ML083260671

Package of Nuclear Safety Review Staff Repts for Which Complete Resolution of safety-related Issues Not Achieved. W/One Oversize Drawing. Continuation of Nuclear Safety Review Staff Repts

ML083260671
Person / Time
Site:	Watts Bar
Issue date:	04/30/2008
From:	Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation
Shared Package
ML082460007	List: ML083260671
References
NUDOCS 8509110145, PROC-800430
Download: ML083260671 (80)

Text

d. Issue of Hold Order to Person Responsible for the Work Section 5.1.4 of AI-3, "Clearance Procedures," states that "no actual work shall begia on the equipment to be included ia the clearance until the clearance has been issued to the person responsible for the work."

Betwee 0220 on April 17 and 0400 on Nay 1 Bold Order No. 1 was issued only to the ASE while work was in pro greas in the instrument room before and after the acci dent. The ASE was not the person responsible for the work. This represents noncopliance with the require maets of section 5.1.4 of AI-3.

For conclusions and recomendations relating to this section, refer to section III.C.6.

D. Work Activities Related to the Thimble Tube Cleanina Prior to the Accident The following is a discussion of the work activities conducted after the planning process to the time the accident occurred:

1. Work Activities During the sveniln of April 18 to Approxi mately 0830 on April 19

a. Fabrication of New Support for the Cleaning Tool The dry brushing tool (handcrank) and its support mechanis that had been used in past thimble tube dry brushing operations had been inadvertently discarded in radwaste. A handcrank device had been acquired from WN. The support for the handcrank was not supplied from the vendor that supplied the dry brushing tool.

The FSG second shift coordinator consulted with an FSG maintenance specialist who had been involved with prior thimble tube cleanina activities to deteraie what type of base support was needed for the new dry brushiag tool. It was suggested that a new support device be fabricated somewhat differently than the one that had been used on previous cleasings. The change involved removing the right angle support on the base support (see figures IIA and 111) to allow the base support to make better contact with the surface of the seal table.

Thb problem with the old tool was that tne support did not always fit up well with soe of the "bosses" on the seal table and allowed the tool to move around during the turarna of the handcraak. Figures 12A and 125 depict the tool and the base support in use when the accident occurred (part of the ejected thiable tube D12 Is still attached to the upper portion is figure 121).

The eveania shift coordinator requested the pS machine shop to fabricate the new base support pieces for the cleaning tool. Note: The new base support pieces were

, e not finished and used until approximately 1500 on April 19. The day shift coordinator and his crew used the tool -with the new base supports and be felt it offered much better support for the tool thea the supports that had been used in the past. The steam fittr- sO the evening shift that was using the tool and support when the accident occurred and had experience with the old support was of the opinion that the new base support was not as good as the old ones usedsome in past cloening operations. He had expressed the concern about the design of the new support to coordinator (see section IV.H.2 of this evening shift report).

The change to the tool base support was made without any technical evaluation of its effect on the echani cal seals. The new base support was not tested before use on the thimble tubes.

b. Disasseably of the Incore Inatrumetation System Drive tahs and Initial Assealy of Dry Brushins Ceaning quime"St. The evening shift coordinator, one steam fitter foreman, three stemfitters, and an iP techni cian entered the instrument room through the personnel airlock at 2300 on April 18 (without verifying that Hold Order No. I was in effect) and worked until approximately 0630 on April 19 freeing two detectors stuck in their thimble tubing, disassembling the over head drive paths at the SWAGELOK union flare fittins, and rolling the path transfer units and associated tubing back out of the way allowing access to the seal table. The high pressure fittings were reportedly not disturbed during this process. During this 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> activity in the instrument room, the maxism whole body radiation does received (based on pocket dosimeters) was 15 millirem.

At approximately 0315 on April 19 the day shift coordi nator, three steasfitters, and a steaofitter foreman reported to work. The day shift coordinator and a steafitter entered the instrument room at approximately 0330 (without verifying that Hold Order No. I was in effect) and worked with the evening shift coordinator and his crew until the evening shift exited the instru ment room through the personnel airlock. At approxi mately 0430 two steamfitters entered the instrument room (without verifying that Hold Order No. I was in effect) ad the compoaite day shift crew removed deck grating froe above the seal table and assembled the dry brushian equipmeat. It was noted at this time that there was no base support for the Teleflex-supplied dry brushiag tool. The day shift coordinator and the three pipetitters exited the instrument roeo at approtstely

0530 on April 19 to fabricate a temporary base support to be used until the naw base support device being fabricated by the machine shop was finished and ready to use. During this two-hour activity in the instru enat room, the mximn whole body radiation dose received (based on pocket dosimeters) was 3 millirem.

A temporary base support for the cleaning tool was fabricated out of angle iron. No technical evaluation was performed on this temporary support to assess the effect it would place on the mechanical seals. The temporary base support was not tested before use on the thimble tubes.

At approximately 0800 on April 19 it was announced at the morning meeting normally attended by most plant managers that the decision had been made to clean the thimble tubes at power. No objections were offered or concerns expressed.

For conclusions and recomendations relating to this section, refer to section III.D.I.

2. Work Activities from 0830 on April 19 until Approximately 1700 on April 19

a. Initial Cleaning of Five Thimble Tubes - 0830-1115 April 19. At approximately 0830 the day shift coordi nator, a steamfitter, and an HP technician entered the instrument room and began to assemble the cleaning tool with the temporary base support. (At 0945 another steamfitter joined the group.) When the cleaning tool was assembled they connected the tool to the SWAGELOK union flare fitting on one of the tubes identified as blocked on the W. The cleaning tool was assembled as depicted in figure 12A with the eaception that the tool support base waa at that time constructed of angle iron. As they had aot previously had success with getting the cable and brush through the thimble tubes the workers decided to try a cable without a brush.

They ran the cable without the brush into the first tube approxuimately 85 turns ( ' 70 feet) and encount er4ed severe reeirtance. They repeated this technique with the other four thimble tubes with the samw approx imate resulta. The day shift coordinator at this point thought that probably somethiang was wrong with the cleaianl cable. The dose rate on the cable when it cam out of the thimble tube was approximately 10-15 mre/hour at contact.

Note: The cleaning operation at this point had been itiated usian 8NL1-0-94-1 as the primary procedural control for the activity. Section 1.1 of SNI-O-94-1

"This states "this system is not to be used at power."cleaner, system" is in reference to the thimble brushing Teleflex part number 43679 which includes the "This assembly. Section 4.3.A of SMI-0-94-1 states plant is at procedure is not to be used while the contact power. If cleaning at power is necessary the plant but Teleflex, Inc." Teleflox was contacted by Using the they would not clean the tubes at power.

equipment and SMI-0-94-1 to perform Teleflexs-upplied a violation of the cleaning operation at power was SQ Unit I Tech procedure and section 6.8.1.s of the of this nical Specifications (see section IV.N.3.a report).

and exited The workers stopped the cleaning operation airlock at 1115 the instrument room via the personnel on April 19.

room, During this 2%-hour activity in the instrument received (based the maximum whole body radiation dose HP techni on pocket dosimeters) was 22 millirem. The opera cian suggested that before resuming the cleaning should be performed. After tion that ALARA preplanning covering leaving the instrument room the HP technician the the job went to the ALARA engineer and discussed be per job and recommeaded that ALARA preplanning the formed. This action by the HP technician initiated job and concern for the radiation safety of the awareness of the hazards of resulted in an increased and HP the job. It should be noted that the workers to technicians did not have an awareness of the hazards this point in the work process.

to this For conclusions and recommendations relating section, refer to sections III.D.2 and III.D.3.

b. Weldina Operatio in Personnel Airlock DurintWork Being erformed the Intrument oo. Section 1...3.a of states that the SQ! unit 1 technical Specificationas with both each containment airlock shall be operable used for doors closed except when the airlock is being normal transit entry and exit through the containment, with one then at least one airlock door shall be closed door containment door inoperable. The operable airlock closed. At 1050 on April 19 the is to be maintained Condition shift engineer entered unit 1 into a Limiting the Techni for Operation (LCO) for section 3.6.1.3 of welding personnel were cal Specifications because FSG lead running in the personnel airlock with a welding door rendering it inoperable because through the outer made operable the door could not be shut. The door was While the at 1121, and unit I went out of the LCO.

outer door was open the inner door could not have been opened in an emergency because of the interLock which will not allow both doors to be open at the same time.

The workers were cleaning thimble tubes, at that time and the day shift coordinator was not aware that the outer airlock door was open thus hindering their egress from the area in the event of an emergency.

When the FSG welders requested permission from the shift engineer (SE) to do the work in the airlock, he informed them that people were working in containment and asked them how long it would take them to get their equipment out of the door. They told him that it would take approximately 15 seconds. Some workers did enter and exit while the welders were working. The workers would shake the handle or tap on the door when they wanted out.

For conclusions and recoemendations relating to this section, refer to section III.D.4.

c. ALARA Preplanning 1115-1520 on April 19 (1) SQN ALARA Policy. Radiation Control Instruction RCI-10, "Hinimizing Occupational Radiation Expo sure," revised June 7, 1983, provides policy guidance to management and supervisory staff involved in the operating and maintenance of SQN so that occupational radiation exposures may be kept as low as reasonably achievable. The RCI states that maintaining occupational radiation exposures at the lowest level reasonably achie vable requires as a minimum the following:

• Management comitment and support 0

Careful design of the facility and equipment

• Good radiation protection practices, includ ing good planning and proper use of appro priate equipment by qualified, well-trained people.

Section VI.C of RCI-10 states that jobs with potentially greater than S man-rem exposure (total radiation exposure accumulated by all persons

&nvolved in the job) shall require an ALARA pre planning report to be completed by the responsible supervisor. The report is to be submitted to the designated ALARA coordinator for review and approval prior to job roemenremnt.

g.*

(2) Processing of Attachment I to RCI-10 At approximately 1130 on April 19 an ALARA HP technician along with a smaintenance specialist (not the responsible supervisor) who wan know ledgeable of the cleaning process with the reactor shutdown and who had been involved in the decision making process initiated an Attachment I to RCI-10, there "ALARA Preplanning." They calculated that would be a total of 154 RWP man-hours at a radia that tion exposure rate of 20 millirem/hour and the job would be 3.08 the estimated man-rem for rem (whole body dose). The feasible considera tions for reducing exposure were as follows:

0 Temporary shielding - "Take shielding in might can be used during job."

0 Special tools - "Use of improved drive box mounting device."

• Reamote operations - "Use of teletector for survey" Note: A "teletector" is a radiation (X-ray, gamia, high energy beta) dose rate measuring instrument with an extendable detector which provides for increasing the distance between the person making the radia tion dose rate measurement and radiation source thus reducing the dose rate to the person.

S Decontamination - "Use of vacuum cleaner with HEPA unit during job to minimize contamina tion." Note: A HEPA filter is a high effi ciency fil-ter for particulate activity (99.97 percent efficient for a 0.3 micron size particle.)

S Remove source - "Special precaution will be used when removing vacuum cleaner from area."

• Improve work instructions - "Reviewed Trojan Nuclear Plant's suggestions from when they did job at 100 percent power."

Note: The Trojan method used a 10-foot conduit and funnel on the end of the cleaning tool so as to enable the worker turning the handcrank to be positioned above the seal table and away from the high dose rates when the cable and brush cam out of the thiable tube and to ease transfer to the other tubes.

The Trojan report suggested the use of a

12-foot rigid conduit, a motorized helical drive, and a support platform above the seal table for the helical drive operator.

SXI-0-94-1 was not revised to incorporate these revisions nor was the Trojan technique used.

• Additional supervision - "HP and engineer at all times."

• Shift turnover discussion - "Turnover is scheduled."

• Proper Ventilation - "Use of vacuum cleaner with HEPA unit to reduce cuntamination."

• Reduce reactor power level - "Unit at 30 percent - trying to prevent reactor shutdown."

o Others:

- "ALARA zone - when not performing work stay in ALARA area - per HP on job."

- "Hold order - Insure hold order on incore probes." Note: Hold Order No. 1 is the applicable hold order.

Attachment I of RCI-10 was completed sometime after 1200 on April 19. The Trojan report was attached to the completed attachment, and the ALARA preplanning was discussed with the day shift coordinator and the recommendations implemented.

With the expected high dose rates the potential exposure would have been greater than 5 man-rem.

However, the ALARA preplanning was only conducted after the job was in prolrest and after the HP technician expressed concern for the job. The lack of awareness of the potential high dose rates on the part of the FSG coordinators promoted this oversight. The lack of awareness was due to poor transfer of information to the coordinators from those making the decision to do the job at power.

The responsible supervisor was not involved in the planning and the suggestions made in the Trojan report were not incorporated. However, even though the total man-rem whole body dose calcu lated out to be less than 5.0 man-rem (3.08 m"n-rem) the ALARA preplanning was implemented and the ALARA technician covered the job in addition to the HP technician assigned to the job.

U.,

(3) Preparation& for Resumini Work in the Instrument Room After lunch the day shift coordinator and his crew collected the additional equipment needed for implementing the ALARA plan. In addition, he acquired the new base support for the handcrank from the machine shop.

For conclusions and recommendations relating to this section, refer to section III.D.5.

d. Restion of Work in the Instrument Room 1520-1705, A ril 19. At 1520 the FSG day shift coordinator, two ithnicians (one vas the ALARA technician who had assisted in the ALARA preplanning), and two FSG steam fitters entered the instrument room to resume the cleaning operation. They changed to the new base support for the dry brushing tool. They continued to insert the cable into the blocked thimble tubes with the some lack of success as they had encountered in the morning. On the fourth thimble tube the cable inserted approximately six feet into the reactor core. As they were withdrawing the cable the HP technicians were measuring the dose rate from the cable as it came out.

