ML20154P382
| ML20154P382 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/21/1988 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20154P354 | List: |
| References | |
| NUDOCS 8810030043 | |
| Download: ML20154P382 (10) | |
Text
.
i e
ENCLOSURE l PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNIT 2 P
DOCKET NO. 50-328 (TVA-SQN-TS-88-18)
. LIST OF AFFECTED PAGES Unit 2 3/4 6-27 P
"i O rr g y j
I CONTAINMENT SYSTEMS 3/4.6.5 ICE CONDENSER ICE BE0 LIMITING CONDITION FOR OPERATION 3.6.5.1 The ice bed shall be OPERABLE with:
a.
The stored ice having a boron concentration of at least'1800 ppm boren as sodium tetraberate and. pH of 9.0 to 9.5, b.
Flow channels through the ice condenser, c.
A maximum ice bed temperature of less than or equal to 27'F, d.
A total ice weight of at least 2,333,100 pounds at a 95?. level of confidence, and e.
1944 ice baskets.
APPLICABILITY: MODES 1, 2, 3 and 4.
ACTION:
'dith the ice bed incperable, restore the ice bed to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or be in at least HOT STANOBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> anc in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
SURVEILLANCE REOUIREMENTS 4.6.5.1 The ice condenser shall be determined OPERABLE:
At least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> by using the ice bed temperature monitoring a.
system to verify that the maximum ice bed temcerit;.'re is less tnan or equal to 27'F.
b.
At least once per 6 months during the first 2 years following initial T
criticality and at least once per 12 monthr thereafter by:
1.
Chemical analyses which ierify that at least 3 representatise samples of stored ice have a boron concentration af at least 1800 ppm as sodium tetraborate and a pH of 9.0 to 9.5 at 20*C.
2.
Weighing a representative sample of at least 144 ice baskets and verifying that each basket contains at least 1200 lbs of ice.
The representative sample thall include 6 baskets from
(
each of the 24 ice condenser bays and shall be constituted of 7 3,~.3 SEQUOYAH - UNIT 2 Ofi3/,4 6-27.
.5 m -
1
- dNFTmh'ffGMW4 TOAf W W #
? ? W ' ? s @ Q 9 " @
?
" M ;.. N l w.
cyae3 &Nw9 ouTA
?'r%N'W.
*C.
\\
W Ml
ENCLOSURE 2 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNIT 2 DOCKET NO. 50-328 (TVA-SQN-TS-88-18)
DESCRIPTION AND JUSTIFICATION FOR EXTENDING SURVEILI.ANCE REQUIREMENT FOR ICE CONDENSER ICE WEIGHING 1
9 I
o ENCLOSURE 2 Description of Change Tennessee Valley Authority proposes to modify the Sequoyah Nuclear Plant Unit 2 Technical Specifications to revise surveillance requirement (SR) 4.6.5.1.b.2 to allow for a one-time extension to the next refueling outage for weighing of ice.
Reason for Change TVA is requesting an extension of SR 4.6.5.1.b.2 to allow weighing of ice in the upcoming refueling outage.
The ice condenser rurveillance is required to be performed by December 4, 1988.
This surveillance can only be performed during shutdown; therefore, to avoid an u.snecessary shutdown of the plant, this surveillance needs to be extended to the upcoming refueling outage. Currently, the refueling outage is scheduled to begin January 22, 1989.
Therefore, this extension is short compared with the overall time of the surveillance interval.
Justification for Change SR 4.6.5.1.b.2 requires that each basket contain at least 1,200 pounds of ice and tiat the average ice weight in the group-row analysis shall not be less than 1,200 pounds per basket at a 95-percent level of confidence.
Also, the minimum total ice condenser ice weight at a 95-percent level of confidence shall not be less than 2.333,100 pounds.
As. defined in the basis of the technical specification, the 1,200 pounds contains a 10-percent conservative allowance for ice loss through sublimation, which is a factor of 10 higher than assumed for the ice condenser design.
Therefore, the basis for the minimum ice weight ist 1,200 pounds - (1,200 x 10 percent) = 1.080 pounds This value (1,080) pounds is used in all containment safety analyses.
Utilizing the data from previous ice weighing surveillances (May 1982 to September 1985), the ice loss for each basket was calculated.
The calculation was run using the average sublimatica rate over the entire period (May 1982 to September 1985).
This method is conservative in that the surveillance history shows that the sublimation rate has decreased since the initial ice weighing.
It was determined that, af ter the initial j
ice weighing, special attention was required for group 1 row 1 and bays 1 and 24 Other ice condenser plants were experiencing similar problems; therefore, an ice condenser improvement program was implemented to identify probable causes for the problems.
Improved maintenance and operation of the ice condenser have reduced the A unt of ice loss in the later surveillance.
4
O O
l !
In order to ensure a sufficient quantity of ice is available, the technical specification SR 4.6.5.1 requires that a sample of at least 144 ice baskets be weighed on a 12-month basis.
