T 0420/93 03-06-1997

Summary of Facts and Submissions

I. European patent No. 0 243 917 was granted to the Respondent.

This patent comprises six claims, those numbered 2 to 6 being dependent claims appended to Claim 1, which reads:

"a nuclear fuel assembly for a nuclear boiling water reactor comprising a fuel channel of substantially square cross-section, a plurality of vertical fuel rods arranged in sub-bundles with substantially square cross-section, a vertical channel-formed support member with a center (7a) for the passage of water, said center being connected to wing parts (8) said sub-bundles of fuel rods being surrounded by said fuel channel and spaced apart by the channel-formed support member (7, 8) fixedly connected to the fuel channel (1), the cruciform center (7a) of said support member being limited by the central parts of the channel-formed support member, which conforms to the corner portions of said sub-bundles, in the region between the corner portions of the sub-bundles directed towards the center, characterized in that in each sub-bundle (6) of fuel rods (10) at least one fuel rod position has been removed from the corner portion of the sub-bundle (6) positioned nearest to the center (7a) of the fuel assembly, and that an enlarged cruciform center (7a) is formed by the channel-formed support member (7, 8), shaped in accordance to the non occupied corner portions of the sub-bundles".

II. An opposition was filed against the European patent on the ground mentioned in Article 100(a) EPC. The Opponent took the view that, having regard to the disclosure in documents:

D1: EP-A-0 099 322 and

D2: US-A-4 683 113,

the latter one corresponding to the JP-A-60/242392 (D2a) published before the date of priority of the European patent, the subject-matter of said patent lacked novelty or at least inventiveness. Later, during oral proceedings held on 13 January 1993 before the Opposition Division, the Opponent also referred to the patent specification

D3: US-A-4 585 614,

mentioned in the preamble to the description of the European patent and corresponding to the document SE-B-423 760, already cited in the ESR (European Search Report) and published before said date of priority.

III. The Opposition Division rejected the opposition, grounding its decision substantially as follows:

Document (Dl) discloses many nuclear fuel assemblies in which the arrangement of the fuel elements is irregular. However, Claim 1 does not mention any such arrangement. Therefore, said claim is to be regarded as related to a "normal" fuel assembly comprising fuel rods arranged in a quadratic lattice, and its subject-matter is new. Furthermore, (Dl) does not mention any assembly from which fuel rods have been removed at the corners of sub-bundles located nearest to the centre in order to achieve an enlarged cruciform centre: in the assembly of Figure 9, the cruciform centre results from the provision of non-quadratic sub-bundles, but (Dl) is silent about measures suitable for enlarging said centre. As a matter of fact, it is by combining different designs envisaged in (Dl) that the Opponent grounds its assertion that (Dl) would disclose an assembly with an enlarged cruciform centre. Such a conclusion, however, is based on hindsight. Furthermore, (Dl) does not suggest to shape the support member in such a way as to achieve an enlarged cruciform centre. Comparable arguments apply to the disclosure in (D3), so that the subject-matter of Claim 1 is new and inventive with respect to the teachings of the latter document and (Dl).

Document (D2) discloses an assembly in which additional water channels are provided in a central portion of the sub-bundles. According to the Opponent, it would be obvious to connect such channels with side walls to build a water cross. However, this would require an inventive step, for whole rows of fuel rods should be removed, whereby the fuel capacity would be significantly reduced.

As further evidence of inventiveness, it should finally be noticed that the sacrifice of fuel capacity in an assembly embodying the invention presents several advantages. For instance, owing to the moderation caused by the water in the enlarged centre, a longer running is possible when the fuel is getting exhausted. Besides, shutdown is more stable and there is less material liable to capture thermal neutrons.

IV. The Opponent lodged an appeal against the decision of the Opposition Division, requesting

(A) that the following questions be referred to the Enlarged Board of Appeal:

(i) does the principle laid down in Section C.IV.7.4 of the Guidelines, namely that a specific disclosure takes away the novelty of a generic claim, remain valid in the proceedings of opposition?

(ii) when an allowed claim can be read by the skilled person from the state of the art, is it admissible or even compulsory in the proceedings of opposition or in subsequent proceedings of appeal to achieve, by means of a change in the formulation such as a disclaimer, a clarification which renders novel the subject-matter of the claim?