The dose rate started increasing rapidly and at 15 rem/hour the HP technician stopped the withdrawal process. The cable was reinserted into the thimble tube until background dose rates (,sIO millirem/hour) were achieved at the seal table. The workers clipped the cable and tied it off so it could be retrieved later after the radiation levels decreased due to the decay of the activation products.

At this point the HP technicians prescribed the use of multidosimeters to ensure that the whole body and extremity radiation dose profile was properly measured.

The workers were equipped with the dosimeters at various positions on the whole body (head, tLank, groin, upper legs, etc.) and extremities (forearms, hands, feet, and ankles).

The cable with the brass brush was connected to the dry brushing tool and the tool was connected to another thimble. The brush and cable were inserted into the thimble tube but met resistance during the insertion.

The brush and cable entered the core but did not go to the end of the thimble tube. As it was being withdrawn a dose rate of 40 rem/hour was measured. The tool base suppcrt was shielded with some lead blankets that had been carried in for that purpose and the cable and brush vere withdrawn and inserted into thimble tube

S S D-12. Note: Subsequent processing of the extremity dosimeters revealed that one steamfitter involved in the transfer of the tool from one thimble tube to the other accrued an extremity dose of 5 rem in the process.

The decision to try thimble tube D-12 was made by the day shift coordinator as he knew D-12 was a thimble tube that had not been identified as blocked and he wanted to determine if the resistance being encountered during insertion of the brush and cable was due to blocked tubes or kinks in the cleaning cable.

The cable brush and cable were inserted into thimble tube D-12 but again not to the end of the tube. As it was being withdrawn the HP technicians stopped the withdrawal when the dose rate increased to 40 rem/hour and instructed the workers to reinsert the brush and cable until the dose rate at the table was approxi mately background (approximately 15 feet). At this point the HP technicians, the day shift coordinator, and the workers were very concerned with the high dose rates being encountered. The day shift coordinator had not expected and had never worked with dose rates of this magnitude. He and the HP technicians decided that the work should be stopped and discussed with manage ment before continuing. The workers exited the instrument room via the personnel airlock at 1705 The highest radiation whole body dose encountered during this portion of the cleaning operation was 145 millirem as measured by pocket dosimeters.

3. Work Activities from 1700 Ajpril 19 to 2120 on April 19 After the workers exited the instrument room, the day shift coordinator and his crew reported the problems they had encountered with the high radiation dose rates to their supervisor (the FSG mechanical supervisor). The HP tech nician &*ported the events to the HP shift supervisor. As a result a meeting was scheduled in the FSG office to discuss the progress of the cleaning activity, and the problems being encountered, and to do sume further planning to better handle the high radiation dose rates. Those in attendance were the following:

• FSG assistant supervisor

• FSG mechanical supervisor

• FIG day shift coordinator S lFSG evening shift coordinator S 1F30 mechanical maintenance specialist

• FIG evening shift mechanical general foreman

• FIG evening shift steamfitter foreman

• lHP shift supervisor

• H(P ALARA technician

During the meting safety factors were discussed conccrning pressure performing the cleaning operation at full reactor the and temperature and the fact that if a leak developed to come off the line to stop it. The unit would have rates problem being encountered with the radiation dose during the were addressed at length. Note: The KP group steamfitters involved in meeting reported that one o-the an extrem the cleaning activity during the day had received ity dose of S rm (quarterly dose limited to the extremities is 18.75 rom as specified in SQI RCI-I, "Radiological lygiene Program"). The supervisors and personnel in the of the meting became very concerned with the safety aspects that job. The primary concern was the radiation dose rates The following additional decisions were beinj encountered.

were made to improve the safety aspect of the job:

• After insertion the cables would be withdrawn until and the dose rate began to increase, cut and tied off, the kept in the thimble tubes to be removed later after dose rate had decreased.

blocked The decision wes made to only clean all 10 short of thimble tubes in C path as they were running time. After cleaning these tubes the path transfer units would be hooked back up and the detectors map inserted. If all 10 tubes were clear, the flux be could be run as 83 percent of the tubes would operable.

to his The evening shift coordinator was very close dose legally allowable quarterly whole body radiation the dose had been limit (3 rem). The majority of 2 refueling outage. The received during the Cycle with a radiation dose rate coordinator was equipped meter to alarm if the dose rate increased. The coordi nator was instructed to remain out of the high radia tion dose rate areas.

The inner door on the personnel airlock would be left open to allow for quicker egress in the event a leak developed. Note: The personnel involved were not aware that th'a-would enter the unit into a limiting condition for operation (LCO). Additionally, leaving the door open would have hampered entry into the instrument room because of the interlocks in the event rescue efforts were required.

of usiag The ALARA HP technician questioned the advisability activity. He so many people from FSG (six) for the cleaning the additional pproonnel were necessary to was informed that and provide additional management oversight for the activity sow of to provide additional training for this activi&y to the nlG craftsmen.

Section IV.5.6 of RCI-14 requires that the plant superinten dent (Plant HManager) review the RYP when the dose rate exceeds 50 rem/hour. The HP shift supervisor, notified the Assistant Plant lanager by phone (the Plant Hanager had been absent from the plant April 19), the shift engineer, and the plant Assistant HP Supervisor temporarily in charge of unit I activities (the plant HP Supervisor was on annual leave) of the dose rate conditions and that it may be necessary to work in a dose rate field of over 50 rem/hour during the cleaning operation. Authorization to continue work was given. The six FSG workers then proceeded to the

!P laboratory to pick up the protective equipment to be used during the work activity.

During the course of the work to this point the HP techni cians covering the job and the FSG personnel took actions comensurate with the increasing hazards that they had identified. These actions were as follows:

• HP technician susggested work stoppage and ALARA preplanning - FSG responded.

• ALARA implementation even though the calculated total man-rem exposure was less than S man-rem.

• Additional ALARA technician coverage during the job (two HP technicians covering the job).

S Health Physics prescribed multidosimters for measuring whole body radiation dose profile.

• Health Physics suggested work stoppage and further discussions with management about hazards of job - FSG responded.

• ALARA technician questioned the use of so many workers for the job.

• Health Physics shift supervisor responded to concerns when identified and participated in discussion with FSG workers and supervision.

S Health Physics notified upper plant management and shift engineer of increasing dose rates as prescribed by RCI-14 and was given permission to continue the cleaning process. Note: There are no requirements in RCI-14 that formal Jacumentation be made for authoriza tion for working in dose rate fields greater than so50 reb/hour. Legal actions being brought against corpora tions for radiological matters are increasing. Author isatioa to work in dose rate fields grqeater than 50 re/hbour should be formally documtted.

V.6 - ..

staff and the FSG The action$ of the Health Physics activity to address personnel involved in the cleaning safety aspects of increasing concerns for the radiological safety aspects the job stimulated discussions about other of the hazards of some increasing the worker awareness the workers in the involved. WMen the accident occurred inatrument room were primed for exit.

relating to this For conclusions and recoimendations 6.

section, refer to sections Ill.D.4 and K. The Accident the worker activities immedi The following Is a discussion of area and worker conditions, the ately prior to the accident, work immediately after the accident:

accident, and the worker actions Prior to the Accident

1. Worker Activities Immediately personnel donned their Between 2120 and 2145, FSG and HP face masks for (including contamination protective clothing dosimeters and entered respiratory protection) and radiation fashion (not all at the instrument roos in a staggered outside the airlock once). An FSG craftsman was stationed A public safety to assist the workers inside if needed. to control access airlock officer was stationed at the outer as per AI-3.

to the reactor building containment one of the first workers The evening shift coordinator was tubes that were to be to enter. He marked the thimble At this time he noticed cleaned (C group) with duct tape. and that there was a that tbh'cleaning tool was on tube D-12 upper and lover portions small gap (^lW2 inch) between the Being awave that the of the cleaning tool base support. solid support from base support had been modified to provide he acquired two shins the cleaning tool to the seal table, the airlock and outside from the ISG worker stationed support to make con shimmed the lover portion of the basethe last of the FSG tact with the upper portion. As they shut the inner employees entered the instrument room This action was airlock door out of force of habit. At this time there contrary to their contingency planning. room. Refer to figures were eight workers in the instrument and respective functions 13A and 135 for their assigned positions for the cleaning operation.

2. The Work Area and Worker Alertness April 19 the work area When work was initiated at 2120 on The tampera was well lighted and reasonably uncluttered. cool. The radiation ture of the work area was reasonably table was aproxi seal dose rate in the area around the were in contamination mately 10 millirm/hour, The workers

zone clothing with respiratory equipment (coveralls, rubber gloves, plastic booties, shoe covers, surgeon caps, canvam hoods, and full face masks). The workers were reportedly fairly well rested and very alert because of the increased concerns for the safety of the job. When they entered the instrument room, the workers involved were acutely aware of the hazards from the high radiation dose rates being emitted from the cleaning cable and the possibility that in the event of a leak the water would be coming straight from the reactor. The workers cleaning the tubes on the day shift did not have the same level of alertness as they had not had benefit of the same level of concerns and discussions prior to beginning work.

3. The A"cident The workers assembled around and above the seal table as depicted in figures 13A and 13B for performing their assigned tasks. The evening shift coordinator noted that the cleaning tool was on thimble tube D-12 which was not included on the list to be cleaned. The cable was inserted approximately 15 feet into the thimble tube. The coordina tor decided that as long as they were connected to thimble tube D-12 they would go ahead and clean it one more time to make sure it was clean. Steamfitter (D) on the cleaning tool turned the handcrank one complete revolution. Coordi nator (A) measured the length of insertion to verify that the insertion was 10 inches per one complete revolution.

Steamfitter (D) continued to turn the crank and stopped at 50 revolutions and called out the number of revolutions.

The number of cranks was verified by steamfitter fore man (C). Steumfitter (D) continued to crank the tool inserting the cable into tube D-12. At approximately 70 cranks a kink was noted in the cleaning cable coming out of the cable container. The workers stopped and examined the kink and decided to proceed. After a total of approximately 79 cranks the cleaning tool offered some resistance to being turned. As the crank started its upward stroke it was noted that additional effort was being required to turn the hand crank. Some movement of the cleaning tool was observed. At this moment the leak occurred spraying water at ambient temperature and slightly wet two of the workers. The clean ing tool pulled loose from the the grasp of steamfitter (M).

Ne reached up, grabbed the tool and pitched it out of his way to the left so he could get out. The water by this time was blowing straight up at a significant rate and was described as hanging up in the overhead. Someone yelled

"°Let's g0."

One of the eight workers (the one farthest from thimble tube D-12) described the first indication of the leak as a bubbling action from around the tool support base. The remaining seven workers assembled around and above D-12

described the leak first as spraying of water from between leak the upper and lower tool support pieces followed by the and straight up rapidly developing into a "gusher" blowing four hanging up in the overhead. As there is approximatelyit is gallnns of relatively cool water in the guide tube burn apparent that initially the spraying water would not up after it started blowing straight the workers. However, above the at 5450 7/2250 psi, it was flashing to steam workers and constituted a life threatening hazard.

little The seal failed and the leak occurred suddenly with turning warning and the tool was pulled away from the worker started the handcrank. This indicates that the thimble tube simultaneously with development out of the guide tube almost of the leak.

cleaning It is evident that kinks were not uncomon in the 3t the cables as workers looking for kinks were stationed its container and that kinks point where the cable left they were caused problems with the cleaning process in that or insert difficult to get through the cleaning tool inter properly into the thimble tubes. Some of the workers the viewed felt that the extra effort required to turn prior to the development of the leak handcrank immediately tool.

was caused by the kink entering the cleaning kinks in the SNI-O-94-1 had no restrictions addressing cable.

For conclusions relating to this section, refer to sections III.E.1 and III.E.2.

(see figures

4. Worker Actions Immediately After the Accident 13A and 138 for exit routes) onto Workers (A), (C), (b), (E), (F) and (G)moved hurriedly (G) the platform and started down the stairs. HP technician hand noted MP technician (H) falling backwards towards the dropped the teletector he was using rail. HP technician (H) a to measure dose rates and fell over the handrail, hitting toward th..

toolbox on elevation 693. He started running airlock.

to When the seven workers reached the airlock, several tried away by open the door together. One worker was pushed seven workers another worker. The door was opened and (G) remembered seeing HP entered the airlock. HP technician and technician (H) falling backwards toward the handrail started became concerned that they had left him behind. He (H) was in asking if anyone had seen him. (HP technician the airloca.] A head count was conducted by the coordinator short.

(A) and the workers realized they were one worker foreman The airlock door was being pulled shut when general The (B) stuck his arm in and stopped the door from tlosing.

< I door wag opened, general foreman (8) entered the airlock, and the door was closed. The HP technician (G) noted that the dose rate inside the airlock was approximately 200 millirem/hour. The coordinator (A) went to the telephone in the airlock with the intention of calling the control room but noted that the telephone had a MR tag on it indicating it was out of sevice. The time elapsed from the incident until everyone was in the airlock was estimated by the workers to be approximately 20 seconds.

A few seconds prior to the incident the coordinator (A) looked at his dose rate meter and noted that the dose rate was approximately 2 millirem/hour. As he entered the air lock the alarm on the dose rate meter activated and he noted that it indicated 25 millirem/hour.

The outer door of the airlock was opened and the workers exited the airlock. The coordinator (A) yelled instructions to the public safety officer to call the control room and notify them that a leak had developed at the seal table.

