ML20199L663

UC Irvine Nuclear Reactor Facility Annual Rept for 960701-970630

ML20199L663
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Site:	University of California - Irvine
Issue date:	06/30/1997
From:	Geoffrey Miller CALIFORNIA, UNIV. OF, IRVINE, CA
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NUDOCS 9712020081
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U.C.lRVINE Nuclear Reactor Facility

- Annual Report '

for July 1st 1996 to June 30th 1997 Facility License R-116 Docket 50-326 Prepared in Accordance with Part 6.7f of the Facility Technical Specifications by Dr. G. E. Miller Reactor Supervisor 9712O20081 971129 EDR ADOCK 05000326-0 PDR s ..

n

-4 Section 1.

Operations

- Oxration of this facility is in support of the lkpanment of Chemistry program of research and et ucation in the use and application of radiochemical techniques m.d radioisotopes in chemical studies.

Reactor utilization, apan from operator training and maintenance, is thus entirely for sample irradiation. Samples come from diverse origins related to forensic science, fossil fuels, geochemistry, art, and archaeological studies, chemical synthesis, industrial quality control, enzyme studies, trace element pollution studies, etc. The reactor is also used in class work by undergraduates learning tracer and actis ation analysis techniques using small quantities of shon-lived activated materials.

Some use is made of the facility by other educational institutions supported by the Reactor Sharing Program of DOE since September 1st 1987. This program has involved tours, class demonstrations.

and analyses of sv.mples submitted by faculty.

Operations have been at a low level. The totel energy generated is equivalent to less than 60 total hours i at full steady state power. No pulse operations hase been performed, even for test purposes, as controle console pulse instrumentation updates have not yet been fully installed.

i

)

4 6

e

4 Section 2.

Data Tabulations for the Period July 1st.1996 to June 30th.1997 TABLEL Experiment Approvals on 61e 8 Experiments performed (including repeats) 151 Samples irradiated 739 Energy generated this period (Megawatt hours) 14.6 Total,69 element core = 127.0

>74 element core = 1112.5 Total energy generated since initial criticality 1267.6 Mwh Pulse operation this period 0 Tt tal pulses to 6/30/97 978 Sours critical this period 100.4 Total hours critical to date 7199 Inadvertent scrams or unplanned shutdowns 2 Visitors to reactor - admitted 64 Maximum dosimeter recorded for visito.. O mrem Visiting researchers (dosimeter issues) 3 Maximum dose recorded 7 mrem Visiting researchers (badged) 2 TABLE 11 4 RtElor Status 6/30/97 Fuel elements in core (including 2 fuel followers) 82 Fuel elements in storage (reactor tank - used) 25 6

Fuel elements unused (4 instrumented elements + 1 element + 1 FFCR)

Graphite reflector elements in core 33 Graphite reflector elements in reactor tank storage 1 Water 611ed fuel element positions 6 Experimental facilities in core positions 4 Non-fuel control rods 2 Total core positions accounted for 127 Core excess, cold, no xenon $2.69 Control rod worths (4/1i/96)[not conducted during this period]

REG $2.84 SlilM $3.66 ATR $ 1.78 Em so.77 Total: 59.05 Maximum possible pulse insertion $2.58 -

Maximum peak power recorded (no pulse operation during this period) -Mw Maximum peak temperature recorded (B-ring) .C

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' Section 3.

- Inadvertent Scrams and Unplanned Shutdowns TABLE 111.

Date Imm Power Type and Causa, y ,. 1922-02/12~ 15:00 <2.5 w Period scram when starting to raise REG rod @ 2.5 watts, due to electronic noise.

05/14 12:09 ' 250 kw - Power Scram - main circuit breaker in console tripped. Short developed in rear connector in controle console. Both M and F portions of

" connectorw rereplaced.

06/03 09:35 <200 mW. External scram. Sesimic sensor device was reset improperly during start up checklist.

06/25.-17:29- 5 kw Manual scram in order to retrieve sample left in PT Terminus after failure of transfer capsule (rabbit). Reactor restarted after FT system re-installed.

