ML030700561
| ML030700561 | |
| Person / Time | |
|---|---|
| Site: | Washington State University |
| Issue date: | 02/28/2003 |
| From: | Tripard G Washington State Univ |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML030700561 (10) | |
Text
Washington State University Nuclear Radiation Center PO Box 641300 Pullman, WA 99164-1300 509-335-8641 FAX 509-335-4433 Friday, February 28, 2003 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Ref: Docket 50-27
Dear Sir:
This letter is a response to a U.S. Nuclear Regulatory Commission request for additional information dated January 9, 2003.
The first item asked the following:
- 1. According to your request to change the Technical Specifications (Amendment No. 18) the new criterion to replace the "absolute filter" will be based purely in the performance of the filter. The pressure drop caused by the "absolute filter" will be the only indicator to ensure that the filter performance is acceptable. Figures 9-1 and 9-2 of the Safety Analysis Report are inconsistent on where the Pressure Elements (PE) are installed with respect to the "absolute filter." Please provide a detailed diagram of the installation of the two pressure elements used to calculate the pressure drop caused by the "absolute filter." This diagram should illustrate the section of the HVAC system that is used in the "dilute mode." The following detailed information should be included with this illustration:
(a) duct dimensions where the "absolute filter", the first pressure element, and second pressure element are installed, and (b) the distances between the two pressure elements and the "absolute filter."
Response to first item:
Attached is a more detailed diagram entitled, "Pressure Sensor Positions Relative to the 'Absolute Filter"'. On this diagram one can see the position of the pressure sensor on the pool side of the absolute filter. In the dilute mode, 300 CFM is being drawn from the pool room. It then passes the first pressure sensor located 37 1/2/2" upstream of the absolute filter. The filter consists of two side by side box shaped objects of dimension 23 1/2" x 23 1/2" x 11 1/2/" oriented as shown. The second pressure sensor in the diagram is located 29 '/2" downstream of the absolute filter in the duct leading to the main ventilation system exhaust. In the dilute mode, 300 CFM of pool room air is passed through the HEPA filter and then mixed with 1700 CFM of "outside air" to produce a "dilution" factor of 6.67 when the filter is new. If the HEPA filter becomes slightly obstructed A
through use, the dilution factor would become larger and therefore the radioactive air release rate would become more conservative. After dilution, the mixed air passes through damper D-6 and enters fan F-3 which draws the air into the main ventilation duct where the "Exhaust Gas Monitor" measures the Argon-41 release. The total distance between the two pressure sensors is 78.5".
The second item asked the following:
- 2. Please provide information on how you are planning to calculate the flow across the absolute filter to ensure that the filter is performing between the limits of pressure drop and volumetric flow specified by the TSs. Please provide an original-copy of the performance chart of the "absolute filter" provided by the manufacturer.
Response to the second item:
It was not our intension to re-calculate the flow across the absolute filter. Measurements of flow rates were made when the system was installed to validate the design. We could arrange to have the flow rates verified again but only if the US NRC considers it to be essential. We do not consider it relevant because if the "absolute filter" became more obstructed with use, the flow through it would be slightly reduced. A flow reduction through this filter would increase the dilution factor, making its performance more conservative than the less obstructed "new" filter.
Please find attached a FAX sent to us by the manufacturer of the "absolute filter" designated YY-F.
It is the third row from the top in the CFM Capacities and Dimensions table.
The third item asked the following:
- 3. According to the SAR and the TSs, the HVAC system will change to emergency-mode if there is a reactor scram. Does the air monitoring system have the capacity to shut down the reactor and change to emergency-mode in case of an excessive airborne radioactive release? Please provide set-points of the air monitoring system used by the HVAC control system to change from dilute mode to emergency-mode.
Response to the third item:
There are three important monitors relevant to the radioactivity in the pool room; namely a Continuous Air Monitor (CAM) close to the pool water just above the reactor, a GM detector on the reactor bridge, and an Exhaust Gas Monitor (EGM). The first two detectors are the most important while the third provides an additional element of safety.