All workers started surveying themselves for radioactive contamination. The coordinator (A) conducted another head count to ensure that everyone was out of the airlock. The public safety officer was unsuccessful in contacting the control room (reason not determined by NSRS). The coordi nator (A) exited the contamination zone, called the control room, and contacted the ASE for unit 1. He informed his that a leak had occurred at the seal table and that it could not be isolated.

The workers removed their protective clothing, surveyed for radioactive contamination (none was detected), and dressed in their personal clothing. The coordinator and the mechani cal general foreman proceeded to the control room to inform the operators and the STA of the conditions inside the instrument room. The time was 2215.

The highest radiation dose recorded on the RWP Timesheet was 200 millirem (determined from pocket dosimeters). This dose was received by general foreman (B) who was the last one to enter the personnel airlock.

All workers were subsequently analyzed by whole body count to determine if they had ingested any radioactive materials during the incident. The whole body counts for all eight indicated that no detectable radioactive materials were ingested.

At approximately 0100 on April 20 the FSG evening shift coordinator and the mechanical general foreman submitted written statements of what they had observed before, duriii, and immediately after the accident.

1 *.

20 In sumary, the egress from the work area was rapid (

until everyone was in seconds from when the leak occurred the airlock) and orderly with the exception that the HP over ALARA technician was startled to the point that.he fell the handrail by the seal table and there was some crowding and pushing at the door. The general foreman who was the located above the seal table was the last to enter The day shift coordinator conducted a head count airlock.

one short.

in the airlock and had identified that they were the public safety officer outside the airlock He instructed exiting the airlock.

to count heads again immediately after not have been It is probable that the general foreman would of the head count. As the workers left behind because airlock they noted that dose rates were substan entered the the exiting the airlock tially higher than usual. After radiation dose received on the RWP workers recorded their person out, the general foreman, had Timesheet. The last which is &most received a radiation dose of 200 millirem (50-125 twice the dose received by any of the other workers The only action with the cleaning tool and millirem).

prior to the accident was driving thimble tube immediately the the cable and brush into the thimble which reduced background radiation. The normal background was described as being approximately 10 pillirem/hour and the general His foreman was in the area for approximately one hour.

prior to the incident should have radiation dose received been 10-20 millirem. The general foreman therefore received approximately 180 millirem in 20 seconds. It is apparent that the thimble tube was out of the guide tube within 20 seconds of the break and before the workers were out of the instrument room.

relating to this For conclusions and recommendations section, refer to sections III.E.3, 4, 5, and 6.

F. Operate. Actions to Mitigate the Accident

1. J.Amediate Operator Action coord At 2200 the ASE/SRO on unit 1 was notified by the FSG inator that the seal on thimble tube guide D-14 (actually was D-12) at the seal table was severed aod a high energy steam blow existed. Concurrently the "Pressurizer Pressure panel Low - Backup Heaters On" alarm on the unit 1 alarm activated. The unit operator noted a decreasing pressurizer gallons water level and increased charging water flow to 130 (Immediate Operator per minute (gpm) per section III.A.

Action) of Abnormal Operating Instruction AOI-6, "Small Reactor Coolant System Leak." (A small leak is defined as one for which pressurizer level can be maintained by the does charging systeam and a reactor trip or safety injection Prior to the leak the charging waterflow had not occur.)

been 85 VPa. At 2215 the pressurizer water level begas to increase. The additional charging waterflow required to maintain pressurizer level was approximately 40 g1m.

2. Subsequent Operator Action At 2217 the SE informed the ASE and unit operator to begin a shutdown of the unit at 1 percent per minute. A 2220 the SE noted in his journal that the leak was a pressure boundary leak and classified the event as an "Unusual Event" in accordance with SQN Radiological Emergency Plan - Imple menting Procedure IP-1, "Emergency Plan Classification Logic," because the primary system leak rate was greater than 10 oPn and the source of the leak was identified. The Unusual Event is the emergency classification used by TVA to provide early and prompt notification of minor events which could develop into or be indicative of more serious condi tions which are not yet fully realized. The purposes of Notification of Unusual Event are to (I) assure that the first steps in activating emergency organizations have been carried out and (2) provide current information on the event.

At 2220, IP-2, "Notification of Unusual Event" was initiated.

IP-2 provides a method for timely notification of appro priate individuals when the SE has determined by IP-l that an incident has occurred which is classified as an Unusual Event and provides a method for periodic reanalysis of the current situation by the Site Emergency Director to deter mine-whether the Notification of Unusual Event action should be cancelled, continued, or upgraded to a more serious classification.

At 2233 with steam generator level controls in manual and the reactor at 12 percent power, the reactor tripped on low-low level in steam generator No. 1. At 2305 the reactor coolant system was at 5000 F and 1900 psig (Hot Standby Mode 3).

At 0110 on April 20 a surveillance instruction (SI 137.1) was completed and indicated 33.25 gpm leakage from unit 1.

3. Cooldown. Depressurization, and Drainins of the Reactor Coolant System (RCS)

Cooldown and depressurization of the RCS continued and at 0508 on April 20 the temperature of the RCS was 3500 F (Hot Shutdown-Node 4).

At 0755 the residual heat removal (RriR) system was initiated and at 1032 the temperature of the RCS was v200e F (Cold Shutdown-Node 5). At 1214 the leak rate from unit I was

approximately 18 We at 250 Psi&. At 1505 on April 20 the Unusual Event was cancelled as the identified leak rate had decreased below 10 pm (estimated to be approximately 5.4 gpm at 40 psi&).

At 0235 on April 21 the operators started draining the reactor coolant system and at 0815 the water in the reactor vessel was at elevation 701 (one foot below the top of the seal table) and the leakage was essentially stopped.

4. Technical Specification Requirements for Reactor Coolant System Operational Leakase Section 3.4.6.2 of the SQN unit 1 Technical Specifications states that RCS leakage shall be limited to "no pressure boundary leakage." If a pressure boundary leak develops while the reactor is in Mode I (power operation) the reactor is required to be in at least Hot Standby (Node 3) within six hours and in Cold Shutdown (Node 5) within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. These actions are considered necessary as pressure boundary leakage of any magnitude is considered unacceptable since it may be an indication of an impending gross failure of the pressure boundary. Therefore, the presence of any pressure boundary leakage requires the unit to be placed in Cold Shutdown.

5. Operator Actions Specified by Abnormal Operating Instruction AOI-6, "Small Reactor Coolant Leak" AOI-6 is an instruction that provides guidelines for RCS leakage where pressurizer level can be maintained with the charging system and does not increase containment pressure to the point of safety injection (SI) activation.Section IV.B.9, "Subsequent Operator Action" of AOI-6 states that if the pressurizer level stabilizes by additional charging pumps the operator is to determine the leakage source; and if the leak is not identified and isolated, and it is appar ent the leak rate is greater than Technical Specification 3.4.6.2 (without running SI-137.1), and a trip will not be generated, the operator is to tri; the reactor and proceed to cold shutdown. The source of the leak was identified to the operators by the FSG personnel, therefore a controlled shutdown was initiated.

Using the information provided by the day shift coordinator and properly analyzing the system responses the operations staff classified the nature of the leak and took imediate and subsequent action in accordance with established proced ures to shut the unit down, declare an Unusual Event, cool down, depressurize, and drain the water level in the reactor below the seal table elevation thus stopping the leak.

For conclusions relating to this section, refer to section III.F.1.

G. Initial Actions Taken to Evaluate Conditions in the Instrument Room

1. Plant Manaement Decision to Enter the Instrument Room Ater the Accident After the leak was stopped, plant management considered their priorities at that point were the following:

• To find out how much vater was in the room.

o To find out the extent of the damage from the vater, steam, and radioactive contamination.

• To determine the radiation levels ia the room.

They knew that they had the following conditions that would prevent them from returning the unit to operation:

o An ice-bed temperature monitoring system was inoperable.

o A containment sump level transmitter was inoperable.

• ýA leak at the seal table that had to be repaired.

Plant management at this point did not know that a thimble tube had been ejected. They had reviewed the written state ment submitted by the FSG Mechanical General Foreman which stated that before he left the work area imediately after the accident he observed the cleaning cable starting to lay back on the grating at the head of the stairs where he was located. He estimated that approximately 30 feet was laid out when he turned to exit. They assumed that the cleaning cable had been ejected from the thimble tube during the incident and the unusual radiation readings were from the cable.

A radiation survey and some pictures of the area were con sidered to be the first step necessary to determine the extent of the damage and the radiation levels in the room.

2. Radiation Work Permit-(RWP) 02-1-0000S RWP 02-1-0005 was issued April 20, 1984, for the lower containment and seal table to provide radiological controls for all activities related to recovery from the seal table accident &and to track total radiation dose acquired by the workers during the recovery effort. The RWP contained an instruction that no entry would be made into the seal table (instrument) room without prior knowledge and approval of the Plant Manager and/or the project supervisor that would be assigned from the Nuclear Central Office (NCO) to direct

the recovery effort. The Plant Manager signed the Rid?.

This action established upper plant management direction and control of the recovery effort.

For conclusions relating to this section, refer to section III.G.1.

3. Initial Entry After the Accident into the Instrument Room At 093S on April 21, four members of the plant health physics staff made the initial entry into the instrument room for the purpose of assessing the damage to the room and to determine the radiation levels.

They found the thimble tube completely ejected from the guide tube and twisted throughout the room. A small amount flowing from the fitting water was observed to still be for thimble D-12. This water was determined to be flowing Of from the system because of the pressure exerted by the and nitrogen blanket in the pressurizer. The temperaturediffi huidity in the room was very high masking conditions cult for the workers. The radiation dose rates at location various locations and a contamination survey taken at one while the workers were in the room is depicted in figure 14.

The initial radiation surveys indicated dose rates of 1-2 rem/hour at the airlock, 300 rem/hr at approximate 1000 rem/ elevation 708 above and to the right of the seal table and thim hour measured 8 inches away from a bend in the ejectedSeveral ble tube located at the surface of the seal table.

pictures were taken of the area. The four individuals were in the area approximately two minutes. The total collective radiation dose received by the four individuals was approxi mately 3 rem. The highest dose received by one-individual was approximately 1.2 rem.

4. Managtement Assessment of the Conditions Found in the Instrument Room During the Initia~lEntry When plant management looked at the pictures taken during the initial entry and evaluated the radiation dose rates measured, they realized that they had a problem of greater magnitude than they had previously thought. They decided that they needed to make another entry and make more detailed pictures using a telephoto lens (to reduce the as radiation dose to the photographer) to get as much detail idea of they could of the ejected tube and a more detailed the condition of the room. They decided that they needed an experienced photographer to take the pictures because of the unusual conditions.

S. The Second Entry into the Instrument Room Plant management located a photographer at the. Power Opera tions Training Center. When he arrived onsite, he was

briefed by the plant management and Health Physics Staff concerning the conditions in the room and radiological aspects of the work. At approximately 1830 on April 21 the photographer and a 1P shift supervisor entered the instru ment room and took photographs of the seal table area. They were in the instrument room for approximately seven minutes and received radiation doses of 1.97 rem and 1.94 rem.

6. Preparation Ejected of Drawing Thimble Tube Deictinl

.. . te Configuration of the The film via developed and the photographs returned to the plant. From the photographs the plant staff composed a drawing of the thimble tube configuration (see figure 15).

An entry into the instrument room was made on April 23 at 1300 by the plant HP section supervisor, an HP shift super visor, and an liP technician to confirm that the actual con figuration was as depicted in the drawing. In addition, contact dose rates were taken at vari.ds locations on the ejected thimble tube with a radiation measuring instrument with an extendable radiation detector (see figure 16 for contact dose rates.) They determined that the actual con figuration of the thimble tube was in agreement with that depicted in the drawing. The highest radiation dose received (based on high-range dosimeters) during the entry was 0.4 rem.

H. The Recovery of the Thimble Tube and Actions Taken to Ensure UE-it 1 was Safe to Return to Power The following actions were taken by NUC PR to recover the ejected thimble tube and to ensure unit I was safe to return to power operation:

L. Assignment of Responsibilities The Nuclear Production Manager and the SQN Plant Maneger assigned a project manager from the NCO to direct the overall effort of recovering and disposing of the ejected thimble tube. This assignment was made in accordance with NUC PR Area Plan Procedure No. 1200A12, "Emergency Project Management. "

The Plant Manager made the following additional assignments to the members or organizations of his staff:

o Mechanical Maintenance - Coordinate the preparation and installation of the new thimble tube, examine the affected guide tube for damage, and examine the remain ing thimble tube mechanical seals at the seal table for proper installation.

evaluate the elec Electrical Maintenance - Examine and room and affected trical equipment in the instrument occurred and to repair areas to determine if any damage any damage to that equipment.

and evaluate the Instrument Maintenance - Examine room and affected instrumentation in the instrument occurred and to repair areas to determine if any damage any damage to that equipment.

Collect and maintain any Plant Compliance Section - to the accident to information and documents pertniningthe accident.

account of preserve the historical the acquisition of NUS 0 Engineering Section - Coordinate thimble tubes.

Corporation services to clean the Coordinate the decontami Maintenance Superintendent - room.

nation efforts of the instrument requested that the NCO Additionally, the Plant Manager of the fitting the examination Mechanical Branch assist in involved in the accident and an assessment of the other fittings on the seal table.

