ML13333B428
| ML13333B428 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/09/1986 |
| From: | Dudley R Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TASK-3.D.3.4, TASK-TM NUDOCS 8607180150 | |
| Download: ML13333B428 (29) | |
Text
JUL 0 9 1989 Docket No. 50-206 LICENSEE: Southern California Edison Company (SCE)
FACILITY: San Onofre Nuclear Generating Station Unit 1 (SONGS-1)
SUBJECT:
SUMMARY
OF MEETING ON JUNE 24, 1986 REGARDING CONTROL ROOM HABITABILITY REQUIREMENTS On June 24, 1986, a meeting was held between members of the NRC staff and personnel from SCE in Bethesda, Maryland. A list of attendees is provided in. Presentation material used by SCE at the meeting is provided in.
The purpose of the meeting was to discuss the control room heating, ventilation and air conditioning (HVAC) system at San Onofre Unit 1 and requirements for control room habitability.
A recent inspection at San Onofre Unit 1 raised concerns about the capability of the control room HVAC system to limit, in the event of a radiological emergency, the thyroid dose to the control room operators. By letter dated June 2, 1986, SCE provided a submittal describing the HVAC system, recent repairs and improvements on the system, and calculated thyroid doses.
Based on the staff's review, a set of criteria considered acceptable to support plant restart were developed.
At the meeting, the licensee discussed the actions they have taken to satisfy the criteria, the test program being performed to validate analysis assumptions and their calculations of dose to control room operators following a postulated accident. In the first part of the presentation, the licensee discussed the models used to calculate thyroid doses as compared to the methods being used by the staff. Initially, there was some difficulty reconciling the staff and licensee analyses; it was finally determined that the source term used by the staff had included a contribution from purging of containment. At present, the purge valves are locked closed and hydrogen control is through the use of recombiners; thus, this term does not need to be included.
E3607180150 860709 PDR A DOC09 P
DOCK 05000206 PDR
-2 Repairs and other improvements have been made to the HVAC system to reduce the inleakage. Following these modifications, testing was performed. Pressure tests with various modes of fan operation were conducted to determine if a positive pressure of at least 1/8" water gauge could be maintained in the control room envelope with positive respect to adjacent boundaries. Measurements were also made of inleakage of air into the control room return air ductwork. Flow tests were in progress with completion scheduled for June 27.
The pressure and flow tests will be repeated on a 6 month +/-30 day interval.
The licensee stated that the test results showed that the control room is maintained at a positive pressure with respect to adjoining areas.
The return duct inleakage, assuming a pressure of 0.65 inches water (negative), was 245 cubic feet per minute (cfm).
The licensee presented revised dose assessments which showed that for an assumed inleakage of 1200 cfm, 8.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of exposure per shift, and three crew shifts per day, thyroid dose to the operators would be limited to 30 rem over the 30 day period after the postulated event. This dose is based on use of respirators during the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> of the accident and thyroid blockage with potassium iodine (KI) pills thereafter. This analysis assumed a filter efficiency of 99% for particulates and adsorber efficiencies of 95% and 90% for elemental and organic forms of radioiodine respectively.
Each of the parts of the staff criteria were then discussed.
Habitability System Criteria for Plant Restart
- 1. Charcoal adsorber efficiency.
The staff position was that flow through the control room emergency filtration unit (A-33) should be limited to 1000 cfm +/- 100 for all combinations of the technical support center (TSC) ventilation system operation. The licensee noted that the flow through A-33 ranged from 920 cfm to 1000 cfm during the tests.
The staff also proposed that laboratory testing of the charcoal beds be performed at a temperature of 300C, relative humidity of 95% utilizing ASTM D-3803-1979 test procedure with an allowable penetration of 0.7%
for methyl radioiodine. Using the guidance of Regulatory Guide 1.52, the charcoal could then be credited with 95% removal efficiency for organic radioiodine. This includes a safety factor of 7 to account for degradation of the charcoal between tests.
The licensee reported that the laboratory tests under the above conditions, with plant-specific residence times, showed a penetration of 5.1%. Using the safety factor for systems without relative humidity control, this would correspond to an assumed adsorber efficiency of 65%. It appears that because of the short residence time for the SONGS-1 adsorber, higher efficiency may not be obtainable. The licensee noted that even with an adsorber efficiency of only 30%, the doses would still meet the 30 rem limit if the inleakage was less than about 800 cfm.
-3 The staff concluded that the licensee should submit a Technical Specifica tion change incorporating the 95% efficiency (5% allowable penetration) charcoal testing requirement. The analysis to support the Technical Specification change will consider the safety factors discussed in Regulatory Guide 1.52.
