ML20081L762
| ML20081L762 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 06/28/1991 |
| From: | J. J. Barton GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C321-91-2111, TAC-59122, TAC-59126, NUDOCS 9107080053 | |
| Download: ML20081L762 (3) | |
Text
l A
+
e.
GPU Nuclear Corporation G 4 Nuclear
- en:r>88
^
Forked Rwer, New Jersey 08731-0388 609 971-4000 Wnter's Direct Dial Nurnber:
C321-91-2111 TAC Nos.59-122 and 56-126 June 28,1991 U.
S. Nuclear Regulatory Commission Att: Document Control Desk Washington, DC 20555 Gentlemen Subjects Oyster Creek Nuclear Generating Station (OCNGS)
Docket No. 50-219 License No. DPR-16 Exemption Request for Alternate Rod Injection (ARI) Diversity per 10 CFR 50.ts2 (ATWS Rule)
References:
- 1. NRC letter dated January 24, 1991, re: Implementation of ARI Diversity Requirements.
- 2. GPUN letter dated March 29, 1991, (letter no. C321-91-2075) in response to Reference 1.
The purpose of this letter is to request exemption from the diversity requirements of 10 CFR 50.62 for the Alternate Rod Injection System ( ARI) at Oyster Creek. GPU Nuclear (GPUN) makes this request pursuant to the provisions of 10 CFR 50.12 (a)(2),(ii) and (iii). This fulfills our commitment to respond as given in Reference 2.
Background and Introduction At issue is the Staff's position (Reference 1) that the signal processing hardware used in the ARI system must be of different manufacture from that used in the Reactor Trip System (RTS) in order to meet the diversity requirement of 10 CFR 50.62.
The purpose of the diversity requirement and underlying basis for the Staff's concern is common cause failures attributed to hardware manufacturing defects.
ARI input signals for reactor water level usa ECCS instrument loops. The ECCS reactor water level instrument loops use Rosemount transmitters with Foxboro Spec 200 signal proc'ssing hardware. The Foxboro hardware is powered from an AC primary power uource with a DC backup. The modification to ARI, to provide divers '.y of signal processing hardware would 1) reduce the overall ARI system reliability; 2) reduce the overall ECCS system reliability; and, 3) cause undue hardship and significant costa. The bases for these concerne and our request for exemption are provided below.
9107080053 910628 PDR ADOCK 0S00021o j7 cmc:(5E[g 01C L, P PDR fv GPU Nuclear Corporation is a subsidiary of Genera! Pubhc Utit:es Corporation iIe
,C3,21-91-3111 Page 2 Exemption Request GPUN requests this exemption on the basis of the following:
1.
Reduction in overall ARI system reliability The current ARI system design, employs the Foxboro spec. 200 electronics, which is lE qualified and is highly reliabis. This design ensures that the purpose of the ATWS Rule and its intent are satisfied. The new electronics would not be qualified as Class lE components, as such qualification is not required by the rule. GPUN and industry experience indicates that Foxboro Spec. 200 electronics have not been subject to common cause failures due to hardware manufacturing defects. The performance of this equipmert at Oyster Creek and at TMI has been and continues to be excellent. Therefore, replacing the Foxboro process electronics with that of another manufacturer will reduce the overall ARI cystem reliability.
2.
Reduction in overall ECCS system reliability The ARI system currently uses ECCS transmitters to measure reactor water level. Meeting the diversity requirements would necessitate breaking into the Class lE current loop, and providing an isolation device between IE current signal and non-lE ARI system before processing the signal for ARI.
This will have negative impact on ECCS reliability due to having more components in the ECCS loop.
In order to maintain ECCS reliability, dedicated trar.smitters would be required resulting in significant additional costs as described below.
3.
Undue hardship and a3gnificant costs Compliance would result in undue hardship and costa significantly in excess of those incurred by "others similarly situated,"
1.e.,
other BWR plants which are required to implement ARI diversity.
Most of the other plants which presently do not comply with the Staff position use Rosecount process electronics in their RTS and ARI system. General Electric.(GE) offers a one for one replacement for the Rosemount units, which are essentially the same in circuit design and fabrication.
Replacing the Rosemount units with GE units is estimated to cost approximately $170K/ plant or less, as noted in Reference 1.
Since Oyster Creek uses Foxboro Spec 200 process electronics, there is no ono for one replacement available. GPUN currently estimates that implementing the Staff's position would cost approximately $622K or more for Oyster Creek.
The difficulty of iri.plementing such an extensive modification at oyster Creek is based on tne considerable work which wculd be required as follows:
Two new enclosures would be required, one to house new Class lE electronics, and the other to house the new bistables. The new enclosures would be located and installed seismically in the control Room, where space is very limited.
,C121-91-2111 Pagp 3 To maintain the same level of reliability in power source, Class 1E power supplies would be required.
In order to maintain ECCS reliability, new transmitters dedicated to ARI could be installed. However, the cost estimate indicated above does not include the cost of installing new transmitters. Providing new transmitters dedicated for the ARI system would add another $500K to the cost.
Additionally, the BWR Owners' Group (BWROG) recently performed an assessment of the Automatic Trip Unit (ATU), which is the logic component subject to the functional diversity requirement. The BWROG's assessment concluded that
" Analog Transmitter Trip Unit (ATTU) failure is a negligible contributor to overall shutdown failure frequency, because of the total number of failures required to prevent automatic shutdown, low common cause failure potential, the availability of diverse level indications and alarms from feedwater control, and the adequate procedural guidance and time available for operator action if automatic actuation fails."
(.9ee BWROG-8962, dated August 11, 1989 to Mr.
James Taylor (NRC) from Stephen D.
Floyd, Chairman DWR Owner's Group).
Based on the above, implementing the staff position at Oyster Creek will result in reduction of overall reliability of the ARI system, and ECCS, and is very costly and time consuming in termr of engineering and construction.
Additionally, the BWROG's quantitative assessment of the scram system's reliability showed the increased costs of providing diverse manufactured trip units was not justified by the insignificant improvement in overall safety.
Accordingly, the commission should grant this exemption request pursuant to 10 CFR 50.12 (a)(2)(ii) and (iii) due to the special circumstances in this cases i.e.,
(1) The GPUN design of the ARI system satisfies the intent and undarlying purpose of the ATWS rule; and, (2) Compliance with the Staff's position would result in undue hardship on GPUN due to costs which are significantly in excess of that contemplated by the Staff; respectively.
We look forward to your expeditious decision in this matter.
If you have any questions, please contact Mr. Mike Laggart, Manager of Corporate Nuclear Licensing at (201) 316-7968.
Sincerely yours, d
=
Jf b J.
r on Vic'# P.esident and Director, Oy te Creek JJB/GMG/plp cci Administrator, Region 1 NRC Resident Inspector Oyster Cre9k NRC Project Manager GMG:C3'12111
-.. _ _. _ _ _ _ _ _ _ - - _ _ _ _ _ -