ML20215C293
| ML20215C293 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 09/29/1986 |
| From: | Fiedler P GENERAL PUBLIC UTILITIES CORP. |
| To: | Zwolinski J Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-3.D.3.4, TASK-TM NUDOCS 8610100216 | |
| Download: ML20215C293 (8) | |
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GPU Nuclear Corporation NUOIM7 100 Interpace Parkway Parsippany. New Jersey 07054-1149 (201)263-6500 TELEX 136-482 Writer's Direct Dial Number:
September 29, 1986 Mr. John A. Zwo11nski, Director BWR Licensing Directorate #1 Division of BWR Licensing U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Zwolinski:
Subject:
Oyster Creek Nuclear Generating Station Docket No. 50-219 Control Room Habitability (NUREG-0737, Item III.D.3.4)
Results of Control Room HVAC System Test In accordance with the interim system upgrades for the Control Room Habitability at Oyster Creek, GPU Nuclear (GPljN) has determined the most limiting infiltration rates which would apply to the chlorine and radiological release scenarios. Af ter perfonning corrective maintenance, a test was conducted to demonstrate the capability of the Control Room HVAC system to maintain a minimum positive pressure of 1/8 inch water gauge in the Control Room Envelope, and to determine the infiltration flow rates. The test was conducted with the HVAC system in the partial and full recirculation modes of operation.
In the full recirculation mode of operation (chlorine release) the l
infiltration rate was measured to be slightly less than 960 cfm.
For the partial recirculation mode of operation (radiological), the total measured makeup plus infiltration air flow was 1830 cfm.
For both modes of operation, the Control Room envelope was held at a minimum of 1/8 inch water gauge positive pressure.
The results of these tests have required a revision to the toxic gas (August 16, 1985) and radiological (June 17, 1985) analyses previously submitted to the staff which were perfonned using the original system design of 450 cfm minimum makeup air.
The intent of the original system design was l
to provide a minimum of 450 cfm makeup air for pressurization and air I
replacement purposes rather than to restrict the infiltration rate to a maximum of 450 cfm. Changes to the previous analyses are described hereinaf ter, with the results from the investigation of potential offsite toxic gas sources.
1 P
j i
A GPU Nuclear Corporatio iis a subsidiary of General Public Utilities Corporation
Mr. John A. Zwolinski, Director USNRC Page 2 CHLORINE GAS TRANSPORT ANALYSIS The chlorine gas transport analysis was reanalyzed considering the above HVAC operating parameters for the two previously submitted chlorine release accidents: the break of a 3/8 inch diameter chlorine transfer tubing line and the rupture of a one ton chlorine tank. These release scenarios were considered to be the limiting Oyster Creek chlorine accidents. The calculational results of the 3/8 inch tubing line break are resubmitted as Table 1.
Likewise, the results from the one ton chlorine tank rupture accident are resubmitted as Tables 2 and 3.
The reanalysis of the 3/8 inch tubing line break showed that at infiltration rates up to 1100 cfm, for all wind speeds and stability classes analyzed, either the toxicity limit of 15 ppm is never reached in the control room or the operators have greater than two minutes af ter receiving the alann to don protective breathing apparatus. Therefore, it was still concluded that for a 3/8 inch chlorine tubing line break, the control room would be habitable and the operators would be adequately protected.
The results of the chlorine tank rupture analysis showed that at infiltration rates up to 680 cfm, for all wind speeds and stability classes analyzed, either the toxicity limit of 15 ppm is never reached in the control room or the operators have greater than two minutes af ter receiving the alann to don protective breathing apparatus. For infiltration rates from 680 cfm to 1000 cfm, the operators have less than two minutes to don protective breathing apparatus only for wind speeds of 2.24 and 3.40 mph in stability classes A and B.
At Oyster Creek, the meteorological data show that this combination of wind speed and stability class occurs approximately 0.31% of the time. GPUN takes the position that the probability of this chlorine accident occurring simultaneously with those infrequent meteorological conditions would be sufficiently low that this scenario may also be disregarded.
Therefore, it was concluded that for a chlorine tank rupture the control room would be habitable and the operators would be adequately protected.
RADIOLOGICAL ANALYSIS The radiological analysis was revised to determine the effect of higher intake rates on the 30-day gamma whole-body and beta skin doses to the operators.
All assumptions and data other than the intake flow rate remain unchanged from those provided to the staff in our June 17, 1985 letter.