- 2. 30-Day Thyroid Dose less than 30 Rem with credit for respirators and KI pills.
The staff criterion is that the thyroid dose to control room operator over the 30-day period after an accident should be less than 30 Rem. As discussed above, the licensee's calculations show that this can be met.
The licensee stated that even for 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> shifts the dose limits could be met with a lower than the maximum assumed inleakage.
The staff will review the licensee's calculations in the light of all the information presented at the meeting concerning adsorber efficiency, inleakage and shift changes in order to assess the doses.
- 3. Positive Pressure in the Control Room.
The staff position was that the control room should be maintained at
+1/8 inch (water) differential pressure with respect to all adjoining areas, considering all ventilation modes. The licensee proposed at the meeting to satisfy + 1/16 inch pressure, with periodic verification every 6 months. The results of the testing showed that the limiting adjacent boundary with respect to maintaining a positive differential pressure is the adjoining TSC, which is also pressurized with respect to the outside.
The staff responded that the minimum value should be 1/10" with respect to adjoining areas. This issue remained open at the end of the meeting.
- 4. Periodic verification of unfiltered inleakage values.
The staff criterion was that the inleakage values assumed in the analysis should be periodically verified. The licensee proposed an inleakage retest every refueling outage, because the HVAC system must be taken out of operation to perform the test. The staff recommended that flow balance tests be conducted every six months as a means to monitor for any degradation over the cycle. The licensee agreed and this item was considered closed.
TMI Action Plan Item III.D.3.4 The staff and licensee also discussed TMI Action Plan Item III.D.3.4, Control Room Habitability. This issue is still open for San Onofre Unit 1. The staff requested the licensee to select a final design alternative for upgrades responsive to the III.D.3.4 requirements and to provide their
-4 proposal to the staff as soon as possible. The staff also noted that certain staff decisions regarding modifications necessary to satisfy thyroid dose requirements under III.D.3.4 (with no credit for respirators and KI pills) have been in abeyance for some plants in anticipation of changes to the source term and thyroid dose conversion factors.
SUMMARY
The licensee agreed to submit the following information by June 30, 1986.
o dose assessment assuming inleakage of 250 cfm; adsorber efficiency to be selected considering the issue discussed under item (1) above.
o dose assessment assuming inleakage of 250 cfm without credit for respirators and thyroid blocking pills.
o dose assessment assuming 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> shifts.
o the results of the tests for inleakage, pressure and flow balance.
o emergency procedures on respirator use and KI pill administration.
o a commitment to modify the Technical Specifications on charcoal testing.
O the results of inspections of the TSC ventilation system, including a schedule for completion of improvements.
0 a summary of all of the modifications/repairs made to the control room HVAC over the last two months.
In addition, the licensee agreed to provide a more detailed submittal addressing TMI Item III.D.3.4 by September 1, 1986. This submittal will include conceptual configurations of the design modifications, flow rates, dose projections based on both current source terms and with new source term and/or thyroid dose conversion factors. Toxic gas considerations will also be addressed.
Richard F udley, Project Manager Project Directorate #1 Division of PWR Licensing-A Office:.
A/PA#
PM/ A P
PD/PAD#1 Surname:
PShuttleworth RDudley/tg E cKenn GLear Date:
6/T/86 0/< /86 0/2/86 4/7/86
Distribution Copies:
Docket No 50-206(s)
NRC PDR Local PDR PAD#1 r/f PAD#1 p/f TNovak, Actg. DD NThompson, DHFT ELD EJordan BGrimes JPartlow GLear RDudley PShuttleworth ACRS (10)
ENCLOSURE 2 CONTROL ROOM HVAC DESIGN SAN ONOFRE UNIT I DOCKET NO. 50-206 SOUTHERN CALIFORNIA EDISON
SONGS I CONTROL ROOM HVAC PRESENTATION
- 1.
OBJECTIVE II.
COMPARISON LOCA DOSE AND MURPHY-CAMPE DOSE ASSESSMENT Ill.
HVAC TEST PLAN AND STATUS IV.
REVISED DOSE ASSESSMENT V.
COMMITMENTS/CONCLUSIONS 2
- 1. OBJECTIVE I.
COMPARE AND RECONCILE DOSE ASSESSMENT II.
REACH AGREEMENT ON METHODS AND ASSUMPTIONS FOR FINAL DOSE EVALUATIONS Ill.
DISCUSS CURRENT TEST PROGRAM AND RESULTS IV.
DISCUSS CURRENT DOSE ESTIMATES V.
