IR 05000295/1993021
| ML20058G094 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 12/01/1993 |
| From: | Cox C, Kozak T, Louden P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20058G092 | List: |
| References | |
| 50-295-93-21, 50-304-93-21, NUDOCS 9312090096 | |
| Download: ML20058G094 (7) | |
Text
{{#Wiki_filter:_.. - _ _ _ , . . ' U.S. NUCLEAR REGULATORY COMMISSION "
REGION III
i i Reports No. 50-295/93021(DRSS); 50-304/93021(DRSS) .l , Dockets No. 50-295; 50-304 License Nos. DPR-39; DPR-48 ! Licensee: Commonwealth Edison Company Executive Towers West III
1400 Opus Place, Suite 300 Downers Grove, IL 60515 Facility Name: Zion Nuclear Generating Station, Units 1-and 2 { Inspection At: Zion Station, Zion, Illinois j Inspection Conducted: November 15 through 19, 1993 .;
! Inspectors: lx[[L C,// /m itA 63 P. L. Loudeh' / Date Radiation Specialist , i i idEl~ cab isi k T.~J. Kozak~ / Date Senior Radiation Specialist k) N -, C Y b~ nAln C. R. Cox ~ /~ Date Radiation Specialist i -
Approved By: /f)8m; G // tiA /r ! William G. Snell, Chief Date l Radiological Programs-Section 2 l l l Inspection Summary' j
Inspection on November 15 throuah 19. 1993 (Reports No. 50-295/93021(DRSS): ! 50-304/93021(DRSS)) i ' Areas Inspected:. Routine, announced inspection of the licensee's radiation protection (RP) program (Inspection Procedure (IP) 83750) during the current dual unit refueling / service water outage.
Inspection activities included reviews in the areas of surveys and contamination control,. maintaining occupational exposures ALARA, source term reduction and general station. tours.
Results: The licensee's program for controlling occupational radiation exposure is generally effective. Dose rates in the Unit I containment missile barrier were unexpectedly high. The licensee appeared to take this in stride 9312090096 931201 ' PDR ADOCK 05000295 a PDR . - - __.
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- . , . . rather than reassessing the work scope and schedule to determine if the work could be done under better radiological conditions (e.g. with loops filled).
' The licensee was effectively tracking dose on a job-by-job basis.
Control of . ' work in high dose areas was effectively accomplished with use of wireless ' remote monitors. The dose equalization policy adopted by the licensee has resulted in several cases in which work was not performed as efficiently as
possible, which has resulted in additional dose, due to replacing workers in the middle of a job. No violations of NRC requirements were identified.
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, DETAILS i 1.
Persons Contacted j
Commonwealth Edison , ,
- D. Bump, Supervisor, Maintenance Support Group
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- K. Dickerson, Regulatory Assurance, NRC Coordinator
- 0. Fick, Senior Radiation Protection Technician
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- K. Hansing, Supervisor, Station Quality Verification l
- S. Kaplan, Supervisor, Regulatory Assurance
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- H. Logaras, Quality Verification Inspector
- G. Ponce, Supervisor, Station Quality Control
- B. Robinson, Lead Operational Health Physicist
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- W. Stone, Performance Improvement Director
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- D. Wozniak, Superintendent, Technical Services
, The inspector also interviewed other licensee personnel in various departments in the course of the inspection.
' Nuclear Reculatory Commission i
- J. D. Smith, Senior Resident Inspector
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- Denotes those present at the Exit Meeting on November 19, 1993.
l r 2.
Recent Airborne Event Durina Unit 2 Reactor Head lift (IP 83750) ' The inspectors reviewed an event which involved the creation of an - ! airborne radioactivity condition in the Unit 2 containment which ! resulted in 29 workers receiving minor intakes of radioactive material.
, On 0ctober 16, 1993, the licensee performed reactor head lift operations in the Unit 2 containment. A pre-job briefing was held to discuss the
evolution. The lift occurred as planned at 1800 hours during the , afternoon shift. The evolution went smoothly and the head was placed on ! the reactor head stand. During movement of the reactor head, a health , physicist noticed a nearby continuous air monitor (CAM) occasionally l went into high alarm. This is not unusual during evolutions in which dose rate changes may be occurring in the area (as with the movement of- ' the reactor head).