The results are presented as follows:
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s Mr. John A. Zwolinski, Director USNRC Page 3 FLOW RATE 30 DAY DOSE (REM)
(cfm)
Gamma Beta 1500 3.05 27.9 2000 3.07 28.2 All of the above doses are less than the S.R.P. 6.4 limits of 5 rem and 30 rem for gamma and beta doses respectively. Although the intake rate has increased by as much as a factor of 4, the doses have not increased in the same proportion.
The reason for this is that when the inflitration is increased, the exfiltration from the control room envelope increases at the same rate, thereby having only a small effect on the isotopic concentrations in the control room at any time over the 30 day period. The slightly increased concentrations produce slightly increased doses to the operators; however, the control room will remain radiologically habitable for 30 days following a design basis LOCA.
OFFSITE T0XIC GAS ANALYSES In letters dated October 8 and 19, 1982, GPUN advised the NRC of the offsite manufacturing, storage and transportation of hazardous chemicals within a 5 mile radius of the plant.
Subsequently, as a result of the NRC/GPUN meeting of March 19, 1985, GPUN has reviewed two potential transportation sources of hazardous chemicals, and has analyzed the effects of these offsite gas releases upon control rocm habitability.
The two offsite scenarios investigated were a chlorine truck transport accident and a natural gas pipeline rupture.
It was assumed that a truck carrying a one ton tank of chlorine either on Route 9 or the Garden State Parkway is involved in an accident which causes the chlorine tank to rupture.
The analysis was performed using the heavier-than-air modification to the " VAPOR" computer code for a postulated offsite accident 423 meters from the control room HVAC outside air intake with the HVAC system, in the normal operation mode.
The results of the " VAPOR" runs indicated that chlorine concentrations could reach as high as 0.2 g/m' (66.7 ppm) with the HVAC system in the normal operation mode.
However, a calculation was performed to determine the probability of the truck accident occurring simultaneously with the meteorological conditions which would produce the 0.2 g/m' chlorine concentration in the control room.
This evaluation considered the probability of a severe truck accident (1.29x10-* accident / truck mile, taken from 3952f
Mr. John A. Zwolinski, Director USNRC Page 4 NUREG/CR-2650), the frequency of chlorine shipments near the site (20/ year),
the length of road traveled within five miles of the site on both Route 9 (11 miles) and the Garden State Parkway (10 miles), and the frequency of winds within 22.5 dg sectors that could transport a release toward the site. Using 1982 and 1983 meteorological data from section 2.3 of the FSAR, which is representative of the general climatic conditions at OCNGS, the highest probability of an operator incapacitation due to a truck accident near the site is 1.7x10" incapacitation per year, which is well below the minimum probability criterion of 1 x10" per year given in Standard Review Plan 2.2.3.
Therefore, it was concluded that in light of the low probability of this accident incapacitating the operators, the operators are adequately protected against an offsite chlorine release accident.
A postulated natural gas pipeline rupture at the discharge canal was analyzed using " VAPOR" in a manner similar to the 3/8 inch chlorine pipe break accident. A release rate of 5248 grams /second was assumed to occur for a one hour time period which, according to the New Jersey Natural Gas Company, is the time it will take to isolate the leak and manually stop the flow of gas.
Again, since this is an offsite accident, the control room HVAC system was assumed to be operating in the normal mode.
Other assumptions and input parameters used in the analysis were as follows:
o The control room fresh air intake is conservatively assumed to be located at ground level.
o The wind direction is such that the centerline of the plume at ground level blows directly toward the outside air intake.
o Pasquill Stability Class G (extremely stable) coupled with a horizontal wind speed of 1.12 mph (0.5 m/s) is assumed.
The results of the analysis indicated that the maximum natural gas concentration within the control room from this pipeline rupture was 42.5 g/m'.
Since this concentration is well below the toxicity limit of 157.1 g/m', a rupture in the natural gas pipeline would not jeopardize the habitability of the Oyster Creek control room.
TECHNICAL SPECIFICATIONS By Amendment 105, GPUN was required to propose appropriate Technical Specifications for the chlorine detection and Control Room HVAC minimum inleakage for the completion of the Interim system upgrades before the restart from Cycle 11 refueling outage.
Subsequent to the issuance of this amendment, GPUN has decided to replace the Fischer & Porter liquid chlorine gas system with a sodium hypochlorite storage and feed system by the Spring of 1987.
This schedule would allow the implementation of this modification during the winter months when the liquid chlorine system is not required.