Section 4 i

Maintenance and Surveillance

. The following non-routine maintenance activities were carried out during this period:

July 1996- July 1997 i

continuous During much of this period, oise or two stations of the Radiation Mo_nitoring System

! were out of service because of failures in the detector units. One unit has proven very difficult to trouble-shoot.and remains out of service. Because these can be interchanged, the unit chosen to be out of service is that in a radiochemical processing laboratory, where an additional station remains functional. The other was repaired by.

replacing a Geiger tube, and returned to service. During periods of occasional malfunction, some failures to high alarm status resulted in emergency alerts to the Police Dept, as designed. No actual radiation releases were ever experienced.

Sufficient units have been in service at all times to satisfy Tech. Spec. and general safety requirements.

- 8/96)6 A new monitor was installed for the security system computer to replace a failed unit.

- 2/18/97 The fume hood in the facility laboratory was found to be out of service. A new fan motor was installed on Feb 19th by UCI maintenance personnel. No experiments needing a hood were conducted in the meantime.

n 4

1. y e e N + - -

4/4/97- Electronic leads were reconnected in the reel of the solenoid fishing pole. It is operable for retrieving samples from the Lasy Susan rack in ibe reactor, liowever for modest and low activity samples, operators prefer to use the simpler " weighted stopper" device for speed of operations.

5/14/97 Both M and F portions of REG rod connector were replaced to cure problim of direct main power short in console.

5/30/97 Two Geiger tubes each in the right and left side panel of the portal monitor were nonoperable during routine check with Sr-90 beta source. Age failure likely. Both were replaced with new operable Geiger tubes.

6/25/97 A sample outer capsule (rabbit) failed in the in-core terminus of the pneumatic transfer (PT) system, leaving the sample in the terminus. Efforts to retrieve with a " sticky" rabbit were unsuccessful, so the PT system was disconnected, removed from core, and inverted at the rear of the facility. The maximum radiation level me.asured was 500 mrem /hr (beta +gamnia) at contact on the aluminum tube of the in-core terminus. No handling of that segmer vas required, and no personnel exposures were recorded on dosimeters worn. The retrieted sample activity was almost background, and the sample was still intact in its inner container.

Section 5 Engility Changes and Snecial Exneriments Appmved No special experiments or additional facility changes were approved during this period.

1

4 Section 6 e

Radioactive Effluent Release.

- (a) Gases.

The major direct release to the environs is Argon 41jeoduced during normal operations. Very small amounts of other gases may be released from irradiatec materials in experiments.

Releases are computed based on original estimates at point of origin within the facility and ,

~

taking only dilution intc> account. Since much of the release is from operation of the pneumatic transfer system for samples, this is a conservative estimate in that assumption is made t* at all use of the PT is at full steac'y state power level (250 kwatts) when,in fact, some use is with the reactor a a lower power level'. In view of the small numbers involved, and the fact that an integrated dose check is provided by an environmental dosimeter (CaSO4-Dy> hanging directly in the exhaust at the point of stack discharge, it is considered unnecessary to provide further checks of these estimates. The dosimeter data confirm that an individual standing directly in the exhaust flow for one year would 7 receive an additional submersion dose from the exhaust less than the reliability limit of the dosimeters, or less than 20 mrem per year. The dosimeter data are presented separately in Section 7. Table IV.

Over the years that data have been collected, the accumulated exposure at the exhaust location have i

been lower than for " control" points because of lower masses of concrete structures in the vicinity, in fact the data have been consistently at 20-25 mrem per year Sackground level, so confidence of exposure less than 5 mrem over background seems possible.

- Release estimates based on operational parameters are as follows:

(1) Operation of pneumatic transfer system (7/1/96-6/30/97):

i a. Minutes of operation: 466.6 minutes i b. Release rate assumed: 6. x 10-8 microcuries/ml 8

- c. Flow rate of exhaust air

1.2 x 10 ml/ min 3

Total release computed: (a x b x c) = 3.4 x 10 microcuries (2) Release from pool surface (7/1/96-6/30/97):

a. Total hours of operation at power (Mwh x 4) = 58.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 5 b. Release rate assumed: < l. x 10-8 microcuries/mi -

8

. c. Flow rate of exhaust air: 1.2 x 10 ml/ min 3

Total release computed:(a x 60 x b x c) = 4.2 x 10 microcuries Total of (1) and (2) emission in 1 year = 7.6 x 10 3 microcuries Concentration-averaged over 12 months = < l.2 x 1010 microcuries/mi This is similar to values repotted in previous years and assumes no dilution of the plume at the stack.