FINALIZE BASIS FOR RETURN TO SERVICE 3
II. COMPARISON - LOCA DOSEMlMURPHY-CAMPE METHODS SOURCE MODEL - IODINE CONCENTRATION AT CONTROL ROOM HVAC INTAKE o
THYROID DOSE MODEL - DOSE AT CONTROL ROOM HVAC INTAKE o
OCCUPANCY MODEL - DOSE AT CONTROL ROOM HVAC INTAKE o
CONTROL ROOM HVAC MODEL - DOSE IN CONTROL ROOM 4
SOURCE MODEL o
SOURCE MODEL CONSIDERS CORE RELEASE, CONTAINMENT LEAKAGE, SPRAY EFFECTS, SI RECIRCULATION LEAKAGE AND X/0, TO PREDICT IODINE CONCENTRATION AT CONTROL ROOM INTAKE o
COMPARISON OF LOCA
- DOSE, MURPHY-CAMPE AND REGULATORY GUIDE 1.4 SHOW COMPARABLE METHODOLOGY o
EXPECT SIMILAR CONTROL ROOM INTAKE IODINE CONCENTRATIONS, BUT POSSIBLE DIFFERENCE ARE X/O; CONTAINMENT LEAKAGE; SPRAY EFFECT, AND CORE AND RECIRCULATION SOURCE o
AVERAGE ISOTOPIC CONCENTRATION AT CONTROL ROOM INTAKE USING LOCA DOSE IS AS FOLLOWS:
AVERAGE CONCENTRATOIN (Cl/CC) AT THE CONTROL ROOM INTAKE)
ISOTOPE 0-8 HR 8-24 HR 24-96 HR 96-720 HR 1-131 3.55E-1 I 2.04E-II I.I0E-I I 1.15E-12 1-132 2.10E-1 I 5.28E-13 3.90E-16
-0 1-133 5.95E-1 I 2.39E-I I 4.36E-12 1.53E-14 1-134 I.73E-1 I 6.36E-15
-0 1-135 4.58E-1 I 8.17E-12 2.64E-13
-0 5
THYROID DOSE MODEL CONSIDERS AIRBORNE IODINE CONCENTRATION AT CONTROL ROOM INTAKE FROM SOURCE MODEL AND CALCULATES THYROID DOSE WITHOUT CONSIDERING CONTROL ROOM HVAC OR OCCUPANCY FACTORS COMPARISON BETWEEN LOCA DOSE AND MURPHY-CAMPE SHOWS SIMILAR METHODOLOGY EXPECT SIMILAR DOSES, BUT POSSIBLE DIFFERENCES ARE THYROID DOSE CONVERSION FACTORS LOCA DOSE OPERATOR THYROID DOSE AT CONTROL ROOM INTAKE, ASSUMING CONTINUOUS OCCUPANCY FOR 0-30 DAYS WITH NO CREDIT CONTROL ROOM HVAC, RESPIRATOR OR IODINE PILLS IS:
CONTAINMENT LEAKAGE 2,565 REM SI RECIRCULATION LEAKAGE 1,821 REM TOTAL 4,386 REM 6
OCCUPANCY DOSE MODEL OCCUPANCY DOSE MODEL CONSIDERS THYROID DOSE MODEL RESULTS AND INCLUDES OCCUPANCY FACTOR, RESPIRATOR, AND KI PILL USAGE TO CALCULATE THYROID DOSE AT INTAKE o
LOCA DOSE USES PLANT SPECIFIC OCCUPANCY FCTOR WHILE MURPHY-CAMPE USES A SUGGESTED OCCUPANCY o
LOCA DOSE OPERATOR THYROID DOSE AT CONTROL ROOM HVAC INTAKE WITHOUT CREDIT FOR CONTROL ROOM HVAC ASSUMING SHIFT CHANGES, RESPIRATOR, OR IODINE PILLS USED ARE:
CONTAINMENT LEAKAGE 31 REM SI RECIRCULATION LEAKAGE 21 REM TOTAL 52 REM 7
INTAKE FILTER CONTROL ROOM UNFILTERED LEAKAGE EXHAUST CONTROL ROOM MODEL
CONTROL ROOM MVAC MODEL CONTROL ROOM HVAC MODEL CONSIDERS "OCCUPANCY MODEL" DOSE RESULTS AND INCLUDES EFFECT ON INTAKE FILTER EFFICIENCIES, FILTERED FLOW AND UNFILTERED IN-LEAKAGE RATES, TO CALCULATE CONTROL OPERATOR THYROID DOSE LOCA DOSE AND MURPHY-CAMPE ARE EQUIVALENT METHODS CRITICAL MODELING PARAMETERS (EXPECTED DIFFERENCES)
IODINE SPECIES DISTRIBUTION (ELEMENTAL, ORGANIC, PARTICULATE)
UNFILTERED IN-LEAKAGE RATE FILTER EFFICIENCY FOR EACH IODINE SPECIES
PREVIOUSLY SUBMITTED (JUNE 2, 1986) o LOCA DOSE RESULTS WITH CORRECTED X/O FILTER EFFICIENCIES 95%
(ELEM)/95% (ORG)/99% (PART),
1,100 CFM FILTERED INTAKE, 290 CFM UNFILTERED IN-LEAKAGE WAS:
7.3 REM CONTAINMENT 5.1 REM RECIRCULATION 12.4 REM THYROID 9
III.