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e Mr. John A. Zwolinski, Director USNRC Page 5 Since sodium hypochlorite is a relatively stable chemical at ambient temperatures and atmospheric pressure, the justification for implementing appropriate Te::hnical Specifications would no longer be valid. Therefore, in light of this decision, GPUN is proposing the deletion of the Technical Specification requirements for the chlorine storage, and in their place, control the liquid chlorine gas storage and usage through the plant procedures until the tanks are removed. These plant procedures provide for Control Room HVAC full recirculation (Proc. 331), prior to chlorine transport or cylinder change-out (Proc. 326), and in response to a Control Room alarm (Proc.
2000-ABN-3200.33) from a toxic gas release at the chlorination facility.
The Control Room HVAC system is also used to limit the dose rates to the operators following a LOCA.
Since this function is still required to complete the interim measures, GPUN will propose prior to Cycle 11 restart, appropriate limiting conditions for operation and surveillance requirements for the Control Room HVAC system.
If you have any questions regarding this information, please contact M. W.
Laggart, Manager, BWR Licensing at (201)299-2341.
Very truly yours, P
Vice President and Director Oyster Creek PBF/0J/pa(3952f) cc: Dr. Thomas E. Murley, Administrator Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA.
19406 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, N.J.
08731 Mr. Jack N. Donohew, Jr.
U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20014 3952f
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TABLE 1 TIME AFTER 3/8 INCH LINE BREAK OCCURS WHEN OCNGS CONTROL ROOM CHLORINE CONCENTRATIONS EXCEEDS THE 15 ppm (0.045 g/m) T0XICITY LIMIT (
Stability.
Horizontal Wind Speed Flow Rate Class 1.12 mph 2.24 mph 5.59 mph-11.12 mph 1000 cfm A
(2) i B
C 231 sec 290 sec (2)
(2)-
l 1100 cfm A.
149 sec -122 sec 182 sec (2) k B
C 223 sec 268 sec (2)
(2) j 1200 cfm A
149 sec 115 sec(1) 167 sec (2)
C 215 sec 252 (2)
(2)
(1) Less than the 120 sec operator response time as required by Regulatory Guide 1.78.
' ~
.(2) Based on the time it takes for all of the chlorine to be discharged from the. tank (i.e., approximately 5 minutes), to the time it takes ~for the
^'
end of the plume to pass by the air intake, this meteorological / infiltration rate combination results in a chlorine concentration inside the control room of less than 15 ppm.
(3) A modified version of SWEC computer program " VAPOR" was used in analyzing the release of chlorine from a hypothesized 3/8 inch tubing line break occurring at the onsite chlorination facility.
The modified " VAPOR"
^
program follows the same methodology as described in GPUN's-August 16, l
1985 submittal, with the exception of the program's capability to handle a chemical released at a constant discharge rate.
For the 3/8 inch pipe break analysis, the rate of 11guld chlorine discharged has been calculatedtobe3,093gramspersec,andwillcontinueatthisrate; until the entire one ton inventory of liquid chlorine contained in the
~
+
supply tank has been exhausted.
l 3952f
,. ~
5 s
TABLE 2 Time (sec) after 2000 lb instantaneous chlorine cylinder rupture when OCNGS control room chlorine concentration exceeds the 15 ppm (0.045 g/m') toxicity limit.
Flow Stability Horizontal Hind Speed (mph)
Rate (cfm)
Class 1.12 2.24 3.40 5.59 11.12 500 A
147 281 B
156 545 C
661 600 A
137 164 654 B
145 273 C
288 700 A
131 115(1) 359 B
137 163 897 C
178 800 A
127 94(1) 221 B
133 112(1) 451 C
155 900 A
125 84(1) 148 B
129 92(1) 278 C
146 1,000 A
123 78(1) 107(1) 741 B
128 83(1) 181 C
141
- Did not exceed toxicity limit at any time.
(1) Exceeds toxicity limit prior to time required to don SCBAs.
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. 3 TABLE 3 Meteorological conditions conducive for exceeding toxicity limit in less'than 120-seconds as a function of flow rate.
Frequency of Occurrence for Flow Rate - 1000 cfm Meteorological conditions 1.12 2.24 3.40 5.59 11.12 A
X X
B X
.31%
C D-F Flow Rate - 900 cfm 1.12 2.24 3.40 5.59 11.12 A
X B
X
.31%
4 C
~
D-F o
Flow Rate - 800 cfm 1.12 2.24 3.40 5.59 11.12 A
X B
.23%
C D-F 4
Flow Rate - 680 cfm
's l.12 2.24 3.40 5.59 11.12 i
A A
B
.00%
C D-F x - Exceeds toxicity limit within 120-seconds.
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