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e (b) Liauids and Solids.

Liquid and solid wastes from utilization of by-product materials are disposed through a University contract. Waste is transferred to the custody of the Campus Environmental Health and Safety Office (EH&S). Direct disposals from this facility are given below, it is important to note that activity values are estimated at the time of transfer to EH&S control, in all instances, considerable time elapses before final shipment from campus, if, any, so that substantial decay may cccur for medium-lived radionuclides.

DRY WASTES:

2 ft 3 bo).---> 24Na and mixed activation products with <.01 mci on 7/2/96.

2 ft 3box---> 24Na and mixed activation products with <0.01 mci on 3/9/97 LIQUIDS: none disposed during this period.

Section 7.

Environmental Surveillance.

Calcium sulfate / Dysprosium themioluminescent dosimeters in packs supplied by the Radiation Detection Company, Sunnyvale, Califomia are placed at nine locations around the UCI Campus. One pack is kept on the edge of campus in a wood frame house in University Hills. In fact, the average of the more remotely located " concrete environment" packs on campus is used as the background for comparison purposes, since a more similar microenvironment is experienced by such packs.

Table of Locations.

1. Window of reactor room east wall (inside the facility).

2. In hallway on exterior of south wall of facility.

3. Loading dock, adjacent to west wall of reactor room.

4. Laboratory 152, directly over reactor facility, approximately over core center.

5. In roof exhaust air Gow from reactor room, rooflevel (hung in center of duct at final release point).

6. Biological Sciences 2 building,5th floor, laboratory near window *.

7. M ain library building across campus,5th floor office in sunny window

8. Computer Science building,4th Door office, in shaded window.

9. Fume hood exhaust, roof level, from reactor laboratory (hung in center of duct).

10.12 Perkins Court, University Hills, private residence (wood frame house).

• The location of this dosimeter was moved on October 31991, following occupancy of the new BS2 building which is closer to the reactor than the older building.

Trible IV shows the data as received from RDC for the period. All levels are as expected and are similar to those reported in recent years. As noted before, areas (1) and (2) are also partly .

controlled so that maximum possible exposure to an individual in an uncontrolled area is very minimal at this facility with current operations. The air released from the facility (measured by locations #5 and

1. 9) continues to give no detectable exposuie above background for dosimeters immersed in it.

Location 7 consistently shows higher readings presumably because it is in a window above a wann, outside, cement wall. Over many years, the data at cach specific location show remarkable consistency. An appreciable change would be easily noticeable TABLE IV.

Environmental Dosimetry Data.

1996-1997 Average Exposures in mr.

Location. Ouarter Annual Tctal less 2/96 3/96 4/96 1/97 Total oackground (26i22) 1 4 2 3 1 10 0 2 8 6 6 3 23 0 3 9 7 9 5 30 4 4 7 4 6 2 19 0 5 3 2 2 0 7 0 3

6 5 3 5 2 15 0 7 16 13 18 11 58 32 8 3 0 2 0 5 0  ;

9 5 4 5 2 16 0 10 2 0 0 0 2 0 Average of locations 6,7, and 8 used for " background" ( = 26)

I i

• i a l Section 8.

Radiation Exoosure to Personnd, The annual exposures reponed as a result of finger dosimeter ring and film badge dosimetry are pre. rented in Table V. No exposures have been reported for individuals involved ' facility operations.

Eight (8) persons were monitored on a continual basis using film badges, and all of these were also issued with rmger dosimeter rings. These were required to be worn while handling isotopes. Film badges were generally wom at waist level by all personnel, Certain additional monitoring is done of visiting individuals who are issued with direct-reading pocket dosimeters in addition to film badges and finger dosimeter rings.

Contamination surveys consisting of wipe tests and G-M surveys have shown significant, removable contamination only in areas coming into direct contact with samples removed from the reactor, and on sample handhng tools.

TABLE V.

Personnel Exoosure Summary for 5/1/96 to 4/30/97 (in mrend Imlitiduals Whole Body Finger Ring Deep Shallow Shallow 1 15 60 420 .