2. Recovery of the Ejected Thimble Tube "Emerlency

a. NUC PR Area Plan Procedure No. 1200A12, of the Management". The current revision Project was issued in emergency project management procedure procedure was of the November 1983. The stated purpose major components or other emergency to ensure that expediting, coordi maintenance projects receive proper and documentation with nation, procedural compliance, in the use of the result being maximum efficiency in implementation. The resources and minimum errors plant forces remain procedure ensures that normal and ensure that available to perform normal maintenance are not availability remaining plant capacity and to any major affected. The procedure is applicable nature with respect to component project of a critical plant availability or nuclear safety.

by the project manager The activities to be performed the scope of the emergency project were to be within management procedure.

with Plant Manage

b. Project Manager's Initial Interface 21, !.he Manager sent. At approximately 1200 on April contacted an NCO senior engineer o-f-Nuclear Production manager for tVe ejected and assigned him as the project instrument.room at SQN.

thimble tube recovery from the Plant Manager during He was to report directly to the

A0 the execution of his duties. The assigned project manager immdiately proceeded to SQN and at approxi mately 1400 on April 21 met with the Plant Mlanager and was briefed on the incident, the activities in progress, and the scope of his assignment.

For conclusions relating to this section, refer to section III.K.l.

C. Planning and Preparation for the Recovery Effort On April 22, after the configuration of the thimble tube was determined, a meeting was held for the purpose of obtaining ideas for the recovery process. The participation of those at the meeting was reportedly very good. Ideas were discussed and evaluated; and during the afternoon of April 22, the general actions that would be taken to recover the tube were estab lished.

Note: Personnel from NUC PR (Emergency Preparedness and Protection and Mechanical Branches), Office of Power (Radiological Hygiene Staff), and EN DES along with the project manager and the plant staff partici pated in planning and preparation for the recovery effort. The 14RC (site resident and Region 11 inspec tors) observed the planning and preparations.

On the morning of April 23, the project manager began directing the planning and preparation for the recovery effort. These activities were conducted with the goal of developing the safest method of recovering the ejected tube while maintaining the radiation dose to those involved in the process as low as possible. The planning and preparation activities involved the fol lowing:

0 Made arrangements with WBN to use their unit 1 instrument room to simulate the existing condi tions in the SQN instrument room.

o Designed and fabricated special tooling necessary to cut and move the tubing to shielded containers.

• Conducted recovery team trial runs at WBN with simulated conditions and mocked up thimble tubing using the special fabricated tooling.

• Health physics personnel projected the radiation dose for the first phase of the operation (cuattinit and removing the highly radioactive portion of the' thimble tube from the instrument room). The pro jected dose for this portion of the recovery was 0.6 "an-rem.

I1 6 0.

• Installed temporary shielding at SQN.

• Obtained a remotely operated robot from the in the Department of Energy (Y-12) to assist recovery effort.

• Prepared the following Special Maintenance the experiences gained Instructions incorporating during the WBN exercise and while installing temporary shielding at SQIN:

SMI-1-94-3, "Retrieval of Approximately 25 Accep Feet of Unit I D-12 Incore Thimble to Work Location," PORC reviewed and Plant table Manager approved April 24.

100 SMI-1-94-4, "Retrieval of Approximately Feet of Unit 1 D-12 Incore Thimble From U-i El 690 Containment to a Barrel Shield in U-l reviewed and Plant Penetration Room," PORC Manager approved on April 25.

o Established maximum stay times for personnel in the instrument room.

in

• Established emergency personnel response teams the event of injury or unforeseen circuastances during the tube recovery.

o Established alternate escape routes.

o Established that recove y team members would were immediately exit the area if conJitions different than those at the encountered that were simulated WBN exercise.

• Established a communication link between the con to allow trol point and the Plant Manager's office the recovery effort.

the Plant Manager to monitor with a tape recorder to record Provided the link the dialogue of the recovery effort.

• Members of POWER's Radiological Health Staff were plans to onsite and reviewed the procedures and to personnel would be ALARA ensure radiation doses during the recovery.

Cable

d. Recovery of the Ejected Thimble Tube and Cleaning the (1) Recovery of the 25-Foot SectionWith Hiaheat Radi-ective-Leve a was conducted in This portion of the recovery accordance with SMI-1-94-3.

Dry runs on the final plans for the operation were conducted at WIN for practice. The recovery team members were briefed on the morning of April 25.

The recovery team leader (an NCO health physicist) entered the personnel airlock on elevation 690 and inspected the inatrument room for obstructions with a mirror. (The airlock was shielded.) He noted an air sampler on the stairs by the seal table. The location of the air sampler was made known to the recovery team members that were going to enter the instrument room. The team leader stayed in the airlock to observe the operations with a mirror.

(a) First Entry to Cut the Thimble Tube The team member designated to cut the thimble (an SQNI HP shift supervisor) entered the instrument room through the airlock equipped with a pair of cutters. He proceeded to the stairs leading to the seal table and noted a portion of the tube laying across the railing on the stairs. He imediately exited the instrument room through the airlock as instructed since the tube in that position was unexpected and he was only weiring a surgeon's cap as specified on the a,.plicable RWP Timesheet. He donned a canvas hood which affords better protection of the head and neck against radioactive contamination and reenterad tUe inatrument room. He proceeded to the sttirs, ducked under the tube, and climbed the access steps to the 10-path trolley elevation and cut off approximately 25 feet of the most radioactive portion of the tube with the cutters. The 25-foot por tion of the tube fell exactly as had the mocked-up portion during the practice ses sions at WUIN. He exited the instrument room through the airlock. During this process he received a radiation dose of approximately 100 millireom.

(b) Second Entry to Attach a Clamating Nerhaniam to the Th*alik Td ait Lto Pul the Ti'he lItlo jthe~jj]a b ow thelatr Team members had iben *sationed i'n -'the race way to pull the ctit portion of the thimble tube into the raceway. One team member placed the clamping mechanism with the cable attached through the submarine hatch on the instrumeat room floor. Two tea members (plant NIP shift supervisors) *astered the instrument room through the airlocka, picked up the clamp aend cable, attached the clamp 69

and caa' " the 25-foot portion of the tube, and immediateLy '*ft the instrumeat roon through the airlock.

Durion this process one team mmber attaching the cable received a radiation dose of approx intely 170 millirem and the other member approximately 10 millirm.

All personnel exited the airlock, both air lock doors were closed, and the team members in the raceway pulled the cut portion of the thimble tube from the seal table across the instrumnt room through the submarine hatch into the racevay. The thimble tube was then pulled to a predetermiaed location that had been marked on the floor with tape. The team members in the raceway exited the race way and reactor building containment.

The accumulated radiation dose for all team members involved in this portion of the recovery was 0.7 man-ree.

(2) Rcovery of the Remanin Porton of the ThibRoom.

Tub aUe Cleanint Ctable Trm rhe=natr-mnt in This portion of th rcovery was coductd accordance with SHI-1-94-4.

After the most radioactive portion of the thimble tube was in the raceway, the radiation dose rates tin he istrument roo were lowered substamtially.

A team leader for this portion of the recovery had On bees appointed and the team members briefed.

personnel entered the instrment room April 25 3P and located the portion of the remainina thimble tube and clesaing cable with the hibghet radiation levels. Team mmber personnel *etered the instru maet roms, cut the most radioactive portions of the remaining thiable tube into 18- to 24-inch sections, placed these cut sections in specially to fabricated buckets, and transported the buckets the airlock. Tam members outside the airlock retrieved the buckets and placed them in a barrel the shield outside the airlock. These sections of thimble tube and cleanian cable were transported to radwste and prepared for shipment to an off site burial site. This portioa of the recovery was completed by 2000 on April 2S.

(3) ui ad torate of the J5-Foot Section- e T5u-bl e ie thaegcea - Fro Aprl 3a to the afterne ao April 2 the following actions wr* the takes to preare for cuttiag sad storage of thimble tube i the racoway:

D Erected scaffolding and special shielding and installed lifting devices in the raceway.

Placed and secured a shielded cask to receive and store the cut sections of tubing in the raceway.

• Moved the robot to the raceway.

Installed video eulipment in tht" raceway to) aid in the cutting and storage operation.

• Designed and fabricated special tools to be used in the cutting operation.

In the afternoon of April 26 a simulation of the cutting and storage operation was conducted, the process finalized and adjustments of tools and equipment were made.

On the morning of April 27, SI-1-94-6, "Reloca tion, Cutting, and Storage of 25 to 40 Feet (approximately) of Unit I D-12 Incore Thimble,'

was prepared, POIC reviewed and approved by the maintenance superintendent for the Plant Nanager.

In the afternoon of April 27 in accordance with SHI-1-94-6 equipment placement and operability were verified, a practice run was completed, and a final briefing was conducted for all team members.

The section of thimble was pulled using the cable previously attached around the raceway to a prede temined position for the cutting and storage operation.

With the aid of installed video equipment the team ambers controlled the robot and the hydraulically operated cutter from a remote location. The robot picked up the thimble tube and transported it to a cutting table. The robot then positioned the thimble tube, and the hydraulic cutter severed approximately 6 feet of the tube believed to have a low radiation level. This section of tubint was then put aside for survey and disposal as low level waste at a later time. The robot then picked up the remaining tubing, positioned the tubing on the cutting table, and the hydraulic cutter severed an approximate l8-inch section.

The severed portion of the tubing was then trans ferred by the robot to the shielded storage cask.

The robot then returned to the cutting tabl and picked up the remaining portion of the thimble tube and repeated the process until all of the

tubing had been cut and placed in the cask (19 cuts were required). The cask was topped off with lead shot for additional shielding and sealed.

The cask containing the highly radioactive portion of the ejected thimble tubing will remain stored in the raceway until removal and disposal at a later date (probably the next refueling outage).

The dose rate at the surface of the cask is approx imately 6 tmllire/hour.

For conclusions relating to this section, refer to sections III.H.2 and 3.

3. Decontamination of the Instrument Room After the ejected thimble tube and cleaning cables had been removed from the instrument room, preparations were made for decontaminating the surfaces and equipment in the room. An instruction (SHI-1-317-22, "Decontamination of Seal Table and Other Components and Structures Located Inside Incore Instrument Room") was prepared, reviewed by PORC, and approved on April 25. The instruction prescribed the clean ing methods to be used in reducing the radioactive contam ination in the room to acceptable levels, disposal ethods for cleaning fluids and equipment, and analytical methods and final acceptance criteria for chlorides and boron con centrationa on the surfaces of equipment.

Personnel from the FSG and fP groups began removing tempo rary shielding and comenced the decontamination effort at approximtely 2200 on April 25 and completed the effort at approximately 2200 on April 26.

4. wUS Cleanina of Unit 1 Thimble Tubes SQN contracted NUS Corporation to perform the cleaning operation of the thbable tubes. On April 26 an instruction (SMI-0-94-2, "Incore Flux Thimble Cleaning and Lubrication")

was reviewed by FPOC and approved for the Plant Nanager.

This procedure was essentially the NUS-supplied procedure applicable to their method for cleaning and their equipment used in the process. tae NUS procedure was changed to the SqN format for special maintenance instructions and changes incorporated to adopt the procedure to specific SQN circuw stances and requiresrts.

The primry steps of the instruction were as follows:

• lush foreign material from the thimble tube with deiserallied water at approximately 200 piug through a flexible tube assembly which is inserted the full length of the thimble.

• 0

• *0

• 0

• Remove the majority of the flush water from the thimble by applying instrument air or nitrogen through the flexible tube assembly.

• Perform a vacuum drying of the thimble tubes to remove all residual moisture.

• Application of a thin film of NEOLUBE lubricant to the thimble bore along the entire thimble length. Note:

The lubrication method utilizes a netered fine spray lubricator nozzle which is withdrawn from the thimble at a controlled rate while spraying the lubricant.

• Performance of a final air drying operation to remove the alcohol vehicle from the lubricant and produce a thin uniform film of lubricant for the entire base length.

• Optional performance of a "dummy" test cable insertion of all thimbles to the "dead end" of the thimble to

-,erify no obstructions or problems.

Using the instruction and the NUS equipment, the thimbles were all cleaned by NUS personnel during the timeframe of April 26-April 30. The cost of NUS cleaning operation was approximately $40,000, of which approximately $12,000 was for the purchase of the NUS cleaning system and training TVA personnel on its use.

SHI-0-94-2 was a better quality aiiatruction for the attivity to be performed and it is apparent that the method of bark flushing at 200 psi and lubrication with NEOLUU was effec tive because after the startup of the unit the blockage in the tubes was removed. However, the instruction still had no cautions or warnings to prevent damage to the mechanical seals, no administrative barrier to prevent cleaning the thimble tubes at pressure, no instructions for disassembly and reassembly of the detector drive systee, no postmainte aaance iaspections after cleaning and before pressurising the reactor, and optional postaintenance testing to assure operability is acceptable. For these reasons the new instruction for cleaning the thimble tubes with the NUS equipment is considered a poor quality procedure and should not be used again until it is upgraded.

For conclusions and recommendatios relating to this sertio0i, refer to sections Ill.N.4 and V.

S. Installation of a New Thimble Tubr Into Guide Tube D-12 06 April 26 an instruction (SlI-l-4-5, "Thiable tube instal lation") was POKC reviewed and approved. Using this instruc tion a new thiable tube was prepared and inserted into guide tube D-12 on April 28.

6. Inspection of the Seal Table High Pressure Seals seals

a. Inspection and Results. All of the high pressure examined for apparent (fittings) on the seal table were During the damage or were gauged for proper tightnees.

inspection, 174 high pressure fittings course of. the were examined. One fitting was found loose when gauged up with a combina and 48 fittings were discovered made and tion of SUAGKLOK and GYROLOK components (SWAGELOK are designed for similar GYROLOK fitting components applications but manufactured by different companies).