The procedure for the CAM states. that an alarm must be. continuous for two minutes to positively identify an airborne
condition. The CAM did not alarm for more than 30 seconds throughout ' the course of the reactor head movement. Shortly thereafter, the CAM ! alcrmed for approximately 40 seconds. The health physicist in the , ' containment, curious of the intermittent alarms, requested a radiation protection technician to frisk the filter media for contamination. The j frisk indicated that an airborne condition was present in the area so
containment was evacuated. All 29 people in the Unit 2 containment
during the evolution were whole body counted. Whole body count results-l 't
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An investigation was immediately initiated to determine the cause of the
airborne condition.
Such en evolution has been performed many times in
' the past and no airborne contamination problems have ever been encountered.
Based on the licensee's reviews, the airborne condition i appeared to be caused by flooding up of the reactor vessel with the-i Residual-Heat-Removal (RHR) system in conjunction with a unique set of ! conditions resulting from the early boration and low letdown flow rates - (see Section 5).
The flow rate for the RHR system is approximately 2800 gpm. This flow rate was believed to create.significant air turbulence through the upper internals region of the reactor causing them to dry out.
The upper internals were observed to be dry during the head move.
The possible settling of additional activation products on the upper . ! intervals (which were added to the coolant from the early boration) as a , result of a low letdown flow, could have caused the airborne problems.
i The station established a number of corrective actions prior to the Unit I reactor head move to avoid recurrence of the airborne s;tuation. The
following changes were implemented-Operating procedures were modified to perform the flood up of the cavity with the charging system when people were still in containment. This system has a much lower (200-300 gpm) flow rate than the RHR system, which should minimize air turbulence and reduce drying and raising as much material into the air.
, Essential personnel were identified during the operation to reduce "
the number of workers in containment during the reactor head move.
Chemistry and RP shall closely monitor the shutdown chemistry to note any abnormalities in soluble and insoluble cobalt-58 activities.
All the personnel who received the intakes of radioactive material ' cleared the material in a short timeframe. The highest dose assigned to , any individual involved with the event was a few millirem (10 to 20 I gSv). Most workers received internal doses of-less than one millirem (10 gSv).
. The licensee performed the reactor head move in the Unit I containment shortly after the implementation of the corrective actions from the Unit 2 event.and no airborne contamination problems were observed.
No violations of NRC requirements were identified.
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Contamination Control (IP 83750) ! The station had recorded 247 personnel contamination events (PCEs) as of November 18, 1993. This was within the established goal to that date in .
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The station's 1993 PCE goal is 325 and should be met based on the
current PCE occurrence rates, a . The inspectors noted the extensive decontamination efforts which were performed prior to the dual unit outage, particularly in the overhead
areas of. the auxiliary building on elevations where major valve
replacement activities were to occur. This effort has resulted in the , accomplishment of work activities in the overhead regions without the
need for protective clothing which has significantly decreased the time l and oversight required for the project.
. No violations of NRC requirements were identified.
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Implementation of Outace Plannina (IP 83750)
Problems were detected in scheduling work activities early in the i outage. A daily outage scheduling meeting was held during which a four day look ahead schedule was reviewed.
Problems with the four day look ahead schedule were experienced such as work being scheduled and due the . same day as the meeting without prior warning. The apparent problem was
that as activities were completed ahead of schedule, other activities ! that were logic tied to the completed activity were automatically moved up by the computer program. This caused some activities to not have-
associated Radiation Work Permits (RWPs) and radiation surveys ready to- ! support the jobs that had been moved up. The various departments' schedulers resolved the problem by placing constraint dates on jobs so + that those jobs could not be moved up before the constraint date.
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! other scheduling implementation problems were identified.
No violations or deviations were identified.
! 5.
Maintainino Occupational Exposures ALARA (IP 83750) .; The inspectors reviewed general area surveys for the dual unit outage l and r,ted higher than normal shutdown dose rates.
The standardized red
diamond surveys indicated 70 per cent higher dose rates inside the Unit ! I missile barrier and 30 per cent higher dose rates inside the Unit 2
missile barrier. A rr, view of the previous operating cycles did not
reveal any probable causes for the increased dose _ rates. The licensee f used early boration to produce a crud burst early in the shutdown i process for both Units.