(iii) are EPO instances entitled to allow or to maintain unchanged a claim which does not need a clarification but of which the wording, for it to be considered as defining patentable subject-matter, shall be interpreted as mentioning a distinguishing feature only disclosed in relation with the embodiments of the invention?

(B) that the decision under appeal be set aside;

(C) that the case be remitted to the opposition Division and

(D) that the appeal fee be refunded.

Subsidiarily, the Appellant requested that oral proceedings be held.

In support of these requests, the Appellant also referred in its Statement of grounds of appeal to the further documents

D3a: DE-A-3 142 300,

D3b: DE-A-3 022 687,

D4: US-A-4 578 241,

D5: EP-A-0 036 142,

D6: EP-A-0 099 323 and

D7: US-A-3 764 471.

Documents (D3a) and (D3b) together contain the matter disclosed in document (D3) and were cited because the latter document had been made available to the public at the date of priority of the European patent, whereas documents (D4, D5 and D6) respectively correspond to the citations SE-B-426 428, SE-B- 421 969 and SE-B-431 691 of the ESR.

V. The Respondent requested that the appeal be rejected as unfounded and, subsidiarily, that oral proceedings be scheduled. Its comments on the grounds of appeal were filed on 11 January 1994.

VI. The Board issued a communication pursuant to article 110(2) EPC taking the preliminary view that, having regard to the state of the art disclosed in the documents (D1, D2 & D2a, D3a, D3b, D4, D5 and D6), no claim of the European patent seemed to cover subject-matter involving an inventive step. The communication also stated that it did not appear to be appropriate or necessary to refer any questions of law to the Enlarged Board, and that refund of the appeal fee was not envisaged.

Though having requested two extensions of the period for filing its observations, the Respondent failed to comment on the Board's communication and, therefore, a summons to attend oral proceedings was sent to the parties.

VII. In a letter dated 29 April 1997, the Respondent further submitted that the documents (D3) to (D7) should not be introduced into the proceedings because of belated file and requested subsidiarily that the European patent be maintained in amended form on the basis of a set of six claims annexed to that letter. This subsidiary request was not maintained in the oral proceedings before the Board.

In said letter, the respondent also referred to the document:

D8: O. Nylund et al.: "SVEA - new generation of BWR fuel assemblies", in Asea journal 3/84, pages 4 to 7.

VIII. The oral proceedings were held on 3 June 1997.

During the hearings, the Appellant's representative handed over two bundles or respectively four and five pages with text and drawings explaining the Appellant's views.

On its part, the Board drew the attention of the parties to Figure 4 of the European patent representing an embodiment of the claimed nuclear fuel assembly where the wing parts (8) of the channel-formed support member consists of thin plates and do not comprise vertical channels.

Before deliberation by the Board, the Respondent's representative submitted two sets of claims forming the respective bases of a first and a second auxiliary request. Disregarding their division into a plurality of numbered clauses, the related versions of Claim 1 are distinguished over Claim 1 of the European patent as granted in that,

- according to the first auxiliary request, the adjective "regular" is inserted between "at least one" and "fuel rod position" in the characterising part and,

- according to the second auxiliary request, a further clause reading "the fuel rods of each sub-bundle being arranged in an essentially regular quadratic lattice, "is inserted after "sub-bundles with substantially square cross-section," in the pre-characterising part.

According to both auxiliary requests, dependent Claims 2 to 6 identical to those of the European patent are appended to Claim 1.

IX. The Appellant maintained its requests and, in support thereof, argued in substance as follows:

Nuclear fuel assemblies according to the pre-characterising part of Claim 1 are already known from documents (Dl) and (D3). In particular, Figures 4 and 8 of document (Dl) show sub-bundles with 25 fuel rods having the same diameter and arranged in arrays of five lines and five columns. From Figure 9, the reader furthermore learns that a broader central channel can be obtained by removing one central fuel rod. Therefore, it is not inventive to remove the rods from the central corners of the sub-bundles to realise a still broader central channel, even if it is borne in mind that the inventions disclosed in (Dl) and (D3) aim at increasing the number of fuel rods. Likewise, the phrase "vier im wesentlichen quadratische Teilbündel" i.e. "four substantially quadratic sub-bundles" in Claim 1 of document (D3a) obviously refers to the presence of corners not provided with fuel rods. Bearing in mind that document (D3a) starts from the teachings of document (D3b) where thinner fuel rods are placed at the corners of the sub-bundles, the lack of novelty of Claim 1 becomes apparent. Besides, another arrangement without fuel rods at the central corners, whereby the possibility of chamfering said corners is obviously offered, is disclosed in document (D7).