The cause of the loose fitting is not known.

b. Tetn and Examination of Various Cobinations of SWAG&L= and CGML-K prand* of FittiuS Hardware.

brands of Various combinations of SWACGLOK and G*ILOK by and examined fitting hardware were cross-sectioned the NCO Mechanical Branch to determine if any combina unfit for tions would render the assembled fittings The results of the study stated that the service.

tested appeared to be various coebinations of fittings intended service (see reference satisfactory for the IV.F.I for details).

c. Repair of Loose Fittingj SMI-1-94-7, "Seal Table High Pressure Seal Repair," was reviewed by PORC and approved for the Plant Hanager on April 30. The loose fitting instruction.

was repaired in accordance with this The

d. Inspection of Guide Tube D-12 at the Seal Table.

at the seal table was visu portion of guide tube D-12 No ally examined and dye penetrant checked for demage.

damage was discovered.

7. Inspection of the Containment Ice Condenser that Inspection of the containment ice condenser indicated and doors never opened during the accident the ice condenser steam did not enter the ice beds. Additionally, drain indicated that no ice papers inspected were intact which melted.

. Inspection of Electrical., Mchanacail.nd Instrumentation tquipsnat pusmIbty All electrical, mechanical., .n4 instrumentatlon and event were nsperted, cleaned, repaired, affected by the recalibrated if necessary.

and Note: A telepheoe located on the polar crane wall to the right of the seal table was approximately five feet from discovered malted and deformed by the heat generated the leak frem guide tubes.

SQN reported in Reportable Occurrence Report SQRO-50-327/

8430, an evaluation of all class It equipment was made to determine if the environmental conditions experienced during this event could be detrimental to their qualified life.

The evaluation determined thai. no deterioration of qualified life was experienced. NSRS did not evaluate this area.

9. NSSS Vendor (Westinghouse) Assessment of Acceptability of the Seal Table for Startu The plant management requested that Westinghouse perform an assessment of the seal table with the various combinations of SWAGELOK and CYROLOK fittings to determine if the con figurations at the seal table were safe to restart the reactor and resme normal operations.

Westinghouse recomended that the reactor could be safely restarted and operated with the existing configuration of the fittings at the seal table for the following reasons:

• The thimble ejection accident occurred during a clean ing operation of the thimble and not during normal operation.

• There was no indication that the thimble ejection was due to mixed fitting components.

• Westinghouse conducted tests at 4250 psi on various fitting coabinations with no leakage.

• SQN fitting design is standard and is the same as at many other plants with thousands of hours of operating experil nce.

• Adequate safeguards exist at SQN to achieve a safe shutdown following ejection of one thimble tube.

For conclusions relating to section IV.N.6 through 9, refer to section III.N.6.

I. .Returnof §0 Unit 1 to Power Operations On Hay 5, unit I reached rated temperature and pressure with no problems encountered at the seal table with thimble tubes. The unit was returned to cold shutdown again on May 6 to repair a leaoking pressuriser safety valve. The reactor was taken critical and brought to 30 percent power on May 10. Unrelated to seal table repairs, howver, the reactor triiped due to low *tea.

generator water level late in the evening on Miy 10. The reactor was again brought critical on Hay II and the flux mappiag testing was successfully completed Nay 12 and 13. All thiable tubes worked well (no leakage and no evidence of hliikage).

exposure of 16.5 man-rem was A period of 21 days and a man-rem operational status (30 per required to restore the unit to the cent) that existed prior to the accident.

J. Accident Investigations (Other than NSRS)

1. NRC Inspection Efforts inspection of the accident The NRC performed an announced protection, preplanning and onsite in the areas of radiation removal of the highly activated ALARA considerations in the The inspection 23-April 28.

incore thimble during April involved one inspector.

preplanning and consideration Per the inspect.ion report the were observed by NRC to be for maintaining exposures ALARA involving the retrieval an adequate for the operation storage of the thimble tube.

observed some of the plan The NRC site resident inspector for the thimble tube recovery ning and practice sessions effort.

of the accident, no Within the scope of the NRC inspections identified by the NRC as been violations or deviations had of June 1, 19864.

2. TVA Investigation Efforts of the

a. Reporting the Accident and Preservation Accident Scene Procedure" The TVA "Serious Accident Investigation event of a that in the issued in January 1984 requires official in serious accident the senior management charge of the site will follow notification procedures n.

established in his organizatio notification of the The procedures are to provide for Safety and Health Office Hanager, the Designated Agency and the Director of tho Division of Officer (DASHO),

U6S) as promptly as Occupational Health and Safety (OC accident includes possible. Definition of a serious an estimated with accidental damage to TVA properly losses.

more excluding operating value of $100,000 or an Accident Investi In the event of a serious accident, to the accident scene no gation Tam (AIT) is to report The senior the accident.

later than the day following where the in charge of the site management official securing the acci accident occurred is responsible for of Ahe evidence dent scene to prevent any disturbance

and protect people and property, frop afg hazards asso c4ite*htiWth 'i41AcidiLt"',i the sckne-is released by the AIT chairan.

At (p r . itmd.st 1 * : - n  ;>rir1l 19 an AI.AHA HP SQN Sreidw 6 'Praetit^ SQX29: _ taV cSf erjn Inveisti ti6" 'fWtAi^"Jain dr r27at eg b during ft*ldr o'rk hours, the' Plant, lj.n argpr t .

senior plant"oficaIl piesent s hti rep4sltj:e c en immediatel -Sy*' 'telephone t' 'th "tanauers, 4 )1c4 e '

roduciit . ' ThW Hmtwier o't NucleTar rouc1i*,q,9 s requiied' *t&"riport the accident meiaey, t(e Division Director and the division DireFtor'sa repuirqr to report the 'accident within twq hours Lo"* desigSeqd Office' f Poerer'representative. SQS 2gsiteat*q .a4* t4ie accident scene shall be preserved in "the accident con figuration until released by the cam rai, of :.te AT.

Notificatiion 'o the declared Unusual tvent was made to the Office Manager's office on April. 19, r ZQ.,,.How ever, the accidnt was not miediately reported as a serious accidei ty plant management in accordance with the TVA procedure as the extent of the d4page v, not.

realized unlfi" a(ter the initial entries Lnto ,.the instrument 'rooi an6 assessment of the damage ba4 beeqn made. Serious' accdent notification to the.. Off;.

Nanager, OC 'NS, and the DASHO was not made until, approximately three weeks after the accident occurreft and an investigation had been conducted by NUC Ph.,

The accident scene was not preserved by the Plant Man ager as required by TVA and SQN procedures in that restoration of the area was completed before theseri ous accident notification was made.

The failure to promptly report the ac.cident as. a seri.y ous accident after the extent of the dia a was m

realized and the failure to preserve the accident scene represents noncompliance with SQN and TVA procedures.

For conclusioqdaen recomendations 'rflatinA to section, refer to section I1t.11.:

b. Conduct of t~k'WM PN Acciidetr lidvestitaion' ' a4n Practice SQ*2 Ijecities t"hat^ e DIirect'orf ' 'uclear Power shall eitablish a division accident investigation committee as soon as practical. The commikee shall,be, responsible Mdr fully investigating al' FirC4mstaiqCe relating to t 'accident and shall submit';. writtenf report to the divtlfon director got late , than ,1. days; 4

after the crdontt. l t!.,,** n t t \ , * , +*  :. i*  : ;,, , *, .+. It*> the th l)t&*!

t , ,' .* 'i ,' '* he other t ill..:.

t l I n , ,. / t ti he usr ot 1

PR Comittee. A NUC was PR (1) Assipned Goals of the NUC coittee (AIC) acc-'ent investigation and review appointed to conduct an investigation aspects of' the thimble of the industrial safety The committee 1984.

tube ejection on May 2, was a manager from the consisted of a chairman who Section, another Industrial Safety Engineering the 50 FSG super and member of the NCO staff, directed to accomplish visor. The comittee was the following:

be investigated

• Determine if the event should"Serious Accident in accordance with the TVA investigation Procedure."

as a result of the

" Identify lessons learned event.

Provide any recommendations when which should be o performing considered in the future similar activities.

The committee completed (2) Committee Investigation. and reported their the assigned investigation 840517 800). The (LOS findings on May 17, 1984 the following:

investigation consisted of area.

• Inspection of the seal table and drawings.

o Review of procedures, sketches,

• Discussions with Westinghouse.

eight employees o Interviews with five of the the accident in the instrument room when occurred.

findings of the committee (3) Comittee Findings. The were as follows:

and low o Adequate prior warning of bubbling water allowed cool volume flow of relatively prior to egress from the most and remote point subsequent thimble total seal failure tube ejection.

of the Note: This description of the nature egress began their TeiI before the workerscontradicts information from the area from the interviews with the obtained by NSRS of this reaport).

workers (see section IV.E.3 of egress, two of There were three paths each other, and the which were remote from

individuals involved were knowledgeable of them. The airlock was the most desirable and the one used.

Note: While this is true, alternate routes of-egress were not discussed in prejob planning. In addition )ne of these paths involved hazards as it was through the polar crane wall where the workers would be exposed to high radiation dose rates due to the gama radiation from nitrogen 16 produced while the reactor is operating.

0 The airlock had been out of service for periods of time during the day making the inner door inoperative. Had the incident occurred during this work, egress through the airlock would have been delayed or primary egress would have been through the submarine hatch.

Note: Some of the workers in the instrument room while the airlock was out of service (including the FSG coordinator) were unaware that the airlock was out of service. Egress through the submarine hatch was not discussed in any prejob planning.

o The incident would exceed $100,000 in prop erty damage, cleanup, and restoration. The majority of costs would result from the radiological aspects of the incident. (The DASHO and the Office Manager were notifed of the accident).

Note: No distinction is made between radio lo-ical and industrial accidents in the corporate accident investigation procedure.

The DASHO and Office Manager were notified three weeks after the accident.

The investigation was not significantly hindered due to the restoration of the area prior to their involvement.

Note: The corporate procedure for accident investigation requires that the accident scene be preserved until released by the AIT appointed by the Oftice Manager and the DASHO. Restoration of the work area betore reporting the accident is a violation of TVA procedure.

• The sequence of events - In the sequence of tube was events the committee stated, "The ejected, nor was steam not observed being time." Looking back through observed at this see steam the airlock portholes they could Exit time from begin to build in the room. was no the platform to safety in the airlock Under the circum greater than 20 seconds.

orderly and stances, the exit appeared very there were no injuries.

the Note: The start of the ejection of almost simultaneous with the thimble tube was tool cleaning development of the leak as the when the was pulled away from the steamfitter to the tool was connected leak developed and to The water was flashing the thimble tube. begin to the steam above the workers prior (see ning of their exit from the platform was report). The exit section IV.E.3 of this IV.E.4 of not altogether orderly (see section this report).

The committee concluded (4) Committee Conclusions.

the following:

o The reason for tht failure was not evident.

hardware of Four possibilities involving the the seals were listed.

o The tlexing activity of the brushing could the hardware conditions have aggravated leading to the failure.

the o The instruction (SMI-0-94-1) states that Since procedure is not to be used at power. was the unit was in Mode 1, the procedure violated.

Coittee Recommendations. The committee included (5) the following recomendations:

o Recommendation No. 1. Cleaning and brushing with the o( thiimble tuheA should be. done reactor in cold shutdown (Mode 5).

0 Recommendation No. 2. If brushing is required past Node 5, a prejob safety analysis should approved by be performed and the procedure to PORC. A mechanism should be installed and a preclude tube ejection and leakage be pstablished.

clear path of egress should

Note: A prejob safety analysis is required by SQM2 for all maintenance activities per formed by an MR, and all work performed on CSSC is required to be performed by PORC reviewed, plant manager-approved procedures.

The quality of the job safety analysis and the procedure that was in use and compliance with existing requirements are the true issues. Improving the quality of the job safety analysis and procedure and compliance with existing requirements should be stressed.

0 Recommendation No. 3. The brushing mechaniJm should be modified to eliminate any stress or flex on the thimble tube connection.

• Recommendation No. 4. All work on any system re there is no secondary pressure boundary should be evaluated on a case-by-casc hasix and adequate means to mitigate an inadvertent pressure failure should be applied.

Recommendation No. S. Ensure the constant availability of the primary egress route, i.e., the airlock. Consideration should be given to leaving the inner door open (with the SE's permission) or providing a person to man the door.

Note: This recommendation should be revised to delete the consideration to leaving the inner door open as the doors are interlocked and having the inner door open would prevent or delay someone from opening the outer door and entering the containment in an emergency for rescue purposes.

Ensure that all emergency notification sys tem are in constant operation.

Commend the eight employees for their cool ness under pressure and their ability to reason through egress options under the stressful situation.

Note: The eight employees did not have to reason through egress options under the stressful situation since the door to the airlock was opened by the employees.

For conclusions and recommendations relating to this section, refer to section 111.1.2.

Fittings and the Dry K. EC PR Special Testins of Thimble Tube Brushing Tool postaccident inspection The NUC PR hechanical Branch performed thimble tube ejection accident testing to provide insight to the if SQP unit I was safe for and to assist in the determination involved the following:

restart after the accident. The tests

• Inspection of hardware from thimble tube D-12.

combinations of

• Cross sectioning and examination of various hardware.

SWAGELOK and GYROLOK brands of fitting

• Tensile testing of similar hardware.

• Examination of an alleged identical assembly.

seal from D-12 indicated The postaccident inspections of the (all components were in that the seal had been properly installedafter the ejection of the place and the nut was reasonably tight that the thimble tube). Postaccident testing also indicated on the assembly and that cleaning tool imposed unusual forces resulted from reasonably strains of considerable magnitude These strains were of applied forces on the fixture handle. of the thimble tube from sufficient magnitude to cause separation at reactor operating pres a properly installed mechanical seal sure of 2250 pgil.

tool supports were designed It should be noted that the cleaning by procedure.

by TVA and the use of the tool was unrestricted was very loose of the tool The control over the change of design as a temporary base support was fabricated and used during the for the tool in use day shift. Additionally, the base support prior to use. No techni when the accident occurred was modified to assess the effect of cal evaluation or testing was performed failure to design, eval the tool on the mechanical seals. The support and the failure to uate, and test a proper tool and support, and cleaning cable in provide restrictions for the tool, of the mechanical seal use are the contributors to the failure and the accident and not the tool itself.

relating to this section, For conclusions and recomendations refer to section III.D.l and 111-9.1.