When the CAM reaches 3.13 x 103 counts/minute a warning alarm sounds. Usually this happens if the diffusion pump is inadvertently off. The operator would then switch the diffusion pump back on and continue operations. When the CAM reaches 3.13 x 104 counts/minute the HVAC automatically switches to the "dilute mode" and the operator, in response, is required to "shutdown" the reactor by switching a reactor control to "rundown". The rundown following a high CAM alarm is intended to avoid "shock" to any leaking fuel element, should that be the cause for the alarm.
If the GM detector mounted on the bridge of the reactor reaches 200 mrem/hour it automatically initiates a reactor SCRAM which causes the HVAC system to switch to the "isolate" mode.
If the EGM reaches a count rate of 96.8 counts/minute (which is less than the DAC) an alarm sounds at the console and the operator is required to switch the 1HVAC system into "isolate" mode and to investigate the cause of the alarm.
The fourth item asked the following:
- 4. Please provide more information regarding the second change you are proposing in the requested amendment of the TSs, and explain why these two items are redundant. Include information on the control and instrumentation system activated by the access gate mentioned in the items 10.c and 10.d of Section 3.15 of the TSs.
Response to the fourth item:
Please note the circuit diagrams enclosed (entitled "BNCT/RX bridge movement panel" and "Beam Room Scram Chain") which should help to understand how the system operates.
10.c states that upon opening the BNC room's access gate the reactor scrams and the bridge moves to the retracted position.
This action was accomplished by placing a spring loaded micro-switch on the inside door frame of the access gate (which is actually a solid door). The micro-switch is Normally Closed (NC) when the switch is compress by a plate attached to the access gate (see switch 28SW6-A on the drawing "Beam Room Scram Chain"). The switch is NC when the gate is closed by this plate attached to the gate. If the access gate is opened a few millimeters, the micro-switch 28SW6-A changes to the "Open" state. This switch is part of the Beam Room scram chain. If any element in this scram chain opens, the reactor automatically scrams and the bridge automatically retracts. This micro switch is actually the switch referred to in 10.d that describes it as "the bridge retraction switch on the access gate".
That means that "opening the access gate" in 10.c and "opening the bridge retraction switch" in 10.d are one and the same action; hence the redundancy.
If you have any questions, please contact Dr. Gerald Tripard, Facility Director (509) 335-0172 Sincerely, Gerald E. Tripard Director
Enclosures:
Figure: Pressure Sensor Postions Relative to the "Absolute Filter" Figure 9-1 Pool Room Ventilation System Fax of manufacturer's transmittal sheet and table for relevant filters Figures: "BNCT/RX bridge movement panel" and "Beam Room Scram Chain" cc: US NRC Headquarters Office
Figure: Pressure Sensor Positions Relative to the "Absolute Filter" 1"1 27.5" -i
- 20.5" pop 1-*ql- 9"-00 S19.5" i"91'-9" -I0-1-i4 - 12" '-0-. 1~
I I I II I I I I I II 300 CFM ! 1- 11 ."1 1 II II I 18" x 12" duct II Damper D2
____4-
- 300CFM
.I
. 18"x 12" duct Pool Side Pressure Sensor #1 I
I I
Damper D6 Downstream Pressure Sensor #2 I I I I I I
- 37.5",,--I i 29.5" *.-
I I I I
0 RM. 201 POOL RM. -a a.P o .V n W. Pool Rin. Vent 4055 4, 30 CFM 43502CFM do
,,13 ..
45, ,,
vvy-ED
- vvSL.f*p L VP NRC FAN PENTHOUSE v\0 A Fi-4 COMMON STACK 9 Absolute Heater Coil 41Ar Sample** F-3
". 150' V%"4 CFM" I
t')
Dilute Fan "
M=MtaticDamper
=aulDamper F-2
- _ (Beam Rm.
I Exhaust 1700 CFM A Beam Rm. Fan F-4 Pool Rbm.Supply Fan Q Coil
_I l
F-o POOL ROOM VENTILATION SYSTEM 08/03/87 JAN Pool Pin. Exhaust Fan 4iflO rFM Figure 9-1
a :t I Lu q
.1.
