, EP8RPB, Region I D.
M. Collins, Chief, EP8RPB, Region II W.
D. Shafer, Chief, EP8RPB, Region III L. A. Yandell, Chief, EP&SB, Region IV bcc w/attachments:
RSB/Document Control Desk (RIDS) (IE06)
Project Inspector Resident Inspector G.
Cook B. Faulkenberry J. Martin Docket File bcc w/o attachments:
LFMB M. Smith Region V
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215-00473-GDP/DH/JBS December 4, 1987 Distribution Prepared by:
Signature Name/Ext.lQtt.
'r Aevtewad By:
Stg natura Name/Ext./Sta.
D. McGe
/60 J.
B. Steward/2728/6281 R.
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/3885/6281 Pile:
SUBJECTt Approved by:
Signature Nama/Ext./Sta.
G. D. Perkins/2646/6090 87-002-419.04 Postulated Exposure Assessment From Co-60 Chips Recently Found During Unit 1 Outage Pork On October 20, 1987, during outage work in Unit 1,
a spot of high activity'ontamination was found during routine hot particle surveys of the tIi2B Reactor Coolant Pump 100'levation platform.
The contamination was localized, removed from the work area, and appropriately placed in shielded storage by Radiation Protection Staff.
Preliminary'ose rate measurements indicated a
20 R/hr gamma component on contact with the source.
Support Staff isolated the contamination as a
discrete particle measuring 600 - 750 microns in diameter.
The particle activity was quantified by gamma spectral analysis using a collimated HPGe detector at 12 feet (free air) from the source.
The efficiency calibration was performed using a
standard source at the same source to detector geometry.
This analysis indicated 9.2 mci of Co-60 (Attachment A).
In the interest of providing a relative assessment of the radiological implications associated with potential direct personnel exposure involving this particle, several evaluations were performed.
Beta Skin Dose Estimate 1. Calculational assessment of direct'kin exposure assuming skin contact and no'self>>absorption:
R - cmz 9193 pci x 4. 314 ~
h 39,659 Rad/hr/cm2 where:
9193 pci ~ particle activity (Co-60)
R cm2 4.314 h
Dose conversion factor for Co-60 pM-hr 2. Using the computer code uUarskin",
a value of 37,900 Rad/hr was obtained (Attachment B).
Note:
The dose rates above are at a depth of 7 mg/cm2 in tissu P
.Page
Distribution 215>>00473-GDP/JBS December 4,
1987 These Beta dose rates correspond to -"ll Rad/sec delivered in exposure incident.
Although it is permissible" to average doses f of z
h h
h 2+06 Rad/hr over a basal c 11 f.
n s
ows t at the true Beta dose sa ce area of.0098 cmz.
Gamma Skin Dose Estimate The amm gamma skin dose component was estimated usi combination with
ca culational techni ues.
The es mate using instrument readings Sa R/h /
z t
ti d
th of 7
/
Direct Measurement Com arisons In an attempt to relate the calculated values to di results, com*parisons were
ues to irect measurememt.
ideal since the extrap 1 ti h '
a so performed.
These measurements are nac greater than
cmz.
Th f
apo at on chamber used has an active surface area distance and normalized to co t ere ore, measurements must bee made at some o contact readings (7 mg/cmz depth).
The particle was isolated under 20 mg/cmz last d
d di t
and gamma dose rate measureme t
s ance 0 cm from the detector surface.
Combined Seta 10 cm.
This value was then normalized.
surements resulted in a value of 1.77 R d/hr ~
1.77 Rad/hr x 650 ~ 1150 Rad/hr at 20 mg/cd where:
650 ~ c distance orrection factor for air abs bti d
or on an This value of 1150 Rad/hr was then corrected t
/
o mg cm tissue depth:
Rad.hr e -(105 4)(0 013)
4527 Rad/hr where:
105.4 attenuation coefficient (p)
0.013
~ density thickness (gms/cd)
This value is not absolute since this approach did not measurement assessment conditions, The difference results obtained f
ons, e i ference between calculational rom gamma spectral analysis and t e
. extrapolation measurements ld i d n
the beta dose component is being attenua h
i 1 i lf
0
. P.age
Distribution 215-00473-GDP/JBS December 4,
1987 Syyno sos This particular discrete particle illustrates associated with hotot particle contamination.
Durin the er c e ustrates the dose rate potential report was being prepared a
th C
magnitude of its postulated h
anot er Co-60 chi was f order of 6 times the magnitude of the article u a e
c aracteristics indicate ot p
entials on the D
o h
i i
d dose rates fall off e
s ze an inverse s uare r
q properties involved, surface o
very rapidly with increas'in distan most available instrumentation will severl un d
mp y y
es gn and because of geometry considerations GDP/DM/RDM/JBS/kdf Distribution:
J.
D, Driscoll L. E. Brown J.
R.
Mann T. P. Gavigan K. R. Oberdorf R. V. Logan R. L. Selman W. E. Sneed-W. H. Doyle