0 l 1 55 0 17 0 0 0 48 0 0 0 (Students in class) }

Totals 5 5 225 0 Additional aggregated data from self-reading pocket dosimeters issued to researchers:

1 9 (3 visits) 1 24 (5 visits) b

i . .. ,

. 1 I

. i i

U.C.lRVINE j i

Nuclear Reactor Facility Annual Report for July 1st 1996 to June 30th 1997

Facility License R-116 Docket 50-326 Prepared in Accordance with Part 6.7f of the Facility Technical Specifications by Dr. G. E. Miller Reactor Supervisor

^

s Section 1. ]

Operations l

l l

O,cration of this facility is in support of the Depanment of Chemistry program of research and ec ucation in the use and application of radiochemical techniques and radioisotopes in chemical studies.

Reactor utilization, apart from operator training and maintenance, is thus entirely for sample  !'

irradiation. Samples come from diverse origins related to forensic science, fossil fuels, geochemistry, art, and archaeological studies, chemical synthesis, industrial quality control, enzyme studies, trace element pollution studies, etc. The reactor is also used in class work by undergraduates learning tracer and activation analysis techniques using small quantities of short-lived activated materials.

Some use is made of the facility by other educational institutions supponed by the Reactor Sharing Program of DOE since September ist 1987. This program has involved tours, class demonstrations, and analyses of samples submitted by faculty.

Operations have been at a low level. The total energy generated is equivalent to less than 60 total hours at full steady state power No pulse operations have been perfomied, even for test purposes, as controle console pulse instr.imentation updates have not yet been fully installed.

Section 2.

Data Tabulations for the Period July 1st.1996 to June 30th.1991 TABLEI.

Experiment Approvals on fL 8 ,

Experiments performed (including repeats) 151 Samples irradiated 739 Energy generated this period (hiegawatt hours) - 14.6 Total,69 element core = 127.0

>74 element core = 1112.5 Total energy generated since initial criticality 1267.6 h1wh Pulse operation this period 0 Total puises to 6/30/97 978 Ilours esitical this period 100.4 Total hours critical to date 7199 Inadvertent scrams or unplanned shutdowns 2 Visitors to reactor - admitted . 64 hiaximum dosimeter recorded for visitors O mrem Visiting researchers (dosimeter issues) 3 h1aximum dose recorded 7 mrem Visiting researchers (badged) 2 TABLEIl Reactor Status 6/30/97 Fuel elements in core (including 2 fuel followers) 82 Fuel elements in storage (reactor tank - used) 25 Fuel elements unused (4 instrumented elements + 1 element + 1 FFCR) 6 Graphite reflector elements in core 33 Graphite reflector elements in reactor tank storage 1 Water filled fuel element positions 6 3xperimental facilities in core positions 4 Non-fuel control rods 2 Total core positions accounted for 127 Core excess, cold, no xenon $2.69 Control rod worths (4/11/96)[not conducted during this period)

REG - $2.84 SHlhi $3.66 ATR $1.78 Em 50.77 1011 59.05 hiaximum possible pulse insertion $2.58 hiaximum peak power recorded (no pulse operation during this period) - h1w h1aximum peak temperature recorded (Bl ring) .C 1

4 Section 3.

' lint dvertent Scrams and Unnlanned Shuldowats TABLE 111.

Date Time Power hne and cause 1222 02/12 15:00 <2.5 w Period scram when starting to raise REG rod @ 2.5 watts, due to electronic noise.

05/14 12:09 250 kw Power Scram - main circuit breaker in console tripped. Short developed in rear connector in controle console. Both M and F portions of connector were replaced.

06/03 09:35 <200 mW. External scram. Sesimic sensor device was reset improperly during star' up checklist.

06/25 17:29 5kw Manual scram in order to retrieve sample left in PT Terminus after failure of transfer capsule (rabbit). Reactor restarted after PT system re-installed.

Section 4 Maintenance and Surveillance

. The following non-routine maintenance activities were carried out during this period:

July 1996- July 1997 continuous During much of this period, one or two stations of the Radiation Monitoring System were out of service because of failures in the detector units. One unit has proven very difficult to trouble-shoot.and r-mains out of service. Because these can be interchanged, the unit chosen to be out of service is that in a radiochemical processing laboratory, where an additional station remains functional. The other was repaired by replacing a Geiger tube, and returned to service. During periods of occasional malfunction, some failures to high alarm status resulted in emergency alerts to the Police Dept, as designed. No actual radiation releases were ever experienced.