L. Worker Backtround involved in the acci The work backgrounds of the eight workers as follows:

dent are shows in Table I and are sumarized in the cleaning Three of the six FSG employees involved prior to the activity had not read the work instruction who performed the accident including the steamfitter foreman job safety analysis.

TABLE I maCKInOGum OF WMRKERS INVOLVED IN THE THIMBLE TUBE EJECTION INCIDENT Previously Cleaned Worker Job Read S"I-0-94-2 Thimble Past Work Experience Working on Identification Title Prior to Incident Tubes Experience Systems at Pressure & Temp A - Evening shift Mechanical Primarily con Knew alternate egress routes.

coordinator is Engineer struction and Had not normally worked on charge of outage work systems at pressure and activity temperature. Knew pressure, temperature, and configura

.tion of system.

I - Observer Mechanical Knew alternate egress routes.

General Knew pressure, temperature, Foreman and configuration of system.

C - Counting num Steanfitter 5 years con Knew alternate egress routes, ber of revolutions Foreman struction and had not worked at these temp on handcrank outage work eratures and pressures. Knew pressure, temperature and configuration of the system.

D - Turning Steamfitter Yes (only Steamfitter Knew alternate egress routes.

the handcrank while unit 15 years, con Did not normally work on shutdown) strction and systems at these temoera outage tures and pressures. Knew pressure, temperature, and configuration of the system.

E - Monitoring Steamfitter Yes (only Steamfitter Knew alternate egress routes.

cable as it came while unit 13 years, con Had worked on systems at out of container shutdown) struction and temperature and pressure but looking for rough outage not that much. Knew pressure, spots on kinks temperature and configuration of the system.

TABLE I (Continued)

BACKGROIUND OF WORKERS INVOLVED IN THE THIMBLE TUBE EJECTION INCIDENT Previously Cleaned Read SKI-0-94-2 Thimble Past Work Experience Working on Worker Job Experience Systems at Pressure & TeM Title Prior to Incident Tubes Identification No S .eamfi.ter S Knew alternate egress routes.

F- Feeding cable Steamfitter Nears con mad worked on systems at into guide tube b.ruction and temperature and pressure but outage not that much. Knew pressure, temperature and configuration of the system.

HP technician G - Taking dose Health Physics at power plants rates technician for 7 years HP technician H - Taking dose Health Physics at power plants rates technician for 5 years Note: No Lnformation (NI) means that the background in this arei was not assessed by NSRS.

0 Two of six FSG employees had cleaned thimble tubes prior to the event but only while the unit was shutdown. The evening shift coordinator in charge of the rleaning operation and the steamfitter foreman who did the job safety analysis had never cleaned thimble tubes before the incident.

• Five of the FSG employees involved in the activity had primarily a construction and outage background with units shutdown and '.pressurized (the general foreman's background was not assessed).

All six FSG employees knew the alternate egress routes before the incident from past experience (the alternate egress routes were not discussed before the accident).

• Even though some of the FSG had worked on some systems at temperature and pressure this type of work this was the exception and not the rule.

o All six FSG employees knew the pressure, temperatures, and configuration of the system before the accident from past experiences or because they had heard it discussed that evening before they entered the instrument room to do the work.

The two HP technicians were permanent staff members with at least five years experience each at power reactors.

For conclusions and recommendations reltiting to this se' tion, refer to sections 111.B.2 And III.C.I.

M. Employee Expression of Concerns for Safety

1. TVA Policy on Expression of Staff Views TVA's policy on expression of staff views is delineated in TVA Code II "Expression of Staff Views." It is TVA policy to encourage and protect the differing views of employees on policy and execution of policy. TVA believes that every responsible view is valuable and ensures that such views are heard and appropriately considered in all decisionmaking processes. TVA encourages expression of safety views involv ing all aspects of its operations, particularly those asso ciated with the design, construction, and operation of TVA nuclear plants. Responsible views may be voiced without fear of recrimination or retribution. TVA employees are responsible for voicing views about significant issues and are encouraged to deal directly with line management so that corrective action may be handled promptly and at the working level. If the views are not resolved at the line management levels, TVA has established methods for handling the views at higher levels which include referring the views to the NSRS for investigation.

2. SON Employee Expression of Concerns Before and During the Cleanina Activity Essentially all employees interviewed by NSRS oIere asked if they openly expressed any concern for safety (nuclear and industrial) to their supervisors before and during the cleaning operation of the thimble tubes. One worker that had experience cleaning the system did express some concern to the steaufitter foreman and the evening shift coordinator it about the new design of the base support system because was different from the base support they had used before.

like this The response to him was that they had used a tool He indicated that he knew the procedure said in the past.

with the reactor not to perform the cleaning operation "gripes" operating, but that they really did not have any about it. They knew "the situation of the reactor," in that the work with "no power you have got to if they performed opinion that take the reactor off the line." He felt in his what they were going to do was relatively safe.

The concern for safety increased (primarily radiological concerns) as the job progressed. The FSG supervisor was contacted and further planning conducted. All workers interviewed indicated that they felt that there were no hazards that would have justified not performing the work.

Some indicated that the work had to be performed to prevent removing unit I from operation. No expression of concern for the safety or the job was related to upper plant manage ment.

For conclusions and recommendations relating to this sec tion, refer to section 1ll.J.1.

N. Proaram Controls Established by SQN Unit I Technical Specifications Technical Specification requirements applicable to review and control of maintenance activities include the following:

1. Section 6.2.3. "Independent Safety Engineering Group (ISEG)".

Section 6.2.3 states that the ISEG shall function to examine plant operating characteristics, NRC issuances, industry advisories, licensee event reports, and ottaer sources which may indicate areas for improving plant safety. Section 6.2.3 further states that ISEG shall be composed of at least five dedicated full-time enpineers located onsite and shall be responsible for maintaining surviillance of plant activi ties to provide independent verification that these activi ties are performed correctly and that human errors are reduced as much as practical. The ISEG at SQN was not composed of five engineers devoting full attention to ISEG functions and had not been effective in providing indepen dent verification that maintenance activities were performed

correctly and that human errors were reduced as murh 4s practical. (See section IV.Q for details on ISEG activi ties).

For conclusions and recommendations relating to this sec tion, refer to III.K.I.

2. Section 6.5.1. "Plant Operations Review Committee (PORC)"

The PORC shall function to advise the plant superintendent on all matters related to nuclear safety and is composed of the following members of the plant staff:

o Plant Superintendent (Manager) 0 Operations Supervisor

• Results (Engineering) Supervisor

• Maintenance Supervisor

• Assistant Plant Superintendent (Manager)

• Health Physicist o Supervisor, Quality Assurance Staff (FQE)

PORC responsibilities include the following:

o Review of all procedures required by section 6.8.1 of the Technical Specifications and changes thereto.

0 Review of unit operations to detect potential nuclear safety hazards.

SMI-O-94-1 was originally PORC reviewed and approved for the plant superintendent in July 1981 and had not been revised since that time. The quality of the procedure was poor when submitted to PORC. SHI-0-94-2 that was written to clean thimble tubes after the accident and was also of poor quality in that it contained no instructions for disassembl ing and reassembling the detector drive system from the thimble tubes, no precautions or warnings to alert personnel of the sensitive nature of the mechanical seals and restric tions for working on the system with the reactor pressur ized, no postmaintenance inspections to ensure the quality of the seals had not been degraded during the maintenance process, and postmaintenance testing was optional. Use of this instruction could degrade the mechanical seals and if performed at pressure could cause a thimble tube to eject or if not inspected, detected, and corrected could cause an ejection during pressurization and startup of the reactor.

Despite these inadequacies and even after the accident the instruction was PORC reviewed and recommended for approval to the Plant Manager. It is apparent th-' the PORC review was ineffective in identifying the proceoure inadequacies in the original instruction and in the instruction recommendedI for approval by PORC after the accident.

For conclusions and recommendations relating to this sec tion, refer to section 1IH5

3. Section 6.8. "Procedures and Programs"

a. Section 6.8.1.s. Section 6.8.1.a states that written procedures *hall be established, implemented, and maintained covering applicable procedures recommended in Appendix A of Regulatory Guide (RG) 1.33, Revision 2, February 1978. Appendix A, section 9.C of RG 1.33 states that procedures for the repair of the incore flux monitoring system should be prepared prior to beginning work.

As discussed in section IV.D.2.a of this report, SIII-0-94-1 was violated and thus not properly imple mented.

b. Section 6.8.2. Section 6.8.2 states that each procebe dure of section 6.8.1 and changes thereto shall reviewed by PORC and approved by the plant manager prior to implementation and that each procedure shall be reviewed periodically as set forth in administrative procedures. Administrative Instruction AI-4, "Plant Instructions - Document Control," revised March 9, 1984, states in section 5.3.2 that each instruction shall be reviewed biennially after issuance to deter mine if changes are necessary or desirable.

Inadequate PORC review of SHIls is discussed in section IV.1I.2 above. Additionally, the biennial review pro cess established by AI-4 was inadequate in that the poor quality of SHI-0-94-1 was not corrected and the instruction was almost three years old when the acci dent occurred and had not been revised since its origi nal issue.

C. Section 6.8.3. Section 6.8.3 states that "temporary changes" to procedures of paragraph 6.8.1 may be made provided:

• The intent of the original procedure is not altered.

• The change is approved by two members of the plant management staff, at least one of whom holds a Senior Reactor Operators License on the unit affected.

O The change is documented, reviewed by PORC and approved by the plant manager within 14 days of implementation.

When asked how SMI-0-94-1 should have been changed to make it appropriate for the dry brushing cleaning operation at power, managers and engineers interviewed resoonded that a temporary change should have been issued to delete the words concerning "do not use the equipment or procedure at power." A change of that nature would be inappropriate as the intent of the instruction would be changed. This type of response is an indication that the people interviewed were not aware of what quality elements are necessary for a good instruction for assuring that the quality of a CSSC is not degraded during the maintenance process, were not aware of the procedure change process, or were express ing a careless attitude toward procedural compliance.

The fact that this lack of awareness or careless atti tude was expressed (toward procedures) after review of the accident indicates an alarming lack of appreciation of the importance of adequate procedures and procedural compliance. Effective preventive action to reduce procedure violation errors will not be successful unless and until the lack of awareness or such atti tudes are changed.

In summary, there was a significant breakdown in the con trols for maintenance activities established by the unit I Technical Specifications in that (1) ISEG activities did not comply with the intent of the Technical Specifications and had been ineffective, (2) PORC review of special maintenance instructions for the cleaning of thimble tubes before and after the accident had been inadequate, and (3) there was a significant breakdown in the SQN procedure process for maintenance activities.

0. Prior Findings and Recommeendations Followint NSRS Investilation of 10-Rem Extremity Exposure at SQN During September and October 1982 NSRS conducted an indepth investigation into the causal factors associated with a 10-rem extremity exposure at SQN. The findings as reported in NSRS Report No. i-82-21-SQN issued December 1, 1982, indicated that the causal factors for the 10-rem extremity exposure were on inadequate hazard assessment, inadequate prejob planning, lack of training, and inadequate adherence to the TVA safety-first policy. Some of the causal factors for that incident are similar to some of the causal factors for this accident. Recomendations were made by NSRS in December 1982 to correct the causal factors of that incident. It is apparent that some of these recommenda tions had not been implemented.

For conclusions and recommendations relating to this section, refer to section III.C.3.

S..

4 P. SQN Licensee Event Report (LER) No. SQRO-50-327/8 030 This LER, prepared by the plant Compliance Staff and transmitted to the NRC on May 18, 1984, provided the details concerning ejection of the incore thimble tube.

Report Sys Paragraph b.(2).ii.I of IOCFR5O.73, "Licensee Event include the follow tem," states "the narrative description must event:

for the particular ing specific information as appropriate failure or component or system The method of discovery of each procedural error."

of discovery was stzted Under "the Event" of the LER the method as "water was noticed on the weal table."

states "for each Paragraphs b.(2)ii.(J)(2)(iI) of IOCFR50.73 the error discuss: whether lersonnel error the licensee shall associated with procedure. . . or was was contrary to an approved approved proce an an activity or task that was not covered by dure."

of procedures in There was no mention of inadequate or violation the narrative of the LER.

Event Report Paragraph b.(4) of 10CFRSO.73 stat.es "The Licensee planned a description of any corrective actions shall contain: probabil those to reduce the as a result of the event, including ity of similar events occurring in the future."

"all short-term The "corrective actions" stated in the LER were in the above text. Per corrective action taken has been dcscribed the seal table and associated fittings vendor recommendations, This inspection determined that no additional were inspected.

action, corrective action was required. For long-term corrective future thimble tube clean management has made the decision that ing will not be performed during power operations."

on May 18, 1984, LER No. SQRO-50-327/84030 transmitted to the NRC of was misleading and did not meet the specified requirements as "water was noticed IOCFR50.73 in that the leak was described accurately on the seal table." (While this is true it does not of the leak as described to NSRS by the describe the true nature There was no mention in the LER that the primary work workers.)

inadequate, was instruction for the activity, SKI-0-94-1 was address specified does not violated, and the long-term correction of the event corrective actions to correct the causal factors of an event of a similar nature.

that may reduce the probability relating to this section, For conclusions and recommendations refer to section III.L.I.