This sample includes one
[
basket from six rows (radial rows 1, 2, 4, 6 S and 9) of each of the 24 i
bays (refer to the attached figures 1 and 2 of this enclosure for a l
l representation of ice condenser bays, groups, and rows).
If any basket is l
l found to contain less than 1,200 pounds of ice, an additional 20 baskets must be weighed. The rows are then subdivided into three groups i
(group 1 - bays 1 through 8, group 2 - bays 9 through 16, group 3 - bays l
17 through 24). The minimum average weight of the group-row combinations I
and bays must not be less than 1,200 pounds per basket at a 95-degree level of confidence.
In addition, these basket weights shall be used to o
determine that the overall ice weight is not less than 2,333,100 pounds, r
The calculation shows that, using the expected sublima' tion rate (average l
rate), five group-row combinations have an average weight that is slightly less than the 1,200 limit (group 1 row 1 is 5.5 percent low, group 2 row 1 l
is 1.9 percent low, group 2 row 2 is 0.17 percent low, group 3 row 1 is t
1.3 percent low, and group 3 row 2 is 0.33 percent low).
Hovaver, all of
{
the group-row combinations and bays are well in excess of the analytical limit (1,080 pounds) that takes into account the amount of ice loss i
allowed between successive weighings and is the amount taken credit for in I
all containment safety analyses.
The average weight per basket for each I
group in the group-row combinations is 1,206 pounds for gr up 1 1.270 po mda for group 21 and 1,223 pounds for group 3.
The overall average weight per basket based o.n the group-row combination calculations is 1.233 pounds, which indicates a total ice condenser ice weight of
(
(1,233) x (81) x (24) = 2,397,000 pounds. The overall weight of the ice condenser based on both the group-row combinations and bays is greater than the minimum allowable amount of 2,333,100 pounds listed in the technical specifications. Therefore, the ice condenser has sufficient l
capability to perform its safety function during the requested extension i
period.
l l
i i
1 i
i
! 1i I
LE 3mw G
t s
R l
EP g-3 4
8 s
1 8
'l
\\
7 2
T I
~
N U
4 3
g
~
8 S
'Y R A I
E B ER S
U NF C
E O I
F D
e 4
A 3
N G g7 l
O N la C
I d
R o
E E B
2 C
M e
I U
r.
ig N
f l
f e
e
/ S 3
f, 1
'2 T
1 I
f U
~
' \\G
~
i k
\\
t f;
!. C
)s E
FIGURE 2 ICE BASKETS NUMBERING SEQUENC5 TYPICAL FOR UNIT 1
ICE CONDENSER (UNIT'E OPPOSITE HAND)
[ RCv LATTICE y FRAME 12 j r
2 II o o o 4
~ u 000 0
4 L
00 0 a e
'i
~
)
O 8000
,/
t 39 9
j H
O F
E D
C 3
A CCLUMN
( B A 'f SHOVN VITH BEAMS AND DOOR FRAT 1ES REMOVED)
DETAIL A
FIGURE 2
f ENCLOSURE 3 Significant Hazards Evaluation l
TVA has evaluated the proposed technical specification change and has
[
determined that it does not represent a significant hazards consideration i
based on criteria established in 10 CFR 50.92(c).
Operation of SQN in i
l accordance with the proposed amendment will nott t
(1); Involve a significant increase in the probability or consequences of l
l an accident previously evaluated.
The ice condenser system is l
provided to absorb thermal energy release following a loss of coolant accident (LOCA) or high-energy line break (HEL3) and to limit the peak pressure inside containment.
The ice condenser analysis shows j
that, with a minimum of 1.080 pounds of ice per basket, the ice condenser will perform its function.
Based on surveillance history of the ice baskets, the calculations of the sublimation rates, and I
the relatively short extension time, this request will not result in a significant increase in the probability or consequences of an accident previous evaluated.
(2) Create tae possibility of a new or different kind of accident from any previously analyzed.
The surveillance extension will not result in a change to the plant configuration or operation.
Therefore, this change will not create the possibility of a new or different kind of accident from any previously analyzed.
i (3)
Involve a significant reduction in a margin of safety.
The Final Safety Analysis Report analysis shows that, with the minimum amount of ice present in the ice condenser. the system will perform its function during a LOCA or HELB.
Based on the improved surveillance performance of the system, the sublimation calculation, and the short j
time period of the extension, this change does not involve a significant reduction in the margin of safety.
l l
i E
I 1
l l
x
t ENCI.0SURE 3 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNIT 2 l
DOCKET NO. 50-328 (TVA-SQN-TS-88-18)
DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATIONS i
i i
i l
a l
l
\\
1 i
l f
a e
4 e
ENCLOSURE 4 TECHNICAL SPECIFICATION 88-18 ICE CONDENSER SUBLIMATION CALCULATION (B45 880817 235)
I
)
e I
?
I a
l j
I i
., _ -.. - _..,