Suflicient units have been in service at all times to satisfy Tech. Spec. and general safety requirements.

8/9/96 A new monitor was installed for the security system computer to replace a failed unit.

2/18/97- The fume h(xxl in the facility laboratory was found to be out of service. A new; fan mo_ tor was installed on Feb 19th by UCI maintenance personnel. No experiments needing a hood were conducted in the meantime.

1

. 1 4/4/97 Electronic leads were reconnected in the ree! of the solenoid fishing pole. It is operable

. for retrieving samples from the Lasy Susan rack in the reactor. liowever for modest and low activity samples, operators prefer to use the simpler " weighted stopper" device for speed of operations.

S/14/97 Both M and F portions of REG rod connector were replaced to cure problem of direct main power shor: in console.

5/30/97 Two Geiger tt.bes each in the right and left side panel of the portal monitor were nonoperable during routine check with Sr-90 beta source. Age failure likely. Both were replaced with new operable Geiger tubes.

6/25/97 A sample cuter capsule (rabbit) failed in the in-core terminus of the pneumatic transfer (PT) system, leaving the sample in the terminus. Efforts to retrieve with a " sticky" rabbit were unsuccessful, so the PT system was disconnected, remo' -d from core, and inverted at the rear of the inci:!!y. The maximum radiation level measured was 500 mrem /hr (beta + gamma) at contact on the aluminum tube of the in-core terminus. No handling of that segmcat was required, and no personnel exposures were recorded on do.simeters worn. The retrieved sample activity was almost background, and the sample was still intact in its inner container.

Section 5 Facility Changes and Snecial Experiments Approved No special experiments or additional facility changes wen: approved during this period.

1 R

a Section 6 -

' Radioactive Effluent Release.

60ftahc1-The major direct release to the environs is Argon-41,roduced during normal operations. Very i small amounts of other gases may be released from irradiatec materials in experiments.

Releases are computed based on original estimates at point of origin within the facility and taking only dilution into account. Since much of the release is i.'om operation of the pneumatic transfer system for samples, this is a conservative esiimate in that assumption is made that all use of the PT is at full steady state power level (250 kwatts) when, in fact, some use is with the reactor at a lower power level.-In view of the small numbers involved, and the fact that an integrated dose check is provided by an environmental dosimeter (CaSO4-Dy) hanging directly in the exhaust at the point of .

stack discharge, it is considered unnecessary to provide further checks of these estimates. The dosimeter data confirm that an individual standing diiectly in the exhaust flow for one year would receive an additional submersion dose from the exhaust less than the reliability limit of the dosimeters, or less than 20 mrem per year. The dosimeter data are presented separately in Section 7, Table IV.

Over the years that data have been collected, the accumulated exposure at the exhaust location have been lower than for " control" points because oflower masses of concrete structures in the vicinity. In fact the data have been consistently at 20 25 mrem per year background level, so confidence of

, exposure less than 5 mrem over background seems possible.

3 Release estimates based on operational parameters are as follows:

(1) Operation of pneumatic transfer system (7/1/96 6/30/97): -3 466.6 minutes -

a. Minutes of operation:

b. Release rate assumed: 6. x 10-8 microcuries/ml 8

c, Flow rate of exhaust air: 1.2 x 10 ml/ min 3

Total miease computed:(a x b x c) = 3.4 x 10 microcuries (2) Release from pool surface (7/1/96-6/30/97):

a. Total hours of operation at power (Mwh x 4) = 58.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />

) b. Release rate assumed: <l. x 10-8 microcuries/mi 8

c. Flow rate of exhaust air: 1.2 x 10 ml/ min 3

Total mlease computed:(a x 60 x b x c) = 4.2 x 10 microcuries 3

. Total of (1) and (2) emission in 1 year = 7.,6 x 10 microcurles Concentration averaged over 12 months = < l.2 x 10-10 microcuries/ml This is similar to values reported in previous years and assumes no dilution cf the plume at the stack.

1

, - - - - - - ,,,ay.,- p - y -:e-o y,mam

i i e' ,

(b) Ltquids and Solids. '!

