ML20064C068
| ML20064C068 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/28/1982 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8301040300 | |
| Download: ML20064C068 (9) | |
Text
e e
TENNkSSEE VALLEY AUTHORITY C H AT T A NOOG A. T EN N ESSEE 37401 400 Chestnut Street Tower II December 28, 1982 Director of Nuclear Reactor Regulation Attention:
Ms. E. Adensam, Chief Licensing Branch No. 4 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Ms. Adensam:
In the Matter of
)
Docket No.
50-327 Tennessee Valley Authority
)
50-328 As stated in the Safety Evaluation Report to Amendment 5 of the Sequoyah Nuclear Plant Operating License, DPR-77, TVA agreed to provide a report on the operating experience, as related to purge / vent system operation, no later than startup after the first refueling outage. Enclosed is the report on the operation of the containment purge and venting systems for Sequoyah Nuclear Plant unit i for March and April of 1982.
If you have any questions concerning this matter, please get in touch with J. E. Wills at FTS 858-2683 Very truly yours, TENNESSEE VALLEY AUTHORITY
'l L. M. Mills, Manager Nuclear Licensing i
l Sworn g d subscr ed before me l
this. g M day of 1082 i
Notary Public Gf My Commission Expires / -2:/ -
l Enclosure l
cc:
U.S. Nuclear Regulatory Commission (Enclosure)
Region II Attn:
Mr. James P. O'Reilly Administrator 7f a a r
303 1
l 8301040300 821228 PDR ADOCK 05000327
(
P PDR
o a
ENCLOSURE SEQUOYAH NUCLEAR PLANT (SQN)
CONTAINMENT PURGE STUDY Introduction The operation of the containment purge and venting systems at SQN units 1 and 2 is limited by plant technical specifications to 1,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> per year per unit during modes 1, 2, 3, and 4 using one pair (one purge supply line and one purge exhaust line) of containment purge system lines. The following is a discussion of the surveillance program conducted to ensure the operability of the purge system as well as a discussion of the time required for purging and venting to date and the reasons for purging and venting.
Surveillance Program The Sequoyah purge system utilizes two pairs of 14,000 cfm supply and exhaust fans along with smaller, approximately 800 cfm, supply and exhaust fans for the incore instrument room. All air discharged by this system is filtered before release through a set of filter banks comprised of prefilters, high efficiency particulate filters, and charcoal filters.
These filter banks are tested every 12 months in accordance with ANSI NS10-1975 and verified to remove greater than or equal to 99 percent of particulate and halogenated hydrocarbon test gas.
Each of the ten purge system line penetrations through the containment vessel has inboard and outboard isolation valves that are periodically tested for leakage and closure time. The surveillance program requires the isolation valve (s) to be leak tested following each c" cling of the valve (s) or every 90 days. The valves are tested for closure time following any maintenance on the valves or every 90 days. The performance of the Sequoyah purge isolation valves has to date been excellent with average closure times well below the required four seconds and leak rates well below the limits specified in the plant technical specifications. In addition, testing of the bypass, override, and reset circuits of all systems receiving engineered safety feature (ESP) signals, including the containment purge system, has been completed at Sequoyah. These tests verified that safety feature actuation signals cannot be inadvertently blocked, overridden, or bypassed, and also verified that safety-related equipment would not return to its nonsafety mode upon reset of the ESF i
i signal.
Containment Venting Requirements Sequoyah technical specifications require that primary containment internal pressure be maintained between -0.1 and 0.3 psig relative to the annulus pressure and that primary contair_ ment jnternal pressure be determined to De within these Ibnits at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The need to vent primary containment to maintain the limits giten above results from the slow increase in containment pressure due to the control air bleedoff frem the i
many air-operated valves inaide containment and the changes in annulus pressure due to changes in environmental temperature and barometric pressure throughout the day.
O O
e
. Table 1 provides a listing of the venting time required for Seqttoyah unit 1 for the 31-day period from March 17, 1982, through April 16, 1982.
As indicated in this table, Sequoyah unit 1 is required to vent to release containment pressure an average of 1.69 hours7.986111e-4 days <br />0.0192 hours <br />1.140873e-4 weeks <br />2.62545e-5 months <br /> / day in order to meet technical specification Ifmits. Based on this data, Sequoyah unit 1 will require 617 hours0.00714 days <br />0.171 hours <br />0.00102 weeks <br />2.347685e-4 months <br /> of vent time each year.
Containment Purging Requirements Containment purging is required to reduce the activity levels inside containment and thereby reduce dose to personnel required to enter containment during operation. Ice condenser containments, such as those found at Sequoyah, require significantly more containment entries than other types of containments. This is due to both additional surveillance required by technical specifications and additional inspection and maintenance of the ice condenser s,.rstems.
1 For example, a routine walk-through inspection of the ice condenser is performed three times daily (once ser shift). This walk-through inspection requires entry into containment and entry into the ice condenser itself.
Since the ice condenser is a closed system with only inleakage from the containment as a source of air, a buildup of airborne activity in the ice condenser is extremely difficult to reduce even though the purge system may reduce the levels in containment relatively fast. It is therefore necessary to keep activity levels in the containment as low as possible to prevent any excessive buildup in the ice condenser. Use of air packs during ice condenser inspections is prohibited due to the increased probability of injury to personnel as a result of the face plate fogging.
It should also be noted that use of an air pack impairs an individual's ability to reach the location of certain pieces of equipment as well as his ability to remain in containment for an extended period of time.