I 9, v a z I
.Q..
a 4 10 I
0 8 U I.
iu, IV Gas 4
I 4vy I I1 4 4v F
.7
OPPOW W648J910d -19 *&WenbwHWmdmdb 94MOPM&MM
- wd @"W LWOPJRd
- a. WX W.M. t Pipwufý wtoo RIF.
Avtuqm wilphoo -111ii "'IN,
..qw"Aw K"
- m. jWkjW jar W* Wm qOW -*A*V
)Pvd vqx" woo""m GAS JOWedos Jew ffmmumo* Aww:*iw Mo..'WOOM vu.
taim po aqdlV WX*WW WNUO"..Wd -VAIY^l - 11101811:111111MIl"t"
-TORM W-4-mv -RWAWW.
OW. PUNW ift Uf ow .00MA Wm wd**dn WwWrOp P*SRAW
- I op" VA.%* eft-:mw ds -v eswu. VA4U
-4dik "Wb*vdos Wi OAd ptW ..jwxft puonwKuw AM ftmw 69 ocipt am u x ornz CLPL WtZ- olot Not 061 ORR.
cc Ogg 9M OCXX U X-OC.
ova 0991 OSUL t ocet m ev x oc 09 oon as 0" -KX' 9a 1 Mý OLU 1w ma 009t scot .
at ME Out m 09 st OM SM..- 099 Et otolL SU W9 99 x -vat.
9z We peg OW cz 0" 9ýv ozz wu*Lt x9mocc - G"nA L OL9 261! 69 6 Ret SOL 04 sw 9zz 9#L at x 090 Oas sn tew te W.' -*
"a soz W- --- U7x ef o0a OOOL Xx #4 Vt 099 S! 03 Ccn) WARveqvul- -00JAWY m *.0,40, 34m,". usm W APO** WO pw moblimirm L9L8TGzGzv 90:41 EOOZ/LZ/10 ZO 3E)Vd STWS 8311IJ Wd8lV
2M114 24 2 F 1S:2 V'W 12M 2T I 4
Ii I'
20n14 The BNCT Scram Chain consists of 7 11M switches in the beam room area.
/
There are 4 switches associated with each of 4 access keys. There are 2 A nmu Scram buttons, one inside and one outside of the treatment room.
FEMRAPV ROOM 4 The Access Door has the 7th switch.
A DO nCS AWC 28K9 is the BNCT Scram Relay. If any of the switches in this chain open or the power to this relay fails, this relay de-energizes and opens a contact in the Reactor's Main Scram Chain.
/I'
-It
'I tic 28TO 4 aN [-]
REVISIONS NUCLEAR RADIATION CENTER WASHINGTON STATE UNIVERSITY PULLMAN, WASHINGTON TrrLE: BEAM ROOM SCRAM (ChAIN 28TB1-10 SCALE: NA IDWG BY: at IT.
FlLENO:
DATE; 07'/N*1 1 BY;xGEF.T. I C-ow
28T18-2 28T18-1 28T11-2 28TB1-4 28T81-3 28TB1-3 28FI 120 VAC
+ 12 VDC a ARIES 28TI 28TB11-1I 28P1-M 28T11-2 +
28K5-2 28K3-2 28K2-2 Close with i0 B loss of AC Power Retract Engage Open when S6 ft position 28K7-1 Limit Cutout 3
280S91 I c 28SW4-C NO I,
I: I _ I 28P1-P A
28TB3 7
L 28P1- { K 28TB1116
-12 VOC ARIES REMOTE COMPONENTr REVISIONS NUCLEAR RADIATION CENTER 051211200003;28/2001 WASHINGTON STATE UNIVERSITY 05129/2000oo PULLMAN, WASHINGTON 0610712000 TITLE: BNCT/RX BRIDGE MOVEMENT PANEL 28182-13 28182-13 28TB2-14 28TB2-14 28T32-14 28T22-14 28TB2-14 28TB2-14 28TB1-10 06/27/2000 28TB3-14 280T3-14 'ALE : N.A . DW G BY: J .A.N. !F IL ENO :I d.2
- t -utut 1Iu.flLtUVU -:.. *s*
¢'*Ik° RV- .f.A.N I 1 10/1112000 , TTE JDAYE: 05/0-8/19" UnlQ7J/IY" 1utt K IiN: Jý . i