Interviews with Chemistry and Operations-personnel indicated that there was good preplanning for the= shutdowns-i between the two groups. A key element to ensure success when'using ! early boration is to maximize the letdown flowrate which in turn allows i for efficient cleanup of the crud burst. The letdown flowrate for the ' dual unit outage shutdowns were low when compared to other similar: units.
i that have used early boration. This may have allowed some radioisotopes I to settle out on piping surfaces thus contributing to-the higher dose l rates inside the missile barriers. The licensee indicated that they
were still trying to determine the optimum shutdown parameters to ensure l' that the crud burst created during early boration was removed as quickly l
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. . I I ' as possible, The inspectors indicated that the results 5f the
licensee's review would be evaluated during future inspections.
Although the licensee was concerned about the higher than expected dose rates, it appeared that there was no attempt to. review the missile i barrier work scope to determine if jobs could be delayed until more ! favorable radiological conditions were established (e.g., after loops , are filled which should provide shielding and lower dose rates). The , licensee acknowledged the inspectors' observation and indicated that the i work scope would be reviewed.
In response to the high dose rates, the licensee developed a Source Term Task Force (STTF) just before the inspection. The STTF is a multi- - disciplinary group, including a consultant, that will perform a global , review of the source term problem and make recommendations for source ! term reduction. The inspectors indicated that they would review the , STTF charter and actions at a later date.
Indications were that the . shutdown process, including ways to maximize letdown flow, and missile barrier work scope would be high priority items on the agenda for review by the STTF.
The licensee established a control point at the containments' entrance _ f at which all personnel entering are questioned on their Radiation Work Permit (RWP), destination, and expected dose rates in the area.
This ' has provided an effective method to limit the number of people entering containment and has resulted in an overall dose savings.
The licensee required the use of wireless remote monitors for all work occurring inside each containment's missile barrier.
This-has been effective as radiation protection technicians are in. constant e communication with workers and can tell the workers when they enter an area with higher dose rates than they need to be in to accomplish their work.
The ALARA group was effectively tracking doses on a job-by-job basis.
This was an improvement item noted during the last outage and the licensee has continued this good practice. The licensee indicated that-they were not going to modify their exposure goal based on the higher ' than expected dose rates but would rather try to meet the goal and if they are unable to, identify the jobs and reasons that resulted in the increased dose.
The inspectors conducted interviews with electrical, instrument, and mechanical maintenance personnel and primary and auxiliary technical support personnel to determine their involvement in ALARA. Most of the personnel interviewed indicated that their groups provided the ALARA _! group with estimated person-hours for ' scheduled jobs and the ALARA group developed exposure goals for each department. Ownership for dose within , the Maintenance Department varied from shop to shop.
Interviews with , the~ Electrical Maintenance (EM) Supervisor and Scheduler indicated that the EM department was closely tracking the dose from the ongoing motor operating valve (MOV) inspections. They noted that while only 27 per-
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.- cent of the job was complete, 37 per cent of the estimated dose for the , ' job was expended. The EM department was reviewing the MOV uork to determine ways to reduce the time to complete the inspections. Other groups interviewed appeared to rely more extensively on the ALARA group , to track exposure.
! > The Maintenance Department has implemented an agreement with the
bargaining unit concerning dose equalization for workers within their respective shop. The inspectors determined through interviews and ' observations that this policy has resulted in several cases in which work was not done efficiently as possible due to replacing workers in
the middle of a job. This also resulted in higher collective doses than i would have been received had the same_ workers been required to complete their job.
The licensee indicated that they were in the process of
reviewing the agreement to modify its implementation such that it does not impact work efficiency.and ALARA policies.
The licensee has developed a valve replacement prioritization list.
, ' During this outage, the charging flow-control valve in each Unit was replaced with a low cobalt valve. The inspectors indicated that source term reduction efforts will continue to be monitored at the station.
' No violations or deviations were identified.
6.
Exit Meetina < The scope and findings of the inspection were discussed with licer :ee
representatives (Section 1) at the conclusion of the inspection on
November 19, 1993.
Specific items discussed during the exit meeting are
summarized below.
Licensee representatives did not identify any documents or processes reviewed during the inspection as proprietary.
The observation of the inspectors with respect to the use of dose
equalization on a daily basis, and how this application of dose , spreading breaks down job continuity and is not the most ALARA way , t to accomplish work in radiation areas.
t The observation of the continued improvemer.t to' containment and _
inner missile barrier access control.
-l > The observation that the optimum shutdown parameters when using
' early boration have not yet been determined by the licensee.
The continued improvements in the dose tracking process during the
, current dual unit outage.
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