• e Q. SQO Compliance Staff/ISEG Activities 1 RBackground bI.tEG 0737, "Clarification of THI Action Plan Requirements,"

issued November 1980 specified post-THI requirements for operating reactors and applicants for operating licenses to be incorporated into plant design and methods of operation for the purpose of minimizing the proL.zlity of a serious reactor accident. One of those items (1.8.1.2) was the requirement of the establishment of an "Independent Safety Engineering Group (ISEG)." The principal function of the ISEG would be to examine plant operating characteristics, NRC issuances, and other appropriate sources of plant design and operating experience information that may indicate areas for improving plant safety. The ISEG would perform indepen dent review and audits of plant activities including mainte nance, operational problems, and aid in the establishment of programmatic requirements for plant activities. Where useful improvements could be achieved, it was expected that this group would develop and present detailed recomenda tions to corporate management for such things as revised procedures or equipment modifications. Another intended function of the ISEG was to maintain surveillance of plant operations and maintenance activities to provide independent verification that these activities were performed correctly and that human errors were reduced as far as practicable.

ISEG would then be in a position to advise utility manage ment on the overall quality and safety of operations.

The ISEG was to be an additional independent group of a minimum of five dedicated, full-time engineers, located onsite but reporting offsite to a corporate official who held a high level, technically oriented position that was not in the management chain for power production. The ISEG would increase the available technicdl expertise located onsite and would provide continuing systematic and indepen dent assessment of plant activities.

The requirement for the ISEG was made a licensing require sent by NRC for the SQN license and included in the Techn, cal Specifications as discussed in section IV.N.I of this report.

2. SQN Implemention of the ISEG Requirement SQN and NUC PR management elected to assign the ISEG func tion to the existing Plant Compliance Staff. SQN Standard Practice SQAII7, "Responsibilities of Nuclear Plant Compli ance Staff for Nuclear Safety Engineering" revised March 1084, defines the responsibilities of the Compliance Staff at SQN in meeting the NRC requirement for a safety engineer ing group. The Standard Practice does not cover all of the

responsibilities of the Compliance Staff not related to the 1SEG function. The defined responsibilities for fulfilling the safety engineering function and providing an independent onsite assessment of nuclear plant activities include review of plant operation and maintenance activities, review of potential reportable occurrences (PROs), and generation of LERs as applicable. (As of May 18 the Compliance Staff had generated 30 LERs for unit 1.)

Additionally, as a compliance function the Compliance Staff logs and tracks regulatory as well as other commitments.

They provide the investigations and the responses to find ings by NRC, Office of Quality Assurance, and others and coordinate- the interface between the plant staff and the inspection, review, investigation, and audit groups. All of these are corsidered ISEG functions by the plant Compliance Staff in that they get involved with problems they or others have identified. They stated that they ensure that in the process of investigating and writing the reports, the right corrective actions have been taken, both short and long term, to prevent recurrence. The Compliance Staff advises the plant management and others on regulatory matters includ ing interpretation of Technical Specifications.

The ISEG concept used at SQN had diverged from the original NRC and Technical Specification intent as interpreted by NSRS in that it is not composed of five full-time senior level engineers located onsite dedicated full time to ISEG functions, is involved in line production functions, is not independent from the power production organization to ensure objectivity, and is not in the position to assess and advise utility management on the overall quality and safety of operations.

At SQN the ISEG function was assigned to the Compliance Staff which performed line functions for the Plant Manager.

These functions performed by the Compliance Staff do afford the opportunity to review plant operation and maintenance activities but do not afford the opportunity to perform the reviews thoroughly and with independence-from pressures of operation of the facility. Additionally, the performance appraisals, and thus the promoLahility in the organization, are performed by the site management. The compliance ftinc Lions performed by the Compliance Staff are line functions and are subject to operational pressures.

The accident was investigated by the SQN Compliance Staff (ISEG) and the description of the event, the cause of fail ure and the long-term corrective action specified in LER SQN-S0-327/84030 were determined by that group. The Compli ance Staff/ISEG conclusions concerning the accident as reflected in the LER failed to recognize any.programuatic problems that may adversely impact the safety of plant personnel or plant operations in the future.

In general, the Compliance Staff/ISEG personnel interviewed expressed that their thoughts concerning the accident were that it was an unfortunate event. They thought that the plant had demonstrated through the outage that they had made tremendous headway in conducting outages and getting through them, and this accident was an unfortunate event that occurred and kept the unit from going back to power.

Based on what they had seen and what the engineering section had done prior to making the decision to clean at power, they did an adequate evaluation, at least talked to industry people that had experience in this area, and came up with a decision that cleaning at power could and had been done.

The thoughts expressed by the Compliancer Staff/ISEG persOlt nel interviewed reflected a line supervisor's attitude and one that was concerned with schedule and not one that was concerned from an independent standpoint for nuclear safety.

The Compliance Staff at SQN has been ineffective in perform ing the ISEG functions of maintaining surveillance of plant activities to provide independent verification that activi ties (including maintenance activities) were performed correctly and that human errors were reduced as much as practical. This lack of effectiveness in identifying prob lem areas with program controls is in itself a program weakness which thus promoted conditions that allowed the accident to occur.

For conclusions and recommendations relating to this sec tion, refer to section III.K.I.

V. PERSONNEL CONTACTED A. Industry I. G. Black Teleflex Corporation

2. A. Burger Beaver Valley Nuclear Plant

3. R. Cockrell INPO

4. M. Garton North Anna Nuclear Plant

5. D. Kane Beaver Valley Nuclear Plant

6. M. Kwitck Kewaunee Nuclear Plant

7. R. Nathieson Westinghouse (SQN Site Rep.)

8. W. Mullet NUS

9. J. Perry Trojan Nuclear Plant

10. A. Stough NUS II. H. Wells INlIO H. TVA Co rpora*

1. J. Thompson OGM (DASHO)

C. Division of Occupational Health and Safet

1. H. Linder OC U&S

D. Office of Power (PWR)

Bugg Kemp Lobdell E. Division of Nuclear Power Abercrombie Campbcll Fox Ellis Kitts Sessoms Wallace F. Sequoyah Nuclear Plant Albury FSC Alexander FSG Baker FSG Byrant FSG Clift FSG Cooper Compliance Section Crawley HP Section Edwards FP Section Fortenberry Engineering Section Gammage FSG Harding Compliance Section Harrison HP Section Holderford HP Section Jackson Safety Scltion Kirk Compl i ;ace Sect son Krell Maintlri; iii'e ScLtion Love Maintenance Section Mason SQN Martin Document Control McKay Engineering Section Nobles SQN Osborne HP Section Paschal FSG Record Master Files Robinson FSG Schofield Engineering Section Simpson Engineering Section Stiegleman HP Section Taylor Safety Section Turie r FS(;

Wa I krr ()eiirni lIar msnSIcIl 1l1 Wl itty E1l l il na'r l ii Sect ion G. Watts Bar Nuclear Plant W. Byrd Compliance Section R. Sauer Compliance Section

• 'a VI. DOCUMENTS REVIEWED A. Regulatory

1. U.S. NRC Report Nos. 50-327/84-14 and 50-328/84-14, received July 2, 1984

2. U.S. NRC Report Nos. 50-327/84-13 and 50-328/84-13, issued June 21, 1984

3. U.S. NRC NUREG-0737, "Clarification of THI Action Plan Requirements," November 1980

4. Code of Federal Regulations 10CFR50.73, "Licensee Event Report System,"

September 30, 1983 O1CFR50 Appendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants," January 1, 1983

5. U.S. NRC Regulatory Guide 1.33, "Quality Assurance Program Requirements (Operation)," February 1978

6. U.S. NRC IE Information Notice NO. 84-55, "Seal Table Leaks at PWRs," July 6, 1984

7. SQN LER No. SQRO-50-327/84030

8. U.S. NRC NUREG/CR-1369, "Procedures Evaluation Checklist for Maintenance, Test and Calibration Procedures Used in Nuclear Power Plants," September 1982 B. Industry

1. Trojan Nuclear Plant, "Flux Thimble Tube Cleanout at Full Power"

2. Management Oversight and Risk Tree Users Manual, EG&G/DOE, Idaho National Engineering Laboratory, ERDA-76/45-4, November 1976

3. Westinghouse Electric Corporation, "Topical Report - Safety Related Research and Development for Westinghouse Pressurized Water Reactors Program Summaries," WCAP-7856, Fall 1971 Spring 1972

4. West inghouse Electric Corporati on, "Toiips.ail KHeport - li-Ct' Instirumentation (Flux Mapping SyVlem and Thermodouiple.) ."

.July 1971

5. Westinghouse Nuclear Energy Systems, "Technical Manual lur In-Core Instrumentation - Tennessee Valley Authority Sequoyah Nuclear Plant Unit No. 1 and No. 2"

6. Occupational Safety and Health, Standards and Interpretations, "Subpart E - Means of Egress"

7. Westinghouse Correspondence from R. Howard to R. Hathieson, "Seal Table Fittings Intermix - SEQ I," May 2, 1981

8. Letter to M. D. Wingo from M. Cuppula, Superintendent of Technical Services, Duquesne Light, "Incore Thimble Maintenance," May 14, 1984 C. Corporate

1. Memorandum from H. N. Culver to W. F. Willis, "Sequoyah Nuclear Plant - Notification of an Unusual Event,"

April 20, 1984 (GNS 840423 100)

2. Memorandum from H. N. Culver to H. G. Parris, "Sequoyah Nuclear Plant - NSRS Investigation of the Unusual Event on April 19, 1984 - NSRS Report No. 1-84-12-SQN," April 25, 1984 (GNS 840425 051)

3. Tennessee Valley Authority, "Severe Accident Investigation Procedure," January 1984

4. Memorandum from H. N. Culver to E. A. Belvin and H. G. Parris, "Sequoyah Nuclear Plant Investigation of 10 Rem Extremity Exposure - Nuclear Safety Review Staff (NSRS) Report No. I-82-21-SQN," December 1, 1982 (GNS 821203 050)

D. Office of Power

1. Office of Power Radiation Plan, Section A, "Nuclear Power Plants," November 2, 1983

2. Memorandum from H. G. Parris to W. F. Willis, "Sequoyah Nuclear Plant - Notification of an Unusual Event," April 20, 1984 (GNS 840423 100)

E. Division of Nuclear Power

1. Operational Quality Assurance Manual Procedure No. N-OQAM, Part II, Section 2.1, "Plant Maintenance," February 7, 1983

2. Divison of Nuclear Power, "Plant New and Escalated Operational Event Report - Seqtioydh Plant Status," April 17-30, 1984

3. Division of Nuclear Power, "Directives Manual," November 15, 1983

4. Are. I'lani Pl'rote iiure No. ()604.0',, "'sl iihisii lhI1i t nI I Nuclear Plant Independent SdIety E'.gincer' ni Group/

Compliance Staff," October 31, 1983

5. Area Plan Procedure No. 0604.04, "Unreviewed Safety Question Determination (USQD - Intent, Method, Review, and Approval," October 13, 1983

6. Operational Quality Assurance Manual Procedure No. SQ-OQAM, Appendix A, "Critical Structures, Systems, and Components (CSSC) List"

7. Operational Quality Assurance Manual, Part III, Section 7.3, "Common-Mode Failures, Maintenance Initiated,"

January 15, 1981

8. Letter from J. A. Coffee to Mr. Larry Sinter, Director, Tennessee Emergency Management Agency, "Sequoyah Nuclear Plant Notification of Unusual Event - April 20, 1984,"

April 25, 1984 (GNS 840430 100)

9. Memorandum from R. A. Sessoms to L. C. Ellis, "Sequoyah Nuclear Plant Unit I - Incore Thimble Ejection - Investiga tion and Review of Events for Industrial Safety Implica tions," May 2, 1984 (L01 840502 802)

10. Memorandum from L. C. Ellis to R. A. Sessons, "Sequoyah Nuclear Plant Unit 1 - Incore Thimble Ejection - Investiga tion and Review of Events for Industrial Safety Implica tions," May 17, 1984 (05 840517 800)

F. Sequoyah Nuclear Plant

1. Draft - "Sequoyah Nuclear Plant Unit I D-12 Traveling Incore Probe Thimble Tube Separation Special Tests,"

May 17, 1984

2. Special Maintenance Instruction SMI-0-94-1, "RPV Bottom Mounted Instrument Thimble Tubes Cleaning and Flushing,"

July 10, 1981

3. Special Maintenance Instruction SMI-0-94-2, "Incore Flux Thimble Cleaning and Lubrication," Revision 0, April 26, 1984

4. Maintenance Request Form, A-238084, April 18, 1984

5. Radiation Work Permit No. 02-1-00102, January 1. 1984

6. Radiation Work Permit Timesheet No. 02-1-00102-0090, April 18, 1984

7. Radiation Work Permit No. 02-1-00005, Issued April 20, 1984

8. Radiation Work Permit rTimesheet Nos. 92-1-00005-0002 through 0062, Issued April 20, 1984 thrnioh May 1. 19A4

9. Whole Body Analysis Records for the following SQN personnel:

J. Clift, FSG D. Albury, FSG H. Gammaae, FSG C. Baker, FSG B. Turner, FSG S. Harrison, HP B. Simpson, FSG M. Edwards, HP D. Paschal, FSG