The Opposition Division took the view that novelty would not be at issue because documents (Dl) and (D2) do not show any fuel assembly from which a "normal fuel rod" has been removed. Nevertheless, stating in Claim 1 that "at least one fuel rod position has been removed" does not reveal anything as regards the type of the fuel rod. Furthermore, from the patent in suit, the skilled person learns no restriction concerning the diameter and arrangement of the fuel rods. As a matter of fact, the adjective "normal" is much too vague for an assessment of novelty and inventiveness. For instance, in the particular case of an arrangement according to Figure 10 of document (D7), where the meshes of the gitter have the same cross-section, it cannot be decided which ones contain "normal fuel rods".

The Opposition Division also took the view that, albeit entailing a reduction of the fuel capacity, the removal of fuel rods would provide advantages. The latter, however, have been known for a long time, as evidenced by the statement in document (D2) that such removal results in improved fuel economy, and by the presence of water rods (14) in the arrangements according to the Figures 4, 12 and 15 of that document.

Headnote III of Decision T 16/87 (OJ EPO 1992, 212), on which the Opposition Division might have relied, is admittedly in contradiction with paragraph C.IV.7.4 of the Guidelines. Nevertheless, is it acceptable that the fate of a claim shall depend on whether the relevant state of the art has been considered during the proceedings up to grant or only during the proceedings of opposition? Hence the first question to be submitted to the Enlarged Board of Appeal. This question is relevant to decide whether the Opposition Division made a substantial procedural violation justifying a refund of the appeal fee.

In the present case, the lack of clarity resulting from the distinction between "normal" and other fuel rods has a consequence from the standpoint of Articles 54 and 56 EPC. In this respect, attention should be paid to headnotes I and II of decision T 170/87 (OJ EPO 1989, 441) stating that an explanatory figure does not clearly exclude a feature which is not represented, and that the use of disclaimers does not render inventive an obvious teaching. Hence the second question of law.

In cases where no reference to the description and drawings is needed in a claim, decision T 16/87 seemingly allows this in order to arrive at a patentable subject-matter without having to define in detail the decisive feature. This applies to the present case. Nevertheless, if a claim clearly defines an object, no restrictive interpretation of its wording should be allowed and, conversely, if inventiveness depends on the provision of a further feature, then the latter should be mentioned in the claim. Decision T 175/85 (OJ EPO 1989, 71) states indeed that, when examining a claim for inventive step in such cases, it should be assumed that it is directed solely to the simultaneous application of all its features. Pursuant thereto, the Opposition Division should have been aware that Claim 1 lacks novelty, since it also covers any irregular arrangements of the fuel rods and any type of rods. Decision T 416/87 (OJ EPO 1990, 415), however, states that, if the description specifies a feature to be an overriding requirement of the invention, the claims may be interpreted as requiring this feature, even though not stating this. A similar case arises in decision T 406/86 (OJ EPO 1989, 302) taking into consideration, for the purpose of assessing novelty, features mentioned in the description of a patent, but not in the claims. Hence the third question of law.

X. The Respondent requested that the appeal be dismissed and that the patent be maintained as granted or, subsidiarily, on the basis of the first or second auxiliary request filed during the oral proceedings dated 3 June 1997. Its argumentation may be summarized as follows:

The Appellant's pleading that Claim 1 would not be formally correct does not even have the quality to enter opposition proceedings. Therefore, under the presumption that Claim 1 covers sub-bundles with irregular lattices, it shall be investigated whether novelty or inventive step are lacking.