HVAC TEST PLAN AND RESULTS o
HVAC DESIGN o
EMERGENCY FILTRATION MAKEUP UNIT FLOW MEASUREMENT o
TEST PROGRAM IN-LEAKAGE FLOW AND PRESSURE o
TEST RESULTS 10
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HVAC TEST PROGRAM IN-LEAKAGE TESTING EVALUATES THOSE PORTIONS OF CONTROL ROOM DUCTING, DAMPERS, A-31 UNIT HOUSING, AND A-33 UNIT HOUSING THAT COULD HAVE NEGATIVE PRESSURES FOLLOWING SLIDE ILLUSTRATES TEST CONFIGURATION TESTING TO VALIDATE DOSE ASSESSMENT IN-LEAKAGE ASSUMPTIONS AND WILL BE REPEATED EACH REFUELING STAGE 12
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IV. REVISED DOSE ASSESSMENT WHAT WAS DONE INCLUDE INGRESS/EGRESS/TOILET BREAKS IN MODEL 15 MINUTES IN AND OUT 30-MINUTE TOILET BREAK AT SHIFT START EXCEPT FIRST SHIFT FIRST SHIFT TOILET BREAK AT 4 HOURS RESPIRATOR DURING TOILET BREAK KI PILL CREDIT INGRESS AND EGRESS THREE SHIFTS PER DAY (6 AVAILABLE CREWS) 14
FILTER EFFICIENCY CASE:
95% (ELEM)/90% (ORG)/99% (PART)
BASIS SONGS I TEST RESULTS.
INCLUDED PLANT-SPECIFIC SHIFT CHANGE DATA 15
o RESULTS OF REVISED DOSE ASSESSMENT FILTERED INTAKE 1,100 CFM UNFILTERED IN-LEAKAGE 1,200 CFM FILTER EFFICIENCIES 95/90/99 OPERATOR THYROID DOSE (REM)
CREW SHIFT SCHEDULE DOSE I
1, 4, AND INTERMITTENT THROUGH 30 DAYS 29 2
2, 5, 8 AND INTERMITTENT THROUGH 30 DAYS 28 3
3, 6, 9, 11, AND IMTERMITTENT THROUGH 30 DAYS 29 4
7 AND REGULAR 7 DAYS ON, 2 DAYS OFF 29 5
13 AND REGULAR 7 DAYS ON, 2 DAYS OFF 15 6
28 AND REGULAR 7 DAYS ON, 2 DAYS OFF 10 16
V.
COMMITMENTSICONCLUSION o
COMMITMENTS NRC CRITERIA 1, 2 AND 4 ARE MET AND POSITIVE PRESSURE IN THE CONTROL ROOM (CRITERION 3) IS
+1/16 INCH W.G.
NRC ACCEPTANCE CRITERIA SONGS I RESTART COMMITMENT A-33 FLOW LIMITED TO 1,000 CFM + 10%
SAME TECHNICAL SPECIFICATION 4.1 I.B.2 CHANGE RESOLVE AFTER START (CHARCOAL TEST) 2 30-DAY CONTROL ROOM OPERATOR DOSE LESS SAME THAN OR EOUAL TO REM WITH CREDIT FOR KI PILLS AND RESPIRATORS 3
CONTROL ROOM +1/8 INCH W.G. WITH RESPECT CONTROL ROOM WILL BE AT LEAST +1/16 INCH TO ALL ADJOINING AREAS, CONSIDERING ALL W.G., RETESTED EVERY 6 MONTHS + 30 DAYS VENTILATION MODES IN-LEAKAGE RETEST EVERY REFUELING 4
PERIODICALLY VERIFY UNFILTERED IN-LEAK-OUTAGE AGE VALUES INHERENT IN DOSE ANALYSIS 17
CONCLUSIONS SAN ONOFRE UNIT I POST-ACCIDENT CONTROL ROOM OPERATOR THYROID DOSE CAN BE LIMITED TO 30 REM TESTING OF SAN ONOFRE UNIT I CONTROL ROOM HVAC DEMONSTRATES ADEQUACY FOR RETURN TO SERVICE 18