10. Radiological Control Instruction RCI-10, "Minimizing Occupational Radiation Exposurr," Revision 8

11. Radiological Control Instructiuon RCI-14, "Radidtion Work Permit (RWP) Program," Revision 2

12. Radiological Control Instruction RCI-10, Attachment 1, "ALARA Preplanning," April 19, 1984

13. Potential Reportable Occurrence, PRO No. 1-84-159, April 20, 1984

14. SQN Technical Specifications - Unit I, Sections:

3.3.3.2 "Movable Incore Detectors" 3/4.3.3.2 "Movable Incore Detectors" 3/4.4.10 "Structural Integrity" 6.2.3 "Independent Safety Engineering Group (ISEG)"

6.5.1 "Plant Operations Review Comittee (PORC)"

6.8 "Procedures anI Programs" IS. SQN Final Safety Analysis Report, Sections:

3.6 "Protection Against Dynamic Effects Associated With the Postulated Rupture of Piping" 5.2 "Integrity of the Reactor Coolant System Boundary" 7.7.1.9.2 "Movable Neutron Flux Detector Drive System" 13.5 "Plant Instructions"

16. Administrative Instruction AI-4, "Plant Instructions Document Control," March 9, 1984

17. Administrative Instruction AI-3, "Clearance Procedures,"

Revision 23

18. Administrative Instruction AI-H, "Access to Containment,"

Revision 10

19. Administrative Instruction Al-13, 'Control of CSSC Equipment,"

Revision 25

20. Administrative Instruction AI-30, "Nuclear Plant Method of Operation," Revision 6

21. Administrative Instruction AI-8, "Containment Entry Checklists," April 18, 1984 - April 19, 1984

22. Clearance Sheets, Hold Order No. 1, "Incore Probes,"

January 1, 1984

23. Standard Practice SQA119, "Unreviewed Safety Question Determinaion," Revision 3

24. Standard Practice SQA 128, "Method of Operation - Policy,"

Revision 0

25. Standard Practice SQA129, "Objectives in Plant Operation Sequoyah Nuclear Plant," Revision 2

26. Standard Practice SQA 131, "Recovery From a Spill of Radioactively Contaminated Liquid," Revision 1

27. Standard Practice SQS29, "Accident Reporting and Investiga tion," Revision 3

28. Abnormal Operating Instruction AOI-6, "Small Reactor Coolant Leak," Revision 13

29. Hazard Control Instruction HCI-Gi, "Hazard Control Instruc tion Manual," April 21, 1976

30. Hazard Control Instruction HCI-G2, "The Supervisor," May 26, 1983

31. Hazard Control Instruction HCI-G3, "The Employee," January 31, 1984

32. Hazard Control Instruction NCI-G6, "Clearance Procedure Requirements." May 26. 1983

33. Hazard Control Instruction HCI-G15, "Initial Accident Reporting and Emergency Actions," March 22, 1983

34. Hazard Control Instruction HCI-Gi6. "General Safe Work Rules and Employee Conduct," May 26, 1983

35. Hazard Control Instruction HCI-G26, "Buddy System in Hazardous Lev Accessibility Areas," March 22, 1983

36. Hazard Control Instruction NCI-G29, "Workplace Hazard Assessment," February 14, 1984

37. Quality Engineering Section Instruction Letter No. 5.3, "Haintenance Requests - FQE Section Review," Revision 9

38. SQN Shift Engineers Journal, April 17, 1984 - April 25, 1984

39. SQN Assistant Shift Engineer (SRO) Journals (Unit 1),

April 17, 1984 - April 26, 1984

40. SQN Unit Operator Journals (Unit I). April 17, 1984 o April 23, 1984

41. SQN Health Physics Journals for 690 HP Lab, April 19, 1984 - April 26, 1984

42. "Superintendent's Letter," Sequoyah Nuclear Plant, Volume 1, No. 6, April 30, 1984 G. Watts Bar Nuclear Plant

1. Standard Practice WB6.S.1, "Engineer Assignment to Plant Systems and Equipment," March 14, 1984

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TKOIA:.; IlLC..Ai( I'.ANI y FLUX TTHIBL B TUE CLEAN\OLT AT *'l;LL TL' I';E Gary ;..,ir INlCIDENT:

On February 1. 1979 dwiung a rout.ine ',::i.;v 1lux r...np a: 10*Z power (3611 KWT). blotk thimbles were tli:.crvrre.;, at 37 of 58 th-:blc locations.

The blockages were at the bend minima.

HISTORY:

', From the Trojan startup in Det-cnber !975 untr. the end of Cycle 1 it.

harchl978. fifty-three full core fux ' aI ;:- .i:;c ni,.c:nu< qu.rter-core maps had been taken with evidence of n;. o::t bjinrk.cd ti;i'jc. Littlc or no neulube h.d been uscJ.

The plant was shutdown fron March 1978 un.il J.i:.u.iry 1979 for refucl;ng/

technical specifications and licensing Interv:-.rvinn rcga.rd-r. seismic integrity. During the refueling:, the tubes wecre cvacj.'cd, flooded vict.

carbon dioxide, and capped off.

During the prolonged outage the flux m.ap;;'p-., sy.stcm wa:J cxcrcisec every S six weeks.

Between the sar t Febrtuary jlockaie.

nine full core flux .mps anJ ,everal qu:srter-,,.re a;.* vwcr. taken with no significant problems encountcre'.

WORK PREPARATIONS:

Arrangements were nmdc with Tc;cflcx. :*!.1 f lwi c",'?-ing sysic.- VCrJar to be on-site to assist in the brur.ninr ne,,,r.at.*t (s.:rt a 22-callber rifle cleaning, brass brush m.chin*ed d'on it' 2*-c..ir and welca to du;..y detector cable w.(k a hcllcjl drive u.nt). Si:;*> i.,v.,vcr Valley h:.Jd lso done a brushing at po.er, they were contart, . to obtain gen~crl in'or mailon. A ten-foot lonp, 1/2-tnch rl, rid .!;'.: obtained to facili:a:t trunsfer of the wire brust between tiimblve locnt-ons. A funnel was made to facilitate brush entry into thimble.

Radiation control piccclurt.. w>>err dev, UKK OPERATION:

The flux m.api)i, *.y.tri, :i ievcJIt l i "bti  : * ,) ..*.. dli.connCt*., t and rolled out of the way..

© The mainteitancerma.i with li.n-n;,-ocr.at.l iii,..: dr..'.c, ;.osLtu.cd hinsel above the seal tuble on tlhe upper st.it loory r .ouiting fr.amc.

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wORK OPERATION (Contd.):

He drove the brush Lhrough the r.i.! cni:  %.l it .1lu .ars!', :l*. ;uc ca:.or.

for brushing.

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!hiii,. wue.:.i

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't!hir.w:..

o >ck~ up Jl'borne activity produced when thwe c..i.. .iJ

• ," The area radiation monitor aliiarJd Vwhen .,ru.Isl rTe..rg:d :ron :hi=ble in:o f'" rigid conduit.

RADIATION CONTROL:

Contact radlact oii levels .st ir.e  : ,.,i .v. :...-.

Prime activacion product was co;,per In ,:-'.s.l (NOTE: Brush durJni; ;hutdo'n cl .i ; '.  :.r ,, ... ,;;:..L)

'. " Contact radiation level ,'i cabl.

.K'r A vacuum cleaner wus us.ct Lo coilct at:;.'r::.i ;,articuli~ct fro.i brush a:~n cable as they were withdr.awn from the Lt,... >le.

Airborne levels 1.5 MPC vcre mv-e*acJl w,.in v.'.a,,.m n,: hI.J close Lt source.

Eventually levels were ne1d to 0.) .:*'C- .,:er ;:.;r-vJ4 vJcr=. cl.a:er suction Smaintained.

. All personnel wure reNpirator..

"". .I t *'t'rii l 1 .* . .**.

.Di assembly 8', n-mir . .. 10 l -.,r  :..i: r.n Bruahing .'lIo's n-mr g..nimi. 177.. e- .. r.. ,,

lI .hei st ><<.an - ( I. '.r. .iv .>>. ii.>in 1- .64 mr Reassembly 73 la-mr K....a, 17 m-rr n.-i:rtn Total Evolution 2267 m-mr gcint,..  :('1 n-n: ncuCrun (Note total dose for biush and flush .at s.utdioi.w was 263 nren.)

SUGCESTlIM; Consider ut I liz Lng to joru:.11 ...... . #.(t o:tn tuisn ciypeLr If piltioIb Ie.

feleflex rcccmmended isos-- ati,l ~~..*:,* is~

Lb uv :a1ard for soft tube. Brushi must lo isr.ar a, . .4*rt.. (its.

2.Use sIrfed hoo~xd res.piratt-r!. ratiehr Liasan m~a-tks (or personnel comfort.

• ~3. Use a 12-fiang rigid c~onduit ractas~r :h.,n LIe. 10-foot conduic if enough overhead space is available.

4. Consider a asotori:ed helical drive. but be aware of kink potencial on hitting obstruction.

• 5. Provide a supporar pl..Atform for htiv;.a; .irjvt uper.arur .2bov4: :.cal ta~ble.

6. Consider routine bru%?1111j  ! ILu.!

uaoad ..t rvfu&-ii:.j: ý?,,,udwrls.

7. Inspect .8,41 rtcpalce sXa!:ILI

,~%t !f.,. .Irive cit.1.~r- even if de.tector still SUUd.

8.During prulon;iv.d ouucaC. wklath,!r 'I L*:uo:Lcnrs back past: saetcy limit switch 11itO ISCats.. and sihiet.cd~ drive~ -hakuing.

• 9. Use no neulube.

10. Exercise s£ytcm m~ottoily.

1 f

1. TfrrCH#/ erm T

.Zqpo STRW MAM4l rEwsii s>0ALL SUBJECT "THIMBLE TUBE", "SEAL TABLE"

• .ri T "TRIMBLE TUBE"t "SEAL TABLE" END

-. .14 HALL (PSrE6/SALM> 031-MY-83 10359

--i* CT>> rpfRE THIMBLE.TUBE BLOCKAGE

... SALEM UR3T7S 4 LOOP WESTINHbOUSE PWRS TO ALL OPErEpi6 PLANTS$

SSALER UNTS HAVE ENCOUNTERED PROBLEMS WITH THE INCORE DETECTOR SYVI$ VER THE YEARS. NE RECURRING PROBLEM IS THE BLOCKAGE

.OF l"' IMBnLE TUBES" WHICH ARE THE ACCESS PATH FOR THE 1

.f TURE DETECTORS TO REACH THE REACTOR CORE. BLOCKAGES

,'SlD TO BUILD UP IN THESE TUBES AT THE POINT WHERE THEY ENTER ThE REACTOR VESSEL. AT THIS AREA THE TUBES 60 FROM A RELATIVELY

"-. a.^ TEMPERATURE ( 100 DE6REES FAHRENHEIT) TO REACTOR COOLANT JtEMP9i8E <S-XC 550 DEGREES FRHRENHEIT). THESE BLOCKAGES lTHE. ZS.SDRlIVE CABLE ASSEMBLIES FROM ENTERING THE l LLfLiE s ESA LEM MANY WESTINGHOUSE PLANTS HAVE BEEN S WHERE THEY COULD NOT MEET THE TECHNICAL SPECIFICATION

. E 75% OF THE THIMBLES USEABLE.

f, DISCOVER THE SOURCE OF THESE BLOCKAGES SRLEM PERSONNEL

. ECENTLY REMOVED TWO THIMBLE TUBES FROM UNIT 2 THAT WERE

"- OWN TO BE ILOCKED. SEVERAL 3 FOOT LONG SAMPLES OF THESE (UBES WERE OBTAINED CONTAINING THE BLOCKAGE. TECHNIQUES WERE USED TO ENSURE THAT NO WATER ENTERED THE TUBES.

1 0 SALEM

.i , I PRESENITLY RECEIVING PROPOSALS FOR ANALYSIS OF

• c-TIDn . ONCE THE ANALYSIS OF THESE SAMPLES "ktlr ILL MAKE THE RESULTS KNOWN VIA NOTEPAD, HOPEFULLY THE SUtnER OF 1983.

ALSO, THESE 3bCKFAGES HAVE BEEN SUCCESSFULLY REMOVED AT SALEM WIH THE' UNIT AT FULL POWER. BY PROBING THE THIMBLE TUBES WITH A TEST CABLE (NO DETECTOR) THE BLOCKAGES CAN BE KNOCKED LSE WN* GROUND UP. THIS IS DONE MANUALLY FROM INSIDE THE CWTMNlMEr T NEAR THE SEAL TABLE. WE REMOVE THE INPUT TUBE' S FRO A 1-PI" TH TRANSFER DEVICE AND ATTACH A TELEFLEX HAND DI*VE WITH A TEST CABLE LOADED INTO IT. WE DRIVE THE CABLE TO THE AREA OF THE BLOCKAGE AND "PUSH" IT OUT OF THE WAY.

CARE MUST BE TAKEN NOT TO DRIVE THE CABLE INTO THE CORE REGION AS IT WILL ACTIVATE THE CABLE VERY OUICKLY A'BOUT 100 R/HR UHMN RETURNED). WE MEASURE THE CABLE INSERTED LENGTH BY'COUNTSM6GTHM TURNS ON THE MANUAL DRIVE HAND CRANK (1 TURN PPr FOOT OF CABLE). WE DRIVE IT UNTIL WE REACH A DISTANCE TFTr IS"SIX FEET FROM THE CORE. AFTER RETRACTION THE 10 SPATH CA" BE ROTATED TO THE NEXT PATH OF INTEREST AND THE S IE2RS ARE LOCATED IN AN AREA OF LESS THAN 1 MR/HR AT FULL S1 URTI R INFSUrITIOD CONTACT JEFF JACKSON, SALEM OPERATIONS.

• ~I60 . eN

, -",*pimMHT ONMTCr