Figure 1 of document (Dl) does not destroy novelty for there is no cruciform centre shaped in accordance with non-occupied corner portions of the sub-bundles. The Appellant's argumentation based on Figure 1 of document (Dl) starts from the wrong assumption that said figure discloses the removal of irregular fuel rods from corners of a sub-bundle. According to (Dl), however, it is sought to increase from 16 to 20 the number of fuel rods in a conventional sub-bundle without increasing the outer dimensions. This is achieved by using two quadratic lattices, each occupying the space on a respective side of a diagonal, said lattices being displaced with respect to one another. Furthermore, document (Dl) points to three openings (9) within the spacer, in which openings water tubes or thinner fuel rods may be arranged. Such teachings may not be interpreted as an incentive to remove fuel rods. Besides, the skilled person would not use the free corner spaces nearest to the centre for enlarging the central part of the cruciform channel. It is indeed stated in (Dl) that these locations are reserved to spacing members or holders. Likewise, the seemingly enlarged centre in Figure 9 is the unavoidable result of using rectangular sub-bundles. It may actually not be considered as "enlarged", since no possibility of decreasing its size is offered and, at the utmost, it corresponds to the removal of only one fuel rod, whereas the invention teaches to remove the four innermost fuel rods.

Document (D3a) too discloses measures for increasing the number of rods in a sub-bundle, and this without changing the dimensions of the fuel rods. This purpose is achieved by means of irregular lattices but, from Figure 2, it is obvious that the free spaces of such lattices are far too small to accommodate a further fuel rod. Document (D3a) suggests to use the free spaces of the lattice to reduce the width of the sidewalls to no more than 65% of the width of a sub-bundle. However, it is not for increasing the amount of non boiling water in the centre of the fuel assembly that it is proposed there to cut off the rounded edges of each fuel channel surrounding a sub-bundle, but for stiffening the fuel channels against the inner pressure. The formation of an enlarged centre of the cruciform water channel is thus merely incidental and, again, this centre has a cross-section much smaller than is contemplated in accordance with the invention. Furthermore, there being no common fuel channel surrounding the groups of four sub-bundles, no need for stiffening such a common channel by means of a cruciform support member can be felt.

Document (D2a) is essentially concerned with the problem of flattening the power distribution in the axial direction of a fuel assembly and, as a solution thereto, proposes the provision of first fuel rods containing a burnable poison and fuel pellets having a higher enrichment in the upper part of these rods and that of second fuel rods containing fuel pellets of uniform enrichment, exclusively. The purpose of the water rods (14, 51) is nowhere disclosed, and neither is it mentioned in document (D2a) that the walls of the fuel channels would bulge. It shall therefore be assumed that said walls are strong enough and, since the fuel assembly is presented as performing perfectly, why should the skilled person have subdivided it into four sub-bundles? Furthermore, the arrangement of a cruciform support member carrying non-boiling water in the fuel assembly of document (D2a) would require narrowing the distance between the fuel rods in order to provide the needed space. Considering that the distribution of boiling and non-boiling water is of decisive importance to the distribution of neutron flux, as appears from document (D8), this would involve tremendous risks, whereas increasing the wall thickness is a safe, simple and efficient measure. Moreover, the arrangement of a central water rod as shown in Figure 19 of document (D2a) and that of a cruciform water channel according to any of the documents (D4) and (D8) are equivalent solutions. Combining them involves the presence of a huge quantity of non-boiling water in the fuel assembly, so that the skilled person would have feared the creation of an unwanted neutron trap. Consequently, he would rather have provided additional water channels at or close to the centres of the individual sub-bundles, as shown in Figure 3 of document (D3b).

The fuel assembly known from document (D3b) is not provided with a channel shaped support-member. To increase the mechanical stability of the channels, fuel rods having a smaller diameter are provided at the four corners of the sub-bundle, thereby making it possible to enlarge the rounded portions of the channel wall at these places. Again, this document does not suggest to remove fuel rods from any place in the sub-bundle. Figure 10 of document (D7) is still less relevant, since it does not disclose any place from which a fuel rod has been removed for whichever reason. Besides, the free spaces at the outer four corners cannot be provided with spacer cells and, therefore, cannot accommodate fuel rods. Finally, nothing in documents (D5) and (D6) is related in any relevant way to the present invention.

XI. At the conclusion of the oral proceedings, it was announced that no questions are referred to the Enlarged Board of Appeal, that the appeal is allowed, that the European patent is revoked and that no apportionment of costs is awarded.