Table 2 provides a general breakdown of the 1,313 containment entrie: cade in modes 1, 2, 3, and 4 from March 5, 1982, through April 22, 1982.
l Table 3 provides a listing of the purging time required for Sequoyah unit 1 for a 32-day period from March 17, 1982, through April 17, 1982, in order lo keep containment activity levels below that which would prevent inspection and maintenance. Based on the data in this table, Sequoyah unit 1 is required to purge an average of 3.69 hours7.986111e-4 days <br />0.0192 hours <br />1.140873e-4 weeks <br />2.62545e-5 months <br /> per day to comply with our (TVA) ALARA approach toward occupational exposure; therefore, Sequoyah unit 1 (using a single pair of lines) will require 1,347 hours0.00402 days <br />0.0964 hours <br />5.737434e-4 weeks <br />1.320335e-4 months <br /> per year to see, its purge requirements.
Summary TIA has self-imposed limits on occupational exposure which are below those set forth in Federal standards. We have in the past and will continue to follow the ALARA approach toward occupational exposure both in the design l
and operation of our nuclear plants. In order to achieve our goal of low occupational exposure, Sequoyah will require, as indicated in the above discussion, approximately 1,964 hours0.0112 days <br />0.268 hours <br />0.00159 weeks <br />3.66802e-4 months <br /> total purge time per year (1,347 l
l
0 purging, 617 venting) or 5 34 hours3.935185e-4 days <br />0.00944 hours <br />5.621693e-5 weeks <br />1.2937e-5 months <br /> per day. The present technical specification limit of 1,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> will limit the time Sequoyah can operate in modes 1, 2, 3, and 4 to approximately six months per year.
~
It is our belief that, given our strict ind comprehensive surveillance program and the performance of our system to date, extending the purge and vent capability at Sequoyah will not significantly increase the probability of an offsite release in excess of 10 CFR 100 guidelines.
TABLE 1 VENTING TIME MARCH 17, 1982 T:lROUGH APRIL 17, 1982 Time Venting Date Initiated Hours Open 3/18 1133 0.75 1750 0.83 3/19 0227 0.30 0535 0.50 1100 0.67 1825 0.50 3/20 0305 1.00 3/21 0200 1.25 1745 1.00 3/22 0900 1.00 1608 0.97 3/23 0504 1.00 1415 0.83 3/24 0055 0.70 0925 0.50 3/25 0910 0.50 1210 0.50 3/26 0158 0.75 0923 0.33 1910 0.67 3/28 0612 0.50 1240 0.67 2210 0.50 3/29 0645 0.75 1615 0.75 3/30 0040 1.00 0859 0.97 0000 0.75 3/31 1042 0.83 2350 0.50 4/1 0920 0.73 1507 1.00
TABLE 1 (cont'd)
Time Venting Date Initiated Hours Open 4/2 1223 1.00
~
2255 1.00 4/3 0727 1.68 4/4 0025 0.75 1057 0.83 1742 1.00 4/5 0622 0.75 1233 1.02 1810 0.50 4/6 1223 0.78 1555 0.42 1850 0.67 4/7 0250 0.50 0810 0 33 4/8 0906 1.13 1815 1.00 4/9 0205 0.75 0.77 1212 2205 0.58 4/10 0634 0.68 l
1414 0.90 4/11 1251 0.47 1733 1.00 4/12 0310 0.50 1110 0.50 1422 0.50 1900 0.50 l
4/13 0400 0.50 1300 0.50 4/14 0845 0.50 1325 0.50 2030 0.50 4/15 0120 0.50 1000 0.50 1400 1.00 g
-a ry
.=
~
TABLE 1 (cont'd)
Time Ventir.g Date Initiated.
Hours Open 4/16 0030 0.50 0835 0.50 1458 1.00 4/17 0130 0.42 0912 0.50 1710 1.00 TOTAL 52.43 I
AVERAGE 1.69 hrs / day" i
O l. _. - - _. _ _ _. _ _ _. _ _ _ _ _. _ -.. _. _ _ _,. _ _ _.,
TABLE 2 CONTAINMENT ENTRIES MODES 1 THROUGH 4 MARCH 5,1982 THROUGH APRII. 22, 1982 Number of Entries Reason 379 Maintenance 314 Health Physics Inspection 196 Surveillance Requirements 155 Quality Assurance 144 Ottice of Power Stores 78 Instrument Maintenance Janitors 17 4
Security 26 Others s
_ _. _ _. ~ _ _. _ _. - _ _ _ _
TABLE 3 PUR0ING TIME MARCH 17, 1982 THROUGH APRIL 17, 1982 Date Time Initiated Hours Open Compartment 3/17 1003 4.33 1705 11.67 3/20 1105 2.12 1338 2.52 1800 2.17 2015 1.17 3/24 1130 5.00 1755 4.00 3/27 0210 7 33 0952 6.18 3/30 1100 6.50 1730 4.00 4/2 0010 4.33 1335 5.00 4/6 0005 4.67 0716 3 23 1434 0.67 1650 0.17 4/7 1050 2.92 1610 7.50 4/8 0005 4.66 4/10 1900 5.00 4/11 0000 1.08 0105 5 33 0658 3 13 4/13 1345 4.00 1900 6.00 4/14 0300 2.50 i
4/17 2300 1.00 TOTAL 118.18 AVERAGE 3 69 hours7.986111e-4 days <br />0.0192 hours <br />1.140873e-4 weeks <br />2.62545e-5 months <br /> / day l
i
__