.1' Liquid and solid wastes from utilization of by-product materials are disposed through a

. University contract. Waste is transferred to the custody of the Campus Environmental Health and Safety Office (Ell &S). Direct disposals from this facility are given below. It is important to note that activity values are estimated at the time of transfer to EH&S control. In all instances, considerable time elapses before final shipment from campus, if, any, so that substantial decay may occur for medium-lived radionuclides.

DRY WASTES:

2 ft 3box--> 24Na and mixed activation products with < 01 mci on 7/2/96.

2 ft 3box---> 24Na and mixed activation products with <0.01 mci on 3/9/97 LlQUIDS: none disposed during this period.

Section 7.

Environmental Sun:21ance.

Calcium sulfate / Dysprosium thermoluminescent dosimeters in packs supplied by the Radiation Detection Company, Sunnyvale, California are placed at nine locations around the UCI Campus. One #

pack is kept on the edge of campus in a wood frame house in University Hills. In fact, the average of the more remotely located " concrete environment" packs on campus is ud as the background for comparison purposes, since a more similar microenvironment is experienced by such packs.

Table of Locationi

1. Window of reactor room east wall (inside the facility). ';

2. In hallway on exterior of south wall of facility.

3. Loading dock, adjacent to west wall of reactor room.

4. Laboratory 152, directly over reactor facility, approximately over core center.

5. In roof exhaust air flow from reactor room, roof level (hung in center of duct at final release point).

6. Biological Sciences 2 building 5th floor, laboratory near window *,

7. Main library building across campus,5th fbor office in sunny window

8. Computer Science building,4th floor office, in shaded window.

9. Fume hood exhaust, roof level, from reactor laboratory (hung in center of duct).

10.12 Perkins Court, University Hills, private residence (wood frame house).

• The location of this dosimeter was moved on October 31991, following occupancy of the new BS2 building which is closer to the reactor than the older building.

. _ . . = - - -. _ - .

l

. , . f

. Table IV shows the data as received from RDC for the period. Alllevels are as expected and are similar to those reported in recent years. As noted before, areas (1) and (2) are also partly controlled so that maximum possible exposure to an individual in an uncontrolled area is very minimal at this facility with current operations. The air released from the facilitf (measured by locations #5 :o:d

1. 9) continues to give no detectable exposure above background for dos. meters immersed in it.

Location 7 consistently shows higher readings presumably because it is in a window above a warm, outside, cement wall. Over many years, the data at each specific location show remarkable consistency. An appreciable change would be easily noticeable.

TABLE IV.

Environmental Dosimetrv Data.

1996-1997 Average Exnosures in mr.

I ocation. Ouarter Annual Total less 2/96 3/96 4/96 1/97 Intal background (26t 22) 1 4 2 3 1 10 0 2 8 6 6 3 23 0 3 9 7 9 5 30 4 4 7 4 6 2 19 0 5 3 2 2 0 7 0 6 5 3 5 2 15 0 7 16 J3 18 11 58 32 8 3 0 2 0 5 0 9 5 4 5 2 16 0 10 2 0 0 0 2 0 Average of locations 6,7, and 8 used for " background" ( = 26)

l Section 8.

Epdiation Exposure to Personnel.

The annual exposures reponed as a result of finger dosimeter ring and film badge desimetry are presented in Table V. No exposures have been reported for individuals involved in fr.ility operations.

liight (8) persons were monitored on a continual basis using Olm badges, and all of these were also issued with hnger dosimeter rings. These were required to be worn while handling isotopes. Film badges were penerally worn at waist level by all personnel. --

Certain additional monitoring is done of visiting individuals who are issued with direct reading pocket dosimeters in addition to Olm badges and finger dosimeter rings.

Contamination surveys consisting of wipe tests and G-M surveys have shown significant, removable contamination only in areas coming into direct contact with samples removed from the reactor, and on sample handhng tools.

TABLE V.

Personnel Exposure Summary for 5/1/96 to 4/30/97 (in mrem)

Ind1Ehlaals Whole Body Finger Ring i Deep Shallow Shallow t

i 15 60 '

420 1 55 0 0 17 0 0 0 48- 0 0 0 (Students in class) l Totals 5 5 5 0 Additional aggregated data from self reading pocket dosimeters issued to researchers:

1 9 (3 visits) 1 24 (5 visits)

.